The Limitless Sky

Air Force Science and Technology Contributions to the Nation

Edited by:

Alexander H. Levis

Chief Scientist, USAF

with the assistance of

Colonel John C. Bedford, USAF, Ret.

Captain Sandra Davis

Air Force History and Museums Program

United States Air Force

Washington, D.C.

2004
“...problems never have a final or universal answer, and only constant 

inquisitive attitude towards science and a ceaseless and swift adaptation 

to new development can maintain the security of this nation through...

air supremacy”

Dr. Theodore von Kármán to General Henry H. “Hap” Arnold

15 December 1945

To the Air Force scientists and engineers,

military and civilian, for keeping true to 

von Kármán’s vision.
Acknowledgement

Neither the Symposium nor this book would have been possible without the support of 

a number of organizations. The Air Force Association provided a venue for the Symposium 

and made it a part of its Fall ’03 convention in Washington, D.C. The Air Force Legislative 

Liaison and the Public Affairs Offices provided administrative support and publicity, while the 

Centennial of Flight Office included this activity in the centennial program. The organizing 

committee was chaired by Col. John B. Bedford, AF/ST, and included Alexander G. Levis 

and Nancy C. Stenger from AF/ST, Bill Heimdahl from AF/HO, Col. Tom Schubert from 

AF/LL, Maj. Michelle Ryan, AF/CVAH, and Napoleon Byars from AFA. The Program 

Committee had the responsibility of selecting the topics and working with the multiple authors 

to produce the papers and the presentations. The committee was chaired by Alexander H. 

Levis, AF/ST, and included Barbara A. Wilson, AFRL/CT, Col. Donald R. Erbschloe, 

AFOSR/CD, George W. Bradley III, AFSC/HO, Ruth P. Liebowitz, ESC/HO, and

Maj. John Beaulieu, AF/HO. Thanks are also due to several individuals who introduced the 

papers at the Symposium: LtGen Tom Hobbins, AF/XI, Maj Gen Don Lamberson (Ret.), 

Barbara Wittig, Jacob Neufeld, and Richard Wolfe, of AF/HO for editorial assistance and 

Susan Linders, of Air Force Media Services for design and layout.
Content

Dedication iii

Acknowledgment iv

The Limitless Sky 1

Dr. Alexander H. Levis

Precision Timing, Location, Navigation: GPS and the Precision Revolution 23 

Michael I. Yarymovych, Bradford W. Parkinson, George W. Bradley III, 

Brigadier General Daniel J. Darnell, USAF, Ivan A. Getting

Tightening the Circle: Scientific Research and the Evolution and Revolution of Precision 

Guided Munitions 21

Lieutenant General Daniel P. Leaf, USAF, Robert I. Sierakowski, Robert P. White

Enlisting the Spectrum for Air Force Advantage: Electro-Optical/Infrared (EO/IR) 47

Ruth P. Liebowitz, Edward A. Watson, Major General Stephen G. Wood, USAF

From the Air: Taking Radar to New Heights 65

Tom W. Thompson, Ruth P. Liebowitz, Jon S. Jones, Robert J. Mailloux, 

Lieutenant General Bruce K. Brown, USAF, Ret., Major General Joseph P. Stein, USAF

Pilots in Extreme Environments: Enforcing U.S. Foreign Policy from the Edge of Space 83

Major General Robert F. Behler, USAF, Ret, Russell R. Burton, George C. Mohr, 

William J. Sears, Billy E. Welch

Exploiting the High Ground: The U.S. Air Force and the Space Environment 109

Barron K. Oder, William F. Denig, Major William B. Cade III, USAF

Space Flight: Long-Range Missiles, Rocket Planes, and Lifting Bodies 145

Rick W. Sturdevant, John H. Darrah, Lieutenant General Forrest McCartney, USAF, Ret.

Military Satellite Communications: From Concept to Reality 171

Harry L. Van Trees, Lieutenant General Harry D. Raduege, USAF, Rick W. Sturdevant, 

Ronald E. Thompson 

Directed Energy: The Wave of the Future 207

Robert W. Duffner, Robert R. Butts, J. Douglas Beason, General Ronald R. Fogleman, USAF, Ret.

Notes and References 233

Acronyms 254

Biographical Sketches of Authors 258
The Limitless Sky

The old dream of mankind to fly and reach the sky—as exemplified by Daedalus and 

Icarus of ancient Greek lore—became a reality on December 17, 1903, at Kitty Hawk, North 

Carolina, and ushered in a period of unprecedented technological development. From Orville 

Wright’s short flight a few feet off the ground, to the commercial airliners flying at 37,000 feet, 

the limits of the sky have receded farther and farther away. In the second half of the twentieth 

century, powered flight extended to satellites orbiting the earth, to landings on the moon, and 

probes that explore our planetary system. The Hubble space telescope has been producing 

breathtaking pictures of distant galaxies not observable from terrestrial telescopes. The sky has 

become limitless.

The Air Force, from its very beginnings as the Army Air Corps, has contributed significantly 

to all aspects of powered flight that have not only enhanced the defense capabilities of the United 

States, but also produced a broad spectrum of non-military applications that have improved 

the quality of life throughout the world. Consequently, to celebrate the centennial of flight, 

a one-day symposium was held on September 17, 2003, in which the stories of some of the 

contributions, and of the people who made them, were told. The objective of the symposium was 

to present technological developments that have produced new capabilities or opened new ways 

for achieving objectives. Each paper is the result of a collaborative effort of historians, who have 

placed the contribution in its historical perspective; technologists, who have described the essence 

of the scientific or technological contribution; and Air Force senior officers, who have shared their 

personal experiences on how that technological development affected operations or missions. 

The nine papers included in this volume were selected because of their diversity and because 

they illustrate clearly several key themes. First, it takes a long time from the onset of a new idea 

to the production of a useful product that enhances operations, something on the order of twenty 

years. One has to believe in the idea and stay the course, in the face of adversity, to obtain results. 

Consistent, steady funding is a must. Second, research results rarely lead to what was envisioned 

in the beginning as a relevant application. Indeed, research in atomic clocks enabled the Global 

Positioning System (GPS), but that was not the motivation for the research. Similarly, early research 

on lasers hardly anticipated the proliferation of commercial products or at-home entertainment 

via DVDs. Third, it usually takes a confluence of several disparate developments to produce a 

new capability. A vibrant, interacting scientific and engineering community is essential to achieve 

the breakthroughs that will continue to provide the nation with air supremacy.

Introduction

1
The first paper tells the story of GPS. It is not only a story of scientific and technical 

achievement, but also one of suspense that illustrates the difficulties of introducing revolutionary 

technologies. The failures and successes in that program attest to the vision and perseverance 

of the people who made it happen. The GPS finally solved the problem that had challenged 

seafarers since antiquity. It has also enabled a multitude of civilian and military applications. 

The second paper looks at a development that has revolutionized the employment of air 

power. The use of laser research and the GPS has enabled ever-increasing precision strikes at 

ever-increasing distances. From tens of bombers dropping hundreds of bombs to hit a single 

target in World War II, now a single aircraft can strike several targets. Precision also raises 

expectations for minimizing collateral damage and puts high priority on detecting targets, 

identifying them correctly, and tracking them. Advances in electro-optical/infrared imaging, in 

radar, and in lasers have become the triad for remote sensing, where the objective has been to 

“overcome the problems of great distances, weather, and darkness,” articulated by von Kármán. 

The third paper focuses on infrared cameras from their first beginnings to their employment in 

unmanned aerial vehicles such as the Predator and Global Hawk. The fourth paper looks at 

airborne radar, whether in AWACS or in Joint STARS, two systems that have revolutionized 

the conduct of air-to-air and air-to-ground operations.

Soon after the first powered flight in 1903, the effects of the high altitude environment on 

the performance of pilots became a concern. Research on the effects of hypoxia went back to 

balloonists in the late nineteenth century. With the creation in 1918 of the Air Service Medical 

Research Laboratory, it became possible to establish the scientific foundation for the development 

of a wide variety of equipment, from oxygen masks to the pressure suits of today, that would 

enable air crews to fly higher and for longer periods of time. The fifth paper traces that history 

and the accomplishments of such pioneers as Armstrong, Stapp, and Kittinger. The paper also 

includes the story of a particular mission of the SR–71, an aircraft that flew at 80,000 feet, at 

the edge of space, at three times the speed of sound—an extreme environment indeed. 

The sixth paper, not presented at the symposium, describes the Air Force research in 

weather, not only the effort to understand terrestrial weather, but also space weather. The 

launching of U.S. satellites, which started in 1958, led to the discovery of the Van Allen belts. 

This was a major scientific discovery that began the mapping of the space environment, a 

necessary condition for sending unmanned and manned spacecraft to space.

To reach space, whether for scientific, military, or commercial purposes, a launch 

capability was needed. In the early years of the space age, this capability was provided by the 

Air Force’s long-range ballistic missiles—Atlas, Titan, and Thor. The seventh paper records 

The Limitless Sky

2
the history and the systems that have allowed the U.S. to launch satellites that have provided 

extraordinary sensing capabilities and global communications. The evolution of military 

satellite communications from concept to reality, an indispensable capability for today’s Air 

Force, is documented in the eighth paper.

Finally, as we start the second century of powered flight, the Air Force is once more expanding 

its capabilities using advanced technology. The wave of the future is directed energy that is 

expected to revolutionize the science and art of warfare. Since the invention of the laser in the 

1960s, the Air Force has been conducting research and development for an operational platform 

that would use lasers to destroy ground or air launched missiles. The Airborne Laser (ABL), now 

in development, is the perfect example of the need for a number of technologies to work together 

– lasers, adaptive optics, and control engineering – to make a new capability a reality. 

These nine papers present only a few of the milestones in this limitless journey of discoveries 

that started at Kitty Hawk and in which millennia-old limits were put aside. It was a journey 

in which the Air Force science and technology enterprise has made immeasurable contributions 

to the development of air power, to the nation’s science and technology base, and to mankind’s 

understanding of our world.

Alexander H. Levis, Sc.D. 15 March 2004

Chief Scientist, USAF

Introduction

3
Precision Timing, Location, Navigation:

GPS and the Precision Revolution

Michael I. Yarymovych

Bradford W. Parkinson

George W. Bradley III

Brigadier General Daniel J. Darnell, USAF

Ivan A. Getting
Abstract

 The history of human navigation extends thousands of years, 

from the invention of the compass needle, sextant, and chronometer, 

and arriving at the introduction of radio navigation in the 1920s 

and its operational use during World War II. Nuclear submarine 

operations created the need for satellite-based navigation, which then 

was further driven by the requirements of fast-moving airplanes. 

In the 1970s, the Global Positioning System (GPS) emerged as a 

radical new way to provide precise navigation for all of the U.S. 

armed forces across the globe. The development of GPS, the most 

revolutionary navigation tool since the invention of the chronometer, 

is described, and the technologies that went into its successful 

implementation are highlighted. Declared operational in 1995, it 

had been exploited while a developmental system by both civilian 

and military users for more than ten years.

 Military use of GPS got its first operational application in 

Desert Storm, was then used for precision warfare in the Kosovo 

operation, and eventually became the major force-enhancer in 

Afghanistan and Iraq. The number of operational receivers has 

increased exponentially over the last decade as the technology has 

moved in diverse and unexpected directions. Although GPS was 

originally designed for defense missions, civilian receivers now far 

outnumber military receivers. GPS has become a global utility with 

immeasurable potential benefits for all humanity, thanks to military 

science and technology development and Air Force implementation.
HISTORY OF NAVIGATION

 Advancing human civilization is motivated 

by three basic drives: to trade, fight enemies, 

and explore the unknown. To accomplish 

these basic objectives, humans have always 

sought ever better means to know where 

they were and where they were going. For 

6,000 years, they have been developing ways 

to navigate to remote destinations. Driven 

mostly by the desire to transport goods by 

ship, early navigators, such as the Phoenicians, 

remained within sight of land, using a technique 

known as piloting that relied on navigators’ 

recognition of coastal features. The magnetic 

compass was one of the most important 

inventions in the history of navigation. It first 

appeared in China around 1100 AD, and in 

Europe, approximately a century later. When 

forced to sail beyond landfall or in inclement 

weather, mariners tracked their position by 

dead reckoning, determining their location 

on the basis of speed, time, and direction, 

using the magnetic compass. This device has 

remained an important navigational tool over 

the years. Early aviators navigated from one 

town to another by using landmarks. Antiquity 

also offered another navigational system 

independent of terrestrial objects: celestial 

navigation. This system used the observed 

motions of the sun and stars. Its effectiveness 

increased over the centuries with advances 

in instrumentation, such as the astrolabe, 

sextant, and accurate portable timepieces.

 Marine pilots would record their heading 

and distance traveled by hourglass, timing the 

passage of wooden logs thrown off the bow. 

Needless to say, this technique was notoriously 

inaccurate. The development of a sextant by 

1731 (early versions existed in the thirteenth 

century) made determining latitude fairly 

routine. But the longitude problem was so vexing 

that England established a Board of Longitude 

in 1714 and offered a King’s ransom of 20,000 

pounds sterling to whoever could resolve it. 

Some of the greatest minds of Europe joined the 

race for a solution. Some believed that variations 

in Earth’s magnetic field held the key; others 

insisted on celestial techniques. John Harrison, 

not a scientist but an artisan clockmaker, 

trumped them all by building a chronometer 

that, during long sea voyages, lost less than 

one second per day. The board was reluctant to 

confer the award on an individual who was not 

a member of the established scientific academy, 

and Harrison, greatly embittered, had to wait 

until 1763 to collect his prize. Harrison’s 

chronometer gradually gained favor, but 

ironically, the pace of navigational advancement 

slowed during the industrial era. Still, the ability 

to move and communicate over long distances by 

telegraph and railroad spurred the need for civil 

and military time coordination. Thus, in 1884, 

at the height of the British Empire, Greenwich, 

England, was established as the world’s Prime 

Meridian. Previously, each major nation 

established its own prime meridian and local 

time; the promulgation of Greenwich Mean 

Time abolished this practice and standardized 

navigational readings throughout the globe.

 At the turn of the twentieth century, 

Guglielmo Marconi successfully transmitted 

radio waves across the Atlantic. The earliest 

radio navigation systems were based on the 

ability of a radio receiver with a loop antenna 

to determine the direction of a radio signal and 

its relative bearing to the transmitter. Over the 

The Limitless Sky

8
years, use of radio signals has become much 

more sophisticated. During World War II, the 

British introduced the Gee system, and scientists 

at the Massachusetts Institute of Technology 

Radiation Laboratory developed the Long Range 

Navigation system, or Loran, which measured 

the difference in time of arrival of signals from 

synchronized pairs of transmitters at different 

locations. To provide better world coverage with 

fewer transmitters, a low-frequency system called 

Omega was developed. Omega used continuous 

wave radiation rather than pulses, as the original 

Loran did, and it gauged the difference in time 

intervals from ground stations by measuring 

the relative phase angles of transmitters from 

pairs of stations. Unfortunately, the accuracy 

of Omega was limited. To increase accuracy, 

Loran-C, using ground-wave propagation, 

was developed for tactical aircraft. It could 

accurately determine position to about 100 to 

200 meters, compared to Omega which had an 

accuracy only within 2,200 meters. Loran-C 

was widely used during Vietnam. Unfortunately, 

all the early Loran systems, as well as Omega, 

were essentially two-dimensional. In effect, 

they located by latitude and longitude but 

not altitude, the third dimension. Today, a 

modernized version of Loran has become a 

worldwide standard for aircraft and coastal 

marine navigation. In the 1950s and 1960s, 

scientists developed inertial navigational 

systems for aircraft and missile systems. Inertial 

navigation uses neither landmarks nor celestial 

observations to determine location. It relies on 

internal systems such as gyros for calculating 

speed, distance, and direction to determine 

location. Nonetheless, what all these systems 

have in common is that they provide the 

user with location information, and military 

theorists from Sun Tzu to Clausewitz have 

emphasized the importance of knowing the 

exact location of friendly and enemy forces.

 While ground-based radio waves proved 

an important innovation in navigation, some 

problems were noted. Low-frequency radio 

waves are not easy to modulate and are subject 

to errors due to ionospheric factors and weather 

turbulence. High-frequency radio waves are 

limited to line of sight. This necessitates 

many fixed-site transmitters. Moreover, it was 

impractical to place a fixed-site transmitter 

at sea. Like ground-based radio navigation, 

celestial navigation was also problematic. 

Mariners had traditionally been faced with 

a limited ability to use celestial navigation 

during periods of intense cloud cover or dense 

fog. What was needed was a way to receive 

radio waves from a fixed point in the sky.

 Before the launch of Sputnik in 1957, 

scientists were attempting to develop a system 

to track future U.S. satellites. In the mid1950s, the Naval Research Laboratory (NRL) 

had proposed a system called Minitrack, 

which was built to track the movement of the 

Navy’s planned Vanguard satellite and other 

early man-made orbiting objects by using the 

signals that they transmitted. Passive satellites, 

those that emitted no signal, however, were 

beyond Minitrack’s capabilities, and a different 

methodology was needed to deal with them. 

Roger I. Easton, Don Lynch, Al Bartholomew, 

and others at the NRL began working on a 

system to track such passive objects. They 

moved an FM transmitter to Fort Monmouth, 

New Jersey, and used it to illuminate the 

Sputnik satellite when it passed over. This 

Precision Timing, Location, Navigation

9
experience led them to conclude that if they 

could radiate a fan-shaped, continuous-wave 

beam, they could detect anything that passed 

through it. This was the origin of the Naval 

Space Surveillance System. Easton’s group then 

turned its attention to devising a navigation 

system based on information obtained from 

orbiting satellites. At NRL they realized that a 

satellite navigation system could be established 

using satellites having synchronized clocks 

transmitting signals to users on the ground, 

who could synchronize their own clocks to 

those in the satellites. The range measured to 

each satellite produced a line position, just as if 

one had obtained a sextant sighting on a star. 

Essentially, Easton’s system was still based on 

celestial navigation. He substituted a satellite 

in a predicted and measured orbit for a star, 

and synchronized clocks for chronometers that 

seafarers had used since the eighteenth century.

 The successful launch of Sputnik allowed 

a practical test because it emitted an active 

signal. Researchers at the Johns Hopkins 

Applied Physics Laboratory (APL) had carefully 

studied Sputnik’s radio signal and noted certain 

regular features. The most interesting of these 

features was the Doppler shift as the satellite 

passed overhead. This effect was caused by 

changes in the length of the line of sight and 

was enhanced by the satellite’s high speed 

and low altitude. These scientists developed 

a computer program to determine Sputnik’s 

orbit. Dr. Frank T. McClure of APL realized 

that the problem could be turned on its head: 

the process could be reversed. By measuring 

the Doppler shift to a satellite of known orbit, 

listeners could calculate their own positions. 

This solved an important problem for the 

U.S. Navy, since it needed precise, all-weather 

positions for submarines and other ships. 

After speedy approval, a satellite navigation 

program, the Navy Navigation Satellite System 

(also known as Transit from its initial birth 

as Project Transit), was initiated under APL’s 

management. The first two developmental 

Transit satellites were launched by 1960, and 

the system became operational by 1964.

 Transit eventually deployed an operational 

constellation that included five polar orbiting 

satellites. They produced fixes every 35 to 100 

minutes and provided horizontal accuracies of 

100 meters or better for a stationary user. A 

moving receiver could compensate for velocity 

with some degradation in accuracy. Transit 

was not generally used by aircraft because of 

its incompatibility with the rapid platform 

motion of an aircraft. Additionally, aircraft 

require the third dimension, altitude, which 

the Transit system did not provide. Transit 

was, however, an important predecessor to 

the Global Positioning System (GPS) and 

pioneered a number of key technologies and 

concepts. Transit led to a great refinement of 

Earth’s gravity-field model, successfully tested 

dual-frequency correction techniques for 

ionospheric-induced delays, and was crucial 

in developing stable and reliable frequency 

sources. Transit provided only periodic updates, 

and degradation for a moving user made it 

unsuitable for aircraft. By the late 1960s, better 

systems were being explored by the Navy. The 

system was renamed the Navy Ionospheric 

Monitoring System when it ceased to provide 

navigational information on 1 January 1997.

 Another key program developed by the 

NRL was Timation. The goal of Timation 

The Limitless Sky

10
was to orbit very accurate clocks. These 

clocks were to be used to transfer precise time 

among various laboratories around Earth. 

Under certain circumstances, users could also 

determine their positions by using the Timation 

signal. The approach was somewhat different 

from Transit in that the radio signal allowed 

direct ranging by using a technique known 

as side-tone ranging. The research that NRL 

conducted for Timation played a key role in 

developing the atomic clocks used on GPS.

 While the Navy pursued Transit and 

Timation, the Air Force was also seeking 

better ways to determine location. Transit was 

less useful for the Air Force because the air 

service needed precise location on systems like 

rapidly moving aircraft and missiles. In 1960, 

the Raytheon Corporation proposed to the Air 

Force a concept for a three-dimensional type of 

Loran called the Mobile System for Accurate 

Intercontinental Ballistic Missile Control, 

or MOSAIC. Basically, MOSAIC used four 

continuous-wave transmitters at somewhat 

different frequencies, with their modulation 

locked to atomic clocks and synchronized via 

communication links. During flight, a missile 

would continuously compute its position by 

using signals from MOSAIC. Through this 

application, guidance of the missile would be 

less dependent on precise knowledge of the 

launch point. A central figure in this proposal 

was Dr. Ivan Getting, the first president of 

The Aerospace Corporation. Before assuming 

that position, however, Dr. Getting had been 

vice president of engineering and research at 

the Raytheon Corporation at the time they 

made their proposal. Many of the personnel 

involved in its conceptual beginnings, including 

Getting, were now working for The Aerospace 

Corporation. This was an important factor, 

because the Department of Defense (DoD) had 

selected the Air Force as its executive agent for 

space launch, and the Air Force had contracted 

The Aerospace Corporation to be its system 

engineer. Over the years, these two figures, Ivan 

Getting from the Air Force and Roger Easton 

from the Navy, would play crucial roles in the 

evolution of the U.S. satellite navigation system

HISTORY OF GPS

One of the precursors to the GPS was an 

Aerospace Corporation and U.S. Air Force 

effort designated Program 621B and managed 

by an office in the Advanced Plans group at 

the Air Force’s Space and Missile Systems 

Organization (SAMSO) in El Segundo, 

California. The Aerospace Corporation’s Dr. 

Getting strongly advocated 621B. This program 

evolved directly into GPS, though not before 

significant modifications were made to the 

original Air Force only concept. By 1972, 

621B had already demonstrated operation of 

a new type of satellite-ranging signal based on 

pseudorandom noise (PRN). Successful aircraft 

tests had demonstrated the PRN technique 

using ground-based “simulated” satellites 

located on the floor of the New Mexican desert. 

The PRN modulation used for ranging was 

essentially a repeated digital sequence of fairly 

random bits that possessed certain useful 

properties. The sequence could be generated by 

using a shift register or, for shorter sequences, 

could be stored in very little memory. Given the 

limited capabilities of contemporary computers, 

this was a crucial feature. A navigation user 

could detect the phase, or start, of the signal 

Precision Timing, Location, Navigation

11
sequence and use this for determining the 

range to the satellite. The PRN signal also has 

powerful noise-rejection features and can be 

detected even when its power density is less 

than one-hundredth that of ambient radio noise. 

Furthermore, all satellites could broadcast on 

the same nominal frequency because properly 

selected PRN codes were nearly orthogonal.

 When locked on to a particular PRN 

sequence, all other PRN sequences appear to 

the user as simple noise. The PRN sequence 

can be tracked even in the presence of large 

amounts of noise, so other signals on the same 

frequency do not generally jam the signal of 

interest. The ability to reject noise also implied 

a powerful ability to reject most forms of 

jamming or unintentional interference. In 

addition, a communication channel could be 

included by inverting groups of the repeated 

sequences at a slow rate (50 bps is used in 

GPS). This communications channel allowed 

the user to receive the ephemeris, clock, and 

health information directly as part of the 

single navigation signal. The original Air 

Force concept visualized several constellations 

of satellites in highly elliptical orbits with 

24-hour periods. This constellation design 

allowed deploying the satellites gradually (for 

example, to cover North America first), but it 

complicated signal tracking because of the very 

high line-of-sight accelerations. Initially, the 

concept relied on continuous signal generation 

on the ground with continuous monitoring 

and compensation for ionospheric delays.

 In 1969, the Air Force awarded contracts to 

four companies—TRW Systems, Magnavox 

Research Laboratories, the Grumman 

Aerospace Corporation, and the Boeing 

Company—to refine the design and determine 

a cost for the proposed 621B navigation system. 

During 1971 and 1972, tests of operator 

equipment using ground and balloon-carried 

transmitters at White Sands Proving Ground 

achieved accuracies to within 50 feet. However, 

the DoD, because of service concerns, would 

still not commit to the Air Force program. 

A new figure emerged who would provide a 

solution to the deadlock. In late 1972, General 

Kenneth Schultz, then commander of SAMSO, 

appointed Colonel (Dr.) Brad Parkinson, one 

of the authors of this article, as the Air Force 

621B program manager and directed him to 

gain approval for the concept-validation phase 

of the Defense Navigation Satellite System, as 

the new DoD satellite navigation system was 

originally known. After many briefings to senior 

personnel in the Pentagon, a Defense Systems 

Acquisition Review Council meeting was held in 

August 1973, at which Dr. Parkinson presented 

a brief on the Air Force 621B program. The 

review council initially denied Parkinson 

approval to proceed with the program.

 Subsequent to the acquisition review council 

briefing, Dr. Parkinson presented the concept 

to the Air Force Chief Scientist, Dr. Michael 

Yarymovych, and the Director of Defense 

Research and Engineering, Dr. Malcom Currie, 

both of whom quickly appreciated the value 

of a three-dimensional, continuous, 10-meter 

positioning system. However, they thought 

the reason the program failed to win approval 

from the acquisition review council was that it 

was not a truly joint endeavor, incorporating 

the best technology and concepts across DoD. 

As a consequence, Dr. Currie essentially asked 

Dr. Parkinson to go back to the drawing 

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12
board. Acting on that guidance, Dr. Parkinson 

assembled about ten of his key program 

members in the halls of the Pentagon during 

the hot Labor Day weekend of 1973. The end 

product of their labors was an all-encompassing 

synthesis system concept that would later be 

named the Global Positioning System. By midDecember 1973, senior DoD officials had been 

briefed, and a reconvened Defense Systems 

Acquisition Review Council granted approval. 

By June of 1974, the satellites, ground control 

system, and user equipment were on contract.

 The Air Force Chief of Staff General John 

D. Ryan directed Air Force Systems Command 

to establish a joint program office at SAMSO 

to manage the program. All three services, 

as well as the Marine Corps and the Defense 

Mapping Agency, participated. The Air Force 

and Navy had reached a compromise program 

that used elements from both the Navy and 

Air Force systems: the Air Force’s signal 

structure and frequencies, and the Navy’s 

satellite orbits. The system would also use 

atomic clocks, which the Navy had already 

successfully tested in its Timation program. The 

initial four-year validation portion comprised 

a four-satellite configuration. In a surprise 

bid, Rockwell International won the first 

development contract. The first GPS satellite 

launch in February 1978 led to successful 

validation of the concept (Figures 1, 2).

 Because the Air Force was not comfortable 

with having to shoulder the entire financial 

burden for the program, it attempted to cancel 

GPS several times. Although Air Force Chief of 

Staff General Lew Allen was a strong advocate 

of GPS, the civilian leadership was responsible 

for keeping the program alive. It took twenty 

years, but finally, in March 1994, the launch of 

the twenty-fourth Block II satellite completed 

the GPS constellation. GPS was declared 

operational in December 1995, although 

Precision Timing, Location, Navigation

13

Figure 1. A Phase I GPS satellite built by Rockwell (now Boeing)

Figure 2. The primary booster for GPS satellites is the Delta II 

rocket
civilian and military users had been using the 

available developmental system for more than 

ten years. The subsequent operational satellites 

incorporated certain additional non-navigation 

payloads, which enhanced their value but also 

delayed full operation. Without a doubt, the 

combination of near-concurrent efforts of the 

Navy and Air Force, efforts of visionaries 

like Getting and Easton, and the spirit of 

compromise under Parkinson’s leadership was 

what made this revolution in precision a reality. 

The DoD had finally made the conceptual 

transition from navigation, which the Navy 

claimed they have been doing for centuries, 

to positioning. Knowing the position of all 

stationary and moving objects on the globe at 

all times and knowing the synchronized time 

with unprecedented accuracy opened infinite 

possibilities for military and civilian operations. 

This was indeed a revolution of the same 

magnitude as the initial development of the 

chronometer in the eighteenth century.

 Because potential enemies might use GPS 

positioning against the United States or her 

allies, the civil signal was intentionally degraded 

through a process known as selective availability. 

This process reduced accuracy for civilian users 

and remained part of GPS as a holdover from 

its original military history. Selective availability 

was generally active, although ironically it was 

turned off during several national emergencies 

and international military campaigns when the 

military use of civilian receivers was widespread. 

It slowly became apparent that the proliferation 

of differential corrections in the form of 

augmentations rendered these perturbations 

totally ineffective. As a result, a Presidential 

Decision Memorandum was signed in 1996 

which ordered the military to discontinue its 

use, pending justification from the DoD. In 

early 2000, selective availability was removed 

from the signals of all orbiting satellites.

 During the first 25 years of GPS, several 

generations of satellite designs have been 

developed or are under development. These 

include Blocks I, II, IIA, IIR, IIRM, and IIF. 

In addition, plans for an upgraded version 

of GPS, known as GPS III, are currently 

being defined. The Block IIRM and Block 

IIF satellites add additional civil GPS signals 

at other microwave-band frequencies which 

should materially improve the accuracy 

and robustness of the civil service.

GPS CONCEPT OF OPERATION

 The design objectives of the GPS system 

were to provide a continuously available, 

worldwide, all-weather, three-dimensional 

precision positioning system for both military 

and civilian users on land, at sea, or in the 

air, even in space. The GPS system had to 

operate on an accelerating platform, such as a 

maneuvering aircraft or missile. Additionally, 

the system had to be passive, or one-way, so that 

it could service an unlimited number of users. 

As a military system, the signal is required 

to be both jam-resistant and antispoof.

 Each of these requirements drives a certain 

set of constraints. To be worldwide and 

continuously available, only a satellite system 

can provide global coverage, especially over 

oceans and polar regions. As a satellite system, 

frequencies less than 1 MHz skip off the 

ionosphere, and frequencies higher than 10 

GHz are very heavily attenuated by atmospheric 

moisture. Satellite signal frequency was a 

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14
compromise among accuracy (ionospheric delay), 

attenuation, and the power to be received by 

an omnidirectional user antenna. Thus, the 

selected signal was placed within the L-band for 

best performance. Two additional constraints 

were established by the military: that the 

satellites could be totally serviced from the 

continental United States (CONUS) and that 

the constellation could be tested by using a small 

number of satellites to minimize project risk. 

These constraints led to satellites in mediumaltitude orbit. The quantitative requirements of 

the original GPS design were to guide a bomb 

to within a 10-meter circle anywhere on the 

planet, and to build an inexpensive (less than 

$10,000 at that time) device that could navigate.

 GPS functions as a multilateration system: 

the range from at least three known locations 

is determined, and the point at which the three 

spheres intersect defines the user’s location. In 

GPS, the system is complicated by the fact that 

the transmitters are moving and that the range 

cannot be measured directly. As a simplification, 

assume that the GPS satellites are stationary 

and that the user is upon a flat, nonrotating 

Earth. All of the satellites are synchronized 

and transmit a signal at the exact same time.

 The user will receive the signal from each 

satellite at a different time due to the time of 

flight of the signal, traveling at the speed of 

light, across the different ranges from each 

satellite to the user. If the user possessed a very 

accurate clock that was time-synchronized with 

the satellites, the product of the time of flight 

and the speed of light would be the true range 

to the satellites. However, because the user is 

unlikely to have an atomic clock (a requirement 

that would make the receivers far too expensive), 

the user is not synchronized to GPS time. Thus, 

the measured range is offset by a consistent bias 

and is thus referred to as pseudorange. This 

measurement is taken simultaneously for each 

satellite. Even without knowledge of the exact 

time, the consistent solution for the ranges based 

on user position and unique time bias can be 

computed. The satellite locations are known 

from the navigation message on the signal. 

There are four unknowns three components 

of position, and time thus measurements 

from a minimum of four satellites are required 

to solve the four simultaneous equations.

GPS SPACE SEGMENT

 The space segment of GPS is the satellite 

constellation (see Figure 3) that consists of 

twenty-four or more vehicles in six orbital 

planes. The planes are inclined at 55 degrees and 

spaced 60 degrees apart. There are four satellites 

in each of the orbital planes, but they are not 

evenly spaced (this to minimize the impact of 

any single satellite failure). Additionally, there 

are typically on-orbit spares in some of the six 

planes. The satellites are in a medium Earth 

orbit at a radius of 26,561.75 kilometers (a mean 

equatorial altitude of 20,163 kilometers). The 

orbits are almost perfectly circular. The orbital 

period is 12 hours of mean sidereal time (a 

mean sidereal day is the rotation of Earth to the 

same position with respect to inertial space, in 

contrast to a solar day, and is approximately four 

minutes shorter than a solar day). Thus, each 

GPS satellite repeats the same ground track, but 

passes the same location four minutes earlier 

each (solar) day. Some of the orbital planes 

may have extra satellites as on-orbit spares.

 The GPS payload consists of redundant 

Precision Timing, Location, Navigation

15
atomic clocks, telemetry and control sections, 

and the signal-generation subsystem. The 

atomic clocks are rubidium and/or cesium 

standards that typically have long-term 

stability of 1 part in 1,013 per day (a drift of 

roughly 9 nanoseconds per day). The master 

control station monitors the atomic clock 

drift rates and models them. GPS is the 

first operational system known to require a 

correction for relativistic effects. All of these 

parameters are sent in the navigation message.

 The satellites’ telemetry subsections are 

responsible for receiving the uploaded navigation 

data from the master control station. The data 

is encrypted before upload to ensure than 

no spoofing can occur. Internal status and 

health are also monitored and relayed back 

to the control station. Note that these power 

levels are well below the ambient noise level. 

From the satellites’ locations, Earth subtends 

an angle of approximately 14 degrees. A user 

at the limb of Earth is significantly farther 

away than one directly under the satellites. To 

compensate for this greater “space loss,” the 

antenna gain pattern on the GPS satellites 

is such that approximately 2.1 decibels more 

gain is at the edge than at the bore sight of the 

beam. The beam is also slightly wider than the 

14 degrees of Earth to allow satellites on the 

other side of Earth to use GPS for positioning.

 The specification for both the C/A code 

(coarse acquisition code) and the P/Y code 

(precise military code) is such that the minimum 

broadcast power is well below the noise floor 

of the in-band radiation. Using the correlation 

properties of the PRN codes, a GPS receiver 

can reconstruct the phase of the signal and use 

this for position and temporal information.

GROUND CONTROL SEGMENT

 The GPS control segment consists of six 

or more monitoring stations around Earth, a 

master control station, and upload groundantenna stations. Each of the monitoring 

stations has a set of accurate atomic clocks and 

tracks both the code and carrier of each GPS 

satellite as it traverses overhead from horizon 

to horizon. The monitoring stations operate 

at L1 and L2 frequencies to permit removing 

excess ionospheric delay. They also monitor 

atmospheric parameters such as temperature, 

atmospheric pressure, and humidity to permit 

estimating the tropospheric delay. By tracking 

the L-band carriers from horizon to horizon to 

a small fraction of a cycle, a series of 15-minute 

averages is created and sent to the master control 

station.

 The master control station receives the 

monitoring station tracking and groundantenna telemetry information and computes 

Figure 3. The GPS constellation consists of 24 satellites in six 

orbital planes.

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16
the current and predicted satellite clock offsets 

and satellite positions. It then converts this 

data to the navigation data formats described 

later. These rather complex satellite orbit/time 

filter estimating algorithms must also model the 

satellite solar radiation pressure; atmospheric 

drag on the satellite; Sun/Moon gravitational 

effects, including solid Earth and ocean tides; 

and Earth’s geopotential model. Improved GPS 

satellite-to-satellite cross-link ranging data may 

also be used in the future. The navigation data is 

uploaded from several 10-meter diameter, 

S-band ground-antenna upload stations.

 The navigation data is encoded on the L1 

C/A signal. This data message is transmitted 

at the rate of 50 bps and consists of a set of 

6-second subframes (ten 30-bit words) and 30-

second frames. The data encoded includes the 

full ephemeris required to calculate the current 

satellite position; the satellite clock quadratic 

polynomial model and corrections to GPS time; 

almanac data used to position all the other 

satellites; and a handover word for P/Y-code

 users. The almanac data allows a user to 

compute the rough positions of the satellite and 

thus narrow the search space both in terms of 

PRN codes and Doppler bins.

USER SEGMENT

 The user segment, or the GPS receiver, is a 

very sophisticated digital signal tracking device 

that allows converting the faint signals from the 

GPS satellites into an accurate position solution. 

The GPS receiver must process the almanac 

(either stored or newly acquired) to generate a 

search space in terms of PRN codes and Doppler 

frequency bins. The incoming radio-frequency 

(RF) signal must be amplified, down-converted 

through an intermediate frequency (using a 

mixing process), and sampled into the digital 

domain. The PRN codes are correlated against 

the incoming digitized stream, and usually 

a delay lock-loop is implemented to keep the 

signal locked.

 Once the signals are tracked, corrections 

are applied to the raw pseudoranges, and the 

position and time bias are computed through an 

iterated least-squares calculation. The positions 

are now reconverted to a useful coordinate 

frame such as latitude, longitude, and altitude. 

The original GPS “manpack” receivers were 

backpack-sized devices costing more than 

$50,000. They did, however, satisfy the original 

mandate to produce an inexpensive device that 

could navigate.

 GPS has benefited greatly from the 

semiconductor revolution, as has the typical 

consumer. Civilian use of commercial GPS 

receivers has grown significantly since the end 

of the first Gulf War. A modern GPS receiver 

costs as little as $100 and is small enough to be 

embedded into a wristwatch. Additionally, the 

computer that calculates the position solution 

can support many 

additional features 

such as map displays 

and waypoint guidance, 

at some additional cost. 

(Figure 4.)

Precision Timing, Location, Navigation

17

Figure 4. The Magellan 

Meridian GPS Receiver 

pictured above is typical of 

the type of receiver available 

to the public. It is a handheld model that stores up to 

20 routes and has a 9MB 

preloaded North American 

database. 
DIFFERENTIAL GPS

 One technique used to augment GPS is 

known as differential. The basic idea is to 

locate one or more reference GPS receivers 

at known locations in users’ vicinities and 

calibrate ranging errors as they occur. These 

errors are transmitted to users in near real 

time. The errors (or their negatives, which 

are corrections) are highly correlated across 

tens of kilometers and across many minutes. 

Use of such corrections can greatly improve 

accuracy and integrity. Several large-scale 

differential networks have been deployed 

in the United States and elsewhere.

 The U.S. Coast Guard (USCG) within 

the United States and the International 

Association of Lighthouse Authorities have 

deployed a marine-beacon differential system 

internationally. In the United States the 

system is known as National Differential GPS. 

The Army Corps of Engineers is currently 

deploying additional National Differential 

GPS compatible beacons to cover the entire 

CONUS. The Federal Aviation Administration 

(FAA) is currently deploying the Wide 

Area Augmentation System. This system is 

intended to provide en route navigation and 

nonprecision approaches for aviation users.

 The FAA is also developing a Local Area 

Augmentation System for Category I, II, and 

III precision landing capability at airports 

(Figure 5). This will require local ground 

monitoring stations to ensure the integrity 

of the system in addition to the nominal 

reference receivers. The exacting requirements 

of Category II and III landings mandate 

that the Local Area Augmentation System 

perform many crosschecks of the GPS 

system to ensure integrity. If one of these 

Figure 5. The LAAS 

system will provide 

precision approach 

capability using GPS.

The Limitless Sky

18
crosschecks fails, the time to alarm of the local 

system is specified at less than 6 seconds.

 Differential carrier tracking is another GPS 

technique that has been used by surveyors since 

the mid-1980s. By reconstructing the L-band 

RF carrier signal, a GPS receiver can attain 

tracking precision of 1 to 10 millimeters. Several 

techniques exist for resolving the integer-cycle 

ambiguity. Satellite motion can be exploited 

to do this differentially. This technique is 

referred to as real-time kinematic GPS. When 

applied, this technique provides survey-level 

differential positioning with relative accuracy 

in millimeters. Thus one can locate very rapidly 

an unknown point on the ground relative to a 

survey mark and then maintain this accuracy 

as the user’s receiver is moved. This is now 

being exploited for both construction survey 

and real-time, automatic, machine control.

 Many additional private and international 

systems are under development or deployed. 

Various private companies sell their own 

proprietary carrier-phase differential GPS 

systems for use in such diverse areas as 

construction, surveying, and archeology. 

Commercial wide-area corrections are carried 

by at least one commercial C-band satellite 

broadcast, and several oil companies have put 

their own differential stations on oil drilling 

platforms to ensure accurate positions for 

the helicopters and ships that service them.

MILITARY APPLICATIONS

 GPS has played a role in military operations 

for more than a decade now. Operation Desert 

Storm was one of the first major military 

campaigns that used GPS applications 

extensively. Most recently, GPS played a 

pivotal role during Operation Iraqi Freedom 

(OIF). About 70 percent of the munitions 

employed in OIF were precision-guided, the 

vast majority being aided by GPS. More than 

7,000 GPS-aided munitions were reportedly 

used in OIF, including the low-cost, highly 

effective Joint Direct Attack Munition 

(JDAM). This contrasts with Operation Desert 

Storm, where only approximately 10 percent 

of the munitions were precision-guided.

 The high levels of accuracy achievable using 

GPS, along with the system’s all-weather 

capability, help explain why GPS-aided 

munitions are so widely used in air campaigns. 

During OIF, the GPS Precise Positioning 

Service (the more accurate signal available to 

“authorized” DoD users) provided an average 

position accuracy of 3.69 meters (compared 

with 24.3 meters during Desert Storm). This 

level of accuracy has not been seen in any 

previous major U.S. military engagements.

 JDAMs were used in a variety of roles. 

The munition’s GPS-aided precision allowed 

air strikes on leadership and command 

and control targets in downtown Baghdad. 

In fact, the 2,000-pound munitions used 

by F117s in the opening night leadership 

decapitation attempt were GPS-guided. 

Delayed fuzing and the uncanny accuracy 

of the weapon mitigated collateral damage 

concerns normally associated with attacking 

military targets in urban locations.

 GPS was also an invaluable navigation aid, as 

fighters, bombers, and intelligence, surveillance, 

and reconnaissance aircraft rendezvoused inflight with air refueling assets. Navigation aids 

normally available did not exist in Iraq’s air 

control structure when combat operations began. 

Precision Timing, Location, Navigation

19
Additionally, adverse weather conditions and 

the country’s featureless landscape complicated 

an already difficult problem as hundreds of 

aircraft flew to predetermined rendezvous 

locations. An onboard GPS-aided, in-flight 

navigation system was the only “nav aid” pilots 

and crews could rely upon to navigate safely 

and to arrive on-time at the correct preplanned 

refueling location. From there the pilot and 

crew would establish radar/visual contact 

with the tanker and effect the rendezvous.

 Assistance to Special Operations Forces 

was often dependent upon the reliability and 

precision of GPS-aided munitions. In the 

opening days of the conflict, Special Operations 

Forces working with indigenous forces in the 

north relied on air strikes provided by B1 

aircraft from the south. The B1s, accompanied 

by F16CJs, were routinely pulled north in 

the dark of night to provide air support for 

small teams in need of immediate assistance. 

The weapon of choice was JDAM because 

weather conditions often precluded the use 

of laser-guided munitions and bomb-laden 

fighters were unable to provide meaningful 

on-station time due to the distances involved. 

Uncontrolled strikes were sometimes a reality 

when an airborne B1 was unable to establish 

voice contact with a tactical air controller on 

the ground. Ground forces insisted on support 

despite their inability to establish contact. 

Target coordinates were relayed through a 

Special Operations Forces control element to 

the combat air operations center, passed to 

an airborne E3, and then communicated to 

the on-site B1. Despite their inability to see 

the target, B1 crews were successful in every 

attack because of the accuracy and precision 

of their 2,000-pound GPS-aided munitions.

 Russian-built Iraqi jammers detected on 

the first day of OIF were taken out by a U.S. 

military trained to deal with this new threat. 

The 527th Space Aggressor Squadron was 

called in to advise the Combined Forces Air 

Component Commander on the evolving 

GPS-jamming situation in Iraq, and it 

suggested courses of action. Ultimately, the 

jammers were destroyed with GPS-aided 

munitions from F117 and B1 aircraft.

 The bottom line is that OIF marks an 

important milestone in Space history. For 

the first time, an adversary attempted to 

deny the United States its access to Space. 

This attempt was completely ineffective 

due to the advanced preparation for exactly 

this type of situation. The Aggressors of 

the 527th were instrumental in helping our 

forces train like they would have to fight.

SELECTED APPLICATIONS

 Applications of GPS have continued to 

multiply, as commercial and civil organizations 

apply creativity in using its capability. This 

section will not attempt to enumerate all 

current and future potential uses. Instead, 

selected examples will illustrate the 

revolutionary advances that have been made 

possible by this remarkable system. Many 

of the topics presented are at the cutting 

edge of current research and may profoundly 

improve our understanding of our world as 

well as improve our productivity and safety.

Survey and Crustal Motion

 Until the advent of carrier-phase differential 

GPS, measuring the relative distance or motion 

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20
of large objects accurately over time required 

painstaking surveys using laser interferometry, 

and they tended to be one-dimensional. 

However, carrier-phase differential GPS 

that can track 3-D relative positions down to 

millimeter levels across very long distances is 

revolutionizing the field of geomatics. Currently, 

experiments are underway that monitor the 

relative positions of the mountain sides of 

several volcanoes in the states of Hawaii and 

Washington. Previous attempts to perform 

these kinds of experiments proved difficult 

due to the requirement for consistent line-ofsight measurements using optical sensors. Data 

recorded by using survey-quality GPS receivers 

have detected bulging of the mountains and 

are providing insights that may one day enable 

scientists to predict volcanic eruptions.

 Similarly, hundreds of GPS receivers have 

been placed along fault lines throughout 

California and other parts of the world to 

validate theories about plate motion and 

gain valuable information on preconditions 

for earthquakes. Again, research in this area 

is still in its infancy, but never before has it 

been so economical or in some cases even 

possible to measure distance across large 

geographic features down to the millimeter 

level. At this time, data is being gathered to 

validate crustal motion that will certainly 

lead to refinements in these models.

Aviation

 The aviation industry has been an early 

adopter of GPS technologies, and it remains at 

the forefront of developing and implementing 

advances in GPS. In the early 1990s, a prototype 

GPS landing system for Category III (zero feet 

ceiling, zero miles visibility) was developed and 

demonstrated by Stanford University under 

an FAA grant. This system used carrier-phase 

differential GPS to ensure a correct position. 

To resolve the integer-cycle ambiguities 

quickly and robustly, two ground transmitters 

that broadcast GPS-like signals were used 

to augment the system. These “pseudolites” 

exhibited a large change in Doppler shift due 

to the rapid geometric change. The resulting 

system demonstrated more than 100 autocoupled landings at Crows Landing Airport in 

California; data was independently validated by 

using the Crows Landing laser tracker. The data 

showed an accuracy of better than 0.5 meter 

(3-D) in the final phase of landing.

 During one of the auto-coupled landings, a 

satellite upload from the Master Control Station 

caused the satellite to interrupt its transmission 

for approximately 1 millisecond. The Stanford 

system detected this glitch in the space segment 

and called off the landing in real time.

 Recently the FAA has approved the GPS 

as a precision navigation aid, but most general 

aviation and commercial pilots have been using 

GPS as a backup system for years. Additionally, 

modern aviation GPS units are programmed 

with a full aviation database and can notify the 

user of airspace violations. In an emergency, 

these units can guide the pilot to the closest 

airport at the touch of a button.

 GPS, as a full thirteen-state sensor for an 

aircraft, provides a powerful suite of information 

at a relatively low cost. Combined with 

inexpensive computer graphics, a synthetic outthe-window perspective display can be used to 

improve vastly the presentation of critical data 

to the pilot. The futuristic vision of tunnelsPrecision Timing, Location, Navigation

21
in-the-sky for improved navigation is being 

tested today in various laboratories around the 

world. Pilots who have experimented with these 

systems report a much reduced workload and 

greater situational awareness. The potential 

to reduce controlled flight into terrain could 

save many lives currently lost due to such 

accidents. Likewise, if all other aircraft are 

prominently displayed, midair collisions can 

be reduced. These displays have also shown 

great promise in enabling closely spaced parallel 

approaches in inclement weather. This alone 

can save the United States billions of dollars 

in runway expansions and avoid environmental 

impacts that such construction would have on 

surrounding areas.

Vehicle Tracking

 The so-called “urban canyon” can adversely 

affect GPS, but vehicle tracking remains a 

very important application. During urbancanyon outages, most vehicle-tracking systems 

use some form of inertial augmentation to 

provide a position solution. Very small nanotechnology inertial units of postage stamp size 

will make this solution even better and cheaper. 

Commercial companies have great interest in 

knowing where their equipment is currently 

located, and GPS provides an ideal answer. 

Many cities now have buses equipped with GPS 

receivers and radio transmitters. Each bus stop 

has a display of the current location of the next 

bus and an estimate of the time until it arrives. 

Likewise, many cities have GPS equipment 

on their emergency service vehicles to better 

manage their response. This has been shown 

very effective in reducing response time and 

managing scarce resources during a large-scale 

disaster.

 Vehicle tracking yields a great competitive 

advantage to a corporation. In one case, a cement 

company in Guadalajara, Mexico, would send 

fully loaded cement trucks into the city every 

morning, even though orders had not yet been 

placed. Using simple radio communication, 

this company responded to orders in less than 

half the time of any of its competitors. Though 

several trucks would return without having 

had a customer by the end of the day, within a 

short time this company dominated the cement 

delivery market.

 Law enforcement officials have been able 

to use GPS to remotely monitor suspects and 

increase their effective manpower. Obtaining 

a court order allowing them to install a GPS 

receiver surreptitiously on a suspect’s car, Seattle 

police were able to reconstruct the time and 

path of a suspect’s location during a two-week 

period, without alerting the individual to the 

surveillance. The information they obtained led 

directly to evidence that convicted the suspect.

Precision Munitions

 No discussion of GPS would be complete 

without a discussion of military applications. 

In spite of its extensive use in many civil 

applications, GPS was designed primarily as a 

military system, and to continually develop, GPS 

must fulfill its primary mission. Several military 

applications for GPS were developed in recent 

years. An example is the JDAM. This precisionguided munition has demonstrated a battlefield 

accuracy of better than 10 meters. The trend in 

the future is to reduce the size of the explosive 

warhead on these munitions, and this can be 

achieved only if the guidance system is capable 

The Limitless Sky

22
of pinpoint accuracy. (See a broader treatment 

in a companion paper at this symposium.)

 In an example of a purely defensive military 

application, the DoD recently deployed a 

Combat Survivor/Evader Locator radio for 

service members. This radio allows downed 

pilots to relay their positions to rescuers directly 

to enable rapid rescue and minimal exposure 

to hostile forces. The Combat Survivor/Evader 

Locator replaces four different individual 

devices with a single integrated package.

Space Applications

 Some of the most innovative and unusual 

applications of GPS occur in the area of Earthsensing and space applications. Low Earthorbiting satellites can use GPS to measure both 

position and attitude. Precise satellite data can 

be used to refine gravitational models of Earth 

and as a sensor for attitude control. A soonto-fly satellite experiment, the Gravity Probe 

B, uses very precise spherical gyroscopes to 

yield a quantitative measurement of Einstein’s 

theory of relativity. For the experiment to be 

valid, Gravity Probe B needs to fly a drag-free 

polar orbit to within 100 meters. GPS is used 

to provide guidance information to position 

the orbit of the satellite initially. One of the 

most unusual applications of GPS is using 

the reflection of GPS signals from waves at 

sea to detect wave height in the open ocean.

FUTURE IMPROVEMENTS

 The first Block IIR GPS satellite was 

launched in 1997. Though later versions of Block 

IIs will be a bridge to a future GPS system, 

known as GPS III, the next generation of GPS 

is still being defined. Future improvements in 

the GPS system are driven by competing civil 

and military requirements. All users desire 

more signal power to ensure resistance to 

interference and/or jamming. In the last decade, 

GPS has become essential to virtually all DoD 

operations. International constraints on RF 

spectrum availability dictate that improvements 

remain within the radio navigation bands. On 

the civil side, the expectation has become that 

GPS will remain continuously available across 

the globe for the foreseeable future. Civilian 

users are urgently requesting the second and 

third frequencies to calibrate ionospheric delays 

and provide a backup if the L1 signal is jammed.

 Several key advances are planned for the end 

of the Block II series of satellites. The most 

important are two additional signals on the 

Block IIRMs and three on the Block IIFs. The 

first additional signal is a replica of the C/A 

code but at the L2 frequency. This will allow 

direct measurement of ionospheric errors for 

civilian users. Military users will have a new 

split-spectrum code (called M-code) on both 

L1 and L2. This code has the advantage of 

transmitting most of its power in the nulls of 

the C/A code, maximizing spectral separation.

 The Block IIFs will include yet another 

civil signal at L5 (1,176 MHz). This signal 

is intended to be a higher accuracy signal, 

which implies a higher chipping rate and a 

longer code sequence. Likely, it will include an 

unmodulated channel to enable much longer 

integration time for superior noise rejection. 

Other technical advances for the late IIFs 

include intersatellite communication as well as 

improvements in the onboard rubidium/cesium 

clocks. Likewise, upgrades in the ground station 

facilities will reduce the errors in ephemeris 

Precision Timing, Location, Navigation

23
predictions. For GPS III, the need for further 

increases in M-code power will probably lead 

to a spot beam of about 1,000 kilometers.

 Though all specifics of the GPS III concept 

are still to be determined, as well as the details 

of the relationship between the U.S. GPS 

and the European Galileo, the United States 

intends to continue providing and improving 

on a worldwide, continuously available, 

precise navigation signal free to all. GPS III 

will undoubtedly follow that tradition and 

provide a yet more robust and more accurate 

system of positioning on a global scale. 

The one thing that is most certain for the 

future of GPS is that its uses will continue 

to multiply and impact our daily lives.

Relationships to Galileo

 Galileo is the European version of GPS. 

The European Union is committed to building 

a thirty-satellite, civil space-based navigation 

system at an estimated cost of 3.4 billion euros. 

The initial funding of 547 million euros is 

intended to fund the study and development 

phase, which is expected to take approximately 

three years. Galileo will be an entirely civil 

system that promises to be independent but 

interoperable with the civil components of GPS.

 Several outstanding issues must be 

resolved before Galileo becomes operational 

(planned for 2008). The most crucial is that 

the Galileo signals not interfere with any of 

the GPS signals. Ideally, Galileo would use a 

compatible geodetic reference frame and time 

base calibrated to GPS. This would present 

the Galileo satellites as an augmentation to 

the GPS constellation or, conversely, the GPS 

constellation as an augmentation to Galileo. 

Barring this level of interoperability, it is likely 

that Galileo’s time base and geodetic reference 

frame will be distinct from GPS’s but will be 

easily translatable if real-time data is available. 

The exact configuration of the Galileo system 

is not yet certain and is the subject of current 

diplomatic negotiation between the United 

States and the European Union.

CONCLUSION

 In the last ten years, GPS has become an 

international utility with more than twenty 

million users. Recent conflicts have conclusively 

shown it to be essential to precision warfare. 

Especially important is the stringent limits 

on “wild weapons” that can lead to undesired 

collateral damage. Thus the U.S. military 

depends on GPS for virtually all combat 

operations.

 Already many civil developers are working on 

augmentations to cell phones that will include 

GPS receivers. This promises to increase civil use 

to hundreds of millions of users. The advances 

in navigational/location science brought about 

by GPS are also significant to future space 

exploration. However, worldwide dependency on 

this global utility requires an increasingly robust 

system. With the advent of Galileo, the roughly 

fifty-five operational navigation satellites should 

provide the needed robustness and lead to even 

further innovative uses.

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24
Tightening the Circle:

Scientific Research and the Evolution and 

Revolution of Precision Guided Munitions

Lieutenant General Daniel P. Leaf, USAF

Robert I. Sierakowski

Robert P. White
Abstract

 Weapons designed to strike the enemy at ever-increasing 

distances and with ever-increasing precision and lethality are the 

result of critical scientific discoveries funded by the Department 

of Defense. The development and refinement of Precision Guided 

Munitions (PGMs) can be traced to initiatives taken before and 

during World War II to increase the effectiveness of aircraftdelivered ordinance.

 The real revolution in PGMs occurred in the 1970s with 

the development and maturity of laser research and space-based 

initiatives such as the Global Positioning System. Beginning with 

their use in Vietnam, through the 1991 Gulf War, Kosovo, and 

Afghanistan, and through their latest employment in Iraq, the 

efficacy of PGMs has improved markedly, as evidenced by the 

incremental improvements in lessons learned.

 These improvements will continue due in large part to the 

technologists and the warfighters who, in concert with military and 

civilian visionaries, conceived unique concepts and possibilities with 

the marriage of seemingly disparate discoveries. The results have 

been revolutionary in the art of warfare.
The Limitless Sky

28

Figure 1. Archimedes’ system of catapults, levered arms, and 

his fabled mirrors that focused the rays of the sun against the 

Roman galleons, were ancient conceptual forerunners of the 

sophisticated precision guided arms employed today.

INTRODUCTION

 In 212 BC Archimedes, the world’s first 

warrior-scientist, employed scientific research 

and applied the resulting principles to his 

war machines to fight the Roman invasion 

of his Greek city-state of Syracuse. The 

weapons he employed kept the enemy at 

bay and effectively struck the Romans from 

a distance while ensuring the safety of the 

Syracusan warriors.1

 Archimedes’ system of 

catapults, levered arms, and his fabled mirrors 

that focused the rays of the sun against the 

Roman galleons were ancient conceptual 

forerunners of the sophisticated precision 

guided arms employed today (Figures 1). 

 Man’s search for sophisticated weapons 

of war, particularly weapons that could be 

delivered from ever-increasing distances with 

accuracy and telling effect, has been an elusive 

goal until relatively recently. The first half of the 

twentieth century witnessed two world wars 

and several regional conflicts when hundreds, 

if not thousands, of bombs were required to 

destroy selected ground targets. Often, these 

bombing attempts were wholly unsuccessful. 

Attacks with unguided iron “dumb” bombs was 

termed area bombing, and not without good 

reason. Indeed, entire cities were considered 

appropriate target areas. During such missions, 

large numbers of lumbering aircraft and many 

crewmen were put at risk, and many were lost. 

The requirement to destroy targets effectively 

with a minimum of force and with minimum 

threat to the attacking forces was obvious.

 The search for weapons designed to strike 

an enemy at ever-increasing distances and with 

ever-increasing precision and lethality while 

ensuring the safety of the attackers depended on 

key scientific discoveries and an organizational 

structure capable of taking advantage of them. 

In the latter part of the twentieth century, the 

vast majority of these critical discoveries were 

funded by Department of Defense (DoD)–

sponsored research programs.2

 Not until the 

late 1960s, though, did scientific advances 

allow the marriage of various technologies 

to permit the development of what are now 

termed precision guided munitions (PGMs). 

As it stands today, we have indeed developed 

an impressive PGM capability, but it need 

not have taken as long as it did. Owing to 

historical vagaries of research and development 

(R&D) funding in munitions and delivery 
Tightening the Circle

29

systems, precision munition development 

sputtered along until discoveries made in the 

past joined with contemporary realizations to 

produce yet another “eureka moment.” What 

is significant about the PGM developmental 

process is that most of the applicable 

technology was available for quite some time. 

Even before the Wright Brothers first flew, 

precision-guided technology was “in the air.”

 The Wrights may have been the first to take 

to the air in manned flight at Kitty Hawk in 

December 1903, but in September of that year 

at an exhibition in Germany, Karl Jatho helped 

set the stage for further advances in unmanned 

airborne weaponry. Jatho designed and flew 

a pilotless biplane 12 feet long powered by a 

9.5 horsepower gasoline engine for a longer 

sortie than the one the Wrights would soon 

attain. In 1908 three Americans, Dr. Elmer 

Sperry, Dr. Peter Cooper, and Lieutenant 

Patrick Bellinger, wed this pilotless capability 

to another technological breakthrough with 

the invention of the automatic gyroscopic 

stabilizer, which permitted an airborne 

craft to fly straight and level.3

 With the 

blossoming of powered flight, both manned 

and unmanned, the prospect of bombing 

from the air was imminent. In 1910, Glenn 

Curtiss demonstrated the concept of aerial 

bombing using simulated bombs on a dummy 

battleship. U.S. Army tests using live bombs 

quickly followed — this, ten years before Billy 

Mitchell sank the Ostfriesland off the Virginia 

Capes!4

 In 1911, eight years after the Wrights 

first flew, aircraft bombardment was first used 

operationally when Italian aviators dropped 

bombs on Turkish forces in the war over Libya.5

 In 1916 the European powers had been at 

war for more than two years, and the U.S. 

War Department recognized it needed a 

developmental, testing, and procurement 

facility for aviation needs. It established an 

experimental station and proving ground at 

Langley Field, Virginia. While the Army’s Air 

Service was getting up to speed in its R&D 

armament program, the U.S. Navy in 1917 

actually conducted tests to take the pilot and 

bombardier out of the bombing loop. The 

Navy funded the first radio-controlled aerial 

torpedo, a converted Navy Curtiss N–9 trainer 

powered by a 40-horsepower engine capable of 

flying 50 miles with a 300-pound bomb load.6

The Army Air Service soon pulled ahead with 

a much more sophisticated unmanned aircraft 

designed and tested by Charles F. Kettering, an 

automobile engineer with Delco Corporation, 

the predecessor of General Motors. At the 

time, Colonel Henry (Hap) Arnold, arranged 

for the field testing in France of what became 

known as the Kettering Bug, the first unmanned 

aerial vehicle (UAV) to be mass produced.7

Having a maximum range of 100 miles, a Sperry 

gyroscope held the “Bug” on course. An aneroid 

barometer maintained its altitude until the craft 

shed its wings after a predetermined number 

of propeller rotations, where upon it plunged 

to earth, and its 300-pound warhead, loaded 

with mustard gas and high explosives, would 

detonate.8

 Exactly where it fell to earth was 

quite problematic. The problem would have to 

wait for another war, for neither the Bug nor 

the Curtiss N–9 was operationally employed 

during the conflict. What became of America’s 

initial endeavor with its first guided bomb, the 

Kettering Bug? According to “An Automatic 

Bomber” that appeared in the 24 May 1919 
The Limitless Sky

30

Figure 2. Sperry Aerial Torpedo, first flight 1918 

Direct ancestor of the modern cruise missile. 

issue of the Army and Navy Journal, the Bug 

was “placed in the secret archives of the War 

Department at Washington, there to remain, 

it is hoped by the inventor, for all times.”9

 The aerial bombardment weapons that 

actually did see operational use during World 

War I were quite crude. Early bomb designs 

consisted of rejected artillery rounds modified 

to accept stabilization fins, and most bombs 

weighed no more than 100 pounds. Aiming was 

primitive. In employing these new weapons, 

belligerents soon realized that hitting where 

you aimed was a significant challenge.10 Many 

variables affected targeting. The ground target 

might or might not be stationary, but the 

aircraft was in motion. The aircraft’s speed, 

direction, and acceleration combined with the 

direction and speed of the wind plus the air 

temperature and humidity all affected the fall 

of its bomb load.11 Bomber aircraft with their 

external carriage-mounted ordnance struck 

what they considered to be strategic targets, 

but by today’s standard they would be tactical 

targets, and the bombers of World War I, just 

like the bomber aircraft to come in World 

War II, were used in mass formations to 

compensate for relatively small munitions and 

lack of precision. In addition, pursuit planes, or 

fighter escorts, were a requirement to safeguard 

the low and slow lumbering bombers.12

WORLD WAR II

 By the end of World War I, American 

Air Service forces, with only 150 strategic 

(interdiction) bombing raids to their credit, had 

obtained relatively little experience in this new 

endeavor.13 With little bombing experience, 

there was no new doctrine to provide the 

rationale to acquire new technology. To the 

Air Services’ credit, a dedicated R&D center 

McCook Field, Ohio, provided a facility where 

the Army conducted its wartime aeronautical 

engineering initiatives that continued 

throughout the interwar period. While advances 

in individual airframe technology, bombsights, 

and doctrine were obtained, little thought was 

given to munitions technology, and no War 

Department funding was available for any 

type of guided air weapon.14 Those who, like 

Douhet, conjectured about getting bombs on 

Figure 3. Kettering “Bug”

The first mass produced guided weapon.
Tightening the Circle

31

target made highly erroneous assumptions: 

that vital targets could be identified and 

found, that they could then be hit from 

altitude, and that they could be destroyed.15

 As we were to learn in World War II, a 

B–17’s fire control did not have pickle-barrel 

parameters. Except for the fact that the bodies 

of the bombs were redesigned to make them 

more compact for internal bomb-bay storage, 

the bombs used in World War II had changed 

little since the previous war, and little thought 

had been given to their fire control system.16

The B–17’s fire control system, the super-secret 

Norden bombsight, began as a U.S. Navy 

program to design a precision bombsight to 

target maneuvering enemy ships, but the Navy 

decided instead to use dive bombing to achieve 

that end.17 Because U.S. Army Air Forces 

bombers could not dive-bomb their targets, 

they employed the Norden bombsight to 

increase their chances of scoring direct hits. In 

one significant example from July 1944, fortyseven B–29s raided the Yawata steel works in 

Figure 4. Bomb technology changed little between 

World War I and World War II.

Figure 5. B–17 mission during “Big Week,” 20–25 February 1944. Area bombing was a hit or miss proposition that 

was costly in men and machines. During “Big Week,” 3,300 

bombers were dispatched from England and 500 from Italy, 

with 137 of the former and 89 of the latter being lost. Also, 28 

Army Air Forces fighters were shot down. The number of U.S. 

personnel killed, missing, and seriously wounded totaled 2,600.

Figure 6. Ploesti, Romania, 1 August 1944. Low level attack 

ensured bomb accuracy—but at a huge cost. Although overall 

damage to target was heavy, of 177 planes and 1,726 men who 

took off on the mission, 54 planes and 532 men failed to return.
The Limitless Sky

32

Japan from bases in China and dropped 376 

general-purpose 500-pound bombs. One bomb 

hit the target, which represented 0.25 percent 

of the bombs dropped during the raid!18 In 

the European theater, things weren’t much 

better: In the fall of 1944, only 7 percent of 

all bombs dropped by the Eighth Air Force 

hit within 1,000 feet of their aim point.19

Hit Probability of 90% against a 60' x 100' Target with the Use of 2,000-Pound 

Unguided Bombs at Medium Altitude20

War Number of Number of CEP (in feet)

 Aircraft Bombs

 WW II 9,070 3,024 3,300

 Given that World War II bombing accuracy 

proved to be a contradiction in terms, it 

seems an effort would have been to remedy 

the situation. When Hap Arnold became 

the commander of the Army Air Corps in 

September 1938, he immediately accelerated Air 

Corps R&D efforts across a wide spectrum of 

long-term technologies and committed the funds 

for massive new R&D facilities at Wright Field, 

Ohio.21 He did this because he realized that 

in the interwar period relatively little thought 

and investment were being directed toward 

futuristic weapon systems. His assessment was 

confirmed when he read the results from a 1939 

special air board that he had commissioned to 

look at future weapons requirements: the board 

made no mention of jet propulsion or missiles, 

much less true precision bombing.22 Arnold 

realized that the National Advisory Committee 

for Aeronautics, the arbiter of aircraft design 

and innovation since its creation in 1915, “had 

made vital contributions to aircraft hardware 

and design...but the organization was doing so 

without considering how the developments fit 

into the Air Corps’s balanced air program.”23

 In late 1939 after witnessing the effects of 

blitzkrieg-based warfare and realizing the need 

to create an effective American fighting air force, 

Arnold drastically curtailed his basic and applied 

research programs and concentrated on R&D. 

He focused on improving current technologies, 

among them the B–17, B–29, rocket propulsion, 

and glide bombs. It is interesting to note that 

during the World War II years, while Arnold 

was committed to the Army Air Forces doctrine 

of precision daylight bombing (as opposed to 

the British Bomber Command’s nighttime area 

bombing philosophy), he was also committed 

to procuring standoff and remotely controlled 

weapons to protect his pilots from harm.24 As 

early as the summer of 1939, Arnold was in 

touch with Charles Kettering and discussed 

resurrecting the World War I–era Kettering 

Bug, but this idea was shelved due to range 

requirements. When Arnold made a visit 

to England in 1942, he noticed that even in 

cities, many bombs fell in open areas. With 

this thought in mind, he concluded that a 

bomb gliding to its target on a flat trajectory 

would, by default, hit a vertical surface.25 What 

resulted was a requirement for a glide bomb 

(GB) that would glide one mile for each 1,000 

feet of altitude and would have a circular error 

probable (CEP) of less than one-half mile.26 The 

resulting weapon, the GB–1, a 2,000-pound 

bomb fitted with wooden wings spanning 12 

feet, was targeted against the German city of 

Cologne in the spring of 1944.27 Operationally, 

B–17s carried one GB–1 under each wing 

with the bombs being released about 20 miles 

from the target, but with an average range-miss 

distance from 3,000 to 5,000 feet and from 
Tightening the Circle

33

Figure 7. The GB–4 (above) was a GB–1 (AZON) with an 

added television camera and radio remote control, which during testing achieved an impressive 200 foot CEP.

Figure 8. The VB or vertical bomb series, (below) consisting 

of 1,000 pound bombs fitted with a steerable tail assembly and 

a tracking flare that were ultimately equipped with a radio 

control system, allowing a bombardier to direct the bomb to a 

target using a joystick.

Figure 8. The VB–9 guided bomb, equipped with a radar seeker.

700 to 1,000 feet in azimuth, the best that 

could be hoped for was that the bombs would 

fall within the city limits, which they did.28 To 

Eighth Air Force commanders, it was simply 

an area bombing weapon, and they rejected 

it. Consequently, the entire developmental 

glide bomb program was diminished to the 

point that almost all glide bomb initiatives did 

not see combat.29 In addition to the targeting 

shortcoming, only two such weapons could be 

carried by each aircraft, significantly increasing 

drag and reducing the B–17’s speed and range.30

By comparison, our allies had better results 

with their guided weaponry. One may even date 

the precision weapon era to 12 May 1943 when 

a Royal Air Force antisubmarine Liberator 

dropped an MK–24 acoustic homing torpedo 

that found and seriously damaged the U–456. 
The Limitless Sky

34

The damage forced the submarine to the surface, 

where convoy escort vessels quickly sank it.31

Though operationally limited, the U.S. glide 

bomb program was developmentally dynamic; 

fifteen types actually came from the WrightPatterson weapons laboratories in Ohio. 

While the GB–1 was guided by a gyroscopic 

stabilization system, others were fitted with 

a variety of guidance systems including light 

contrast, infrared, active radar seekers, and 

television imagers.32 The only other glide bomb 

to see combat, the GB–4, was a GB–1 with an 

added television camera and radio remote 

control that achieved an impressive 200-foot 

CEP during testing.33 The poor quality of the 

GB–4’s television technology and its inability to 

penetrate hardened concrete targets limited its 

usefulness.34 Also coming from the Wright labs 

was the vertical bomb (VB) series, 1,000-pound 

bombs fitted with a steerable tail assembly and 

a tracking flare, and ultimately equipped with a 

radio control system that allowed a bombardier 

to direct the bomb to target with a joystick.35

This azimuth only (Azon) weapon was used 

extensively to target bridges in Burma, the 

World War II chokepoints of the Japanese 

supply chain. Of the 459 Azons used in Burma, 

27 took out bridges: a success rate of nearly 6 

percent. This particular guided weapon concept 

was not new, for the Germans had experimented 

with such weapons during the First World 

War and continued their tests in the 1930s, 

ultimately refining several guided weapons 

that were successfully employed during the 

Second World War, in one instance, sinking 

the 42,000-ton Italian battleship, Roma.

KOREA AND VIETNAM

 By the end of the World War II, both the 

U.S. Army Air Forces’ and the U.S. Navy’s 

weapons laboratories had produced relatively 

sophisticated guided weapons programs based 

largely on scientific advances made by the 

weapons guidance division of the National 

Defense Research Committee.36 Technical 

advances in the field of guided weapons included 

radio remote control, a light contrast seeker 

warhead (VB–5), a heat seeker (VB–6), a 

series of television bombs, and a radar seeker 

(VB–9).37 In fact, the guided weapons program 

became the Army Air Forces’ third largest 

development program, exceeded in investment 

only by the unguided bomb and jet propulsion 

initiatives.38 Regardless of the large degree 

of investment, as with all new technology, 

drawbacks persisted. These new guided 

weapons “generally required clear weather, easily 

identifiable targets, and air superiority” not to 

mention that many aircrews found the visually 

guided weapons delivery process to be far 

more dangerous than a conventional bombing 

mission, given the amount of time required 

over the target area.39 This issue would repeat 

itself in the Korean and Vietnam conflicts.

 In retrospect, except for the laser, the 

scientific and technical basis of current PGMs 

can be traced to initiatives taken before 

and during World War II to increase the 

effectiveness of aircraft-delivered ordnance. 

In the United States, these initiatives were 

generally met with official indifference and 

the consequent lack of funding.40 Much the 

same can also be said for the period following 

World War II when emphasis shifted to the 

perceived requirements for the Cold War: 
Tightening the Circle

35

Figure 10. The B–29 carried the 12,000 pound TARZON 

(VB), used during the Korean War.

nuclear weapons, jet aircraft, and missiles.41 The 

Azon program was canceled and the limited 

R&D funds available for guided weapons 

development for the now-independent Air Force 

were spent on the potentially more capable 

Razon, which was controllable in both the 

vertical and horizontal axes.42 When war broke 

out in Korea in June of 1950, several Razonmodified B–29s were on-station in Guam, but 

so were the very much neglected, rusted, and 

damaged tail assemblies of the Razon-modified 

1,000-pound bombs. After a rough start, the 

Razon-equipped bombing units took to the air 

and succeeded in destroying several bridges, 

but it took, on average, four direct hits from 

the thousand-pounders to bring down these 

relatively narrow, hard targets.43 The Razon had 

potential but lacked the required punch for large 

reinforced targets. The result was a marriage 

of Razon guided-bomb technology and World 

War II–era British big-bomb technology: the 

12,000-pound Tarzon guided bomb seemed 

the right answer when, in early 1951, it took out 

several bridges in one shot.44 The subsequent 

loss of one Tarzon-equipped B–29, the near loss 

of another, and the complex training and loading 

procedures required suspending the program. 

Even with a rather sketchy performance record, 

the latest guided bombs proved they could 

take on small, tough targets, and could do so 

with far better precision and with fewer sorties 

than conventional bomb missions could.45

 The results of the Korean War guided-bomb 

experience proved little different from what 

was learned in World War II: clear weather 

and air superiority were necessary to deliver 

the bomb on target.46 While conventional 

iron bomb delivery had improved during 

the Korean War, the idealized process of 

precision bombing remained elusive.

Hit Probability of 90% against a 60' x 100'

Target with the Use of 2,000-Pound 

Unguided Bombs at Medium Altitude20

War Number of Number of CEP (in feet) Aircraft Bombs

 WW II 9,070 3,024 3,300

Korea 1,100 550 1,000

One historian, in commenting on the 

development of precision guided bombs 

during the 1950s, makes the point that the 

problems with the then-current guided weapons 

could have been solved with relatively little 

engineering effort. “None of the problems 

were very complex nor required new scientific 

discoveries for solution...they were engineering 

puzzles that were less dependent upon inspired 

imagination and more responsive to time 

and effort,” rather than basic research.48

 If the problems facing precision bombing 

were relatively easy to solve, why weren’t they? 

The answer lies in how Air Force R&D was 

organized, especially when it came to something 
The Limitless Sky

36

Figure 11. USAF B–29 “Superfortress” 

equipped with Bullpup guided missiles. In April 

1965, USAF and USN Bullpups and Bulldogs 

“bounced off” the Thanh Hoa “Dragon’s Jaw” 

bridge in North Vietnam.

as basic as bombs. From the 1907 establishment 

of the Aeronautical Division under the Signal 

Corps, until 1962, fifteen years after the Air 

Force became a separate service, the U.S. Army 

Ordnance Department was responsible for the 

development of all high-explosive, fragmentation, 

and semi-armor-piercing bombs. Basically, 

weapons that departed the aircraft became the 

responsibility of Army Ordnance, and those 

that stayed with the plane belonged to the Air 

Service/Air Corps/Air Force. To make matters 

worse, incendiary bombs were the responsibility 

of the Army’s Chemical Service, and the 

development of armor-piercing bombs was the 

responsibility of the Navy’s Bureau of Ordnance. 

In essence, no strong air advocate existed for 

precision guided ordnance.49 The seeds for 

such an advocate were born in December 

1949 when the Air Material Armament Test 

Center was established at Eglin AFB, Florida, 

to “concentrate at one location the widely 

scattered activities engaged in air armament 

development.”50 Separate from the Air Proving 

Ground Command, which had been operating 

at Eglin since the 1930s, this small organization 

was made responsible for nonnuclear air 

armament developmental testing in the middle 

of the acquisition cycle. Funding priorities after 

the Korean War, though, emphasized strategic 

nuclear warfare, and any money allotted to 

tactical bombing efforts went toward tactical 

nuclear weapons and its supporting structure. 

Again, precision guided weapons development 

for the Air Force was put on hold.51

 The same could not be said for the Navy, 

which developed the 250-pound Bullpup and 

1,000-pound Bulldog guided missiles as an 

answer to their Korean War bridge problem. 

The 1952 Bullpup U.S. Navy requirement 

reached initial operational capability in 1958 

and entered Air Force stockpiles in the early 

1960s, and the bigger Bulldog reached initial 

operational capability in 1964. Both weapons 

were based on the same technology as that 

found in the World War II Razon and Korean 

War–era Tarzon bombs, except for the addition 

of rocket propulsion. 

 This daytime, clear weather weapon had its 
Tightening the Circle

37

drawbacks, and twenty years after the end of 

World War II it was not much better than its 

predecessors. Proof was forthcoming when the 

Bullpups and Bulldogs went up against the 

Thanh Hoa railroad Bridge in North Vietnam 

in the spring and summer of 1965, only to 

strike their target, explode, and, as one pilot 

described it, just “bounce off.”52 The Thanh 

Hoa Bridge was called the Dragon’s Jaw by the 

North Vietnamese, and throughout Rolling 

Thunder, U.S. pilots acknowledged it as the 

bridge that “would never go down.”53 In the 

first attack against the Dragon’s Jaw on 3 April 

1965, 79 F–105s dropped 638 750-pound 

bombs and fired 298 rockets. Five aircraft were 

lost. The bridge was scratched but remained 

very serviceable.54 Over the next seven years, 

U.S. airmen paid a heavy price in their many 

attempts to down the bridge using dumb bombs 

and performance-limited guided weapons 

based on World War II–era technology. The 

answer was to come in two parts: technological 

change, if not revolution, in the research lab 

was occurring and was slowly making its way 

into aerial weapons applications, and several 

bureaucratic lines were being breached. 

 Three significant changes occurred with 

respect to Air Force guided weapons in the 

years leading up to the Vietnam War: two 

were organizational, the other was technical. 

In 1962 Army Ordnance relinquished its 

55-year-old grip on bomb development and 

it finally became an Air Force responsibility. 

Organizationally, the other change was that part 

of this responsibility now rested in the relatively 

obscure Eglin-based Detachments 4 and 5 of the 

Research and Technology Division of Air Force 

Systems Command. What had begun in 1949 

as the Air Material Armament Test Center had 

finally found its voice, and in 1964 it argued that 

something should be done.55 No one knew it at 

the time, but thanks to the DoD basic research 

funding in the 1950s that resulted in the 

invention of the laser, a revolution in precision 

bombing was at hand. With the first operational 

laser demonstration in 1960, new technology 

was now available, and Detachment 4, soon to 

become the Air Force Armament Technology 

Laboratory (AFATL) in 1966, became a strong 

advocate for its development.56 Detachment 4 

began its laser research in 1961 and continued 

its experiments through 1965. Coincidentally, 

the Air Staff at this time concluded that tactical 

conventional ordnance was abysmally inadequate 

and recognized the benefits inherent in standoff 

launch capabilities.57 But the key requirement 

to make that possible came not from the Air 

Staff nor from the laser experiments ongoing 

at Detachment 4, but from U.S. Army 

scientists who were interested in applying 

the power of the laser to ground warfare.

 Between 1962 and 1965, scientists at the 

Army’s Missile Command in Huntsville, 

Alabama, worked on producing a pulsed laser 

generator as well as a laser detector that could 

identify reflected laser light. They envisioned 

a soldier using the laser to help guide antitank 

missiles, but the enemy threat in the early years 

of the Vietnam War did not include armor, so 

the laser program lost its urgency.58 Thus, in 

1964, laser enthusiasts at Huntsville crossed 

bureaucratic lines and brought their research 

results to the Aeronautical Systems Division 

at Wright-Patterson. The Systems Division 

gave the information to Detachment 5 at Eglin, 

whose charter “was to seek out ways in which 
The Limitless Sky

38

Figure 12. The Thanh Hoa Bridge, the 

“Dragon’s Jaw”, goes down May 1972. The Seventh Air Force study concluded: “It would have 

taken 2,400 unguided bombs” to accomplish the 

same degree of damage.

technology could be employed to bring about 

an immediate improvement in the combat 

potential of air weapons in Southeast Asia.”59

So it came to be that, in the fall of 1964, the 

commander of Detachment 5, Colonel Joe 

Davis, watched as Martin Marietta Corporation 

engineers demonstrated in Orlando, Florida, 

what they called a laser.60 As he watched the 

laser image remain focused while its reflected 

shine tracked a piece of plywood 2,000 feet 

distant, Colonel Davis realized, “we ought to get 

this laser to steer our bombs.”61 Detachment 5 

launched its laser bomb development program 

in the spring of 1965, and by late 1967 the Air 

Force was ready to test the results in Vietnam 

with a 750-pound version. The laser-guided 

bomb (LGB) tests in Vietnam throughout 

1968 made it clear that this new weapon 

would be very effective on high-value targets. 

By 1971, kits had been designed for 500-, 

1,000-, 2,000-, and 3,000-pound bombs.62

 As a result of the 1968 bombing halt, the 

North Vietnamese lines of communication 

and supply had enjoyed a four-year respite 

from attack. When the North Vietnamese 

launched their Easter Offensive of 1972, the 

new Paveway LGB was ready. The weapon was 

used in two significant ways: against the main 

ground and armored invasion thrust, and in 

the early May resumption of bombing in the 

North.63 With regard to stopping the infantry 

and armored thrust, the U.S. Air Force achieved 

a significant success against tank and artillery 

forces with LGBs.64 Battlefield chokepoints 

were targeted. As the Seventh Air Force 

commander put it, “we earmarked a certain 

number of F–4s on a daily basis with LGBs 

[and] began the destruction of these points. 

Such was the accuracy of a laser bomb...we 

were getting 6 foot CEPs...with 2000-pound 

bombs.”65 One of the most significant supply 

chokepoints in North Vietnam remained: the 

Thanh Hoa Bridge. Attacked on 27 April with 

electro-optical guided bombs (the weather did 

not permit the launching of the flight’s LGBs), 

it received several hits from the 2,000-pound 

Mk 84s, but it remained open for business. On 

13 May, with better visibility, 16 F–4s armed 

with 15 LGB Mk–84s, 9 guided 3,000 pound 

Mk–118s, and 48 unguided Mk–82 bombs 

succeeded in dropping a span and wrecking 

the remainder.66 The Seventh Air Force 

calculated that to inflict the same damage with 

unguided bombs, no fewer than 2,400 would 
Tightening the Circle

39

Figure 13. F–111 with GBU–28 “Bunker 

Buster.”

have been required.67 The Vietnam War still 

holds the record for the greatest number of 

PGMs used in combat — more than 24,000. 

 The lesson learned from the employment 

of LGBs in Vietnam was that good results 

can be achieved in good weather when a man 

designated the target during the weapon’s 

flight. What was also learned was that in 

the case of a hardened target, whether it 

be the overengineered Thanh Hoa bridge 

or an underground bunker, the munition 

must have an adequately sized warhead 

and an accurate guidance system.

 What is also interesting to note is that the 

art of aircraft gunnery and bomb delivery had 

improved dramatically since World War II and 

Korea, as the following table shows. By the time 

Vietnam heated up, a great deal of training went 

into teaching munitions delivery as it related 

to the science of windage, aim points, and 

offsets. Not only did we have munitions-related 

education, we also developed aircraft systems 

with constantly computed impact points to 

assist greatly in that endeavor. Nothing, though, 

came close to the precision that was available 

with a munition that had terminal guidance.

Hit Probability of 90% against a 60' x 100'

Target with the Use of 2,000-Pound 

Unguided Bombs at Medium Altitude20

War Number of Number of CEP (in feet)

 Aircraft Bombs

 WW II 9,070 3,024 3,300

Korea 1,100 550 1,000

Vietnam 176 44 400

Guided and Unguided Bomb Usage in Vietnam69

Bomb Type

Guided Unguided

Total Number of Bombs 26,690 3,476,000*

Total % of Bombs 0.2 99.8

CEP 23 447

Percent of Bomb Direct Hits 55 5.5

Percent of Strike Aircraft in Fleet 1

Guided-Munition Capable

 With the end of Vietnam involvement, 

research on guided munitions did not follow 

historical precedent and come to an abrupt halt. 

Unlike the period after World War II and Korea 

when guided weapons lessons were ignored, 

some post-Vietnam lessons were taken to heart. 

The development of even more sophisticated 

and capable LGBs assumed a high priority in 

the Air Force. Based on the impressive accuracy 

of the Paveway I, the next major advance came 
The Limitless Sky

40

with the GBU–16 Paveway II of the early 1970s 

with its folding wings and improved guidance.70

Unfortunately, congressional cutbacks in the 

FY1974 budget request forced the Air Force 

to divert funds from other programs to keep 

the Paveway program on track. The lowpriority GBU–24 Paveway III was initiated 

in 1976.71 In the late 1970s, various high-tech 

weaponry programs, including PGMs, received 

Undersecretary of Defense for Research and 

Engineering William J. Perry’s support, and 

the Air Force made a corporate commitment to 

the Paveway program. As such, the GBU–24’s 

future was assured, and it first saw combat 

in the 1991 Gulf War, making an impressive 

showing. Another PGM made an impressive 

showing during Desert Storm, not only because 

of its ballistic effect, which was massive, but 

because of the speed with which it was fielded.

 Shortly after Iraq invaded Kuwait in 

August 1990, U.S. intelligence sources began 

to verify and list the relatively large number 

of key hardened targets. To attempt their 

elimination but still ensure the survivability 

of the delivery aircraft, the size of the weapon 

would have to be severely limited owing to 

internal carriage requirements. But two days 

after Desert Storm began, with air superiority 

in hand, we could fly where and when we 

wanted, with what we wanted. As such, the 

internal carriage requirement disappeared for 

the demanding bunker-busting jobs on the 

air tasking order, and the externally carried 

bomb could be heavier and longer to achieve 

the required terminal effects.72 In discussion 

with various Air Force Research Laboratory 

(AFRL) Munitions Directorate personnel, 

the name that emerges as the individual who 

was the inspiration for what came to be the 

GBU–28 Bunker-Buster is Al Weimorts.

 Weimorts was long aware of the informal 

requirement for such a weapon. With the 

informal requirement in hand, he made an 

observation and proposed a question: “We’ve got 

a BLU–82 that is a big bomb with a 500-foot 

CEP. What would happen if we put a 

precision guidance package on it?” That 

was the inspiration for the bunker buster, 

though Weimorts goes to great lengths to 

minimize his role and point out that everyone 

contributed significantly to the team effort.73

As Weimorts himself described it, “people 

were lining up to help in any way they could.”74

Fabrication began on 1 February 1991, and 

the bomb was dropped over Iraq on 27 

February — a record twenty-seven days. 

 The 4,700-pound GBU–28 Bunker Buster 

was developed specifically to attack buried Iraqi 

bunkers. The warhead was machined from 

surplus 8-inch Army artillery tubes that were 

recommended and procured by a technical lead 

from the Lockheed Corporation.75 Guidance 

was provided by a Paveway III LGB kit with 

minor software changes.76 A team of government 

and industry people came together striving for 

the resolution of a difficult technical challenge, 

and they did so in record time.77 To be able 

to pull it off, they had to use as much off-theshelf hardware as they could, and the only item 

that was really new was the warhead itself, the 

BLU–113 penetrator, with the rest of the GBU–28 

system already existing in other forms (guidance 

software, and nose and tail kits). The BLU–113 

warhead, based on the BLU–109 warhead, was 

made of high-grade forged steel with a narrow 

body that testing proved enhanced the warhead’s 
Tightening the Circle

41

penetration. The BLU–113 target penetration 

capability quadrupled that of the BLU–109.78

Two were ultimately employed in Iraq.79

 Superficially, some may infer from the 

GBU–28 story that the lesson to be learned 

is that science and technology programs 

take too long to transition to acquisition 

programs and that the R&D investment is 

unnecessary because a product like GBU–28 

can go from concept to employment in twentyseven days. The truth of the matter is that 

the long-term historical investment in basic 

research, modeling technology, and hardware 

development (warhead, explosives, fuzing, and 

guidance) under the LGB program allowed us 

to respond with a state-of-the-art point-design 

very quickly.80 These research programs reach 

back to the early 1970s when AFATL (the 

forerunner of the current AFRL/Munitions 

Directorate) developed in-house simulation 

capability for all LGB variants, and these 

initiatives continued through the 1970s when 

Munitions Directorate analysis led to the 

eventual successful testing and acquisition of the 

GBU–10 (MK–84), GBU–12 (MK–82), and 

the GBU–16. This was also true for the Low 

Level LGB simulation developed to support 

System Project Office development, acquisition, 

and testing, which was ultimately used to 

analyze performance and modify the guidance 

law and generate delivery data used in all Desert 

Storm LGBs. The bottom line was that the 

technical data and knowledgeable personnel 

were in place to support the development of 

the required guidance and control aspects of 

the GBU–28.81 Though the GBU–28 was, 

for the most part, off-the-shelf, the on-theshelf items had a thirty-year heritage, as did 

all the LGBs used in the 1991 Gulf War.

 Just as there were guided munitions lessons 

learned from Vietnam, significant lessons came 

from the 1991 Gulf War. You cannot fly electrooptically guided weapons in sandstorms, thick 

oil smoke, or heavy weather. These drawbacks 

were resolved in another PGM program that 

possessed a long heritage as well: the Global 

Positioning System (GPS)-guided munition.

 With the initiation of the GPS program 

in 1973, AFATL began work to develop 

an affordable GPS-aided inertial guidance 

and navigation munition package. This 

R&D ultimately resulted in an affordable 

technique for GPS-equipped weapons by the 

early 1990s, but it was not early enough for 

Desert Storm. The dramatic use of “smart” 

bombs during the 1991 Gulf War, which 

many observers thought revolutionary, 

was nothing more than a refinement of the 

guided weapons employed twenty years 

previously in Vietnam. Much of the GPS 

technological heritage can be traced directly to 

revolutionary breakthroughs in basic research.

 In 1964, the Air Force Office of Scientific 

Research (AFOSR) initiated a program 

to develop and test a coded transmission 

technique that would provide precise ranging 

and target data. This Code Division Multiple 

Access System would allow all satellites in 

a constellation to broadcast on the same 

frequency without interfering with one another. 

In 1967, AFOSR grant research resulted in 

a conceptualized design for a low-cost GPS. 

These initiatives were joined with related 

U.S. Navy programs and came to fruition at 

a DoD conference in 1973. Today, GPS is 

a constellation of twenty-four satellites that 
The Limitless Sky

42

provides instantaneous location and navigation 

information to all U.S. military services. The 

system has become second nature as a tool 

in reconnaissance, search and rescue, and 

especially in targeting. It is also significant 

to note that the work of two earlier Air 

Force–funded basic researchers was essential 

in making the GPS a viable system. In 1958, 

Rudolf Kalman perfected a mathematical 

algorithm filtering system that permits the 

routines that determine GPS positioning 

to update system parameters and to zero in 

on the correct satellite range and azimuth. 

Charles Townes’s DoD-funded work on the 

maser in the late 1950s and early 1960s led to 

superior atomic clocks integral to the operation 

of every GPS satellite: the more precise the 

GPS signal, the more precise a GPS munition 

will be. Basic and developmental research 

resulted in the GPS constellation’s being used 

as a foundation for a quantum increase in 

bombing accuracy—especially in the case of 

the Joint Direct Attack Munition (JDAM.)

 Given the results and limitations of the LGB 

arsenal as demonstrated during the 1991 Gulf 

War, the Pentagon directed that a new weapon 

be designed to overcome LGB shortcomings: 

a day/night, all-weather, GPS-based smart 

weapon. In addition, it had to utilize existing 

air-delivered munitions’ warheads (the MK 

and BLU series) as an economy measure.82 To 

satisfy this requirement, an AFRL Munitions 

Tiger Team developed an Inertial Navigation 

System (INS)/GPS-guided all-weather weapon. 

This initiative leveraged earlier work under the 

Operational Concept Demonstration High 

Gear program, which eventually produced 

the JDAM.83 In its ultimate form, the JDAM 

is a $20,000 bolt-on kit, typically attached 

to a 2,000-pound free-fall bomb that, using 

position updates from orbiting GPS satellites, 

can maneuver to its target by the adjustment 

of its tail fins.84 Whereas laser-guided weapons 

require that a person be part of the decisionmaking process (an individual to aim the laser), 

the JDAM is preprogrammed to hit a particular 

GPS coordinate. The Tiger Team decision to 

add an INS capability is an additional guarantee 

of success. If the GPS signal is not available, 

the JDAM’s INS can be programmed from the 

launching platform.85 The JDAM does have 

some drawbacks: its typical 13-yard CEP is 

not as accurate as an LGB, and its effectiveness 

against moving targets is problematic.

 Thanks to years of basic, applied, and 

advanced research, the JDAM ultimately 

proved its exceptional worth in the weather 

over Yugoslavia/Kosovo during 1999’s 

Operation Allied Force, and subsequently in 

Afghanistan and Operation Iraqi Freedom. 

Figure 14. The JDAM has been the result of a long heritage in 

basic, applied, and advanced research.
Tightening the Circle

43

JDAM Research Timeline86

Basic Research

■ Adaptive Neural Net Control (theory),

 mid 1990s

■ Modern Control Theory AP (theory, algorithms), late 1980s

■ Optimal Trajectory Shaping Guidance

 Laws (theory, algorithms), 1980s

■ CFD (algorithms), 1980s

Applied Research

■ Triservice IMU (HG–1700), 1989–1992

■ Tactical GPS Guidance (Kalman filter 

 integrated with INS/GPS), 1990–1993

■ Adv Adaptive Autopilot (neural 

 network autopilot), 2001

■Weapon Integration and Design Tech 

 (compact (compact wing kits), 1997–1999

Advanced Development

■ Operational Concept Demo (INS/GPS),

 1990–1991 ■ AGTFT (antijam), 1995–1998

■ JDAM ER Demo (wing kit), 2000

In addition, scientific research has further 

enhanced PGM delivery with advances in 

the INS, a critical element of the JDAM.87

Historically, all PGMs have had an INS. To 

be more precise, most PGMs have an Inertial 

Measurement Unit (IMU) that consists of three 

gyroscopes and three accelerometers which 

output changes in angle rate and acceleration. 

The output of the IMU is fed to a guidance 

processor that makes use of a Kalman filter. It 

is at this point, in the guidance processor, that 

the navigation data is computed: the latitude, 

longitude, and altitude. The IMU can be 

loosely, tightly, or ultratightly coupled to an 

update system like the GPS. A baro-altimeter 

can also be added. In fact, it can be said that 

the heart of the navigation system of most 

PGMs is the inertial system. A few PGMs like 

the early GBU–15s used only rate gyroscopes 

and had no inertial system. PGM guidance 

with only an IMU was first demonstrated at 

Eglin in a program called Inertially Guided 

Technology Demonstration in the early 1980s. 

This program demonstrated that an inertial 

system on a PGM could be aligned to a higher 

quality INS, launched from an aircraft, and 

autonomously guided to a designated target.

 In the early 1990s, subsequent to the 

Inertially Guided Technology Demonstration 

program, Air Force Materiel Command 

Commander General Ronald W. Yates initiated 

the Operational Concept Demonstration High 

Gear in which Eglin demonstrated integrated 

GPS/inertial guidance on a GBU–15. This 

Team Eglin effort resulted in the integration 

of an IMU and GPS receiver as well as a 

navigation processor. Following the concept 

demonstration, Team Eglin produced a 

differential GPS version in a program called 

Exploitation of Differential-GPS for Guidance 

Enhancement in which, using a wide-area GPS 

network, they demonstrated very accurate 

GPS guidance against surveyed targets.

 The current state-of-the-art IMU, integrated 

with a GPS receiver, is being flown on JDAM. 

It is projected that future IMUs will replace 

ring laser gyroscopes with MicroElectroMecha

nicalSystems (MEMS) devices. These MEMS 

devices (both gyroscopes and accelerometers) 

are currently in development. Tests are 

being conducted at Eglin demonstrating a 

prototype MEMS IMU in a JDAM. Thus it 

is that current systems such as JDAM, Joint 

Standoff Weapon, Wind-Corrected Munition 

Dispenser, Joint Air-to-Surface Standoff 

Missile, and cruise missiles all employ inertial 
The Limitless Sky

44

systems, so their value cannot be overlooked, 

and the DoD research community will 

continue to enhance this valuable system.

 The result of this R&D, to include basic 

research, has been the rise to preeminence of 

PGMs as the air-to-ground attack weapon 

of choice. In Vietnam, only 0.2 percent of 

the bombs used in were precision-guided; 

in Desert Storm, the figure stood at about 

9 percent. During 1995 in Deliberate Force 

over Bosnia, of the 1,026 munitions dropped, 

708 were PGMs, accounting for 69 percent of 

the total. In Operation Allied Force in 1999, 

fully 80 percent of the bombs dropped were 

PGMs.88 With regard to operation Allied 

Force, Lieutenant General Dan Leaf provides 

a personal perspective of PGM employment 

in combat and some lessons learned.

During operation Allied Force, I was 

fortunate to command the 31st Fighter 

Wing at Aviano, and during that my time 

there, we really expanded the flexibility of 

precision munition employment of Laser 

Guided Bombs. In particular, using them 

against mobile and fielded forces. My 

personal example is representative of 

such: In April 1999, I was flying on 

a FAC [forward air control] mission. 

My wingman and I spent an extended 

period of time looking for targets and 

we finally found a Serb convoy that was 

racing towards a town, and in our sense 

of the battle, was racing towards the town 

seeking sanctuary from us. We tried to 

stop the convoy with a couple rockets that 

my wingman fired, but this only prompted 

the convoy to increase their speed. My 

aircraft was loaded with two 500 pound 

laser-guided bombs. But I did not have 

time to set up a laser guidance pass, and 

in the interest of time, I dropped them 

both manually. One missed, because I did 

not have enough lead; and on the second, 

the reattack, I pulled enough lead and 

hit the lead vehicles of the convoy. Now, 

I lucked out and accomplished a pretty 

precise bit of bombing with a convoy 

moving somewhere between 30 and 60 

miles an hour, and hitting them on the 

run. But it was really quite simple—you 

just have to pull enough lead to hit a 

moving target and you have to aim in 

the right place. But the fact that I elected 

to employ them unguided, because there 

wasn’t time to set up the guidance, led me 

to have to make two passes, and led me 

to take significantly more risk. So when 

it comes to lessons learned, our PGM 

enhancements have to do with not only 

tightening the circle, but it is also very 

much an issue of tightening the kill chain 

by improving the employability of the 

PGM—making them more responsive, 

making them less operator intensive, while 

still allowing for execution of the operator’s 

intent. Increased target processing speed 

begets improved accuracy begets greater 

situational awareness which results in 

more bombs on target, and a much safer 

mission.89

 All of this also relates to time, which is a 

critical aspect of the PGM system. Time is 

not just speed. In PGM employment, it is the 

correct time, defined as when you will achieve 

the most desired effects, being able to respond 

when a target of opportunity presents itself, 
Tightening the Circle

45

assisting in a ground attack or other joint 

operation, or when you will negate or at least 

minimize any unintended consequences or 

collateral damage. We tend to think of PGM 

speed as being the be-all and end-all, but while 

faster is indeed better, time is a very complex 

element of precision. It is the correct time, 

whether it be the immediate moment or having 

a sensor system provide information to allow 

use of the weapon to its best advantage. And the 

way we will arrive at the use of future PGMs 

at just the right time is through research.

 Research is the foundation for future 

weapons systems, and it is the driver behind 

enhancements of existing weapons. For 

example, an AFOSR basic research program 

grant contributed significantly to PGM 

accuracy when new mathematical architectures 

for control algorithms were used in field 

upgrades of the JDAM. The result was a 

significant increase in precision, as JDAM 

was declared the most effective munition 

recently used in Afghanistan and Iraq.90

 Other areas where improvement can 

radically enhance PGM performance include 

the development of the Small-Diameter 

Bomb (SDB). In 1995 the commander of Air 

Combat Command asked the AFRL Munitions 

Directorate if a way existed to increase the 

bomb payload on our fighter aircraft so that 

Graphic and data (1943–1999) courtesy of Dr. David Mets, School of Advanced Airpower Studies, Maxwell AFB, AL; 2004 

data courtesy of AFRL/MN, Eglin AFB, Florida.
The Limitless Sky

46

more munitions could be carried to target with 

a commensurate reduction in the number of 

sorties required.91 The munitions scientists’ 

and engineers’ starting philosophy was to use a 

small warhead, in this case, a 250-pound bomb 

with only 42 pounds of explosive, that would 

provide the same effectiveness as the JDAM, but 

with enhanced guidance. If one could improve 

the precision of a small bomb, plus improve its 

penetration, one would have a force multiplier.

A fighter weapons platform with numerous 

small bombs could surpass the capability of 

two larger, in this case JDAM munitions. The 

resulting SDB owes its capability to a tritonic 

shaped nose to aid penetration coupled with 

guidance laws that zero out “angle of attack on 

impact” to optimize its penetration. In addition, 

these smaller warheads are independently 

targetable, allowing the attacking aircraft to 

ripple a large number of SDBs over a wide target 

area, with each bomb seeking its own (World 

Geodetic System 1984) loaded target location. 

Through range extension technology, which 

includes its compressed design, the SDB flight 

envelope has increased at least three times over 

JDAM distances. The result is that, from a single 

launch point, a B–2 can launch up to sixty-four 

independently targeted SDBs, thus becoming 

a force multiplier that can reduce sortie rates 

and enhance platform survivability.92 Future 

versions of the SDB may have extended-range 

capability with pop-out wings and the ability 

to loiter or autonomously seek out targets.93

PGMs that seek out their targets are now on the 

drawing board and offer unique capabilities. 

 With regard to autonomous loitering 

Automatic Target Recognition (ATR) platforms 

now in development, fielded results must be 

driven by the desired concept of operations and 

capabilities put forth in Air Force operational 

doctrine. ATR, in particular, is a very complex 

issue with numerous variables, and it is a 

system that may be easily countered. Clearly, 

autonomous loitering PGM systems face key 

challenges that have yet to be resolved, the 

critical one being target identification. Targeting 

can be thought of as a fifth variable in the 

four-element, precision-guided-munition-time 

process. Throughout the history of PGMs, 

targeting has been critical to the process, but 

with the proposed introduction of autonomous 

weapons, proper identification of the target 

becomes an absolutely critical burden: What 

is it that you are going to hit? Currently we 

rely on before-the-fact intelligence, not on realtime target identification, except when humans 

visually identify targeting opportunities. Thus, 

the critical link in the autonomous weapons 

platform will be identification to prevent 

unintended error. To emphasize just how 

imperfect this part of the process is, one need 

only be reminded of the JDAM attack on the 

Chinese embassy in Belgrade on 7 May 1999 

during Operation Allied Force. Throughout 

Allied Force, the JDAM was employed only 

from B–2s, and it was very effective; for 

example, it hit precise intersections at targeted 

airfields. But the B–2/JDAM combination 

was also used in the strike on what we did not 

at the time know was the Chinese embassy. 

In this case, the JDAM hit exactly where it 

was supposed to hit. It went exactly where 

it was told to go, but it was told to go to the 

wrong place. The lesson here is that precision 

weaponry is much more than precision 

delivery: it is precision identification. Getting 
Tightening the Circle

47

a PGM precisely to the wrong location can 

undo what a thousand PGMs accomplish 

that get precisely to the right location.

 One of the state-of-the-art ATR systems now 

in development must address this challenging 

targeting issue, and a significant amount of 

past and ongoing research will determine its 

final capabilities. Like their predecessors, ATR 

systems have a rich heritage that derives from 

significant basic research discoveries and the 

enhancement of proven technology—primarily 

miniaturization, improved data processing 

speeds, and munitions enhancements. 

Autonomous PGM Research Timeline94

Basic Research ■ LADAR ATR (algorithms), 2000–present

■ Modern Control Theory AP (theory), 

 early 1980s ■ Multimode Warhead 

 (phenomenology, theory), early 1980s ■ Cooperative Attack (theory, 

concepts), 1999–present

■ Agile Autonomous Control 

 (theory, concepts), 2000–present

Applied Research ■ Advanced Submunition 

 Warhead Technology, 1995–1998 ■ LADAR Technology, 1994–2002

■ Automatic Target Recognition 

 Algorithms, 1994–2002 ■ Small Turbojet, early 1990s

■ Multimode Warhead, 

 mid-1980s–early 1990s ■ Triservice IMU (HG–1700), 1989–1992

Advanced Research ■ LOCASS (glider-armor), 1991–1994

■ LORISK (SEAD/TBM), 1995–1997

■ PLOCASS (powered), 1999–2002

■ MALD engine, 1996–1998

 The ATR PGM is only part of the future 

for PGM platforms. New and varied key 

technologies promise much more. Munitions 

now on the drawing board can be described as 

“O” technologies: nano, info, bio, robo, micro, 

meso, and macro.95 These technologies support 

the drive toward miniature systems with the 

potential for innovative payloads that enhance 

maximized load-out of delivery platforms and 

lead to low collateral effects.96 For success in 

these effects-based targeting initiatives, R&D 

will focus on five areas: compact energy sources; 

mobility technology; miniature guidance 

technology; operations/communications 

technology; and manufacturing technology. 

With that as background, we can briefly 

explore the issue of future PGM development 

by keeping in mind two observations: we are 

now getting very target-specific, and a PGM 

doesn’t always have to be something that 

blows up.97 In fact, one could characterize 

this newapproach as a niche-based targeting 

system. These airborne-delivered PGMs would 

contain a sophisticated guidance system and 

a very tailored terminal effects package. For 

example, the weapon would arrive at its target 

area assisted by advances in aerodynamic 

shaping based on smart materials and structures 

and utilizing MEMS. Plasma or morphing 

technology would optimize the cruise conditions 

Figure 15. The autononous loitering Automatic Target Recognition (ATR) platforms now in development may share very 

little, from technical standpoint, with the 1918 Kettering Bug, 

but it is a direct decendent nonetheless.
The Limitless Sky

48

such as ATR, which allows a PGM to choose 

the correct target from a set of potential aim 

points. Today, much of this research has 

transitioned to the applied research arena.99

 One area under development, which will be 

an outgrowth of guidance and control initiatives, 

concerns Micro Air-Delivered Munitions, 

which allows small munitions to adapt to their 

surroundings in a relatively crowded urban 

environment or be able to penetrate cave or 

underground complexes. These micro-platform 

systems could operate covertly to navigate, 

sense, map, reconnoiter, and attack targets 

from behind enemy lines. Specific missions 

would include the neutralization of critical 

underground nodes to compromise facilities 

containing hazardous chemical, biological, 

and nuclear weapon storage. They could also 

be used in an area dominance role to aid in 

searching a target area and identifying and 

defeating a specific target. In a bomb damage 

assessment role they would collect and transmit 

data for weapon detonation assessment in real 

time. Some of the many warfighter benefits 

that would accrue from the insertion and 

use of micro weapons and munitions include 

improved target intelligence, covert disablement 

of targets, remote mapping, long-residence 

time-on-target, controlled collateral damage, 

and a cost-effective weapon system.100

 Not only warfighter benefits accrue from 

scientific advances in guidance and control. 

Dual-use opportunities are numerous: mapping, 

medical imaging, data compression, vehicle 

identification, collision avoidance, autonomous 

landing systems, commercial navigation, 

environmental monitoring, and intelligent 

highway systems, to name but a few.101 The 

of an air vehicle based on flight regimes and 

atmospheric conditions. Once on the ground, 

the delivery vehicle itself would release a 

multitude of small PGMs that could themselves 

either fly or maneuver on land and arrive 

at preprogrammed destinations to perform 

reconnaissance or weapons functions based 

on immediate or future requirements. Further 

out on the technology horizon is an air vehicle 

that, once it lands, would not release seeker 

PGMs, but would itself morph into an entirely 

different vehicle utilizing many-structured 

or biomimetics-based materials to become a 

multifunctional PGM. As far as future terminal 

effects are concerned, once they arrive at their 

target location they could be electronically 

debilitating, structurally corrosive, an auditory 

or olfactory weapon, or reconnaissance-specific.98

 The guidance and control of PGM weapons 

is the critical issue. Political, environmental, and 

moral considerations, not to mention critical 

warfighting requirements, place great demands 

on our scientific munitions-related community. 

To answer these demands, the basic research 

community is providing the required building 

blocks based on nanoelectromechanical and 

microelectromechanical systems, biomimetics, 

and intelligent systems research. For example, 

future nanosystems will provide accelerometers 

and gyroscopes based on micromachined 

inertial measurement devices. MEMS research 

will provide the required microswitches for 

superior low-cost millimeter-wave antenna 

elements. Biomimetics, by reverse engineering 

biological processing systems (using insect 

models) will develop new image-processing 

techniques. Intelligent systems research will 

support autonomous munition development 
Tightening the Circle

49

fact is that the U.S. scientific community 

does not own the monopoly on advanced 

technological solutions. Take, for example, 

the existing unique lattice, grid-fin steering 

assemblies employed on some current and future 

PGMs. These box kite–like fins enable a large 

amount of lifting surface to be packaged in a 

compact space, and they have an interesting 

background. They would not have been possible 

without the developmental grid fin-work 

accomplished by Russian and Soviet scientists 

over the past forty years, who ultimately 

shared them with their munition designer 

counterparts at the Eglin munitions lab.102

 In looking back over the long, evolutionary 

history of guided-munition development, one 

is indeed struck by what has been a 100-year 

process — from Karl Jatho’s pilotless biplane 

of 1903 to the autonomous PGM-equipped 

weapons in development today. While much has 

changed, much has not. For instance, PGMs 

will not replace the requirement for an areabombing capability. Area bombing is not the 

indiscriminate evil some portray it to be. There 

will continue to be large target areas such as 

facilities, fielded forces, and other nonspecific 

targets that could be better exploited with 

area munitions. A related issue dealing with 

the moral aspect of area bombing is an even 

greater moral obligation and burden placed on 

U.S. forces with regard to PGM employment. 

Given the television showcased capabilities of 

PGMs in recent conflicts, the American public, 

and to an even greater degree, the rest of the 

world, may be utterly convinced that anything 

we bomb, we bomb on purpose, that there are 

no accidents of war, that if we hit a nonmilitary 

target, we were aiming for that target. As such, 

this is one aspect where our PGM success has 

highlighted our failures. Our success is a twoedged sword, and we must be constantly aware 

of both edges because heightened success in 

the employment of PGMs will only increase 

the pressure to perform always to perfection. 

We will, though, look to the continued results 

of the scientific community to help us toward 

that end, always striving to better perfect 

this new “revolution in warfare” that they 

made possible, and it will be a continuing 

revolution.103 What Lieutenant General Buster 

C. Glosson wrote in 1993 is still valid today:

Any way you cut it, we will need smart 

airplanes with smart weapons to meet the 

challenges of the future. However, during 

this period of frenetic change, we would do 

well to remember King Solomon’s counsel 

that “wisdom is more important than 

the weapons of war.” He is right. People 

are always more important. All the socalled smart weapons in the world could 

not distinguish their own tail fins from 

the Pentagon if it were not for the smart 

people who develop, build, maintain and 

program them [and] they are already 

developing the weapons we will need to 

win the next one.104
Enlisting the Spectrum for 

Air Force Advantage:

Electro-Optical/Infrared (EO/IR)

Ruth P. Liebowitz

Edward A. Watson

Major General Stephen G. Wood, USAF
Abstract

The electro-optical/infrared (EO/IR) wavelength in the spectrum 

has provided a versatile sensing tool for military use since at least 

the 1950s. EO/IR imaging technologies have contributed significant 

capabilities to meet Air Force requirements for detecting, identifying, and 

tracking military targets. The EO/IR has proved to be a versatile sensing 

tool for many applications since the 1950s. Although each system and 

platform utilizing EO/IR sensors requires a different design, all share 

some basic technical parameters and components.

This paper describes the EO/IR technologies developed to achieve 

current Air Force capabilities. It focuses on infrared thermal imaging 

systems and places the development of these technologies in the context 

of changing political-military conditions. It also includes a discussion by 

an Air Force operator of his experience with an EO/IR application of 

growing importance: sensors on unmanned aerial vehicles.
The Limitless Sky

54

INTRODUCTION

 Seven years ago we could not begin to imagine 

the level of impact that placing an electro-optical/

infrared (EO/IR) camera on a medium-endurance, 

remotely piloted vehicle would have on combat 

aviation. The Predator weapon system has 

heralded a revolution as significant as any since the 

Wright brothers’ first flight. It is through imaging 

technologies that we have been able to expand our 

situational awareness and capture knowledge for 

real-time use as well as for postflight analysis. The 

unique characteristics of the EO/IR spectrum have 

provided us with very precise information upon 

which we have based a myriad of decisions. The 

unmanned aerial vehicle (UAV) known as Predator 

(see figure 1) provides a microcosm wherein we can 

see the synergy of imaging technology and aviation.

 The current success of the imaging systems 

onboard the Predator is based on a long history 

of research and development. For the last fifty 

years, the Air Force has funded broad research on 

remote sensing in the visual wavelengths of the 

spectrum and beyond the visual, that is, the EO/

IR range, in order to gain this kind of advantage. 

EO/IR technologies emerging from this research 

have been developed into sensor systems. These 

systems provide the Air Force with a powerful 

tool for detecting, identifying, and tracking 

military targets. For many years, these sensor 

systems were a force multiplier for fighters and 

bombers before they assumed a dramatic new role 

on UAVs. This paper will give special attention 

to one subset of electro-optical systems, namely 

infrared cameras, because they have contributed 

a key capability for the military the ability to 

conduct nighttime operations and because their 

realization has involved major technical challenges.

THE HISTORICAL CONTEXT

 The original impetus for research and 

development programs in the EO/IR area came 

from the experience of World War II. The 

leaders of the Army Air Forces were 

impressed with the importance of 

science in the victory of the Allies. 

They cited the key roles of radar 

and the atomic bomb, to name two 

of the most important products of 

science enlisted for the war effort. 

In planning for the future, Army 

Air Forces leaders organized a 

program of long-range research 

and development to continue to 

exploit the advantages of scientific 

knowledge to help meet military challenges of 

the future. Late in 1944 the Army Air Forces’ 

General Henry H. (Hap) Arnold observed to 

his science advisor, Dr. Theodore von Kármán, 

As yet we have not overcome the problems of 

great distances, weather, and darkness.1

 For the 

new Air Force (as of 1947), these deficiencies 

translated into efforts toward achieving three 

Figure 1. The Predator.
Enlisting the Spectrum for Air Force Advantage

55

ambitious goals: a greatly extended range for air 

operations, an all-weather flying force, and the 

ability to conduct round-the-clock operations. 

This last goal, nighttime capability, provided a 

clear rationale for investing in research in the 

EO/IR wavelengths of the spectrum. EO/IR 

systems, along with radar and lasers, became 

the three main prongs in remote sensing for 

military applications. Support for research 

in these areas was also informed by a more 

general goal, namely, to limit U.S. casualties in 

warfare. This axiom, as articulated by General 

Arnold late in 1944, stated: “It is a fundamental 

principle of American democracy that personnel 

casualties are distasteful. We will continue to 

fight mechanical rather than manpower wars.”2

 The priorities of the Cold War reinforced 

this initial impetus toward advanced technology 

for military capability. Ongoing concern 

about numerical superiority in the Soviet 

bloc sustained the strategy of reliance on 

the countervailing resources of science and 

technology. In the 1990s, the first post Cold 

War decade, this strategy continued, but it was 

now augmented with information superiority to 

provide an asymmetric advantage against threats 

posed by terrorism and regional instability. 

Infrared remote sensing offered promise for 

operations in total darkness, a capability much 

sought-after during the Vietnam War as a 

means to interdict enemy resupply efforts and 

supply routes. Infrared remote sensing also had 

a role in plans to hold off potential assaults 

from the Soviet bloc. During the first Gulf 

War it provided a tool for dealing with mobile 

Scud missile launchers. Its ability to identify 

hot spots in aircraft, tanks, motorized vehicles, 

and facilities (see Figure 2) is of continuing 

importance for targeting, as is its ability to 

be used in battlefield conditions of smoke or 

dust (though not in rain or fog). Since infrared 

cameras are passive systems, they do not 

transmit signals that an enemy could utilize 

for targeting. Though infrared imaging systems 

lack the vast detection range and all-weather 

capability of radar, their strengths, when 

used for reconnaissance missions, are higher 

resolution and more naturally appearing images. 

Therefore, they have found application in the 

identification and verification of targets close-in.

 Air Force supported work in infrared 

technology has focused on developing 

capabilities in navigation, targeting, and 

reconnaissance as a force multiplier for airborne 

operations. Since the later 1940s, laboratories 

run by the service have conducted ongoing 

research programs to investigate materials and 

designs suitable for infrared imaging systems, 

to specify atmospheric conditions relevant to 

“seeing” at different wavelengths, and to solve 

Figure 2. Thermal imagery of a truck and a van. Since a small 

amount of infrared light depends on the temperature of the 

object, brighter features represent hotter parts of the object.
The Limitless Sky

56

technical challenges in the processing and 

display of infrared data.3

 Historically, airborne 

infrared programs have been centered at 

Wright-Patterson AFB’s Avionics Laboratory, 

with significant work done at Hanscom 

AFB’s Electromagnetic and Geophysics 

Divisions and at Griffiss AFB’s Rome Air 

Development Center (RADC) (later named 

Rome Laboratory).4

 In the current, consolidated 

Air Force Research Laboratory, most of these 

programs now reside in its Sensors Directorate.

TECHNICAL CHALLENGES

 To achieve the desired capabilities for the 

warfighter, a number of important technical 

challenges had to be met. The development 

since World War II of detector technology for 

infrared systems has been a long and difficult, 

though eventually highly successful, process. 

As with radars and lasers, the design of the 

instrumentation requires carefully considered 

tradeoffs to optimize the system for different 

operational configurations. Sophisticated image 

processing done by computers is sometimes 

desirable to enhance particular features of 

the image and, in some cases, necessary to 

compensate for limitations in the optical 

instrumentation. With time, efforts have 

focused on combining infrared, radar, and 

laser remote-sensing technologies in suites 

of sensors to augment their capabilities and 

allow greater operational flexibility. Studies 

are currently underway on integrating and 

fusing data from different remote-sensing 

instruments. Another major technical challenge 

has been the realization of techniques to 

improve the discernment of targets in the 

infrared against their natural backgrounds. 

Much progress has been made in this area 

since the 1960s, and the results of this 

research have been packaged for ease of use 

by the operators. Some aspects of the infrared 

military research have given rise to significant 

spinoffs for scientific and commercial use.

DETECTOR TECHNOLOGY OF 

INFRARED CAMERAS

 The development of detector technology 

for infrared imaging systems has emerged in 

roughly three stages, with full flowering not 

attained until the 1980s and 1990s. Before this, 

in the early 1950s, the Air Force had adapted 

a direct, heat-seeking infrared technology for 

use with air-to-air missiles on fighter aircraft. 

The early versions of the AIM9 Sidewinder, 

which was first fired successfully in September 

1953, typically had only single detectors and did 

not form an image per se; rather, the receiver 

contained a spinning reticle that modulated the 

signal the detector saw. This modulation was 

used to guide the missile to its target. Later 

versions of the Sidewinder, however, began to 

use infrared imaging technologies to make the 

missiles more robust from longer ranges.5

 It is the detector technology that has 

essentially defined the three generations of 

infrared cameras. The cameras share the 

characteristic of all electro-optical systems 

of being sampling imagers, in contrast to the 

continuous vision of the human eye or of typical 

film cameras. Electrical signals generated by the 

detector are relayed to some form of computer 

for processing and display. Sampling methods, 

however, have been quite varied. First-generation 

systems generally consisted of a single detector. 

Scan mirrors were used in the optical system 
Enlisting the Spectrum for Air Force Advantage

57

Electrical

connections to 

output

Light-sensitive

area of pixel

to scan the detector over the 

required viewing angle. Usually one 

mirror would scan rapidly in the 

horizontal direction while a second 

would scan more slowly vertically. 

A complete scan of the viewing 

angle had to be made within the 

time allotted to a single frame, 

about one-thirtieth of a second, 

thus limiting the number of samples that the 

imager could make. This also made the imager 

less sensitive because the detector could not 

gather large amounts of light by staring for a 

very long time at a single point in the scene.

 Second-generation infrared cameras made 

use of linear arrays of detectors, that is, a line 

of detectors as shown in Figure 3. Many points 

in the scene could be sampled simultaneously. 

Use of a linear array greatly reduced scanning 

requirements, since only the single, slower 

scanning mirror was required to scan the array 

in one direction. The sensitivity of the array 

was also better because each detector could 

stare at a point in the scene for a longer period. 

This infrared camera typically had two fields 

of view: the wide field of view was for target 

acquisition; the narrow field of view provided 

a magnified view of a smaller portion of the 

image, providing better resolution for target 

identification. Mounted on fighter aircraft with 

a forward view for navigation and targeting, 

their orientation gave them the nickname 

FLIRs (forward-looking infrared systems).

 The Avionics Laboratory at Wright-Patterson 

was primarily responsible for developing this 

generation of infrared cameras as part of its 

broader work on technology for targeting and 

weapons guidance in air-to-ground scenarios.6

FLIRs were an important component for the 

smart weapons that emerged in the decade 

after the Vietnam War. Seekers for an air-toground missile such as the AGM65 Maverick 

meant a television camera in its early versions, 

but later versions employed infrared cameras 

to allow performance at night and better 

operation through battlefield obscurants such 

as smoke and dust. FLIRs were frequently used 

in conjunction with laser designators for bombs 

equipped with laser guidance systems. One 

challenge accompanying this new technology 

was to get it integrated into fighter avionics 

and platforms. Sometimes the sensors were 

placed inside the airframe; more often they 

were suspended below it in pods. Another 

related challenge, especially in the years when 

FLIRs were first introduced, was to acquaint 

pilots with the new technology and train them 

so they were comfortable with using it. By the 

1980s, the Air Force’s main fighter aircraft like 

the F4E were carrying EO/IR systems such 

as Pave Tack along with their munitions. The 

newer Low Altitude Navigation and Targeting 

Infrared for Night, or LANTIRN as it is 

usually called, which was under development in 

Figure 3. Schematic of a linear detector array. The detectors can 

be electrically connected to the output circuitry through their 

free sides.
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58

Light-sensitive

Pixel area of pixel

Spacing

the 1980s, was a two-pod system (see Figure 4). 

LANTIRN’s AAQ13 navigation pod contained 

a wide-field-of-view FLIR and a terrainfollowing radar. Its AAQ14 targeting pod 

included a targeting FLIR, a laser designator/

ranger, an automatic tracker, and an automatic 

handoff of the target to a Maverick missile.7

 Third-generation infrared cameras are known 

as staring-sensor systems. They made use of 

two-dimensional arrays of detectors (Figure 5) 

in which each pixel could now stare at a single 

point in the image for an entire frame time. 

This made the third-generation system more 

sensitive. In addition, the need for a mechanical 

scanning system was eliminated, making 

the optical system less complicated and less 

expensive to maintain. The intent of these new 

cameras was to achieve a parallel technology 

to home video-camera technology at infrared 

wavelengths. This approach had been tried 

earlier in the first two decades after World War 

II, but it failed because of an inability to achieve 

sufficient contrast in infrared scenes. The new 

design, first proposed by Air Force scientists at 

the Electromagnetic Division at Hanscom and 

at RADC in 1973, led to a pioneering platinum 

silicide camera, the first staring camera that 

could be used effectively for infrared thermal 

imaging.8

 The camera held the promise of being 

able to detect very small variations 

in temperature and to yield images 

with better resolution. Key to its 

success was the use of the new 

combined material, platinum silicide 

(PtSi), for the detector substrate. 

It offered characteristics that could 

help offset the difficulties with 

nonuniformities in the arrays and 

other sampling issues inherent 

in staring systems. By the 1990s, 

infrared cameras were able to 

detect extremely small variations in 

temperature and provide high-resolution images.9

 Improvements to the staring camera have 

Figure 4. LANTIRN – An F–16C/D Fighting Falcon 

fighter plane with LANTIRN pods mounted externally 

beneath the body of the aircraft. On the left, the targeting pod; 

on the right, the navigation pod.

Figure 5. Schematic of the detector array used in the electro-optical imaging systems. Each detector is made of a light sensitive 

material in the wavelength region of interest. The size of each 

detector (small is better) and the number of detectors in the array 

(larger is better) affects the quality of the image produced by the 

array. Arrays for visible light tend to have much smaller pixel 

sizes and much larger numbers than arrays for infrared light.
Enlisting the Spectrum for Air Force Advantage

59

continued, leading to further improvements 

in detector materials and in techniques for 

dealing with nonuniformities in the array 

and sampling issues. Additional research on 

other materials such as indium antimonide 

and mercury cadmium telluride has produced 

infrared cameras with increased sensitivity at 

many different wavelengths of the infrared. 

A technique called microscanning has been 

developed to overcome the effects of sampling. 

In the microscan process, several images are 

collected, but each is shifted a fraction of a 

detector element with respect to the other 

images. By appropriately recombining these 

images, a greatly enhanced image can be 

produced.10 The nonuniformity of staring 

arrays can be dealt with to some extent by 

post-detection processing, which produces an 

enhanced final image for display. To compensate 

for the variations in each detector element, 

periodic calibrations are performed and are 

applied after the image is detected to remove 

the effects of nonuniformity. Additional postdetection processing can include techniques 

to remove blurring and remove other effects 

associated with sampling by the detector array. 

Some of these processing techniques are quite 

computationally intensive and can be applied 

only after the imagery has been gathered. Other 

techniques are simpler and can be applied as 

the imagery is gathered and displayed to the 

operator in real time. The increasing capability 

for processing images has also enlarged the 

options for their display to the operator. For 

reconnaissance applications, the images have 

tended to be transmitted as stills. When the 

processing before display keeps pace with the 

sampling rate of the camera, however, a stream 

of images with seeming continuity can be 

created. This mode of transmission has led to 

creative new operational uses of the technology.

 The extent of technical achievement in 

infrared technology can be appreciated 

by comparing infrared cameras with the 

technology for electro-optical systems that use 

visible light. The latter include such devices 

as low-light cameras and night vision goggles, 

electronic cameras, and television. They use 

low-level visible, or near visible, light, such 

as moonlight or starlight as an illumination 

source, and then amplify it. In contrast to these 

visible systems, which work off reflected light, 

infrared cameras operate by receiving thermal 

light emitted by an object on the basis of its 

temperature (see Figure 2). The development 

of infrared cameras has been more technically 

challenging in a number of ways. Because the 

common glass used for fabricating the optics 

for visible systems does not transmit in much 

of the infrared region, designers of infrared 

systems have had to use other materials. These 

can be more difficult to work with, possibly 

being water-soluble or toxic. Similar issues exist 

with the detection component. Detector arrays 

for visible light are typically based on silicon, 

the material from which computer chips and 

most other electronics are fabricated. After 

many years of huge commercial investment, 

silicon is a very well-understood material. 

Military applications for low-light cameras have 

leveraged off this investment. In contrast, the 

materials for infrared detectors are typically 

made from material alloys such as mercurycadmium-telluride, platinum silicide, and 

indium antimonide. The military has devoted 

long-term resources to research alloys, but 
The Limitless Sky

60

the utilization of alloys has not reached the 

same level as the utilization of silicon. Lastly, 

unlike low-light cameras, the detectors for 

infrared cameras and their surrounding area 

have to be cooled to very low temperatures 

to reduce background emissions. Only with 

recent advances in cryogenic technology 

has this become less of a practical issue.

 By the 1990s, operational versions of PtSi 

cameras were being installed on Air Force 

airborne platforms, including the B52 bomber 

fleet.11 They also became elements of suites of 

sensors for new platforms being developed. 

An array of next-generation sensor systems, 

including electro-optical systems primarily 

in the infrared spectrum, was reported in the 

planning for the Joint Strike Fighter.12 The 

two endurance UAVs, the Predator and the 

Global Hawk, which the Air Force has been 

managing since the mid-1990s, utilize the latest 

versions of infrared cameras. The Predator, a 

medium-altitude endurance UAV, flies under 

25,000 feet. It carries electro-optical systems 

configured for this altitude, tightly packaged 

into a small space. For the first version of the 

Predator to go operational, the suite of sensors 

included a synthetic aperture radar and a 

combined EO/IR camera. The video footage 

from the sensors is sent down live, in real 

time.13 The Global Hawk, still in development 

and acquisition, is a longer-standoff platform 

that flies at high altitudes (greater than 60,000 

feet). This platform can carry several different 

types of sensors including synthetic aperture 

radar and visible electro-optical and infrared 

sensors. The infrared sensor is based on an 

indium antimonidestaring array sensitive in 

the midwave infrared band. The visible sensor 

is a Kodak detector array based on silicon.

FUTURE DIRECTIONS

 The capability of electro-optical systems 

continues to advance. Research in active 

electro-optical systems is receiving considerable 

attention. These can complement the use 

of infrared cameras under obscured visual 

conditions, such as clouds, dust, and smoke. 

In electro-optical systems, a laser is used as 

an illumination source. It is analogous to 

conventional radar in which radio frequency 

energy is directed toward an object and the 

backscattered energy is collected. A primary 

advantage is its ability to range gate. A laser 

pulse is directed toward the object of interest, 

but the camera in the receiver is kept off while 

the pulse travels to the object and the scattered 

light returns. Just before the pulse returns 

to the receiver’s optical system, the camera is 

turned on. It therefore captures light reflected 

only from the object of interest and not light 

scattered from any intervening obscurant. 

While these obscurants do reduce the amount 

of light that is returned to the receiver, they do 

Figure 6. Example of laser-illuminated imagery. Note that 

because the laser sends out the light in pulses, only the region 

about the object is illuminated. This allows the camera to 

ignore scattered returns from intervening obscurants such as 

smoke and dust.
Enlisting the Spectrum for Air Force Advantage

61

REFLECTED

SUNLIGHT

RADIANCE 400nm

Blue Green Red Near

Infrared

Shortwave

Infrared

Microwave

Infrared

Longwave

Infrared

500 600 700 1100nm 3000nm 5000nm 14000nm

THERMAL

EMISSION

not affect the image resolution greatly (Figure 

6). Other features of active electro-optical 

systems include the ability to measure many 

different features of an object, including its 

vibration, color, and surface characteristics.14

TARGET/BACKGROUND CONTRASTS

 In fielding these generations of electrooptical and infrared systems, one major 

technical challenge has been to understand 

the atmospheric channel through which 

images of targets present themselves to the 

optical system. The passage of light can be 

affected by attenuation because molecules 

and particulates constituting the atmosphere 

absorb or scatter the propagating light. The 

attenuation at some wavelengths is so great that 

it prevents their use in electro-optical systems.

Similarly, atmospheric optical turbulence the 

same process that causes stars to twinkle 

can also blur images produced by imaging 

systems. To improve the operational use of 

these systems, Air Force researchers at the 

Air Force’s Geophysics Division at Hanscom 

developed a set of atmospheric transmission 

models based on atmospheric properties 

and meteorological variables. The models, 

which have become standard Department of 

Defense (DoD) and industry codes under 

the names LOWTRAN and MODTRAN, 

give transmittance/radiance predictions 

for electro-optical and infrared systems.

 In this area also, infrared imaging systems 

pose particular problems. The infrared target/

background contrasts for an infrared image 

can be quite variable. The image is determined 

by a set of sometimes complex relationships 

involving temperature differences between the 

target itself and objects surrounding it, and the 

background is determined by atmospheric and 

meteorological conditions. Unexpected reversals 

of anticipated target/background contrasts can 

sometimes occur (see Figure 8). Early in the 

Vietnam War, the Air Force took measurements 

of remote sensing in the infrared in Thailand 

Figure 7. The light reflected and emitted from a “typical” 

object is shown here. The wavelength scale at the bottom has 

been altered to move easily show the visible portion of the 

spectrum. Note that most of the emitted light is in the long 

and mid wave infrared, while most of the light in the visible 

portion of the spectrum is due to reflected sunlight. The transmission characteristics of the atmosphere are impressed on the 

curves. The lack of light near 3,000nm, 5,000-8,000nm, and 

at various portions in the near and short wave infrared is due 

to atmospheric absorption in these regions.

Figure 8. A T–62 tank against a soil background presents a 

very different image under clear, overcast, windy and rainy conditions. Variations in the optical and meteorological environment for a mission result in different target acquisition distances 

for a specific electro-optical system.
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62

to assess the expected performance of early 

sensors in the tropical jungles of Southeast Asia. 

Similarly, when military attention returned to 

Central Europe in the 1970s, an extensive set 

of measurements was made there. In the 1980s 

the atmospheric transmission models were 

combined with weather and infrared target/

background data to create a set of electro-optical 

tactical decision aids. These tools enabled 

pilots to compare maximum acquisition range 

for a variety of smart weapons under given 

atmospheric/meteorological conditions so that 

they could select the best munitions package for 

a mission.15 Another tool both for operations 

and for training simulated scene generators 

was developed to assist Air Force operators 

in visualizing their targets in the infrared. 

A current version of this tool, the Infrared 

Target-Scene Simulation Software, was recently 

adapted for use in urban target areas of interest 

in Iraq.16 The extensive research conducted 

in the EO/IR area has produced effective 

technologies that maximize system performance.

SPINOFFS

 The detector technology for the infrared 

staring cameras has some nonmilitary 

applications, particularly in scientific fields 

that require low-cost and high-precision 

measurement systems. One of the most exciting 

uses is in infrared astronomy where the infrared 

staring cameras provide a tool to study regions 

of star formation.17 The technology is also 

being explored for possible uses in medicine. In 

industrial applications, a variety of applications 

employ thermal imagers, including process 

control, monitoring of high temperature 

components, energy management, checking for 

leaks in systems, and identifying weaknesses 

in structures. Thermal imagers are also finding 

their way into the automotive industry. A few 

models of cars now have a thermal imager as 

an option which can be purchased to achieve 

improved road awareness at night. Because 

of cost considerations, these imagers usually 

employ simpler detectors that do not have 

to be cooled.18 The atmospheric research 

that supports the software for maximizing 

the performance of FLIRs has been widely 

utilized for civilian and commercial purposes. 

In particular, DoD’s atmospheric transmission 

code, LOWTRAN, has become ubiquitous.

CAPABILITIES FOR AIR FORCE 

OPERATIONS FROM VIETNAM TO 

KOSOVO19

 Early electro-optical and infrared imaging 

systems saw some utilization in the Vietnam 

War and then played a much more significant 

and expanded role in the first Gulf War. 

Beginning in Bosnia and continuing in Kosovo, 

Afghanistan, and Iraq, these systems have 

become central to the new capabilities in 

reconnaissance and battle management.

 In the Vietnam War, early versions of 

the AIM–9 Sidewinder missile were used 

extensively by fighter aircraft, and their later 

versions have been part of the inventory in 

succeeding campaigns (see Figure 9).20 The 

AC–130 gunships in charge of search and 

rescue operations in Vietnam carried what 

was very sophisticated equipment for the 

time: low-light-level television cameras, and 

early infrared sensors. Infrared detection was 

considered as the most promising technology 

to permit combat aircrew recoveries at 
Enlisting the Spectrum for Air Force Advantage

63

night. A limiting factor, however, was the 

technology’s inability to distinguish between 

the body heat of a downed aircrew and 

that of an enemy soldier.21 RADC installed 

airborne infrared systems to provide pilots 

with instantaneous data during reconnaissance 

flights. It also trained C47 gunship aircrews 

in the use of FLIRs. RADC’s base security 

programs in the Vietnam era utilized the 

infrared as one of their technologies.22

 By the time of the first Gulf War, a group of 

mature, infrared imaging systems had entered 

the Air Force inventory. There were the PAVE 

systems and advanced infrared versions of the 

AGM65 Maverick (Figure 10). Moreover, the 

new LANTIRN pods came into the operational 

inventory in the later 1980s and were carried 

on the F15E Strike Eagle and the F16C/D 

Fighting Falcon. They allowed the fighters to 

fly at low altitudes, at night, and under the 

weather to attack ground targets with a variety 

of precision-guided and unguided weapons. 

Like the Joint Surveillance Target Attack Radar 

System, or Joint STARS as it is usually called, 

LANTIRN was conceived as a counter to Soviet 

and Warsaw Pact capabilities and was then 

pressed into service in the Gulf War before it 

was fully ready for operational use. During the 

Gulf War, infrared imaging systems were used to 

good effect under conditions of adverse visibility. 

The capabilities of the LANTIRN 

targeting system resulted in the 

Tactical Air Command giving 

LANTIRN-equipped F15s the 

mission of finding and destroying 

mobile Scud missile launchers.23

 As of the mid 1990s, the latest 

electro-optical systems were to 

be seen on Air Force platforms 

beyond manned fighters, bombers, 

and gunships, marking the 

start of a new era. Equipped with video and 

infrared cameras, the Predator UAV began to 

assist with monitoring operations in Bosnia 

late in 1995 while still an Advanced Concept 

Technology Demonstration. The Global Hawk 

UAV (Figure 11) did not make its debut until 

2001 in Operation Enduring Freedom (OEF) 

in Afghanistan.24 Although the Predator was 

originally a Navy program, its sensor capability 

has been expanded since 1996 under Air 

Force management, and it has been put to 

dramatic new uses in situational awareness 

and battle management. These operational 

breakthroughs depended on the availability of 

advanced satellite communications technology.

 In its monitoring operations in Bosnia and 

Figure 9. From left, Airman 1st Class Bradley Smith, Staff 

Sergeant Jessica German and Airman 1st Class Gerardo 

Gonzalez hoist an AIM–9 Sidewinder missile before mounting 

it to an F–16 Fighting Falcon aircraft. The airmen are assigned 

to the 379th Expeditionary Aircraft Maintenance Squadron 

at a forward-deployed location in Southwast Asia supporting 

Operation Enduring Freedom. 

(Photo by Master Sergeant Terry L. Blevins)
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64

Figure 10. AGM–65 Maverick Launched from an F–16 

fighter. Courtesy of Raytheon Company.

then in the air campaign over Kosovo in the 

spring of 1999, the Predator was increasingly 

deployed in tandem with other Air Force 

platforms. In Bosnia, the Joint STARS E8 

aircraft cued the Predator to execute closer 

searches in difficult terrain. The use of a 

long-flying, unmanned vehicle, one that was 

inexpensive enough to be considered as an 

expendable, allowed much greater freedom 

in reconnaissance and surveillance. Later in 

Kosovo, both the Predator and the high-altitude 

U2 reconnaissance plane were electronically 

linked to Joint STARS. All were coordinated 

through command and control centers in order 

to conduct more effective search-and-destroy 

missions.25 The Air Force was to make an 

even more creative and far-reaching use of the 

Predator two years later in Afghanistan.

THE PREDATOR IN 

OPERATION ENDURING 

FREEDOM: AN OPERATOR’S 

COMMENTS26

 The integration of modern EO/

IR sensors on the Predator enabled 

us to follow every significant 

movement of our enemies in 

Afghanistan and Iraq. With the 

use of traditional intelligence 

collection, it could take hours or 

even days to process an image, 

assess that image, and then task a 

strike mission against the potential target. In 

times past, our adversaries observed this cycle 

and learned to move its equipment to survive. 

We were always one step behind and only lucky 

enough to destroy a portion of the targets we 

planned each day. This chess game of move 

and countermove provided our enemies with 

a tool to limit our combat effectiveness. The 

introduction of streaming video has changed 

the rules of the game and forced our enemy 

into a constant state of defense and fear. The 

use of live EO/IR feeds has provided a decided 

improvement and subsequent advantage. Our 

enemy has lost the sanctuary of time between 

when we observe his actions, assess the military 

viability of the target, and execute a strike.

 The original Predator aircraft, RQ1, used 

off-the-shelf cameras and commercial data links 

to send the picture instantaneously (we refer to 

this technology as streaming video), first to the 

pilot and sensor operator and then to anyone 

given the link receiver. Air Force Chief of Staff 

General John Jumper, then Commander, United 

States Air Forces in Europe, was handed this 
Enlisting the Spectrum for Air Force Advantage

65

Figure 11. Global Hawk unmanned aerial vehicle.

capability to augment his operations, including 

the tactical search for targets in Bosnia. The fullmotion, real-time, in-your-face video converted 

him to a UAV believer. General Jumper 

understood the real value of this capability and 

envisioned it could do much more than just 

watch the enemy. He saw its ability to not only 

locate potential targets, but to guide weapons 

to a precise location or provide other weapons 

systems with precision location 

data in a killerscout role, even laserdesignating the target for weapons 

delivered by other platforms. As 

the conflict was winding down, 

he took the first steps in fulfilling 

this vision by having the Predator 

outfitted with a laser targeting 

system aligned with the cameras. 

The rest of the vision was fulfilled as 

General Jumper saw the fielding of a 

complete weapons system when the 

Hellfire missile was integrated into the Predator 

(Figure 12). The fulfillment of this vision was a 

natural evolution of technology and operations.

 Predator aircraft are designated two ways: 

the RQ1 has a sensor ball equipped only with 

cameras; the MQ1 has a laser integrated with 

the cameras. We use the RQ1 with its 20-hour 

mission time to search for and track specific 

enemy targets. During the day, the primary 

cameras used are the electro-optical cameras 

with the 16- to 160-millimeter Zoom lens and 

the 955-millimeter fixed Spotter 

lens. This gives a National Imagery 

Interpretability Rating Scale 

(NIIRS) 7 rating at the 5 nautical 

mile slant range. Operationally 

this means I can track a specific 

a person or vehicle in moderate 

traffic beyond the range in which 

they can hear or see the Predator. 

Integrated in the sensor ball is 

the infrared camera capable of 

seeing in the 3 to 5 micron range. 

It has a six-stepped Zoom from 

11 millimeters to 560 millimeters. 

This gives a NIIRS 4 rating at the 5 nautical 

Figure 12. Demonstration of a Predator-launched Hellfire missile blowing up a tank.
The Limitless Sky

66

mile slant range. During the day this camera 

gives us the ability to find hot targets. It is 

the camera that watches through the night.

 The live video of the war produced by these 

cameras brought extraordinary situational 

awareness and was quite addicting. While 

I was the night director for the Combined 

Air Operations Center at Prince Sultan AB 

during OEF, I had the video displayed on the 

wall-sized situation display we called the Big 

Board. The capability to capture and display 

this time-critical information was invaluable 

to the decision-making process and was often 

the focal point for all those not engaged in 

critical taskings on the operations center 

floor. This was truly the first reality show.

 While all our systems and airmen performed 

admirably, we could not have done our job as 

well as we did without the Predator. The ability 

to watch the Toyota truck transporting Al 

Queada fighters as it drove through the city or 

watch in real time the rescue of the Christian 

Aid workers was indispensable to fighting 

the war. There was and continues to be more 

demand for Predator than we can possibly 

fulfill. We are striving to put the necessary 

resources in place to meet the need, but demand 

often outstrips availability. The Predator 

system has become a must-have capability. The 

demand for Predator support is pervasive. I 

was not the only one who absolutely relied 

on the video feed. For certain decisions, the 

National Command Authorities and often the 

President himself watched the video feed.

 Throughout the course of OEF, success 

brought new concepts of operation, which 

brought even more success. Before the war we 

worked hard to train our aircrews to direct 

fighter attacks on enemy positions. In one small 

city in Afghanistan, Predator crews located an 

Al Queada cell meeting in one section of a mudbrick complex. Even with precise knowledge of 

the target location, dropping a large conventional 

bomb could produce significant collateral 

damage and possibly kill a number of innocent 

civilians. To avoid this potential, an AC130 

gunship was called in to take out the apartment. 

In the middle of the night, the Predator pilot 

[sic] walked the gunner’s eyes from the town 

square, down narrow twisting alleyways, past 

numerous look-alike buildings, to the specific 

room, which was then precisely attacked. 

The surgical-strike capability of the gunship 

combined with the acute situational awareness 

and precision of the Predator had a tremendous 

synergistic effect. On another occasion, a truck 

with enemy fighters fled from a building that 

was under attack. They ditched their car and 

began walking across fields away from the truck, 

thinking they were safe. It wasn’t their day. 

Predator was watching every move they made, 

and one by one, our forces tracked them down.

 While we were regularly successful, It took 

time and skill to talk an attack aircraft onto a 

specific target at night. Some incredibly smart 

people asked the question, Why can’t we send 

the picture directly to the cockpit of the striker? 

This was the genesis of the Rover modification. 

Predator was modified to turn its line-of-sight 

antennae toward a specific AC130 or a receiverequipped ground party. The person needing 

the information received the signal and was 

rewarded with awesome situational awareness.

 During Operation Anaconda it was not 

uncommon for Al Queada fighters to hide in 

ambush, waiting for our advancing ground 
Enlisting the Spectrum for Air Force Advantage

67

forces. As our special operations forces moved 

in, it looked like someone had kicked an anthill. 

Our enemy crawled out of their caves and hid 

among the trees to try to cut our forces down. 

Predator was watching and tracking each 

enemy tree. As our forces advanced through 

the woods, Predator video was sent directly to 

the AC130 to highlight which tree belonged 

to us and which to the enemy. One by one we 

dismantled the ambush and took the stronghold.

 These are but a few of many successes that 

sparked the idea for another improvement, 

the MQ1 equipped with a laser designator 

and Hellfire air-to-ground missiles. All of you 

have undoubtedly seen the precise attacks 

Predator made. Military equipment hidden near 

mosques was taken out without disrupting the 

meeting going on inside. A specific car parked 

among other cars, one particular element in a 

group meeting at a camp, and one antenna on 

top of a building in Iraq were each precisely 

struck with no collateral damage. This is 

unprecedented accuracy never before seen 

in the history of modern combat. Predator 

has no unique technology, but the synergy 

of fielded technology has made it the poster 

child of revolutionary weapon systems.

 Improvements are still in the works for the 

MQ1. We have purchased a new sensor ball 

with expanded capabilities that will generate 

even better employment tactics. The infrared 

camera is significantly better than what the 

RQ1 had onboard. Not only has the image 

fidelity improved, full zoom instead of step 

focal lengths will be featured. The new sensor 

ball adds low-light television sensitive to the 

near-infrared spectrum, nominally 0.7 to 0.9 

microns. Predator will see the markers used in 

the night vision range. Image processing has 

been added to give point or area track capability 

as has a coast function that will keep the camera 

moving to aid in reacquiring a target that has 

become obscured. The video display will also 

fuse all the cameras onto one picture. In the 

automatic mode, it will select exactly what 

percent of electro-optical, low-light television, 

and infrared will be presented. These changes 

will keep the system locked on the target 

longer, especially as conditions deteriorate.

 The next-generation Predator, MQ9, will 

fly even higher and faster. The RQ1 typically 

flies at medium altitudes (~20,000 feet) at 

80 knots indicated. The MQ9 will fly up to 

50,000 feet in altitude at 275 indicated and 

will carry full-size weapons. The debate is 

ongoing over what camera system will be fielded. 

Initially, only still images are being targeted 

for collection. Based on operational experience 

with the MQ1, high-quality, affordable, motion 

video would be the operator’s desire. I would 

challenge academia and industry to work 

together and deliver the technology that will 

enable our continued battlefield dominance 

through superior situational awareness and 

precision weapons delivery capability.

CONCLUSION

 Since the 1950s, EO/IR technologies 

have evolved enormously. Infrared cameras, 

in particular, have achieved a key capability 

for the Air Force the ability to conduct 

operations in total darkness and this had a 

significant impact during the first Gulf War. 

Used in conjunction with radar and lasers, they 

provided an important tool for reconnaissance, 

navigation, and targeting. Upgraded FLIRs 
The Limitless Sky

68

have been mounted on each new generation 

of the Air Force’s fighter aircraft. To arrive 

at this accomplishment, extensive research 

in difficult materials was undertaken, and 

challenging design problems were surmounted. 

The increasing availability of computer software 

for sophisticated image processing has also 

been an enabler for infrared cameras. Similarly, 

supporting research into the performance 

of FLIRs under different climatic and 

meteorological conditions kept pace with U.S. 

engagements in different parts of the globe.

 Thus, by the 1990s, EO/IR technologies 

had been greatly advanced and constituted a 

significant force multiplier to the Air Force’s 

fighter, bomber, and gunship fleets. Although 

this development represented many steps 

forward and a few major breakthroughs, such as 

the creation of the PtSi staring-sensor camera, 

there was not a great element of surprise in this 

area until the mid 1990s when mature EO/IR 

technologies were incorporated into the Air 

Force’s new UAVs. As this combination was 

being used in Predator operations in Bosnia 

and Kosovo, the realization of its potential for 

expanded situational awareness emerged. The 

potential, of course, depended on capabilities 

offered by the latest satellite communications 

technology. From this beginning came the 

glimpse of exciting new scenarios for missions 

in which targets could be very narrowly defined, 

and the whole sequence of the action observed 

and assessed close-in, without risks to personnel. 

This gave impetus to further technical 

development of the Predator improving 

the EO/IR sensors, adding a laser for target 

guidance, and exploring the option of a missile 

to fire from the platform. At the beginning of 

the new century, the Air Force was beginning to 

realize some of these unanticipated possibilities 

in OEF, with an expectation of more to come.
From the Air:

Taking Radar to New Heights

Tom W. Thompson

Ruth P. Liebowitz

Jon S. Jones

Robert J. Mailloux

Lieutenant General Bruce K. Brown, USAF, Ret.

Major General Joseph P. Stein, USAF
Abstract

 The advantage of the vertical, that is, the capability to see farther 

and better than the adversary, has long been a cardinal principle of 

warfare. This paper explores how radar and sensor technologies 

developed in Air Force laboratories have permitted application of the 

principle in what is perhaps its most effective use to date: airborne 

remote sensing for purposes of command and control.

 Beginning in 1954, the Air Force organized airborne radar 

early-warning units with EC–121 aircraft. The Airborne Warning 

and Control System, the Joint Surveillance Target Attack Radar 

System, and fighter-based airborne remote sensing systems followed. 

Key to our success were Air Force enabling technologies, particularly 

low side-lobe antennas, signal processing, airborne moving target 

indicator and ground moving target indicator systems, forwardlooking solid-state radars, and sensor fusion. Numerous examples, 

most recently, Operations Enduring Freedom and Iraqi Freedom, 

attest to the operational utility of airborne remote sensing.
The Limitless Sky

72

Figure 1. EC–121 Warning Star aircraft.

INTRODUCTION

 Niccolò Machiavelli (14691527) thought 

a general should possess a perfect knowledge 

of the localities where he is carrying on war.1

Today, United States Air Force airborne 

remote sensing2

 stands close to making that 

ideal a reality. Airborne remote sensing 

provides the means not only to seize and hold 

space over the field of battle but, even more 

significantly, to understand it in ways that 

permit exploitation in a manner Machiavelli 

and the generations of military theorists who 

followed him almost certainly never imagined.

HISTORY

 The history of Air Force airborne remote 

sensing stretches over half a century, beginning 

when the Air Force became a separate armed 

service with its own laboratory and research 

and development (R&D) structure. Several 

technologies attracted Air Force interest during 

these early years, but radio detection and 

ranging (radar) stood out. A closely guarded 

secret during the Second World War, radar 

became a vital component in national defense 

strategy during the Cold War, and Air Force 

laboratories spared no effort in exploring 

ways to improve and apply the technology 

more widely and effectively. Research gained 

momentum in the wake of recent developments 

in military aviation, like jets, supersonic 

flight, and ballistic missiles, all of which 

required better and sometimes new means for 

surveillance, tracking, and target engagement. 

Air Force laboratories turned to klystrons,3

traveling wave tubes, and more powerful 

magnetrons to boost radar performance. Other 

efforts focused on improving ways to process 

radar signals, a major goal being to eliminate 

clutter, or unwanted radar returns. Lighter, 

more reliable components and moving-target 

indicators (MTIs) that eliminated blind spots 

and canceled electronic interference emerged 

as research priorities. Infrared and electrooptical sensors attracted research interest as 

well for their potential to buttress radar.

 Symbolic of early Air Force airborne 

remote sensing was the EC–121 Warning 

Star (Figure 1) originally developed by 

Lockheed Corporation for the Navy. The 

Air Force, which designated the system 

RC–121, procured fifty-six of the pistondriven planes and used them to warn of 

approaching unidentified aircraft and ships. 

Warning Star carried an S-band APS20 

surveillance radar and an X-band APS4 heightfinding radar.4

 By 1957, the Air Force had 

several squadrons of the aircraft in service.5

Reliability problems plagued the EC–121’s 

radar and electronics. However, improvements 

like data-link communications and increased 

radar range6

 improved reliability but ultimately 

proved inadequate. Reality was that more 

formidable targets and missions called for 

better technology. Moreover, the problem of 

ground clutter persisted, particularly over land, 
From the Air

73

where it obscured targets and offered potential 

adversaries an opportunity to avoid detection.7

In 1967, the Pentagon approved a modernization 

plan that called for over-the-horizon backscatter 

radar, a new interceptor, and an Airborne 

Warning and Control System (AWACS). 

AWACS, known as the E–3 Sentry, represented 

a significant advance over its EC–121 Warning 

Star forebear. An outgrowth of the Overland 

Radar Technology program, which developed 

pulse-Doppler techniques for rejecting radar 

clutter, its AN/APY1 radar was superior to the 

EC–121’s APS20. The AN/APY1 was a lookdown radar whose antenna operated from the 

top of a specially modified Boeing 707 aircraft 

in an elliptically shaped rotodome 30 feet in 

diameter and 6 feet thick. With AWACS, the 

Air Force acquired the extended radar coverage 

and increased capability it had wanted to detect 

and track low-flying targets.8

 By 1977, Electronic 

Systems Center began transitioning the first of 

the aircraft to Tactical Air Command (TAC), 

and the AWACS achieved initial operating 

capability in April 1978. All told, thirty-four 

E–3A Sentries entered Air Force service.9

 Besides new technology, AWACS introduced 

new operational concepts for airborne platforms. 

AWACS, though a greatly improved airborne 

platform for radar-guided air-to-air intercepts, 

was more than that; it was also a command 

and control system: the AWACS would 

facilitate command and control of deployed 

tactical forces. Such tactical air operations as 

rendezvous, aerial refueling, air traffic control, 

interception, search and rescue, reconnaissance, 

counter air, battle damage assessment, direct air 

support and aerial resupply could be monitored 

and controlled by AWACS.10

 New technology made such command 

and control possible, principally consisting 

of longer-range radar, better radios, digital 

communications, and computer displays. 

Enhanced command and control, including the 

means to monitor enemy air activity beyond 

the forward edge of the battle area, became 

possible.11

 Meanwhile, more powerful computers and 

more precise navigational guidance had begun 

to presage the next round of airborne remote 

sensing advances. During the Vietnam War, 

Rome Laboratory12 scientists and engineers 

devised ways to improve the targeting of enemy 

communications. Although the war ended 

before the technology could be placed on the 

battlefield, it was, perhaps, the most significant 

Air Force technology development of the 

period. The Advanced Location Strike System 

(ALSS) represented the state of the art, zeroing 

in on enemy electronic emissions for guided 

air-to-ground weapons. Designed to locate and 

strike enemy surface-to-air missile (SAM) firecontrol radar and supporting communications, 

ALSS used ground control stations, beacons, 

and airborne relay platforms to direct airborne 

munitions. Employing coherent correlation 

Figure 2. Airborne Warning and Control System (AWACS).
The Limitless Sky

74

and Kalman filtering techniques in a coherentemitter location testbed, researchers tested 

ALSS at the White Sands Missile Range, New 

Mexico, and in Europe. The technology would 

carry over into other programs, eventually 

finding its way into Air Force and Army weapon 

systems of the 1980s and 1990s.

 By the 1980s, such technology was 

underpinning a doctrine known as Assault 

Breaker which emphasized precision 

conventional munitions delivered by tactical 

aircraft and radars against second-echelon 

Warsaw Pact forces. The idea was to stabilize 

an initial Soviet Union assault against 

Western Europe and then bring it to heel 

by destroying its capability to replenish and 

regroup from reserve or second-echelon forces. 

Optimists saw the new doctrine as offering 

a possible means for ending conflict by using 

conventional weapons and tactics. Remote 

airborne sensing systems figured prominently 

in the strategy, especially the part that 

emphasized targeting enemy command and 

control and other surface targets from afar.

 Pave Mover, an Air Force program that 

sought radar capable of picking out targets on 

the ground and directing munitions against 

them, and the Standoff Target Acquisition 

System, a U.S. Army effort to develop a 

helicopter-mounted MTI radar that detected 

enemy armor beyond the forward area of battle, 

illustrated the technological and doctrinal 

change (Figure 3). Working with the Defense 

Advanced Research Projects Agency (DARPA) 

and the Electronic Systems Division, Rome 

Laboratory used several technologies, most 

notably airborne phased-array antennas, 

synthetic aperture radar, high-speed analog/

digital converters, beam-steering computers, 

distance-measuring equipment, parallel signal 

processors, and sophisticated algorithms, to 

develop Pave Mover radar. The system utilized 

two communications links. One provided a 

surveillance picture to a ground station while 

the other sent target coordinates for munitions. 

The high point of the program occurred in 

1982 when, during tests in New Mexico, Pave 

Mover radar 75 miles away guided a fighter 

aircraft as it dropped dummy weapons on a 

moving tank column the pilot never even saw.13

Both Pave Mover and the Standoff Target 

Acquisition System transitioned to the Joint 

Surveillance Target and Attack Radar System 

(Joint STARS) program. The Air Force had 

responsibility for the airborne part of the 

system, and the Army, the ground portion. In 

1984 the Air Force selected the Boeing 707 

airframe for Joint STARS. Like AWACS, Joint 

STARS was to operate from a modified Boeing 

707.14 Their similarities tended to end there. 

Although Joint STARS was also a long-range 

command and control system, its command 

control extended to mobile surface targets. 

Figure 3. Standoff Target Acquisition System (SOTAS).
From the Air

75

Housed in a canoe-shaped radome under its 

fuselage was a side-looking phased-array antenna 

capable of detecting, tracking, and targeting 

enemy ground forces, whether in motion or 

stationary (Figure 4). The radar possessed 

wide-area surveillance, MTI, and synthetic 

aperture capabilities. The result was an airborne 

command and control system capable of using 

aircraft to target surface targets up to 150 miles 

away.15 Flight-testing of Joint STARS began on 

1 April 1988;16 it achieved initial operational 

capability in December 1997.17 Eventually, 

the Air Force plans to operate a fleet of Joint 

STARS, with fleet size estimates ranging 

from twelve to as many as nineteen aircraft.18

Nor were airborne command and control 

platforms the only aircraft benefiting from 

ongoing advances in airborne remote-sensing 

technology. Air Force fighter and bomber 

aircraft benefited too. Lighter, more compact 

avionics permitted the use of more sensors per 

platform, which in turn increased operational 

capabilities.19 Forward-looking infrared extended 

distances aircraft could search, and lasers 

allowed for more precise target-ranging and 

acquisition. By the 1990s, Air Force fighter 

and bomber aircraft carried sensors that, when 

combined with systems like AWACS and Joint 

STARS, greatly enhanced the effectiveness 

of the United States military (Figure 5).

 The Affordable Moving Surface Target 

Engagement (AMSTE) program, which applies 

Ground Moving-Target Indicator (GMTI) 

radar along with high-speed processors, 

low-cost standoff precision weapons, and 

communications networks to the task of 

destroying mobile ground targets, seeks to 

improve on Joint STARS.20 Unlike Joint 

Figure 4. Boeing 707 retrofitted with Joint STARS under the 

fuselage.

Figure 5. F–15 (above) and F–16 (below) carring sensors 

that, combined with AWACS and Joint STARS, enhanced the 

effectiveness of the United States military.
The Limitless Sky

76

STARS, which identifies targets and tasks other 

aircraft to track and destroy them, AMSTE 

monitors targets until their destruction. The 

heart of AMSTE is a computer processor that 

fuses data from two separate airborne groundsurveillance radars and simultaneously transmits 

the information to missile-firing aircraft.21

The Air Force is currently evaluating AMSTE 

technology for possible use in Joint STARS, 

Global Hawk, the F/A–22 Advanced Tactical 

Fighter, and the F–35 Joint Strike Fighter.22

Interest in the technology stems from what such 

airborne remote sensing potentially offers: the 

capability to find, strike, and destroy targets 

sooner, even if they turn, brake, or accelerate.23

 Because the success of AMSTE depends 

on fusing data from different sensor and 

information systems, tools to accomplish 

this have received research emphasis. Such 

tools include automatic tracking that converts 

GMTI detection data into tracks; motionpattern analysis that analyzes GMTI tracks 

for significance; behavioral pattern analysis 

that considers enemy intent; and resource and 

scheduling that commits multiple platforms 

against targets. Algorithms, particularly those 

that distinguish moving ground targets among 

objects on the battlefield, form a conspicuous 

part of all research. The objective is a familiar 

one: engagement of time-critical targets 

in near real time.24 In parallel with these 

developments, the Aeronautical Systems Center 

performed upgrades and enhancements to 

the U–2’s radar, giving it a higher resolution 

capability and an MTI mode. In 1996, 

development of an unmanned aerial vehicle 

(UAV) that carried a low-cost radar with both 

synthetic aperture and MTI modes began.

 Impressive as each of the aforementioned 

airborne remote sensing systems is, their 

effectiveness depends on how well they work 

together. The reason is simple but critical: no 

one sensor suffices to meet the challenges of 

the modern battlefield. Rather, the situation 

demands many sensors operating as a single 

system. The Air Force describes such sensing 

as multispectral, a data-fusing technique that 

relies on many types of sensors, not just on 

radar alone. Multispectral experiments that 

tested concepts and technologies for fusing 

data from different types of sensors became 

common in Air Force laboratories during the 

1980s and 1990s.25 This fusion requirement 

created its own set of challenges, not the least 

of which was how to correlate data generated 

by different sensors operating miles apart 

among a variety of platforms.26 In addition, 

this process had to occur in near real time for 

munitions to be targeted effectively against 

moving targets. The enabling technology in this 

instance was the electronic computer, which 

had grown increasingly powerful as it shrank 

in size. Both AWACS and Joint STARS relied 

on computers to correlate and track the data 

their sensors provided. During the 1990s, 

Off-Board Augmented Theater Surveillance 

research explored ways to integrate intelligence, 

surveillance, and reconnaissance (ISR) among 

Joint STARS, AWACS, and Rivet Joint 

aircraft to assist in target identification. Of 

particular interest was how such technology 

might be used to distinguish between friend 

and foe and to identify neutrals during the fog 

of battle. Work went forward under the aegis 

of Network Centric Collaborative Targeting, 

which planned to demonstrate fusion technology 
From the Air

77

connecting the three aircraft with the off-board 

surveillance information in a series of future 

exercises.27 Ultimately, what the Air Force 

wanted was automatic target recognition.28

TECHNOLOGY

 That Air Force laboratories developed 

better radar and sensor technologies and then 

fashioned them into operational airborne remote 

sensing systems, while impressive, forms just 

part of the Air Force airborne remote sensing 

R&D story. The other, equally impressive 

part is how they allowed sensors to operate as 

a single entity. What characterizes modern 

airborne remote sensing is its dependence 

on a range of technologies, integrated and 

cooperating, to detect and eventually engage 

the target. This is no small accomplishment, 

given the challenge of integrating voluminous 

amounts of information from multiple sources 

at various locations. For decades, it was the 

long pole, as it were, in the airborne remote 

sensing R&D tent, and solving it took consistent 

commitment over many years. Sustaining 

that commitment was the understanding that 

future airborne remote sensing capabilities 

depended on obtaining solutions.

 Although no single technology brought forth 

this fusion capability, solid-state electronics 

deserves much of the credit, principally because 

it made the essential computer and signal 

processing possible. Revolution may be too 

strong a descriptive, but the term comes close 

to acknowledging the significance of what was 

happening as solid-state integrated circuits 

became smaller, more efficient, and, most 

importantly, more economical to produce. 

The 1970s ushered in minicomputers, called 

microprocessors. Compared to the Electronic 

Numerical Integrator and Computer (Eniac), 

the first electronic digital computer, the 

typical microprocessor was 30,000 times 

cheaper, 300,000 times smaller, consumed 

56,000 times less power, and performed 200 

times more calculations.29 The Air Force 

quickly grasped the significance of this and 

began developing integrated avionics systems 

that could be embedded in aircraft.

 Programs like Digital Avionics Information 

System, Pave Pillar, and Pave Pace used 

solid-state components to integrate, improve, 

and reduce the size and weight of avionic 

architectures, including sensors. Solid-state 

components in radars made them more 

reliable, improved their capability to track 

targets in clutter, and gave them better 

countermeasures. Forward looking airborne 

radar, incorporating solid-state technology, 

performed more functions. It was not long 

before forward-looking radar possessed modes 

for navigation and weather, terrain following/

terrain avoidance, precision target mapping 

(synthetic aperture mapping), air-to-ground 

weapon delivery, and countermeasures. This 

combining of multiple modes in radar with rapid 

electronic beam scanning became the basis for 

the modern solid-state, multifunction radar.30

 Trends toward greater computerization and 

better signal processing carried over into antenna 

technology. Typifying these efforts was the 

Avionics Laboratory’s31 Molecular Electronics 

for Radar Applications (MERA), a solid-state 

module and antenna array. Initially, MERA’s 

objective was to advance microwave integrated 

circuits, but it expanded to components and 

antenna arrays.32 The MERA module and 
The Limitless Sky

78

array had multiple radar modes for ground 

mapping, terrain following/avoidance, and 

air-to-ground ranging. The array had 604 

elements, produced 32 dB gain on transmit and 

30 on receive, transmitted 352 watts peak at 

9 GHz, and had a system noise figure of 12.5 

dB. Another Avionics Laboratory effort, the 

radome antenna and radio-frequency circuitry 

program, sought simple, lightweight, economical 

ferrite phase-shifter scanning arrays. An 

electronically agile radar followed. It employed 

mass-produced phase-shifter/radiator elements 

costing approximately $300 each, considerably 

less expensive than the technology developed 

under MERA.33 The electronically agile radar 

influenced design of the B–1B avionics.34

 Despite the achievements of these early 

passive arrays, they suffered reliability problems 

because of their continued reliance on tubes and 

high-power voltages. More solid-state technology 

became the remedy. The reason was obvious: 

solid-state array modules not only required 

less power, they delivered higher mean times 

between failure. Solid-state antenna arrays 

tolerated hundreds of module failures before 

needing repair, a fact that gave them a crucial 

edge over their tube-based cousins. 

The Avionics Laboratory’s reliable 

advanced solid-state radar, developed 

during the 1970s, boasted an array of 

1,648 elements, each transmitting 1.4 

watts peak power at a 5 percent duty 

cycle. The reliable advanced solid-state 

radar achieved a mean time between 

failures of 27,000 hours based on one 

transmit or one receive failure.35

 The solid-state, phased-array radar 

program took advances to new levels 

before ending in 1988. It used microwave 

integrated circuit technology to demonstrate 

even more convincingly the increased capability 

and reliability that solid-state antenna arrays 

provided. If there was a negative, it was cost, 

which remained relatively high compared to 

more traditional technologies. A breakthrough 

in affordability arrived with the availability 

of monolithic microwave integrated circuit 

technology, which DARPA began sponsoring 

as a means for improving advanced solidstate technology. Monolithic microwave 

integrated circuits and solid-state phasedarray radar modules found their way into the 

ultrareliable radar, which would later support 

Advanced Tactical Fighter and F–22 radars.

 The technology that transformed fighter 

and bomber aircraft produced equally 

significant changes in Air Force early-warning 

and command-and-control platforms. With 

AWACS, they manifested themselves in a 

pulse-Doppler airborne, moving-target indicator 

(ATMI) antenna (Figure 6). Since AWACS 

flew at approximately 30,000 feet, it needed 

an antenna that surveyed 360 degrees of 

azimuth while looking downward at airborne 

Figure 6. A pulse-Doppler airborne moving target indicator 

(ATMI) antenna.
From the Air

79

targets as low as 500 feet above the ground. 

Separating radar returns of airborne targets 

from radar clutter originating from the ground 

posed a daunting challenge. Very low antenna 

side lobes, along with much improved signal 

processing, provided the solution. Basically, 

MTIs eliminated ground clutter immediately 

beneath the target while the very low, side-lobe 

antenna suppressed clutter originating elsewhere. 

Doppler radar-filtering helped too, enhancing 

target signals. Actual target detection occurred 

in a pulsed-Doppler mode.36 To determine 

elevation, the antenna employed a planar S-band 

array of horizontal rows of edge-slotted wave 

guides. The main beam measured approximately 

1 degree wide in azimuth and 5 degrees wide 

in elevation.37 Equally impressive was what was 

achieved in size and weight. The entire antenna 

operated from a 30-foot-wide rotating radome.

 The basic antenna design, a slot array, was not 

revolutionary, but its precision signal control was. 

Precision stemmed from row-arrays that kept 

antenna side-lobe radiation low. The method, 

which owed much to Air Force Cambridge 

Research Center studies of computer codes for 

antenna interelement coupling,38 proved essential 

in the design of the array.39 Precision extended 

to measuring equipment too, making it possible 

to find and evaluate previously undetectable 

signal errors. Finally, computer-controlled 

milling machines cut the waveguide slots with 

unprecedented precision. It was the most precise, 

lowest, side-lobe antenna array yet built.40

 Upgrades throughout the 1980s and 1990s 

ensured the continued viability of AWACS. 

New and more powerful computers and more 

sensitive radar components boosted the system’s 

performance. A fiberglass radome reduced 

weight; new software permitted tracking 

ships; and additional radios and consoles 

made communications more reliable.41 Later 

enhancements allowed detection of targets 

traveling at less than 85 knots and its operation 

with the Joint Tactical Information Distribution 

System. Designed to eliminate security 

problems associated with voice communications, 

this joint distribution system provided 

computerized communications links between 

AWACS and the forces over which it exercised 

command and control.42

 The Joint STARS radar antenna was even 

more advanced, its phased-array design and 

signal processing permitting detection from the 

air of slow-moving ground targets in clutter.43

Designed to operate in a displaced phase center 

mode that compensated for the motion of the 

aircraft, the antenna processed radar returns 

while canceling clutter and tracking ground 

targets. The antenna, a planar array of 456

X-band slotted waveguides, was 24 feet wide and 

2 feet high. Each waveguide slot array provided 

a low side-lobe fixed beam for elevation. Signal 

processing combined signals from all 456 

waveguides to form either a narrow beam 

pattern or three wider beams. Phase-shifters 

kept antenna side lobes low in all modes and 

distributed power across the antenna aperture 

with unprecedented precision. Unlike the 

AWACS array, which had very low side lobes 

in a plane of the array that did not scan, the 

Joint STARS array formed low side lobes in 

all planes, including the plane of the electronic 

scan. Phase-shifters also distributed power in a 

way that set the amplitude for the narrow beam 

as well as the three wider displaced beams.

 Enhancements to Joint STARS throughout 
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80

the 1990s boosted overall capabilities. New 

satellite communications links improved 

capabilities to transmit Joint STARS data 

through the Air Force chain of command. A 

computer replacement program reduced the 

number of onboard main computers from five 

to two and increased processing power, speed, 

and reliability with a fiber-optic local area 

network technology.44 New algorithms played 

an essential part in upgrades too, principally 

as a means to give Joint STARS the ability 

to distinguish more rapidly targets from vast 

amounts of data. Research included algorithms 

for rotating-antenna identification, MTI data 

synthesis, off-board data cueing and correlation, 

high-range resolution, convoy detection, motion 

pattern analysis, and modeling. A moving-target 

exploitation effort got underway to develop 

automatic tracking of targets, which included 

combining high-range resolution radar with 

MTI to produce a single dimensional radar 

cross section of a moving vehicle. That these 

advanced algorithms supported open computer 

architecture designs made future changes easier 

to make. Subsequent development of Moving 

Target Information Exploitation made much 

of this moving-target information available to 

ground stations. The addition of World Wide 

Web capability allowed Internet technology 

to be used for exploiting data. Early in 2001, 

Joint STARS, U–2, and Global Hawk aircraft 

shared GMTI data in an experiment.45

 Such developments, particularly the 

increasing role of algorithms, underscored the 

critical link between remote airborne sensing 

and computer software. Software told computers 

what to do, and, as computers improved, 

demands for software capable of exploiting 

them to the full increased. For airborne remote 

sensing, computer software became essential to 

efforts seeking to computerize more and more 

radar functions, a trend that continues. Driving 

this trend is the opportunity to shift some of the 

burden of further improvement from radar and 

other sensor systems to computer processing, 

which, potentially, improves performance 

and cuts costs. But software had to be made 

affordable, a tall order given the relatively 

labor-intensive characteristics of software 

writing and engineering. By the mid 1970s, the 

Department of Defense was spending three 

times as much for computer software as it was 

for computer hardware.46 Costs had to come 

down if the Air Force was to realize the full 

potential of the computer. Not surprisingly, 

the Air Force worked the software cost issue 

intensively throughout the 1980s and 1990s, 

developing systems that automated formerly 

manual processes associated with software 

production. Computer programming languages 

improved, and processes associated with 

software development got automated.47 Software 

costs fell, and computer processing became 

even more embedded in Air Force systems.

OPERATIONS

 Research in Air Force laboratories, while it 

focused on long-term objectives, always had a 

more immediate concern: the warfighter. This 

became apparent during war or national crisis 

when priorities inevitably shifted to supporting 

current operations. Airborne remote sensing 

was no exception, a fact exemplified in the case 

of the EC–121 Warning Star. Besides serving 

as an early-warning system of bomber attack 

against the United States, it became, during 
From the Air

81

the Vietnam War, an airborne, tactical aircraft 

radar-control facility. Radar weapons controllers 

on Warning Star coordinated with forward 

air controllers to deliver air strikes on enemy 

targets, effected midair refueling with tankers, 

assisted in search and rescue, and helped recover 

aircraft to home bases.48

 In 1966, Warning Star began supporting 

Igloo White, a program designed to interrupt 

the enemy’s use of the Ho Chi Minh Trail 

as a route for resupplying its forces in South 

Vietnam. By the close of 1967, parts of the Igloo 

White system were in place. Essentially it sowed 

the trail with innumerable electronic sensors. 

These sensors, relying on seismic, acoustical, 

and chemical data to determine the presence 

of the enemy, tracked attempted infiltrations 

into South Vietnam. EC–121 aircraft, flying 

above, relayed the received information to a 

computer-monitoring station where planners 

interpreted it.49 The computer station, located 

at Nakhon Phanom AB, Thailand, processed 

the information and gave it to strike aircraft for 

immediate attack.50

 Like its EC–121 predecessor, AWACS came 

to play an important air defense role. North 

American Air Defense Command assumed 

control of AWACS in 1979, which involved 

keeping a significant portion of the aircraft 

on alert. The AWACS had other roles too, 

in particular with the North Atlantic Treaty 

Organization (NATO) forces in Europe. From 

1978 until 1989, AWACS, flying from Keflavik, 

Iceland, provided long-range surveillance of 

and airborne intercept control against Soviet 

bombers. In Europe itself, AWACS supported 

United States Air Forces in Europe (USAFE) 

in its mission to deter the Soviet Union from 

launching a surprise attack on Western Europe.51

All told, eighteen AWACS deployed to Europe. 

One contingent, based at Geilenkirchen, 

Germany, was operated by NATO crews.52

 AWACS mirrored Warning Star in that 

operators, ultimately, determined the success or 

failure of the system. Lieutenant General Bruce 

Brown, for example, remembers how AWACS 

skeptics in TAC became believers when, during 

an exercise, they witnessed what the system 

working with F–101, F–102, and F–106 

fighter aircraft and AWACS radar weapons 

controllers could do in a tactical scenario: Not 

a bad night; 199 kills out of 200. The same 

guys who said it was too expensive, was too 

easy to jam, and couldn’t survive (among their 

many criticisms) were now trying to convince 

me what a marvelous machine we had on our 

hands.53 Similarly, General William Creech 

has recalled how operators, during exercises, 

played an essential role in AWACS’s acceptance: 

We had a lengthy demonstration in Europe of 

the AWACS for the NATO brass while I was 

USAFE Director of Operations, Intelligence 

an initiative that culminated in the NATO 

AWACS program. The System was so impressive 

that it sold itself.54 As for those, who, in the early 

1970s, had considered AWACS too big, too slow, 

too expensive, and too vulnerable, he had but one 

reply: dumb.55

 Military contingencies also revealed AWACS’ 

worth. Urgent Fury, the 1983 United States 

operation against Granada, provides an early 

case in point when AWACS were pressed into 

service, helping direct and control air operations. 

Then, in 1989, AWACS supported Operation 

Just Cause in Panama. Less than two years later, 

during the Persian Gulf War, AWACS again 
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82

saw action. During Desert Shield, the buildup 

of United States and Coalition forces in the 

Persian Gulf, AWACS deployed to Saudi Arabia 

to guard the skies against possible Iraqi attack. 

Later, during Desert Storm, the ground invasion 

by United States and Coalition forces that 

expelled Iraqis from Kuwait, AWACS controlled 

the air-to-air war and coordinated the hunt for 

Iraqi Scud missiles.56 AWACS saw action again 

during Operation Deny Flight, the operation 

designed to keep Serbian aircraft grounded 

during the Bosnian Crisis.57 In 1999, during 

Operation Allied Force, AWACS directed and 

controlled NATO air strikes against Serbian 

forces in Kosovo. Fourteen AWACS aircraft flew 

656 sorties in support of NATO operations.58

AWACS also supported Operations Enduring 

Freedom and Iraqi Freedom.

 Joint STARS received its baptism of fire even 

before it became fully operational. The occasion 

was the Persian Gulf War of 1990–91. During 

Desert Shield, General Norman Schwarzkopf, 

Commander in Chief of Central Command, 

ordered two Joint STARS aircraft to deploy 

to Saudi Arabia. The two aircraft took turns 

monitoring Iraqi armor and troop movements. 

During Desert Storm, Joint STARS flew 

over the battle area, providing information 

on Scud missile sites and giving intelligence 

about Iraqi troop movements. Joint STARS 

proved particularly effective at identifying the 

paths of attacking and retreating columns of 

Iraqi armor. Intelligence units made good use 

of the information, relying on it to establish 

the precise location of Iraqi units during 

the battle for the town of Al Kahafji.59

 Other missions occurred throughout 

the 1990s. In 1995, during Operation Joint 

Endeavor, Joint STARS supported NATO 

peacekeeping efforts in Bosnia. Flying from 

Rhein-Main AB, Germany, a testbed E–8A 

and a preproduction E–8C aircraft monitored 

troop movements on the ground as part of 

the Dayton Peace Accords. The mission also 

encompassed surveillance of Bosnian airspace, 

which involved linking up and communicating 

with F–16s flying from Aviano AB, Italy.60

Subsequent missions included Allied Force61

in 1999 and, most recently, Iraqi Freedom.62

 The conspicuous place AWACS and Joint 

STARS occupied in Air Force operations 

throughout the 1990s and their roles in 

Enduring Freedom and Iraqi Freedom speaks 

to their importance as airborne remote 

sensors. Both systems have earned niches in 

current and future Air Force missions, but 

neither attracts the interest and publicity that 

UAVs, the most recent addition to Air Force 

airborne remote sensing platforms, now do 

(Figure 7). Interest no doubt lies, at least in 

part, with the novelty of the technology, whose 

practicality and utility for airborne remote 

sensing only began to emerge during the 1990s. 

In 1996 the Air Force activated three UAV 

squadrons of Predators at Indian Springs Air 

Force Auxiliary Field, Nevada.63 Equipped 

with electro-optical and infrared sensors, 

Predator can fly 24-hour missions 5,000 miles 

from its home base.64 Global Hawk, another 

Air Force UAV, began flying in 1998.65

Despite their relatively recent appearance, 

UAVs have found a range of operational 

uses. They collected intelligence on Serbian 

air activity during Deny Flight and played 

an important role in the air campaign 

during Enduring Freedom and operations in 
From the Air

83

Afghanistan after the 11 September 2001 

attacks. Equipped with sensors, they collected 

ISR information and battle damage assessment 

(BDA) data, without endangering a pilot. Their 

loiter time over target proved another asset. 

During Iraqi Freedom, R–Q1 Predator UAVs 

provided aerial reconnaissance and targeted Iraqi 

radar-guided antiaircraft systems.66 Predators 

also performed electronic countermeasures.67

The other Air Force UAV, the R–4A Global 

Hawk, saw action too.68 UAVs, working with 

AWACS and Joint STARS, gave remote 

sensing yet more capability. That they 

would become more and more important to 

airborne remote sensing seems inevitable.

 More significant than any particular airborne 

sensing platform, though, was the overall 

capability achieved. Nowhere was this more 

dramatically demonstrated than in Enduring 

Freedom and Iraqi Freedom. Both operations 

showed how vast amounts of data, principally 

from ISR sensors, could be collected from, 

literally, around the globe, exploited 

in the United States, and then applied 

to combat operations thousands of 

miles away. General Joseph Stein, 

Air Combat Command Director of 

Operations, has noted how within 

scant minutes, products were in the 

hands of operators at the Combined 

Air Operations Center (CAOC) in 

Southwest Asia and fed to strike 

platforms for attack.69 In short, these 

airborne sensing systems possessed 

reachback capability, that is, the 

means to rapidly access information 

and specialized personnel skills in 

the United States during war. This not only 

reduced the size of the deployment required 

but, more importantly, compressed the socalled kill chain, the process of finding, fixing, 

targeting, engaging, and assessing targets.

 In one instance, target analysts in the United 

States, reviewing live Predator videos, found 

Iraqi tanks hidden in tree lines and relayed 

the information to the CAOC, which directed 

their destruction minutes later.70 On another 

occasion, imagery analysts in the United States, 

reviewing live Global Hawk imaging data of 

the battle area, discovered a SAM site in two 

minutes. The information, which went to the 

CAOC, allowed B–2s to destroy the target. 

Later, the same Global Hawk provided BDA of 

the target area. The whole process, from initial 

discovery of the SAM site, to its destruction, to 

the BDA report that went worldwide, took but 

a scant 80 minutes. Other operations occurred 

even faster. Modification to the Predator video, 

for example, permitted live transmissions to 

C–130 gunships attacking ground targets.71

Figure 7. Unmanned Aerial Vehicle (UAV).
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84

Such airborne remote sensing technology 

provides the unprecedented capability to enter, 

as it were, the enemy’s decision loop and destroy 

his forces quickly, before they can be placed in 

battle. Furthermore, General Stein predicts, 

future advances will undoubtedly enable us 

to compress that kill chain even further.72

CONCLUSION

 The last half century has witnessed 

a steady improvement in airborne radar 

remote sensing. Better vacuum tubes boosted 

power; solid-state components reduced size 

and improved reliability; and computers 

permitted the first practical phased array 

antennas. These improvements in turn 

created new missions for radar and enhanced 

airborne ISR generally. Yet important parts 

of the surveillance mission remained unmet. 

Developments of other military technologies, 

in particular, radar-absorbing aircraft surfaces 

and precision airborne munitions capable of 

striking radar transmitters at unprecedented 

distances, revealed the need for additional 

measures, and Air Force laboratories set about 

fashioning them. Bistatic radar,73 photonics, 

infrared technology, and passive detection 

techniques, to cite but a few examples, received 

increasing emphasis for their potential to 

bolster radar as an airborne remote sensor. 

Airborne remote sensing, while still heavily 

dependent on radar, more and more came to 

rely on a myriad of sensors. Radar continued 

to hold center stage in the airborne remote 

sensing mission, but its relative importance 

declined as other technologies assumed 

increasingly greater roles (Figure 8).

 Viewed through the prism of history, this 

change appears less a break with the past 

than a logical consequence of technological 

advance, which the Air Force, to its credit, 

readily recognized and implemented. Air Force 

research, for instance, always emphasized 

that effective use of air power depended 

on instantaneous (real-time), useful sensor 

information and that it included more than just 

radar. The problem was combining information 

and displaying it in the cockpit, which 

during the 1950s and 1960s was technically 

impracticable. But the ideal persisted, drawing 

increased strength whenever technological 

advance seemed to bring it closer to realization. 

This persistence proved fortuitous since, when 

enabling technologies did materialize, concepts 

stood ready for application, having been tried 

and practiced for years, sometimes for decades. 

Air Force experimentation with, say, long-range 

navigation techniques in the 1950s for precision 

bombing and reconnaissance, while it appears 

primitive today, actually played a critical role in 

providing the institutional experience needed to 

exploit satellite communications, the integrated 

circuit, the laser, and other technologies as they 

Figure 8. An illustration of AWACS operations.
From the Air

85

became available.

 Similarly, in airborne remote sensing 

research, long-established principles and 

concepts helped prepare the way for the 

introduction of technologies like personal 

computers and microcircuitry. Application of 

new technology, moreover, often challenged 

existing engineering assumptions and areas of 

research, once considered separate, frequently 

merging them in response to innovation. 

Consequently, radar and radio became integral 

to communications satellite research; laser and 

solid-state electronics to munitions research; and 

the computer, arguably, to all research. Absent 

the accumulated institutional experience of 

its laboratories in researching and developing 

and experimenting with aviation and related 

technologies, it is difficult to imagine the 

Air Force managing technological change, 

imperfect though it sometimes was, effectively. 

Air Force technological innovation did not 

occur in a vacuum; it took root in institutional 

ground nurtured by decades of R&D, R&D 

that ran the gamut from papers published in 

research journals and symposia to technology 

demonstrations and experiments at the 

laboratory workbench (Figure 9).

 The course of technological change, especially 

for technology advancing as rapidly as airborne 

remote sensing, deifies prediction. Nevertheless, 

certain trends stand out, the most obvious being 

the continuing growth of sensor capabilities 

and the advantage they bring to air combat 

operations. Not as obvious perhaps, but equally 

significant, are burgeoning capabilities for 

receiving airborne remote sensing information 

and putting it to timely use, primarily for 

decision making. The latter may still lag the 

former in clearly manifest utility, but the 

gap seems to have closed. Indeed, airborne 

remote sensing may have reached a stage in 

which consolidation and implementation of 

existing technology more nearly become the 

norm. Innovations will continue, but emphasis 

may shift to new stratagems and operational 

doctrines. If so, the next round of advancement 

in airborne remote sensing is as likely to come 

from the hand of the operator or strategic 

planner as from the researcher or technologist.

Figure 9. An illustration of COMSAT research.
Pilots in Extreme Environments:

Enforcing U.S. Foreign Policy from the 

Edge of Space

Major General Robert F. Behler, USAF, Ret.

Russell R. Burton

George C. Mohr

William J. Sears

Billy E. Welch
Abstract

 The USAF SR–71 Blackbird is a superb example of the 

application of science and technology in service to the nation. The 

far-sighted and often heroic efforts of human system researchers 

laid the foundation for life-support technologies that allowed pilots 

to operate in extreme environments. As a result, the SR–71, since 

its development in the 1960s, has taken pilots and reconnaissance 

systems officers to the edge of space and back while providing 

the nation’s top decision makers awesome capabilities in a single 

platform to demonstrate national power.

 From 80,000 feet and at Mach 3, the Blackbird reliably 

provided our leaders critically important national intelligence from 

an evolving array of the most advanced reconnaissance sensors 

that the U.S. science and technology community could provide. 

Underlying this impressive capability are the steady developments in 

human systems research, which led to ever-improving capabilities for 

crew members to fly higher, faster, and longer.

 The role of the Blackbird in the 1984 MiG21 crisis is a case 

study in the nation’s use of intelligence. In October 1984, intelligence 

reported that Soviet MiG fighters were crated and being shipped on 

a Bulgarian freighter. Three SR–71 missions, piloted by the first 

author, provided decision makers critical intelligence on the location 

and destination of the possible MiGs while placing our Soviet and 

Sandinista adversaries on notice that we were watching closely and 

were willing to act to enforce the Monroe Doctrine.
INTRODUCTION

 Late in October of 1984, I was tasked to 

fly an intelligence reconnaissance mission 

over Nicaragua. As a result of rising tensions 

between the United States and Communist 

regimes developing around the world, I would 

be an integral player in the demilitarization of 

Nicaragua (Figure 1). My mission was to fly 

the fastest, most physically demanding plane 

the world has ever known to gather vital data 

on the Soviet Union’s operations in and around 

Nicaragua. Based on previously gathered 

intelligence data, the U.S. government believed 

these two countries were exchanging advanced 

weapon systems to rival neighboring countries.

 As an SR–71 Blackbird pilot, I spent many 

fast hours in extreme environments, performing 

high-altitude reconnaissance, while defending 

America’s freedoms from those who would 

oppose us. The earth is much smaller when 

you’re traveling three times the speed of sound 

at 80,000 feet just along the edge of space in the 

world’s fastest manned aircraft. The SR–71 was 

the premier high-altitude reconnaissance aircraft 

designed to provide the right information 

at the right time to the right person.

 Development of the SR–71 began during the 

administration of President John F. Kennedy in 

1962. President Lyndon B. Johnson announced 

in late February 1964 the existence of a 

Blackbird prototype, the first experimental jet 

aircraft that could maintain sustained flight in 

excess of 2,000 mph at an altitude above 70,000 

feet. The first Blackbird (A–12) pilots donned 

their newly developed S901 full pressure suits 

and breathed pure oxygen to protect their bodies 

from the unbearably low pressure. When the 

SR–71 was finally developed several years later, 

highly sensitive sensors were installed making 

the aircraft more conducive to gathering highly 

specific intelligence data. Equipment bays in 

the aircraft carried compressed-length cameras, 

which used highly advanced optics, allowing 

the SR–71 to photograph 100,000 square 

miles of terrain in one hour, a landmass larger 

than the state of Wyoming. In 1972, the Joint 

Chiefs of Staff’s Joint Reconnaissance Center 

prioritized the purpose of the SR–71, which 

was to gather intelligence information for five 

specific intelligence agencies. This brought about 

a highly intricate development of the premier 

intelligence-gathering aircraft in the Department 

of Defense (DoD), which would be the primary 

source of information for those agencies.

 In early October 1984, intelligence analysts 

Figure 1. Maj Gen Robert Behler (author) in front of his SR–71. pieced together various bits of information 

The Limitless Sky

90
that led them to believe Soviet MiG21s were 

being crated for the Bulgarian ocean freighter 

Bukuriani for delivery to a destination 

somewhere in South America. U.S. intelligencegathering satellites had spotted the freighter 

in a Soviet seaport in the Black Sea loading 

supposedly highly sophisticated military 

defense supplies. Because the crates were 

so large, it seemed logical that the defense 

materials being supplied would be jet fighters 

and MIG21s. These events set the stage for a 

critical mission made possible because of the 

unique flight performance of the SR–71 and 

the physiologic protection systems available 

to its aircrew. In reality, preparation for this 

mission began sixty-six years earlier. Over 

succeeding decades, generations of research 

scientists probed the limits of human tolerance 

to the extreme conditions characteristic of the 

SR–71 flight environment. The basic science 

contributions from wide-ranging disciplines, 

when blended together, provided the human 

systems technology required for the successful 

completion of this landmark SR–71 mission.

Medical Pioneers: 1903–1930

 Shortly after the first powered flight in 1903, 

scientific interest in the medical aspects of aerial 

flight grew dramatically. It became obvious 

very quickly that this extreme environment of 

aviation was different from the environment on 

the ground. As the country prepared to move 

into air operations in World War I, the War 

Department was keenly aware of the need to 

improve the fitness and efficiency of military 

aviators to perform combat operations. In 

1917, a Medical Research Board was chartered 

to investigate all conditions that affect the 

efficiency of pilots, to determine the ability 

of pilots to fly at high altitudes, to develop 

suitable apparatus for supplying oxygen to 

pilots at high altitudes, and to consider all 

matters relating to the physical fitness of pilots. 

This led to the establishment of the Medical 

Research Laboratory of the Army Signal Corps 

on Friday, 19 January 1918, at Hazelhurst 

Field on the outskirts of Mineola, New York 

(Figure 2). General Harry G. Armstrong, 

the second Surgeon General of the U.S. Air 

Force remarked, “The Air Service Medical 

Research Laboratory was the first of its kind 

to be established and its contributions to 

aviation medicine are incalculable in relation 

to the saving of lives and equipment. Of equal 

importance is the fact that this institution was 

the medium through which aviation medicine 

in all its ramifications was placed on a sound 

scientific basis in America.” The laboratory’s 

research scientists initially focused on developing 

pilot selection standards and understanding the 

human effects of exposure to high altitude.

 Even in these early times, aeromedical 

scientists were well aware that oxygen want 

(hypoxia) was the pivotal hazard encountered 

Figure 2. The home of the original Medical Research Labratory 

on Huzelhurst Field, NY (1918).

Pilots in Extreme Environments

91
during aerial flight. The effects of hypoxia 

had been thoroughly investigated by a French 

physician-scientist, Paul Bert, who performed 

670 separate experiments from 1870 to 1878 on 

the physiologic effects of altered atmospheric 

pressure. In 1874, Professor Bert subjected 

two aeronauts, balloon pilot Théodore Sivel 

and engineer Joseph Crocé-Spinelli, to a 

simulated altitude of 23,000 feet in the lowpressure chamber installed in his laboratory. 

The aeronauts learned about the use of oxygen 

to prevent hypoxia. On 15 April 1875, Gaston 

Tissandier joined the aeronauts as a passenger 

on a balloon flight that reached an altitude of 

28,820 feet before descending on its own accord 

after all three occupants had lost consciousness. 

Unfortunately, they had decided not to use the 

onboard oxygen until it was too late to do so. 

Tissandier survived; his two companions did not 

the first reported casualties due to hypoxia.1

 During World War I combat pilots soon 

found it necessary to fly above 15,000 feet to 

avoid lethal ground fire. Shortly thereafter, 

reports began trickling in about troubling 

symptoms including headache, loss of muscle 

strength, dizziness, and extreme fatigue. In 

addition, unexplained losses of aircraft began to 

accumulate. The medical authorities recognized 

the root cause as oxygen want. Accordingly, 

a major effort was mounted by the Army Air 

Service to develop an oxygen delivery system 

for pilots performing aerial combat. In 1918, 

production of the Clark-Dreyer Oxygen System, 

consisting of an automatic regulator and a 

leather and rubber mask, got underway. The 

war ended before the new oxygen system could 

be installed in other than a small fraction of 

the Army Air Service’s combat aircraft.2

 Shortly before the end of the war, a young 

chemical engineer, Lieutenant Harold Pierce, 

joined the Air Service Medical Research 

Laboratory after he completed a teaching 

fellowship in physiology at Harvard University. 

In 1919 he designed a second-generation altitude 

chamber fabricated by the Lancaster Iron 

Works (Figure 3). The chamber, insulated with 

cork and equipped with a refrigeration unit, 

enabled scientists to study human response 

to combined cold stress, reduced atmospheric 

pressure, and oxygen want that occur at 

altitude. During unmanned tests, the chamber 

reached an equivalent height of 75,000 feet at 

a temperature of minus 31 degrees Fahrenheit. 

This new chamber was the most advanced 

piece of experimental equipment in the world. 

Designed specifically for high-altitude research, 

it obviously outstripped the technological 

capabilities of aircraft of the time. Using this 

facility, medical pioneers at Hazelhurst built 

a scientific foundation for the development 

of modern-day protective flying equipment 

that would enable aircrew to fly higher, faster, 

and longer with each passing decade.

Figure 3. Mineola Low Pressure Chamber.

The Limitless Sky

92
 In November 1919, the Air Service 

Laboratory moved to nearby Mitchel Field 

and on 18 November 1922, was subsequently 

redesignated the School of Aviation Medicine. 

Mitchel Field was named in honor of a former 

New York City mayor, John Purroy Mitchel, 

who was killed while training for the Air Service 

in Louisiana.3

 Before the war ended, Mitchel 

Field served as a major training base for the 

rapidly expanding Air Service and proved to be 

an ideal home for the new School of Aviation 

Medicine. Four years later, in the summer of 

1926, following the rapid postwar drawdown of 

the Air Service, the War Department decided to 

move the School of Aviation Medicine to Brooks 

Field, Texas, collocated with the flying training 

program still active on that air base. The school’s 

research program was redirected to focus on 

understanding the practical requirements for 

the care and selection of the flyer. The Mineola 

chamber was declared surplus and subsequently 

shipped to the Equipment Branch at Wright 

Field, Ohio. This decision was based on the 

school commander’s annual report that declared: 

“There is reason to believe that the facts of 

physiology which have been so extensively 

investigated during the past six years are far in 

advance of the immediate requirements for the 

Air Service.”4 This conclusion proved to be 

false, but it serendipitously set the stage 

for a major resurgence in scientific 

investigation of the physiologic requirements 

for flying at high altitudes.

The Genesis of Modern Air Warfare:

1930–1950

 After Charles Lindbergh’s solo, trans-Atlantic 

flight and Jimmy Doolittle’s successful allinstrument flight, the fledgling Army Air Corps 

recognized the potential of airpower in a world 

heading for global war. Shortly thereafter, in the 

fall of 1929, a young physician named Harry 

George Armstrong graduated from the School 

of Aviation Medicine and decided his future also 

lay with the rapid growth of military aviation. 

During his first assignment as the flight surgeon 

for the famed First Pursuit Group at Selfridge 

Field, Michigan, Dr. Armstrong discovered 

for himself how inadequate was the military 

pilot’s protective equipment (Figure 4). While 

flying in a P–16 open-cockpit pursuit plane 

from Minneapolis, Minnesota, to Chicago, 

Illinois, on a winter day in 1934, he discovered 

his flight clothing provided little protection 

against the elements. Exposed to a minus 40 

degrees Fahrenheit air temperature, he suffered 

severe frostbite, and his aviator’s goggles frosted 

over, obscuring his vision. Moreover, no oxygen 

mask was available to compensate for altitude 

effects. Following his return to Selfridge, he 

thought about the obvious physiologic threat 

to combat effectiveness and decided to write 

a letter to the Air Surgeon in Washington 

recounting his experiences. He concluded 

his letter with a strong recommendation that 

the Air Corps Research and Development 

Center at Wright Field address the deficiencies 

in protective flying equipment immediately. 

As a result, Captain (Dr.) Armstrong was 

“rewarded” with an assignment to the 

Equipment Branch of the Engineering Section 

at Wright Field to serve as an aeromedical 

advisor. So began the distinguished career 

of a prolific aeromedical scientist whose 

pioneering research led to the development of 

progressively more effective protective flying 

Pilots in Extreme Environments

93
equipment essential for the SR–71 aircrew 

to accomplish their mission objectives.

 In 1935, Armstrong established the 

Physiological Research Unit as a branch in the 

Equipment Section of the Materiel Division 

at Wright Field. He discovered the Mineola 

chamber sitting idle, covered with dust in a 

storage room in the basement of the Equipment 

Branch laboratory building. He had the 

chamber refurbished and used it for two 

years to conduct research on the physiologic 

effects of altitude. During this period, the Air 

Service had an intense interest in developing a 

capability for long-range bombardment, which 

would again redefine the meaning of extreme 

environments. The Equipment Branch was 

assigned responsibility for development of a 

sealed pressure cabin for high-flying bomber 

aircraft. Dr. Armstrong was tasked to define 

the physiologic requirements for inclusion 

in a sealed cabin aircraft specification.5

 To meet this challenge, Captain Armstrong 

recruited several talented scientists from the 

academic community. One was J. William (Bill) 

Heim, Ph.D., about to complete postgraduate 

training in physiology at Harvard University. 

Dr. Heim accepted Captain Armstrong’s 

invitation to join the Wright Field Laboratory 

and remained to serve with distinction for 

more than thirty-one years. Bill Heim, after his 

retirement, reflected on his perceptions about 

Captain Armstrong, writing in his memoirs,

I should like to include some observations 

of this remarkable man who had such 

a profound influence on the future of 

aerospace medicine. I was soon to learn 

that Armstrong was a dedicated medical 

officer, soft spoken, with great personal 

charm and possessing a strong but not 

uncritical loyalty to the service. I was 

always amazed by the quiet, relaxed, yet 

self-assured manner in which he carried 

out his activities. No thrashing about, no 

hurried pace, no long over-time hours, yet 

everything he did seemed to count. As an 

outstanding characteristic, he appeared to 

be thoroughly enjoying everything he did 

and his enthusiasm was infectious. An 

almost undetected talent was his ability 

as an entrepreneur par excellence. With 

his disarming and convincing manner, he 

was a master of the soft sell; one found it 

Figure 4. Captain Harry Armstrong, Flight Surgeon, First 

Pursuit Group, Selfridge Field, MI, 1913-1934.

The Limitless Sky

94
extremely difficult to say no. Armstrong 

with his creative mind was a penetrating 

observer and a superb pragmatist, with 

the almost uncanny ability to isolate the 

core of a problem, perform a minimum of 

critical experiments, and apply the results 

to a practical solution.6

 Dr. Armstrong and his scientific team 

successfully developed the design requirements 

for pressurized cabins (Figure 5). The 

prototype system was incorporated into the 

XC35 aircraft, delivered by the Lockheed 

Corporation to Wright Field for flight-testing 

in the spring of 1937. Sealed-cabin technology 

was subsequently widely applied for inclusion 

in future commercial passenger aircraft 

and advanced Air Corps bomber aircraft 

beginning with the B29 Stratofortress.

 Recognizing that in addition to the effects 

of altitude, pilots were exposed to substantially 

increased G-forces during aerial maneuvers. 

Dr. Armstrong designed and had installed in 

a vacant balloon hangar on Wright Field the 

first human centrifuge to be used in the United 

States. Though exceedingly unsophisticated 

by modern standards, this novel research 

tool fabricated in the Equipment Branch 

machine shops served well. Dr. Armstrong 

performed extensive studies of the effects 

of accelerative forces on blood pressure, 

first using goats and finally humans.

 Dr. Armstrong’s research contributions 

encompassed virtually all aspects of aerospace 

medicine. The majority of his investigations 

were the first of their kind to be carried out 

anywhere in the world. An abbreviated list 

of the aeromedical problems he investigated 

during the six years he was director of 

the laboratory include the following:7

■ Oxygen want (hypoxia) and 

requirements for supplemental oxygen

■ Reduced atmospheric pressure effects 

on the middle ear, nasal sinuses and 

dental fillings

■ Explosive decompression, the risk 

of gas bubbles forming in the body 

and pre-breathing requirements

■ High altitude flight stresses including

cold exposure loss of body fluids and

flying fatigue

■ High positive and negative acceleration 

effects on blood pressure and vision

■ Pilot vertigo, airsickness and spatial

disorientation

■ Toxic hazards in the cockpit including

carbon monoxide and radioactive 

materials

 Dr. Armstrong perceived from the outset 

that the human element was one of the most 

important factors in aircraft system design; yet 

design engineers of his time paid little attention 

to the pilot’s needs for protection against the 

harsh environments encountered in flight. 

His goal was to develop robust, protection 

system design criteria backed up by rigorous 

Figure 5. Dr. Armstrong (seated) at work with his new altitude 

chamber (1937).

Pilots in Extreme Environments

95
scientific data, anticipating future advances in 

aircraft system development. This vision of Dr. 

Armstrong was strengthened and expanded by 

the pioneers who succeeded him. Another young 

physician, Dr. Otis O. Benson (then a captain) 

became the second chief of the laboratory. Under 

his direction, the Aeromedical Research Unit 

was withdrawn from the Equipment Laboratory 

and made a separate laboratory with three 

units of its own (Physiological, Biophysics, and 

Clinical Research). The Aeromedical Laboratory 

moved from its overcrowded quarters to a new 

building on Wright Field and was joined by 

its sister organization, the School of Aviation 

Medicine from Randolph AFB. Dr. Benson 

organized a research program for the laboratory 

that persisted throughout World War II. He 

staffed the laboratory with nationally known 

scientists, drawing significantly upon the 

contacts he had developed earlier in his training 

with the Mayo Clinic and the Harvard Fatigue 

Laboratory. Collaborating with the Mayo 

Clinic and other researchers, he established 

the human centrifuge unit that contributed 

to the development of the anti-G suit. Before 

World War II, he recognized the need for a 

radically different method of supplying oxygen 

to aircrews during high-altitude bombing. 

Under his leadership, the diluter-demand 

oxygen system was designed and perfected.8

The Demand for Advanced Technology: 

1950–1985

 Following World War II, Air Force 

aeromedical scientists at both the School 

of Aviation Medicine and the Aeromedical 

Research Laboratory continued to expand the 

scientific knowledge needed for new systems. 

From this living database came the criteria 

for protection systems and cockpit designs to 

enable aircrew to perform safely at extreme 

altitudes and supersonic speeds, in high and 

low ambient temperatures, exposed to high 

maneuvering acceleration forces, intense noise, 

and vibration, and fatiguing flight durations. 

As in its earliest days, the aeromedical 

scientist of the Air Force laboratories also 

continued to support the flyer in increasingly 

extreme environments and missions.

 With the advent of jet aircraft and the need 

to escape under adverse conditions, Colonel 

(Dr.) John Stapp led the way in his pioneering 

impact and deceleration research to define the 

limits of human tolerance. He recognized the 

Air Force would continue to fly higher and 

faster until it all but shattered the barriers of 

physical forces, but human limitations would 

persist unchanged with each new generation 

of aircraft. Early in his quest to define human 

impact limits, he earned the title The Fastest 

Man Aliveî when, on 10 December 1954, he 

rode the Sonic Wind I rocket sled, attaining 

a maximum speed of 639 mph in 5 seconds 

and decelerating in 1.25 seconds, sustaining a 

peak stopping-force of more than 40 Gs. His 

body, for brief moments, weighed 6,800 pounds 

(Figures 6, 7). The windblast and deceleration 

forces at his top speed were roughly equivalent 

to ejecting in an open seat at three times the 

speed of sound and from an altitude between 

55,000 and 60,000 feet. Escape from an aircraft 

during flight at high altitude and supersonic 

speed exposes the pilot to a variety of potentially 

lethal events. First the ejection force required 

to clear the aircraft empennage can cause 

crushing injury to the spinal column. Then, 

The Limitless Sky

96
the sudden exposure to windblast and winddrag deceleration can cause the limbs to flail 

and induce dangerous tumbling and spinning. 

In addition, the pilot ejecting at high altitude 

needs to be provided supplemental oxygen 

and be protected against exposure to intense 

cold and dangerously low barometric pressure. 

When Colonel Stapp began investigating these 

risk factors at Holloman AFB in the 1950s, 

aircraft escape systems were either inadequate 

or of unproven worth for aircraft flying faster 

than Mach 1 or at altitudes above 45,000 feet. 

Over the ensuing three years, Colonel Stapp 

personally made twenty-seven of the seventythree manned sled tests conducted as part of 

the deceleration project (Figure 8). The research 

data obtained from these groundbreaking 

studies, and from follow-on work using the 

Daisy Decelerator (a specially designed human 

impact simulator), defined human tolerance to 

windblast and a broad range of impact forces 

in all planes of body orientation. This data 

provided the designers the means to develop 

successive generations of highly capable escape 

systems.9

 During the 1970s and 1980s other 

aeromedical scientists developed mathematical 

models to support the system design process; 

however, it was the Air Force scientist, 

Colonel John Stapp, who forged the way.

Figure 6. Dr. Stapp riding Sonic Wind I Rocket Sled.

Figure 7. Dr. Stapp Windblast Exposure.

Figure 8. Dr. Stapp Deceleration Test.

Pilots in Extreme Environments

97
 Also in the early part of this period, there 

was significant research in support of full 

and partial pressure suit assemblies to meet 

high altitude emergency requirements. Stapp 

recruited Captain Joe Kittinger for Project 

Man High, a project begun in 1955 that would 

use balloons capable of high-altitude flight and 

a pressurized gondola (the basket or capsule 

suspended from the balloon) to study cosmic 

rays and determine if humans were physically 

and psychologically capable of extended travel 

at space-like altitude (above 99 percent of 

the Earth’s atmosphere). The Air Force had 

determined that a high-altitude balloon flight 

was the best way to conduct these studies 

because the periods that aircraft could remain 

at these altitudes would be too short to provide 

useful data. Using a two million cubic foot 

(56,634 cubic meter), 172.6-foot (52.6-meter) 

diameter balloon and a cramped aluminum alloy 

capsule manufactured by Winzen Research 

of Minneapolis, Kittinger made the first Man 

High ascent in June 1957, remaining aloft for 

almost seven hours and climbing to 96,000 feet 

(29,261 meters). Two additional Man High 

flights were made, one by Major Dave Simons 

to an altitude of 101,516 feet (a world altitude 

record at that time) and the other by Lieutenant 

Clifton McClure to 90,000 feet. Subsequent 

flights to test equipment and explore escape 

from high-altitude platforms were also flown 

in balloons, but with open gondolas. In 1960, 

Captain Joe Kittinger, floated to 102,800 

feet (31,333 meters) in Excelsior III, an open 

gondola adorned with a paper license plate 

that his five-year-old son had cut out of a cereal 

box (Figure 9). Protected against the subzero 

temperatures by layers of clothes and a pressure 

suit he experienced air temperatures as low as

 minus 94 degrees Fahrenheit (minus 70 degrees 

Celsius) and loaded down with gear that nearly 

doubled his weight, he climbed to his maximum 

Figure 9. Beginning the ascent in the Excelsior III gondola.

Figure 10. Captain Kittinger photographed by an automatic 

camera as he prepared to jump from 102,800 ft.

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98
altitude in one hour and 31 minutes, even 

though at 43,000 feet (13,106 meters) he began 

experiencing severe pain in his right hand that 

occurred as a result of a failure in his pressure 

glove and could have scrubbed the mission. He 

remained at peak altitude for about 12 minutes 

before he stepped from his gondola into the 

darkness of space (Figures 10, 11). After falling 

for 13 seconds, his 6-foot (1.8-meter) canopy 

parachute opened and stabilized his fall, 

preventing the flat spin that could have killed 

him. Only 4 minutes and 36 seconds were 

needed to bring him down to about 17,500 

feet (5,334 meters), where his regular 28-foot 

(8.5-meter) parachute opened, allowing him 

to float for the remainder of the way to Earth. 

His descent set the record for the longest 

parachute freefall, a record that stands today.9

In the 1960s and 1970s, the appearance of 

new operational requirements and new 

technologies to make them possible 

simultaneously led to another round of the 

definition of extreme environments. Flying 

higher, faster, longer, more maneuverably, and 

with increased workload, this all combined to 

stimulate the development of new scientific data 

to expand the envelope “and create new 

technologies to support the aircrew in their 

mission of To Fly and To Fight.” A 

comprehensive list of aircraft, medical, and 

protective equipment issues that must be 

considered for high-altitude flight is shown 

in Table 1.

Physiological Issues of High Altitude Flight

 In high-altitude flight, including space flight, 

a structural failure in a pressurized cabin or loss 

of cabin pressure control would be catastrophic 

without protection for the crew. Physiological 

effects of rapid decompression include acute 

hypoxia, effects on the gas-containing cavities 

of the body, decompression sickness, ebullism 

(vaporization of body fluids), and thermal 

exposure. Less rapid but equally debilitating 

effects of unpressurized flight at high altitude 

include hyperventilation, fatigue, reduction in 

effective circulating blood volume, and fainting 

associated with pressure breathing. Also, 

acceleration forces during high-speed egress can 

have a profound consequence on the skeletal 

structure and the cardiovascular system. All 

can have potentially grave effects upon aircrew 

performance and mission effectiveness, and all 

are avoidable by the employment of appropriate 

life-support equipment and adequate training. 

The SR–71 pressure suit maintains the 

crewmember at an equivalent altitude of 35,000 

Figure 11. Captain Kittinger stepts into space.

Pilots in Extreme Environments

99
feet breathing 100 percent oxygen (equivalent 

to being at sea level and breathing air), thereby 

preventing most of these problems.10, 11

Hypoxia

 Altitude hypoxia results when the oxygen 

partial pressure in the lungs falls below that 

comparable to sea level, but it is insignificant 

until the alveolar oxygen tension falls below 

a 10,000-foot equivalent. At 10,000 feet, 

the reduced ability to learn new tasks can be 

measured; consequently, 10,000 feet is used 

as the altitude that supplemental oxygen is 

considered necessary. As the partial pressure of 

oxygen in the inspired air continues to drop, the 

signs and symptoms of hypoxia become more 

evident and include loss of peripheral vision, 

skin sensations (numbness, tingling, or hot 

and cold sensations), cyanosis, euphoria, and 

eventually unconsciousness at higher altitudes. 

Up to an altitude of 34,000 feet, increasing 

the percentage of oxygen to 100 percent allows 

a sea-level oxygen equivalent. Above 40,000 

feet, breathing 100 percent oxygen without 

additional pressure is not sufficient for efficient 

aircrew performance. Positive pressure breathing 

is required and is accomplished by use of an 

oxygen system that delivers 100 percent oxygen 

at greater than ambient pressures. Without 

higher than tolerable pressure breathing, even 

a short exposure to altitudes higher than 

50,000 feet leads rapidly to unconsciousness. 

Thus, all aircrew must wear a partial or 

full pressure suit above this level.11, 12

Mechanical Effects

 During a cabin depressurization, gases 

trapped within the intestinal tract, nasal 

sinuses, middle ear, and lung will expand. The 

magnitude of the effect on the gas-containing 

cavities of the body is directly proportional 

to the range and rate of change of pressure. 

Serious consequences result when an occlusion 

or partial occlusion occurs between a gascontaining cavity and the environment.11, 12

Decompression Sickness

 Body tissues contain dissolved gases, 

principally nitrogen, in equilibrium with 

ambient atmospheric pressure. When ambient 

pressure is reduced, nitrogen bubbles form in 

body tissues. If the drop in pressure is not too 

great or too fast, bubbles evolved in the tissues 

are safely carried by the vascular system to the 

lungs where the evolved nitrogen is eliminated. 

Prolonged exposure to altitudes in excess of 

25,000 feet (occasionally between 20,000 and 

25,000 feet) may lead to one or more of the 

symptoms of decompression sickness, that is, 

bends, chokes, and circulatory and neurological 

disturbances Recent research has established 

the need for increasing the pressure differential 

(from 5 to 7 psi) in future aircraft that may 

fly at these higher altitudes.13 An increased 

variable-pressure differential has recently 

been suggested by Air Force researchers to 

provide less risk of decompression sickness 

resulting from potential of prolonged exposure 

to cabin altitudes in excess of ,000 feet.14

Ebullism

 When the total barometric pressure is 

less than the vapor pressure of tissue fluid at 

body temperature (47 mm Hg), vaporization 

of the body fluids occurs. This occurs in 

the nonpressurized portions of the body 

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100
at altitudes above 63,000 feet. However, 

exposure of peripheral regions of the body, 

for example, the hands, to pressures less than 

the vapor pressure of the tissue fluids leads to 

vaporization of these fluids with little or no 

impairment of performance. When combined 

with low environmental temperatures, 

the evaporative cooling associated with 

vaporization may accelerate freezing/drying 

of exposed tissues. When wearing only a 

mask for short exposures above 63,000 feet, 

vision is affected as a result of tearing and 

blinking during positive pressure breathing, 

effectively blinding the crewmember.14, 15

Thermal Extremes

 Low temperatures following the loss of 

cabin pressure at high altitude can cause 

impaired function and eventual tissue damage 

to exposed regions of the body or, in longer 

duration exposures, a drop in core temperature 

leading to progressingly impaired performance 

followed by unconsciousness and eventually 

death. An aircrew member wearing normal 

flying clothing with mask and gloves will 

not suffer any serious damage during a short 

exposure (5 minutes) to the lowest temperature 

conditions encountered at high altitude. 

Exposure beyond this time will lead to more 

severe peripheral cold injury unless appropriate 

clothing/heating garments are worn.2, 3 The 

garment must also protect against the heat 

where the temperatures on the outer surfaces 

of the SR–71 at cruise approach 560 degrees 

Fahrenheit as well as provide heat protection 

during the thermal pulse of ejection at Mach 3.16

Pressure Suit Development

 The first recorded suggestion for the use of 

pressure suits was by J.S. Haldane in 1920, 

who stated:

If it were required to go much above 40,000, 

and to a barometric pressure below 130 

mm Hg, it would be necessary to enclose the 

airman in an air-tight dress, somewhat similar 

to a diving dress, but capable of resisting an 

internal pressure of say 130 mm of mercury. 

This dress would be so arranged that even in a 

complete vacuum the contained oxygen would 

still have a pressure of 130 mm Hg. There 

would then be no physiological limit to the 

height attainable.

 Military application of pressure suits was 

limited in the early years, and efforts involving 

high-altitude protection were generally left to 

adventurers and their scientific advisers. Early 

pressure-suit development flourished as a result 

of both aviation and balloon contests. Over 

the years a multitude of developmental and 

operational pressure protection systems have 

been produced. Most of the developmental and 

production pressure suits naturally evolved 

as attempts to provide a more comfortable, 

lightweight, and functional protective system 

that conformed to the requirements of specific 

operational conditions, for example, from shortterm exposure to altitudes above 50,000 feet 

to moon walks in a vacuum. Full pressure suits 

(protective ensembles with associated regulators, 

oxygen systems, and ancillary hardware that 

completely enclose the aircrew member) have 

been shown to provide long-term protection 

against many of the effects of high-altitude 

exposure, but their acceptance has been limited, 

Pilots in Extreme Environments

101
except for high-altitude reconnaissance or 

flight-test missions. Their use often involves 

restrictions to the pilot’s visibility, mobility, 

and dexterity and tends to reduce mission 

effectiveness, as when a visor in front of the eyes 

makes night refueling difficult, even dangerous. 

Additionally, the visor acts as a condensing 

lens and becomes especially disturbing when 

the sun is in the forward field of vision.

 The first full pressure suit was developed by 

an English firm for American balloonist Mark 

Ridge in 1933. The suit was taken to 84,000 

feet with the body pressurized to 36,500 feet. 

This suit was used to break two world records 

in 1935. After several attempts to develop a suit 

that was reasonably comfortable, B.F. Goodrich 

built a suit of double-ply rubberized parachute 

fabric for Wiley Post in 1934. Components 

included pigskin gloves, rubber boots, and an 

aluminum helmet. The suit was pressurized 

to 7 psi, and ten flights were conducted before 

Post’s death in 1935. Several other countries, 

most notably the USSR, England, Germany, 

France, and Italy, developed full pressure suits 

during this period. Most of the emphasis in 

the newly formed U.S. Air Force in 1947, 

however, was directed toward partial pressure 

suits, suits that partially enclose the body 

and apply mechanical counterpressure, which 

generally provides shorter term protection to 

the effects of high-altitude exposure. On the 

other hand, the U.S. Navy placed their emphasis 

on omni-environmental, full pressure suits to 

combine altitude and immersion protection.

 From 1943 through 1948, the Air Force’s Dr. 

James Henry and others from the University of 

Southern California designed the capstan partial 

pressure suit and exposed subjects to 80,000 feet 

for varying lengths of time. The David Clark 

Company subsequently developed Dr. Henry’s 

original capstan partial pressure suit and 

produced the first operational models in custom 

sizes for early rocket-powered Xplane test pilots, 

for example, Yeager et al. They produced the T1 

capstan pressure suit in standardized sizes made 

of nylon cotton twill. It was chamber-tested to 

106,000 feet and subsequently flown in a variety 

of high-altitude aircraft. The T1 capstan suit 

(5-to-1 capstan to suit ratio) incorporated an 

anti-G suit, had no chest bladder, and was made 

in twelve standardized sizes for fighter aircraft. 

This was followed by several modified capstan 

suits, for example, the MC1, MB1, MC3(A), 

MC4(A), CSU2P, and S100, that incorporated 

standard sizing, chest bladders for easier 

breathing at extreme altitudes, and looser fit for 

more comfort, as well as anti-G suits for fighter 

aircraft. Capstan partial pressure suits were 

adopted for the original U2 pilots and continued 

in use until the last original U2C model was 

retired from service in 1989. A bladder-type 

partial pressure suit produced by David Clark, 

the CSU4/P, was used by Colonel Joe Kittinger 

in the stratosphere jump. Interestingly, a variant 

of the CSU4/P, the 1032 Launch Entry Suit, 

was produced by the David Clark Company 

many years later for National Aeronautics and 

Space Administration (NASA) astronauts

 The B.F. Goodrich Omni-Environmental 

Full Pressure Suit was developed in 1948 by 

the Navy. Suits had earlier been developed by 

Goodrich for the Doolittle mission in 1942. 

In 1951, an entirely new full pressure suit was 

produced by the David Clark Company for 

D5582 Douglas Skyrocket test pilots. It was 

first flown by Scott Crossfield for his recordThe Limitless Sky

102
breaking Mach 2 flight in the D5582 and later 

by Navy test pilot Marion Carl for an 85,000-

foot altitude record flight (Figure 12). This 

suit became the forerunner of the Air Force’s 

X15 full pressure suits produced by David 

Clark Company for Scott Crossfield, NACA 

(Figure 13). A custom-modified U.S. Navy 

Mark IV Series full pressure suit produced 

by B.F. Goodrich was also developed as a 

backup emergency system for intravehicular 

activity for the Mercury program. In the early 

1960s, the David Clark Company produced 

the Air Force’s first standardized full pressure 

suit, the A/P 22S2. Numerous other models 

(the 4, 6, and 6A) followed over the years.

 Except for the space suits produced by 

ILC Dover for NASA (for the Apollo, 

Lunar, and Skylab programs), most of the 

full pressure suits from the 1950s on were 

produced by the David Clark Company, 

including NASA, Gemini, and Apollo Block 

1 spacesuits. The MC2 full pressure suit was 

developed with an integrated parachute harness 

and was first used in the X15 aircraft.

 The first high-altitude S901 series full 

pressure suits were produced by the David 

Clark Company in early 1960 specifically for 

Figure 12. Navy test pilot, Marion Carl, in D–558–2 the Blackbird (Figure 14). These suits went 

pressure suit.

Figure 13 Test piolt, Scott Crossfield, in front of his X–15. Figure 14. SR–71 pressure suit cira 1968.

Pilots in Extreme Environments

103
through continued design changes through the 

A12, YF12A, and SR–71 programs. It was a 

full pressure suit with integrated subsystems, 

parachute harness, automatic flotation system, 

urine collection device, redundant pressure 

control and breathing system, thermal protective 

garment, custom sizing plus twelve standard 

sizes, and various models leading to the S901J 

which was specifically developed for the SR–71 

aircraft. In 1977 the S901J was replaced by 

the S1030 series suit, a full pressure suit with 

link net and integrated subsystems. This suit 

incorporated five layers: the first consisted of 

long cotton underwear, glove liners, a ventilating 

system, and socks that wick moisture from the 

skin and provide a means for removing heat 

buildup; the second was a pressure containment 

layer; the third, a restraint layer; the fourth, a 

coverall; and the fifth, a vest that integrated the 

parachute, survival kit, and flotation system. 

By the mid-1980s, the S1031 had become the 

protective suit for the SR–71 as well as the 

newer U2R aircraft and was later modified to fit 

female pilots. In the 1990s, the S1034 replaced 

the S1031 combining integrated life support 

systems with breathable pressure bladders of 

Goretex. A variant of the S1034 was adopted by 

NASA for shuttle astronauts in the early 1990s, 

designated the S1035 Advanced Crew Escape 

Suit, replacing the S1032 launch/entry suit.17

 Over the past three decades, several other 

suits have been prototyped and tested by U.S. 

Air Force research laboratories at WrightPatterson and Brooks AFBs in cooperation with 

the Life Support System Program Office to 

provide protection from newer threats as well as 

to test innovative concepts that potentially would 

provide greater safety, mobility and comfort for 

the aircrew of high-altitude aircraft (Figure 15):

■ Prototype High-Altitude Flying Outfit 

(PHAFO): A 1979 prototype partial 

pressure suit by David Clark to integrate 

altitude, thermal, immersion, chemical 

defense, and anti-G protection. It 

incorporated a nonconformal (Dome Type) 

full pressure helmet with oxygen mask.

■ High-Altitude Flying Outfit (HAFO): 

A 1979 prototype developmental full 

pressure suit with integrated thermal/

pressure/chemical defense/immersion and 

anti-G protection, produced by ILC Dover.

■ Advanced High-Altitude Flight Suit 

(AHAFS): A high-pressure (56 psi) 

full pressure suit developed for the 

Air Force by ILC Dover to increase 

mobility at higher operating pressures 

and reduce the possibility of bends 

at the higher cabin altitudes.

■ Tactical Life Support System (TLSS): 

Developed by, among others, the 

USAF School of Aerospace Medicine, 

Life Support System Program Office, 

and Boeing/Gentex to provide shortterm protection from 60,000 feet. It 

incorporated many new features combining 

a modular high-pressure mask, vest, antiG suit ensemble integrated to provide 

Pressure Breathing for G (PBG) for high 

G-maneuvers, and Pressure Breathing for 

Altitude (PBA) for altitude, with 

G-trousers providing four times the 

breathing pressure from a molecular 

sieve oxygen-concentration system. As 

an Advanced Development program, the 

charter of the TLSS effort was to provide 

a vehicle to incorporate the laboratorygenerated technical advancements into 

an integrated system to improve aircrew 

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104
life support. Concepts advanced by TLSS 

are being used in current life-support 

systems and are being evaluated for the 

next generation of life-support equipment. 

Specifically, TLSS pressure breathing 

concepts are flying today in Combat Edge 

and in a pressure breathing system for both 

altitude and +Gz protection developed for 

the F22.18 The United Kingdom, Canada, 

Sweden, Finland, and France use many 

variants of similar protective design.

While it is nearly impossible to predict all 

new threat scenarios that may emerge over the 

next ten to twenty years, attempts to outline 

anticipated needs for high-altitude systems have 

been proposed by U.S. Air Force laboratory 

personnel. For full pressure systems associated 

with reconnaissance flights, the following apply:

■ Protection to altitudes above 80,000 

for extended periods (16 hours).

■ Ejection/windblast protection.

■ Protection against high and 

low temperatures.

■ Protection against nuclear, biological, 

and chemical (NBC) agents and 

provide for selfdon/doff capability 

in the NBC environment.

■ Provide a system that is lightweight, 

durable, and easily maintained in 

an NBC environment, to include 

being decontaminable.

■ Provide adequate mobility for 

accessibility to aircraft and 

instruments without assistance.

■ Eliminate requirement for prebreathing 

100 percent oxygen with oxygenation 

equivalent to breathing air at sea level.

■ Allow fluid intake, feeding, urine 

output, temperature regulation, and 

increased tactile capabilities.

■ Provide a lightweight helmet, optically 

correct visor with unrestricted 

vision, visor heating and defogging, 

anti-reflectance coating, improved 

spectacle mounting, communications, 

and improved head mobility.

■ Provide anti-drown and antisuffocation features.

■ Provide laser and flash protection.

■ Provide coverall with improved hold-down, 

integrated flotation, parachute harness, 

fire protection, and ancillary hardware.

■ Provide gloves with improved

sizing, tactility, and dexterity.

■ Provide built-in test features.

■ Provide better supportability and 

reduce training with minimum 

service life of six years.

 The ideal life-support system should not 

reduce routine flying efficiency. A compromise 

however is necessary between minimal reduction 

in performance and adequate protection after 

loss of cabin pressure or during egress. The 

success of the crew station pressurization 

system/configuration and protective clothing 

and equipment will depend on the correctness 

of trade studies and evaluations and on the 

Figure 15. Francis Gary Powers, Jr., suited up for U–2 flight, 

circa 2000.

Pilots in Extreme Environments

105
verify that this was the same freighter that 

sailed from Bulgaria carrying sophisticated 

military aircraft and weaponry.

 The U.S. intelligence community, not 

wanting to be surprised by another Cuban 

missile crisis or military buildup, tapped a 

Giant Clipper SR–71 mission to fly from Beale 

AFB, California, to monitor activities in and 

around Cuba, focusing on any military activity 

in Nicaragua. The belief was that the Soviet 

Union was supplying the Nicaraguan defense 

ministry so that it could become a dominant 

communist regime in Central America which 

would possibly threaten the United States 

and neighboring Latin American states. The 

SR–71 crews knew an equally important part 

of their mission was to show the flag and let 

the bad guys know we were watching them.

 At first, it appeared the Bukuriani was 

heading through the Mediterranean and 

straight across the Atlantic for Cuba. But in 

mid-October, an SR–71 Giant Clipper mission 

determined that the freighter had altered its 

course and was sailing around Cape Horn. 

Its destination, while still unknown, was now 

assessment of other requirements such as 

oxygen regulation systems; head protection 

from impact and buffeting; eye protection from 

laser hazards; dazzling glare and nuclear flash; 

head-up-displays; aircraft escape/evasion; and 

chemical, biological, and radiation protection.

Applying Science and Technology: The 

Bukuriani Mission

 The real meaning of what we do in our 

laboratories and why it is vital to our national 

security becomes clear when you consider the 

results that can be achieved by these capabilities. 

One example involved me in an up-close and 

personalî fashion and, I believe, makes the point 

about the importance of science and technology.

 The circumstances leading up to my mission 

on 31 October 1984, evolved quickly. The 

Bulgarian ocean freighter Bukuriani had been 

continuously tracked during her transatlantic 

voyage. At times during the several weeks the 

freighter was tracked, clouds and severe weather 

blurred the satellite images, and at times U.S. 

intelligence personnel lost track of the ship. 

When the weather cleared, they located the 

freighter in port 

in Nicaragua 

where port 

authority 

personnel were 

photographed 

unloading the 

suspicious large 

cargo crates. The 

U.S. military 

decided to send 

reconnaissance 

aircraft to Figure 16. An SR–71 Blackbird at rotation.

The Limitless Sky

106
thought to be Peru. On October 26th, Major 

Ron Tabor, my reconnaissance systems officer 

(RSO), and I were tasked to fly a routine 

Clipper mission a normal launch at the crackof-dawn, California time, refueling thirty 

minutes after takeoff over Idaho, Mach 3 across 

the south-central United States, and descending 

to a KC10 from Barksdale AFB, Louisiana, over 

the Gulf of Mexico (Figure 16). The weather in 

the take area “was excellent; therefore we were 

sure the intelligence data was going to be of the 

highest quality. We didn’t realize it then, but 

we already had the proof that the Bukuriani 

was not going to Cuba. It would arrive two 

weeks later on Wednesday, November 7th, in 

the Nicaraguan port of Corinto, on the Pacific 

side. As U.S. voters were reelecting President 

Reagan for his second term, my crew and 

another were both in the vault,” planning a very 

unusual Clipper mission. This time the take 

area was not Cuba; rather, it was Nicaragua.

 Because the SR–71 can achieve speeds of 

over thousands of miles per hour, coupled with 

the fact that Nicaragua is such a small country, 

the target area for intelligence reconnaissance 

looked to be very difficult to approach and 

photograph. Besides the peculiar target area, 

this mission was unusual for several reasons. 

Instead of arriving in the area of interest at 

about noon, when sun-angles were at their 

optimum for a photo mission, we were going 

to arrive just after sunrise in order to wake upî 

the Sandinistas. Even at altitudes above 80,000 

feet, the shock wave from an SR–71 creates 

window-shaking double-booms on the ground. 

A Nicaraguan Defense Ministry spokesman 

later said the sonic booms caused mass panic 

that morning as Nicaraguan ministers told 

the people the United States was mobilizing 

for an intense war against them. When they 

heard the “booms” they assumed a military 

onslaught from the United States was imminent. 

Residents in Central and South America 

were accustomed to U.S. reconnaissance 

missions by both SR–71s and C130 cargo 

planes, but this time, it was different. They 

were told to be ready for war with the United 

States Frightened residents poured into the 

streets of Managua, Nicaragua’s capital city.

 Another reason this mission was unusual 

was the requirement to stay within Nicaraguan 

airspace. Generally, during night missions, 

aircraft bank-angles were limited to 30 degrees. 

On this mission however, because of the 

speed and small area of interest, we had to 

bank the SR–71 up to 45 degrees. This type 

of maneuvering is dangerous because above 

80,000 feet at nighttime, visual references to 

a natural horizon are virtually nonexistent. If 

we missed the target area, we would have to 

do a literal U-turn and return to the target 

area, which at Mach 3 involves hundreds of 

miles to maneuver and complete. If the aircraft 

instrumentation and autopilot malfunctioned, 

the Blackbird would more than likely transition 

to an uncontrollable, unrecoverable attitude.

 The most unusual aspect of this mission was 

that we were going to launch two SR–71s. The 

plan was to launch a second, spare SR–71 thirty 

minutes after the first one departed. If for any 

reason the primary aircraft aborted, the second 

aircraft would continue to fly through the takearea. I was scheduled to fly the backup SR–71. 

The reason we used two aircraft was that this 

mission had the highest interest level that of 

the President. One of President Reagan’s issues 

Pilots in Extreme Environments

107
in his platform for his second election regarded 

more peaceful foreign diplomacy with the 

Soviet Union. Because the DoD and the White 

House believed that Moscow was aggravating 

U.S. foreign policies with its military support 

of the Nicaraguan communist government, 

Reagan’s desires for peace settlements with the 

Soviet Union would be most likely postponed.

 At Strategic Air Command Headquarters, 

a three-star general was the action officer 

calling the shots on this mission. During 

the initial planning session, I was designated 

to fly the backup SR–71, which I didn’t 

expect to fly because the primary aircraft 

had a very high launch rate. The scheduled 

launch on October 31st for the first plane 

was 2:30 AM; my launch was at 3:00 if the 

primary bird had a problem. As a standard 

procedure, we started engines forty minutes 

prior to a launch. Both aircraft went through 

normal starting and taxiing procedures. By 

the time I got to the last-chance inspection 

area at the end of the runway, the primary 

aircraft was on the runway ready to launch.

 Then I heard the primary pilot say “Tower, 

Aspen 30 request a 180 to taxi off the active and 

abort the launch.” My aircraft was now the only 

one able to accomplish the mission. The next 

thing I heard over our special Aspen Control 

frequency was “good luck Lorenzo” (Lorenzo 

was my call sign). I asked my RSO “are we ready 

for this?” His reply to me was a confident “you 

bet,” and then to the tower, “Aspen 31 is ready 

for departure.” We launched at 3 AM and zero 

seconds. After a great sortie, we returned to 

Beale at about 9:30 AM. The imagery confirmed 

the Bukuriani was in port, but the crates 

had not yet been offloaded. Once more the 

Soviet Union and the United States were on 

opposite sides of an international controversy.

 A couple of days later, on November 9th, 

we were preparing to fly back to Nicaragua, 

this time in the primary aircraft. International 

tensions were growing rapidly. Nicaraguan 

military intelligence personnel claimed a 

U.S. military ship had entered their waters, 

posing a threat to their national security. 

U.S. officials claimed that the ship was 

more than twelve miles off the coast, not 

inflicting any threats. Nicaraguan military 

personnel also fired antiaircraft missiles 

at a U.S. C–130, which they believed was 

flying too close to the ground. While the 

U.S. contended that it was flying a routine 

mission over South America in international 

airspace, not threatening the Nicaraguan 

national security, the Nicaraguan government 

informed its citizens that the United States 

was mobilizing to go to war against them and 

bid its people to prepare to fight U.S. soldiers.

 The mission planners were unable to give 

us a flight profile in advance because they were 

building it until just a few hours before launch 

time. My RSO and I finally received the mission 

profile at 1 AM during breakfast. Fortunately, 

the only changes were in the take-area. I had to 

fly at Mach 2.8 because the turning radius was 

too great for anything faster. Our launch was 

flawless. Once again the Sandinistas were able 

to set their alarm clocks at 8:30 in Managua 

to our thunderous sonic boom. This time they 

were on the edge of their seats starting to 

mobilize their citizens for the potential war with 

the United States. One of their revolutionary 

commanders said that they were preparing for 

a Reagan-launched direct and massive war.

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108
 By Saturday morning, 10 November 1984, 

we were exhausted. Two back-to-back SR–71 

sorties drained us physically and mentally. 

This plane was the most intense aircraft to fly, 

and after just a single mission even the most 

physically fit have to rest and recuperate. It was 

time for a break. Since we were on early wakeup 

for the last two weeks, we were up early and had 

a normal, relaxing breakfast. When I returned 

home at 11 AM, I found about twenty messages 

on my answering machine. We were to go back 

to Nicaragua a third time. My RSO and I were 

ready, but when we returned to Beale, the State 

Department declared the MiG21 crisis over.

 Though few knew what we were doing, 

the purpose of the SR–71 missions was to 

ensure that U.S. foreign policy was enforced in 

belligerent communist countries. Those who flew 

these planes were the Air Force’s elite pilots and 

RSOs, as there were fewer SR–71 pilots than 

there were U.S. astronauts. The world may never 

know if the Bukuriani was actually carrying 

crated MiG21 fighters to the Nicaraguan port 

of Corinto. Officials said privately that the 

department’s objective was to allow the Soviets 

an opportunity to take the jets home without 

having to admit they were even there in the 

first place. This strategy was believed to be 

the best way to end this matter peacefull.

EPILOGUE

 Military mastery of air and space places the 

air crewman in the harshest of environments. 

The in-house aeromedical laboratories are 

steadfast in their pursuit of basic science, 

producing new technologies often before a 

formal operational requirement is endorsed 

by the user. The lesson to be learned from this 

historical review is that research consumes 

a great deal of time, and technology-push 

is an important research concept that must 

not be overlooked in the rush to support 

the user’s perceived immediate need.

 Forecasting potentially useful new 

mission capabilities for aircraft entering 

the operational inventory will sometimes 

identify future technology challenges not yet 

validated by the operational community.

 The Air Force Research Laboratory’s Human 

Effectiveness Directorate recently initiated 

an in-house, technology-push project called 

the Sustained High Altitude Respiratory 

Protection and Enhanced Design G Ensemble 

(Sharp Edge).19 The potential operational 

need for a new altitude protective system was 

examined and the physiologic implications of 

a rapid decompression were addressed. The 

requirements for an altitude protective system 

to permit flight above 60,000 feet were outlined, 

followed by a technology assessment of current 

life support systems. The Sharp Edge system 

would be required to interface with current 

life-support systems, including helmet-mounted 

displays, chemical and biological defense 

systems, and oxygen and anti-G ensembles. 

Figure 17. Enforcing U.S. foreign policy from the edge of space.

Pilots in Extreme Environments

109
These interface and integration requirements 

were summarized, and the difficulties 

likely to be encountered were identified Finally, 

design recommendations were made for the 

development of the Sharp Edge ensemble. 

In addition to this effort, a technology 

watch for newer materials that should lead 

to aircrew acceptability of an enhanced 

life-support system is ongoing.

 The Air Force human systems scientists and 

engineers continue to fulfill the vital role of 

developing the technology for protecting the 

human operator, keeping pace with expanding 

operational demands. The Air Force owes 

much to the pioneers at Hazelhurst Field and 

all those who followed in their footstepts.

The Limitless Sky

110
Aircraft/Crew Issues

Flight Scenarios

Flight altitude

Duration of flight

Cabin Pressurization

Cabin pressure differential

Cabin volume

Size orifice

Decompression rate

Transient cabin pressure after RD

Flight altitude required post RD

Human Factors

Performance degradation

Workspace limitations

Equipment acceptability

Fit/Function of equipment

Crew comfort

Crew safety

Physiological Issues

Hypoxia

Oxygen concentration required

Oxygen pressure/flow schedule

Time of exposure to altitude

Breathing resistance

Breathing pressure swings

Decompression Sickness

Bends, chokes, CNS disturbances

Exposure times

Prebreathe requirements

Workload

Positive Pressure Breathing

Pressure/flow requirements

Cardiovascular effects

Relative gas expansion

Hyperventilation

Pressure breathing limits

Mask vs. intrathoracic pressures

Pulmonary overpressure

Gas embolism

Pneumothorax

Training

Ebullism

Altitude/duration of exposure

Unpressurized areas of body

Short-/long-term effects

Trapped Gas

Pulmonary overpressure

Rapid decompression

Delayed ear block

G-induced atelectasis

Sinuses

GI tract

Thermal

Temperature

Duration of exposure

Protective clothing

Life Suport Systems

Oxygen Systems

MSOC Volume/Flow Requirements

Concentration schedules

Filtered air bypass

Purge valves

Sensors/indicators

LOX Converters

Supply requirements

Storage requirements

Indicators/regulators

Gauges/heat exchangers

Gas High Pressures

Supply requirements

Volume/flow requirements

Backup to MSOC

Emergency oxygen

Regulators

Concentration schedules

Pressure schedules

Diluter demand vs. 100 percent

Delivery rates

Inlet/outlet pressures

Breathing resistance

Oscillatory behavior

Relief valves

Panel/seat/man mounting

Vest/no vest press sched

Indicators/connectors

Shut-off valves

Masks

 Retention capabilities

 Auto/manual tensioning

 Mask cavity pressures

 Breathing resistance

 Pressure compensation

 Quick disconnect warning

 Comfort

Pressure Ensembles

Mask/Vest/G-Suit

PBA Schedules

PBG Schedules

Post-ejection schedules

Dual anti-G suit bladders

Sleeved vest/venous pooling

Fully Enclosed Mask/Helmet

Isolation valves

Mask/vest differentials

Max. acceptable protection

Partial-pressure Suit/Enclosed Helmet

Pressure schedule 140 TORR ABS

Full-pressure Suit/Enclosed Helmet Complexity of Issues Involved in High Altitude Flight. Pressure Schedule 180 TORR ABS

Pilots in Extreme Environments

111
Exploiting the High Ground:

The U.S. Air Force and the Space Environment

Barron K. Oder

William F. Denig

Major William B. Cade III, USAF
Abstract

 Since the 1930s, the U.S. Air Force and its predecessor 

organizations conducted state-of-the-art research into natural events 

in the atmosphere that affected air operations. Because atmospheric 

conditions frequently inhibited or prohibited Air Force missions 

during World War II, the service deployed its scientists and 

engineers to study, understand, and overcome these obstacles to 

national defense. After that war, Air Force experts developed 

many advanced solutions to atmospheric challenges, including an 

understanding of how solar activity interfered with high-frequency 

radio transmissions. At the same time, the Air Force conducted 

research of the upper atmosphere in anticipation of supersonic jet 

and guided missile operations. Before the start of the space age in 

October 1957, Air Force scientists and engineers had conducted 

research to characterize and understand the space environment. 

During the 1960s, space weather capabilities began to evolve into 

a separate expertise, largely in response to the North American 

Aerospace Defense Command’s mission. Ever since, the Air Force, 

in cooperation with the Department of Commerce, has consistently 

added new capabilities for understanding and forecasting space 

weather. These accomplishments built upon one another over time 

to create some of the most sophisticated space weather systems that 

support operations by the world’s finest air and space force.

 An often-overlooked aspect of the success of the evolution and 

development of the United States Air Force’s air power is the effect 

of weather on flight operations. Perhaps an even less appreciated 

aspect of the Air Force’s warfighting capability has been the effect of 

the space environment upon Air Force systems that operate within 

and through space. It is now recognized that without a thorough 

understanding of the harsh realities of the space environment the 

technological superiority of the United States may be compromised. 

The ability of the U.S. Air Force to fully exploit the advantages 
of space, often called the ultimate high ground, was the result of 

science and technology investments in understanding the space 

environment. Recent advancements in specifying and forecasting the 

space environment has led to a realization that space weather is the 

high-altitude counterpart of terrestrial weather. Yet space weather 

is in its infancy when compared with terrestrial weather due in 

large part to the complexity of the near-Earth space environment 

and the general paucity of measurements. A maturation of space 

weather requires a national strategy in which the Air Force has and 

is playing a key role. Like many other new areas of research, the 

history of space weather is a tale of cooperation between America’s 

civilian and military scientists and engineers.
EVOLUTION OF TERRESTRIAL 

WEATHER

 Americans have a long history of interest in 

weather conditions. In what would become the 

United States, the earliest records of regular 

weather condition observations date to 1644, 

more than 125 years before the Declaration of 

Independence. Thomas Jefferson, remembered 

for his work on the Declaration in 1776 and 

as the third President of the United States 

from 1801 to 1809, was also considered a 

weather expert in his day and often responded 

to questions about American weather and 

climate1 based on his almost unbroken series 

of weather observations from 1776 to 1816.2

A lack of adequate tools hampered these early 

weather enthusiasts but did not diminish their 

interest and pursuit of knowledge and the 

advancement of science. Benjamin Franklin, for 

example, charted the Gulf Stream remarkably 

well from observations obtained during his 

many trips across the Atlantic Ocean, tried to 

study a whirlwind while riding a horse, and 

plotted the movement of a hurricane after 

evaluating reports from fellow postmasters.3

 During the War of 1812, the United 

States government made its first entry into 

routine weather data collection. In 1814, Dr. 

James Tilton, Surgeon General of the U.S. 

Army, directed hospital surgeons to observe 

the weather and keep climatological records 

because of widespread interest in finding a 

relationship between weather and health.4

 Dr. 

Joseph Lovell, Dr. Tilton’s successor, ordered 

Army surgeons at hospitals throughout the 

nation to prepare reports which outlined the 

climate, diseases most prevalent in the vicinity, 

their most probable causes, and the general 

state of the local weather-temperature, wind, 

rain, etc. Initially using only thermometers 

and weathervanes, by the early 1840s Army 

surgeons eventually added rain gauges, 

barometers, and hygrometers. In 1842, 

Congress appointed the first Meteorologist 

to the U.S. Government and assigned the 

position to the Surgeon General’s Office.5

 The U.S. military continued to serve as the 

nation’s leader for weather data collection and 

dissemination through the Civil War and later. 

Acting in accordance with directions from 

Congress, the War Department, starting in 

1870, collected meteorological observations 

at the military stations in the interior of the 

continent and at other points in the states 

and territories of the United States, and for 

giving notice on the northern lakes and on the 

seacoast, by magnetic telegraph and marine 

signals, of the approach and force of the storms. 

The Army responded by establishing a school 

of instruction in meteorology that helped 

train troops for their new weather-related 

duties. In 1870, the first bulletin announcing 

storms on the Great Lakes was published. In 

January of the following year the first ‘weather 

probabilities’ were published, offering forecasts 

three times daily for eight regions in the nation.6

 On 1 October 1890, Congress directed the 

U.S. military to turn over its infrastructure 

(which included 178 weather stations, of 

which 26 featured automatic instruments), 

personnel, and responsibility for weather duty 

to the newly created U.S. Weather Bureau, 

then part of the Department of Agriculture, 

effective 1 July 1891. This transfer effectively 

ended the military’s role in the nation’s weather 

service, except for a limited capability to 

Exploiting the High Ground

117
provide ballistic data for artillery firing, until 

America’s entry into World War I in 1917.7

WEATHER EFFECTS ON SYSTEMS: 

WORLD WAR I THROUGH THE 

GREAT DEPRESSION

 During the years before America’s declaration 

of war, European belligerents quickly learned 

that weather conditions not only affected 

ground and naval operations, but also the newer 

weapons of modern warfare. For example, at 

the Battle of Jutland, the only major surface 

engagement between the British and German 

battle fleets during World War I, bad weather 

prevented German zeppelins from flying 

scouting missions prior to battle. This lack of 

reconnaissance kept the Germans unaware that 

the greatly superior British fleet had put out 

to sea and had every intention of surprising 

the German fleet in what the British hoped 

would be the decisive engagement of the war.8

On 31 January 1915, the Germans unleashed 

the first use of poison gas during the Battle 

of Bolimov on the Russian front. Because of 

extremely low temperatures on the battlefield, 

the gas was so ineffective that the Russians did 

not report the gas attack to the other Allies. 

The Russian failure to communicate the news 

about the poison gas attack made the first 

use of the weapon by the Germans on the 

Western Front during the Second Battle of 

Ypres in April 1915 all the more shocking to 

the Allies.9

 Another weather-related limitation 

on the use of poison gas was more obvious: gas 

could only be used when the wind blew in the 

proper direction for a useful length of time.

 After America entered the war, weather 

became one of the nation’s most challenging 

foes, and bad weather often spoiled the plans 

of America’s Airmen in 1918. In May 1918, 

rain caused the loss of six of the Ninety-Sixth 

Aero Squadron’s seven aircraft when the planes 

had to admit they could not only not find their 

target, but that they were lost and had to land 

behind German lines. Even strong-willed air 

power advocate Colonel Billy Mitchell could 

not conquer the weather. As part of the major 

American St. Mihiel offensive, Mitchell had 

planned to conduct the largest air show of the 

whole war 1,481 aircraft, 609 of which were 

American. However, heavy rains from early 

September through the signing of the Armistice 

on 11 November 1918 meant formation 

flying by bombers was impossible. Under 

the best of conditions, mud made airfields 

almost useless, which meant the formations 

that managed to take to the air were small 

and unable to withstand aggressive attacks 

from intercepting German fighter aircraft.10

 Because of these experiences in how weather 

could impair or halt the most promising 

operations, America’s warfighters appreciated 

the need for further integration between tactics 

and meteorology. One Department of Defense 

(DoD) study noted that, as of the beginning 

of the Second World War, all the military 

forces of the world had more or less adequate 

meteorological services. At the same time, 

civilian meteorology had likewise gained in 

experience, but the problems that confronted 

the military meteorologists differed in many 

respects from those encountered by their civilian 

counterparts, and a great deal of research by 

military and civilian experts would later have to 

be done at the height of World War II to help 

secure final victory over the Axis powers.11

The Limitless Sky

118
 The reasons for the shortcomings in weather 

services were several. In the years after the 

First World War the United States reverted 

to its isolationist tendencies, endured the 

hardships of the Great Depression in the 1930s, 

and made no meaningful investments in air 

power or weather forecasting techniques nor 

equipment.12 According to one recent study, 

During the depression, careful thought had to 

go into the development of technology before 

awarding a contract for aircraft purchase. 

Because rapid aeronautical advances and new 

ideas for tactical employment had created 

demand for an improved version, a new aircraft 

was often obsolete by the time it hit the field.13

Attempts to create a separate United States 

Air Force met with limited success, despite 

Brigadier General Billy Mitchell’s successful 

demonstration in 1921, when he and aircraft 

under his command sank the German 

battleship Ostfriesland, a prize of war from 

World War I. Mitchell’s subsequent demotion 

to colonel and court-martial in 1925, for his 

outspoken opposition to the status quo in the 

military’s hierarchy, likewise failed to achieve 

the establishment of a separate air force.1

 When the Army Air Corps began to deliver 

the nation’s airmail in February 1934, it was 

ill-prepared to do so. In less than one month 

of poor flying conditions, ten Air Corps 

pilots lost their lives,15 scant recompense for 

the claim that despite the many crashes and 

deaths, not one pound of the 777,389 pounds 

of mail flown was ever lost.16 The Air Corps 

took the brunt of the blame for the serious 

degradation in mail service, and few accepted 

the explanation that flying conditions in 

February 1934 were unusually harsh and that 

sorrowful meteorological and ground support 

hindered Air Corps effectiveness.17 Based 

on results or on impressions formed from 

media reports, this additional duty failed to 

demonstrate to any decision makers the value 

of, or the need for, a separate U.S. Air Force.

 Nevertheless, several important events, 

discoveries, and inventions marked this period. 

In 1924, Edward V. Appleton led an effort to 

verify the 1902 theory of Oliver Heaviside and 

Arthur Edwin Kennelly, who independently 

and almost simultaneously theorized the 

existence of the ionosphere, which allowed 

radio waves to bend with the earth’s curvature. 

Appleton’s 1924 work, in cooperation with 

the British Broadcasting Corporation, proved 

the existence of the E-layer of the ionosphere 

and measured the layer’s height. During an 

additional experiment in 1926, Appleton 

discovered an upper area of the ionosphere, 

called the F-region. He went on to study radiowave propagation in the ionosphere, which 

ultimately made significant contributions to the 

timely invention of radar during World War II.18

General Billy Mitchell 

demonstrated that 

aircraft could sink a 

battleship, but the 

weather hindered his

efforts to stage the

largest offensive

during World War I. 

Exploiting the High Ground

119
WEATHER, BOMBERS, AND 

ROCKETS–WORLD WAR II RAISES 

THE ALTITUDE

 World War II demonstrated the versatility 

and power of a modern air force. From the role 

of aircraft in the innovative German blitzkrieg 

to aircraft carrier operations over vast stretches 

of the Pacific Ocean to the strategic bombing 

campaign against the Axis powers, America’s 

Army Air Forces made significant contributions 

to the ultimate Allied victory in 1945. Events 

during the war showed that weather forecasts for 

military purposes relied more on past weather 

trends than provided a reliable, accurate forecast 

of what tomorrow’s weather might bring.19

Tides played an important role in deciding 

when amphibious operations could most likely 

meet with success. The most widely circulated 

account of the importance of weather to an 

Allied operation is the weather forecast for 

the Allied invasion of Europe at Normandy, 

Operation Overlord, on 6 June 1944.20

 World War II also provided other clues to 

the effects of the Sun and the space environment 

on man-made systems. Interruptions in highfrequency radio signals hinted at ionospheric 

influences. British radar operators, in February 

1942, encountered such severe interference 

that they feared the Nazis were actively 

jamming British radar stations as a novel type 

of preinvasion bombardment. However, British 

scientists discovered that the Sun was a powerful 

and highly variable radio transmitter and that 

sunspots and other forms of solar activity were 

producing potent radio emissions. The enemy of 

the radar was not the Germans but the Sun.21

This was the first time scientists had proved 

the sun was a source of radio waves, which had 

many important implications for future systems.

 The operational altitude of America’s most 

advanced bombers, the B–17 Flying Fortress and 

the B–29 Superfortress, rose to approximately 

35,000 feet and 33,600 feet, respectively.22 At 

these altitudes, pilots encountered a number of 

weather-induced events that impaired mission 

success. Lightning strikes on aircraft mostly 

caused incidental damage, but observations by 

eyewitnesses in a few exceptional cases suggest 

that lightning caused explosions and destruction 

of airplanes. Atmospheric electricity, as one 

DoD researcher recalled, was also a concern 

to the ordnance experts when manufacturing 

powders and explosives, because of the explosion 

hazards connected with static discharges. The 

relatively high-speed aircraft used in World War 

II frequently had their communications and 

navigation aids degraded by precipitation static, 

a problem only partially solved in the form of 

discharge wicks which became standard aircraft 

equipment. Improvements in radios, antenna 

designs, and other advances during the 1940s 

and 1950s helped, but researchers knew that as 

aircraft and missile speeds go up, static charging 

goes up even more rapidly, and the problem 

of how to get rid of it equally fast remained a 

challenge to researchers in the early 1950s. In 

short, the DoD realized that even if we were 

never to fly anything at a higher ceiling than the 

30,000 feet of World War II, the atmospheric 

layers of 60 to 100 miles up would be of vital 

importance for military operations.23 Years later, 

a similar arcing problem faced spacecraft, and 

Air Force researchers helped lead the way in 

finding a solution for the nation’s space vehicles.

 Even with the help of early weather watchers 

like Thomas Jefferson and Benjamin Franklin 

The Limitless Sky

120
and numerous others who followed them over 

the years until the end of World War II, no 

accurate method was available to forecast the 

weather for the next few days. More data still 

needed to be collected, and computers did not 

yet fully support the types of calculations and 

displays required to create meaningful weather 

projections. Modeling of weather events is a 

fairly recent breakthrough. Interest in weather 

forecasting by both military and civilian 

agencies kept researchers hard at work and still 

keeps them looking for newer, smarter ways of 

gathering, applying, and sharing their work and 

advancing the interests of the nation. Once manmade satellites entered the equation and started 

photographing wide areas of weather patterns 

and taking other measurements, the ability 

to forecast weather improved dramatically. 

But even today, with fast computers and space 

assets, it is not yet possible to offer a warning 

well in advance of some weather events, such as 

a tornado. This type of prediction tool would 

have helped the nation on 1 September 1952 

when a tornado made a direct hit on the 7th 

and 11th Bomb Wings’ new B-36 bombers at 

Carswell AFB, near Fort Worth, Texas.24

 If a similar pattern holds true for the ability 

to research and develop the means to accurately 

forecast space weather in a timely manner, the 

Air Force and its partners the National Weather 

Service, National Oceanic and Atmospheric 

Administration, and academia have made a 

tremendous start. The laws of science and basic 

research have not changed dramatically despite 

High-Altitude bombers such as the B–17 Flying Fortress (above) and the B–29 Superfortress (top) encountered new atmospheric 

conditions that often hindered operations. [Photos from U.S. Air Force Museum web page.]

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the advent of the space age and fast, capable, and 

affordable computers. It takes time to gather 

enough data to start modeling and simulation 

work of an event, and it takes more time to refine 

and update models and simulations of natural 

events. Using the technologies gained in World 

War II-jet aircraft and rockets-as the starting 

point for modern investigations into the space 

environment and space weather, the Air Force 

has been on the leading edge for almost 60 years.

 Because of many aerospace breakthroughs 

during the World War II years, the Air Force 

would soon be flying higher and faster than ever 

before. The Second World War saw the first 

steps leading to jet aircraft and intercontinental 

ballistic missiles, both of which significantly 

affected the subsequent history of the U.S. 

Air Force and the world during the Cold War 

and beyond. While Germany was the only 

nation to field an operational jet fighter and 

long-range rocket weapon (the V–2) during 

the war, these innovations marked a new era 

in air power, with a concomitant demand 

for a greater understanding of the space 

environment, including space weather.25

 These two breakthroughs-jet aircraft and 

missiles opened the door for a new push into 

understanding the natures of the atmosphere 

and ionosphere and their impact on current 

and future Air Force systems. Army Air Forces 

leaders appreciated the work of American 

scientists and researchers during World War II 

and took steps shortly afterward to ensure they 

had the people and resources to explore these 

new realms. The Army Air Forces, because 

of the teamwork of General of the Army26

Henry H. (Hap) Arnold and Dr. Theodore von 

Kármán, renowned head of the Guggenheim 

Aeronautical Laboratory at the California 

Institute of Technology, helped pave the way 

for the Air Force to become tightly bound to 

the opportunities presented by state-of-the-art 

science and technology. These two men stood 

in contrast with other significant thinkers, 

including Dr. Vannevar Bush, the first chairman 

of the National Defense Research Committee 

who became Director of the Office of Scientific 

Research and Development in 1941.27 Bush 

and others like him believed that the military 

services should confine themselves to improving 

existing weapons and leave new scientific ideas 

to the civilian experts. General Arnold and 

Dr. von Kármán, however, staked out a role for 

military research and produced a revolutionary 

roadmap for the Air Force’s future in terms 

of its participation in innovative research and 

development on air and space systems.28

 While General Arnold and Dr. von Kármán 

staked a theoretical claim for the Army Air 

Forces in establishing a vital high-technology 

base for the future, the Army Air Forces acted 

to make this vision a practice. With the official 

surrender of the Japanese aboard the USS 

Missouri on 2 September 1945, many anticipated 

the quick demobilization of America’s 

military. An even more rapid demobilization 

occurred among the civilians who had created 

the weapons the Allies used to win the war. 

Recognizing this potential brain drain, the Army 

Air Forces decided to recruit wartime personnel 

with expertise in electronics and geophysics 

for postwar employment in military research. 

Therefore, shortly after the disbanding of the 

Radiation Laboratory at the Massachusetts 

Institute of Technology, the Army Air Forces 

issued a directive to begin recruiting postwar 

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scientists and engineers on 20 September 1945. 

This marked the beginning of the Cambridge 

Field Station in Massachusetts, which later 

became the Air Force Cambridge Research 

Laboratories (AFCRL),29 and a new era in what 

would become Air Forcesponsored geophysics 

and space environment research, an effort 

that continues to this day at the Air Force 

Research Laboratory. Many of the personnel 

who formed the core of AFCRL came from 

the Massachusetts Institute of Technology 

(MIT) Radiation Laboratory, which had its 

origins in developing microwave radar systems 

essential to Allied victory in World War II. 

At the time of its establishment, AFCRL was 

located next door to MIT in Cambridge.30

THE AIR FORCE AND POSTWORLD 

WAR II RESEARCH ON THE 

IONOSPHERE

 Major General Curtis E. LeMay, the Army 

Air Forces’ Deputy Chief of Air Staff for 

Research and Development, considered space 

operations to be an extension of air operations. 

LeMay challenged Project RAND, then a part 

of the Douglas Aircraft Company’s Engineering 

Division in Santa Monica, California, to quickly 

complete a feasibility study for space operations. 

RAND released this study, Preliminary Design 

of an Experimental World-Circling Spaceship, 

on 2 May 1946 a mere “two days before a critical 

review of the subject with the Navy.31” The team 

at RAND reported, “We have undertaken a 

conservative and realistic engineering appraisal 

of the possibilities of building a spaceship 

which will circle the earth as a satellite.” 

The authors noted that “such a vehicle will 

undoubtedly prove to be of great military value,” 

mostly for its observation and reconnaissance 

potential. Even without future technological 

breakthroughs, such as atomic energy, the 

project could take up to five years and cost 

$150 million. The study also noted the first 

nation to place a satellite into Earth orbit would 

win tremendous respect from other nations 

and “inflame the imagination of mankind.32”

 Because it would be slightly more than 

eleven years before the first man-made 

satellite did circle the Earth, it is impossible 

to know whether or not this vision, based 

on V–2 rocket technology, could have 

worked. But the authors of the report 

were prescient in at least one respect:

The craft which would result from such 

an undertaking would almost certainly 

The original headquarters of Cambridge field station, later the 

Air Force Cambridge Research Laboratory, located at 224 and 

230 Albany Street, Cambridge, Massachusetts, as seen in 1945. 

Exploiting the High Ground

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do the job of becoming a satellite, but it 

would clearly be bulky, expensive, and 

inefficient in terms of the spaceship we 

shall be able to design after twenty years 

of intensive work in this field. In making 

the decision as to whether or not to 

undertake construction of such a craft 

now, it is not inappropriate to view our 

present situation as similar to that in 

airplanes prior to the flight of the Wright 

brothers. We can see no more clearly all 

the utility and implications of spaceships 

than the Wright brothers could see fleets of 

B–29’s bombing Japan and air transports 

circling the globe.33

 At the end of World War II, then, many 

separate streams converged: interest in weather 

conditions around the world; the future of 

military research and development in relation 

to such work in industry and academia; rapid 

technological breakthroughs as a result of the 

United States’ having become the “Arsenal of 

Democracy”; a new willingness to understand 

the atmosphere; and faith that rocket technology 

(perhaps coupled with atomic energy) was 

ready to conquer the challenges of spaceflight, 

whenever the national will demanded it. The 

advent of higher-flying aircraft, observations 

of the jet stream in World War II, and the 

beginning of the rocket era had major impact. 

In part, the fierce rivalry between the “free 

world” and the Soviet Union and the role 

of technology as a way to gain respect and 

followers during the Cold War helped spur 

America’s willingness to conquer space.

 During the early years after World War II, 

the Army Air Forces (which became the United 

States Air Force in September 1947) continued 

its pioneering work in developing the tools 

necessary to explore the upper atmosphere and 

the ionosphere, especially in light of the new age 

of rockets, initiated with the appearance of the 

V–2. Using captured V–2 rockets and German 

scientists familiar with the V–2, the United 

States began a series of rocket firings that had 

both military and scientific missions and which 

“gave American scientists an early opportunity 

to develop rocket research techniques as well as 

make some fundamental scientific discoveries at 

high altitudes.” The U.S. Navy had established 

a Rocket-Sonde Research Branch within the 

Naval Research Laboratory, but it had no 

V–2 rockets. The U.S. Army, which had 300 

boxcars full of V–2 parts and equipment, had 

the potential to assemble dozens of V–2s, 

but it lacked an organized group of scientists. 

Therefore, in early January 1946, the Army and 

Navy, and joined later by the newly independent 

Air Force, cooperated in laying the groundwork 

for future V–2 rocket launches from White 

Sands Proving Ground (WSPG) (its current 

name is the White Sands Missile Range), New 

Mexico.34 Russia had also captured a number 

of V–2 rockets and scientists. This added to 

the sense of importance of the work at WSPG 

because of the growing tensions of the Cold 

War. More and more people were coming to 

the same conclusion that the 1946 RAND 

report had reached: the first nation to launch a 

satellite from a rocket would gain the admiration 

and respect of the world and demonstrate 

a palpable superiority over its rivals.35

 At WSPG, the American team conducted 

its first-ever static test firing of a V–2 rocket on 

15 March 1946, with the first flight following 

on 16 April 1946.36 On 22 August 1946, the 

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newly created Air Force Cambridge Research 

Laboratories took part in its first V–2 launch 

and experiments, “Day Airglow (Photometric 

Technique); Propagation (Retardation and 

Bi-Polar Probe Methods), and Pressure, 

Temperature, and Density Measurements.” 

As was true for almost half of the other 

V–2 missions at WSPG, officials declared 

this mission a failure. Because the V–2 vehicle 

failed, none of the experiments on the rocket 

could be completed. In late November 1946, 

the AFCRL team tried again, and with a 

properly operating V–2, they succeeded in 

getting at least partial test data from all three 

experiments run during the rocket’s flight.37

 A review of AFCRL’s early V–2 flights shows 

a number of experiments designed to gather a 

variety of data like that gathered on the first 

rocket launch as well as solar spectroscopy, 

magnetic fields, composition studies, cosmic 

rays, micrometeors, and solar constant 

measurements. In total, AFCRL fired more 

than a dozen V–2s of the more than 60 fired by 

all the services at WSPG.38 During these V–2 

flights, AFCRL scientists, who had an interest 

in the neutral composition of the atmosphere to 

support Air Force missions at altitudes above 

35,000 feet, measured the atmosphere’s density 

at various altitudes. The highest altitude reached 

by an AFCRL V–2 was eighty-five miles on 31 

August 1950. AFCRL researchers also increased 

the midsections of seven V–2s “by about 65 

inches” to allow the addition of “scientific 

instruments and thus allow a larger set of 

simultaneous measurements to be collected for 

study.” The data collected in these V–2 flights 

helped shape the scientists’ understanding 

of the atmosphere for years to come.39

 The growing consensus among the 

services’ scientists held that V–2 rockets 

lacked the stability necessary to serve as 

effective test platforms. Nevertheless, by the 

time of the last AFCRL V–2 launch on 22 

August 1952, researchers had amassed an 

important amount of data. A record of all 

three services’ rocket experiments states,

V–2s took the first solar ultraviolet 

spectrograms above the Earth’s ozone 

layer. They captured spectacular 

photographs of Earth from high altitudes; 

they brought back air samples and cosmicray measurements. Although valuable 

atmospheric data were obtained, it is more 

 The Army Air Forces launched captured German V–2 rockets 

from the White Sands Proving Ground, New Mexico, starting 

in 1946. Scientists at the Air Force Cambridge Research Laboratories flew instruments on select V–2s to probe the upper 

atmosphere and measure its pressure, density, and temperature.

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honest to regard the series of [V–2] flights 

as scientific test vehicles upon which new 

instrument and telemetering techniques 

were perfected. Experimenters learned 

how to build compact, rugged, reliable 

equipment, while rocket engineers found 

how to give the instruments a smooth, 

clean ride. Advances were also made in 

instrument pointing and recovery. This 

was technology rather than science,...but 

experience with the V–2s provided just 

what American scientists and engineers 

needed to build sounding rockets tailored 

specifically to space research.40

 With the shortcomings of the V–2 more 

apparent, AFCRL and others interested in 

researching the ionosphere and beyond did 

indeed turn to developing sounding rockets 

and newer, ever more sophisticated payloads 

of scientific instruments to advance their 

work. The shift in vehicles to sounding rockets 

relocated much of AFCRL’s work from WSPG 

to Holloman AFB, near Alamogordo, New 

Mexico. AFCRL also shifted to a new sounding 

rocket, the Aerobee, with its first Aerobee-borne 

experiment launched on 16 September 1949. 

However, the Aerobee sounding rockets showed 

some early developmental problems which, 

coupled with some equipment anomalies, led 

to many of these early experiments failing to 

collect useful data. Within a year or so, though, 

AFCRL began compiling a sterling record of 

successful experiments. Between 1952 and 1958, 

AFCRL’s experiments used a series of different 

sounding rockets-improved Aerobees, such as 

the Air Force Hi-Aerobee featuring a “nose 

cone containing data-recording instruments” 

capable of being “recovered by parachute,41 and 

the Nike-Deacon and Nike-Cajun rockets.42

These sounding rocket experiments collected 

valuable data and also paid other dividends. 

By the late 1950s “Thirty colleges, universities, 

and research institutes were participants in the 

Air Force study program on the relationship 

between weather and solar activity.43

 These and other sounding rockets allowed 

affordable access to space for experiments 

Line drawings of a few of the types of sounding rockets Air 

Force experts used to study the upper atmosphere and some 

of the ground-based trackers used in conjunction with various 

sounding rockets.

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and near-Earth observations. Because these 

were suborbital rockets, experiment packages 

routinely did not achieve Earth orbit and their 

payloads were relatively small, though the 

Nike-Deacon was a two-stage rocket. AFCRL 

experiments helped researchers understand 

the operational environment for the latest 

generation of high-altitude jet aircraft as well 

as the new field of missile guidance applicable 

to the latest weapon in the nation’s arsenal, the 

Intercontinental Ballistic Missile (ICBM). In 

just ten years, Air Force and other researchers 

working with sounding rockets had raised 

“the engineering standard atmosphere...from 

20 to above 100 km [kilometers],” developed 

a means of photographing weather over wide 

areas that “applied to the study of hurricanes,” 

and developed newer, more accurate telemetry 

packages as part of these early efforts. In 

addition, sufficiently accurate measurements 

have been made of the altitude variation of 

pressure, cosmic-ray intensity, solar X-ray 

intensity, and airglow which could “be used 

as the basis for moderately accurate absolute 

altimeter systems.44 AFCRL researchers, 

through their V–2 and sounding rocket work, 

helped the nation amass the data that brought 

about “the basic knowledge of the upper 

atmosphere and the technology necessary 

for the later planetary exploration and space 

science, as well as for the military development 

of ICBMs and supersonic aircraft.45

THE AIR FORCE, THE VAN ALLEN 

BELTS, AND THE START OF THE 

SPACE AGE

 Arguably, though, the most significant 

consequence of the sounding rocket work by 

AFCRL and other pioneers became clear only 

after years of work. “The ability to launch 

an artificial earth satellite by means of the 

Vanguard vehicles is a direct outgrowth of 

experience gained in performing upper-air 

rocket experiments.46

 Before the Vanguard 

vehicle successfully lifted its first satellite into 

orbit on 17 March 1958, the Soviet Union had 

launched both Sputnik I on 4 October 1957 and 

Sputnik II on 3 November 1957, and the United 

States had launched its first satellite, Explorer I,

on a Jupiter–C launch vehicle on 31 January 

1958, a direct descendant of the German A–4 

(V–2) rocket. The third U.S. satellite launch, 

Explorer III on 26 March 1958, confirmed the 

existence of the Van Allen belts.47 These initial 

successful launches of man-made satellites 

represented varying degrees of significance for 

the International Geophysical Year (IGY). The 

IGY ran from July 1957 through December 

1958 and “was timed to coincide with the 

high point of the eleven-year cycle of sunspot 

activity.48 A remarkable demonstration of the 

willingness to share information during the Cold 

War, the IGY ultimately involved researchers 

from sixty-seven nations for “cooperative 

study of the solar-terrestrial environment.49

 The first two Soviet satellites were relatively 

large and did not return much useful scientific 

data. Nonetheless, the mere fact that these were 

on orbit earlier than any satellite from the “free 

world” gave prestige to the Soviet Union, exactly 

as the 1946 RAND study on the world-circling 

satellite had predicted. Ironically, though, the 

smallest of the first three man-made satellites, 

Explorer I, contributed the most to the IGY 

and future of space systems in its discovery 

of what were later called the Van Allen belts. 

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Explorer I established “a lasting American 

superiority in miniaturized electronics.50”

 On 1 May 1958, Dr. James A. Van Allen 

of the State University of Iowa and his team 

of researchers announced that data taken 

from scientific equipments on Explorer I and 

Explorer III “disclosed an unexpected band of 

high-intensity radiation extending from 600 

miles above earth to possibly an 8,000-mile 

altitude.” Dr. Van Allen said the radiation was 

1,000 times as intense as could be attributed 

to cosmic rays.51 The discovery of the inner 

Van Allen radiation belt opened a new area for 

Air Force research: the magnetosphere. This 

is the part of space that picks up where the 

ionosphere leaves off and “is filled with magnetic 

fields, electric fields, matter, energy, and activity 

invisible to the naked eye but readily apparent 

to more sensitive scientific instruments.52”

 People have used the magnetic compass 

since its discovery in China in approximately 

1000 AD. In 1600, William Gilbert concluded 

the compass worked because “the Earth is 

a giant magnet.53” The Earth, resembling a 

dipole bar magnet, exerts a magnetic force 

field that controls the magnetosphere. The 

magnetosphere, encompassing the inner and 

outer Van Allen belts, is where manned and 

most unmanned spacecraft operate. The many 

space vehicles that have probed this region have 

more clearly mapped its shape and elucidated its 

varying conditions and have laid the groundwork 

for exploiting modern space-based systems.54

 The discovery of the Van Allen belts and the 

exploration and mapping of the magnetosphere 

for more than a decade point to an integral 

aspect of scientific research and technology 

development: time is the first ingredient. For 

years, scientists had theorized the existence of 

a protective barrier around the Earth shielding 

us from the many solar irregularities observed 

since the time of Aristotle. Ground-based 

observations had yielded a good start, and 

the V–2 and sounding rockets added to this 

Explorer I, officially known as Satellite 1958 Alpha, was the first U.S. satellite, and third satellite overall, to obtain Earth orbit. 

Explorer I carried the first AFCRL, experiment into space, making the start of the Air Force’s prominent role in space. Once in 

orbit, Explorer I indicated a much lower cosmic ray count than Dr. Van Allen had expected. He theorized the existence of a belt 

of charged particles trapped in space by the earth’s magnetic field. The existence of these belts, later named the Van Allen belts, was 

confirmed by measurements taken during the flight of Explorer III.

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collective knowledge from about 100 to 130 

miles in space. Sounding rockets provided 

Dr. Van Allen and his colleagues with a 

solid understanding that the atmosphere 

thinned with increasing distance from 

Earth’s surface. Logically, then, he expected 

that the amount of cosmic radiation, fatal 

to humans if unattenuated atmospherically, 

would increase as one’s altitude in space 

increased. Therefore, when Van Allen sent 

his first Geiger counter into orbit on Explorer 

I, he had already surmised the existence of 

a radiation belt surrounding the globe.55

 When Van Allen received data from the 

experiment, results contradicted common 

sense: data sent to ground stations showed a 

lack of radiation. With a new instrument on 

board Explorer III a few months later, Van 

Allen and others reducing the data realized 

the unexpected results from his first mission 

could be explained consistently with previous 

observations. At altitudes lower than 400 miles 

above Earth, radiation could be counted with 

relatively routine devices. Beyond that distance, 

though, “there was so much radiation...that it 

could not be accounted for by simple cosmic-ray 

bombardment.” Plus, “careful analysis of the data 

proved that there were two roughly doughnutshaped belts, or a single gigantic one, of trapped 

radiation circling Earth.” This marked the first 

time that scientists had “defined the barrier that 

protects it [Earth] from the deadly barrage of 

celestial radiation.” By the time the Van Allen 

belts were fully measured and characterized, 

scientists realized that Van Allen’s initial 

height of the belts, 8,000 miles, was hindered 

by young technology. As technology matured, 

scientists mapped the Van Allen radiation belts 

out to 40,000 miles around the Earth.56 This 

underscored the “push-me pull-you” nature of 

technology and space exploration. As technology 

improves, scientists are able to launch ever moresophisticated equipment to take increasingly 

precise measurements to produce a better, 

more accurate understanding of the space 

environment. Because new technology is often 

more susceptible to the impact of the space 

environment and space weather, new research 

areas are revealed to understand and counter 

any negative impacts on new systems.

 The discovery of the Van Allen belts opened 

a new door to space research. Catalyzing 

space exploration, in addition to the interest 

sparked by the IGY and the creation of the 

National Aeronautics and Space Administration 

(NASA) and the concept of solar wind 

articulated in 1958, was, of course, the Cold 

War. President Eisenhower, fearing a surprise 

attack from Russia or another source, had 

sought high-altitude aircraft for surreptitious 

reconnaissance flights. However, the concept 

of national airspace hindered spy flights over 

hostile territory. Both the United States 

and the Soviet Union had made it clear that 

spy planes could easily be the reason for the 

next war, which all parties knew could easily 

escalate to a full thermonuclear event.57

 In one sense, the fact that the Soviet Union 

orbited the first man-made satellite offered 

the United States an opportunity to answer 

a question that had long burned within 

Washington, D.C.: How would a nation respond 

to a hostile nation’s flying a satellite over the 

homeland? Because the United States did not 

declare Sputnik’s path over the United States 

an intrusion of national airspace or a hostile act, 

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some credit the peaceful uses of outer space to 

President Eisenhower’s measured response to 

the Soviet space challenge. Thus the corollary, 

the Soviet Union could not challenge the flights 

of U.S. communications and surveillance 

satellites over the Soviet Union.58 This 

thoughtful American response also set the stage 

for the duality common in America’s science and 

technology history continue moving forward 

simultaneously with clearly defined military 

missions and civilian goals, with a minimum 

amount of friction and a maximum benefit to 

the nation. This had been true of the earliest 

weather forecasting efforts and continues today 

with respect to space environment research.59

INNOVATIVE AIR FORCE 

GROUNDBASED AND 

BALLOONBORNE PROGRAMS

 The 1950s also marked a period of 

diversification in the Air Force’s approach to 

learning about the space environment. It had 

been clearly understood that the Sun was 

the ultimate source of energy for the upper 

atmosphere and ionosphere. However, the causal 

relationship between solar disturbances and 

variations in the near-Earth space environment, 

or what eventually became known as space 

weather, was not well known. AFCRL 

experts now branched out to establish a new, 

state-of-the-art coronagraphic observatory 

at Sacramento Peak near in the felicitously 

named Sunspot, New Mexico.60 In 1952 this 

site began basic research on “solar physics and 

solar-terrestrial effects.” Later in the 1950s, 

programs in “solar radio astronomy and transionopsheric propagation” began at the Peak. 

Later work at the site included “long-term 

measurements of solar extreme ultraviolet 

radiation.” The site later became part of the 

National Solar Observatory, with on-site Air 

Force scientists and engineers contributing 

to its research on the sun and its influence 

on modern electric equipment, including 

communications and navigation systems.61

 Other work with solar-observing ground 

stations advanced by the Air Force over the 

years includes participation in the Solar 

Electro-Optical Network (SEON), which 

consists of the Solar Optical Observing 

Network and the Radio Solar Telescope 

Network. The global network of SEON 

sensors continuously monitors the sun at visible 

wavelengths and at radio frequencies to detect 

The Sacrament Peak Observatory includes the Solar Vacuum 

Telescope (top), which features a 220-foot vertical shaft and 

a connecting laboratory building. The site also includes a 16" 

coronagraph and a 12" coelosts telescope for solar observation.

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Charts created by Air Force scientists show some of their discoveries over time and their conclusions about nature and effects of the 

space environment.

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solar flares and identify active solar regions 

that have potential for erupting into a solar 

flare.62 SEON became an operational asset 

used by the Air Force Space Command after 

the Command stood up in 1982 Continuing 

solar research at Sunspot has resulted in the 

development of an Improved Solar Optical 

Observing Network, a semiautonomous, 

remotely commandable system that may enable 

scientists in the future to predict with some 

certainty the occurrence of a solar flare.

 Solar flares, tremendous explosions on 

the surface of the Sun, can heat material to 

many millions of degrees in mere minutes and 

release as much energy as a billion megatons 

of TNT.63 Solar flares, in other words, create 

a massive electromagnetic explosion in the 

upper solar atmosphere which can disrupt 

radio and telephone communications on Earth, 

cause power surges and blackouts and damage 

satellites.64 A visible manifestation of a solar 

flare can be the uncharacteristic appearance of 

X-rays and ultraviolet radiation from the sun is absorbed in the upper atmosphere, heating it and causing it to expand. If a solar 

flare occurs, greatly increased numbers of energetic particles cause auroras to become much more active, changing the radio signal 

propagation qualities of the ionosphere.

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the Aurora Borealis as far down as Illinois and 

Oregon, a result of solar wind and energetic 

particles created by a solar flare.65 The SEON 

complements the work of the National 

Oceanic and Atmospheric Administration 

which “sponsors the Geostationary Orbiting 

Environmental Satellite (GOES) series that 

monitors solar flare X-ray emissions.66” This type 

of cooperation between military and civilian 

research communities had been important in 

the early days of terrestrial weather observation 

and the evolution of weather forecasting, and 

it continues today in the ongoing efforts to 

create the ability to forecast the space weather.

 These newer systems built upon pioneering 

work on solar flares conducted by AFCRL 

researchers in the early 1960s, making the 

laboratory “one of the earliest players in the 

development of ‘space weather’ forecasting 

in the US. AFCRL studied ways to identify 

specific ‘precursors’ of solar flares that, in 

turn, could provide some ability to forecast 

their occurrence.” Yet other work at AFCRL 

“looked for the ‘signatures’ of the solar flares 

that released high-energy protons” in the hope 

that researchers could find a way “to provide 

some advance warning of disturbances that 

would occur at Earth within minutes or a 

few hours” of the observed event. This type 

of work led to the development of the Proton 

Prediction Model, which incorporated computer 

algorithms “to predict the occurrence and 

arrival time of solar energetic particles at the 

Earth.” This innovative system “became an 

operational space weather tool at the Air Force 

Global Weather Central at the end of 1987.67”

 Another approach championed by AFCRL 

to understand, characterize, and map the 

space environment involved the use of highaltitude balloons. In fact, Project Mogul, “the 

first major geophysics program that the Army 

Air Forces started early in 1946,” looked at 

“the feasibility of using balloon-borne acoustic 

sensors for long-range detection of potential 

Soviet missile launches and atomic tests” during 

the early years of the Cold War. In 1951, when 

the DoD transferred the duty of creating 

experimental equipment for meteorological 

purposes to the Air Force, specifically to 

one of AFCRL’s directorates, more balloonrelated programs came to the laboratory. In 

the 1960s, with the nation swept up by the 

space race and the race to the moon, AFCRL 

engineers used their “expertise in balloon 

design and launching” created “during the 

1950s with programs like Project Moby Dick, 

which measured upper atmospheric winds” to 

support the emerging U.S. role in space. Then, 

in the 1960s, with the nation’s eyes on landing 

probes and ultimately men on the moon, these 

“balloon engineers began a new area of work, 

providing drop-tests for re-entry systems to 

be used in lunar and planetary probes.68”

 Drop-tests by AFCRL personnel supported 

several NASA missions starting in the early 

1960s and continued until the last droptests in 1982. The 70 drop-tests conducted in 

support of the Surveyor mission to the moon 

required AFCRL engineers to simulate “the 

descent of Surveyor’s lunar landing vehicle...by 

releasing the vehicle suspended under its open 

parachutes from a balloon...tethered at 1,500 

feet.” Conducted at Holloman AFB, these drop 

tests helped to verify the Surveyor spacecraft’s 

ability to retrofire its rockets and achieve a 

soft landing. In July and August of 1965, 

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similar tests on a much larger scale dropping 

a one-ton reentry system from 130,000 feet 

supported NASA’s Voyager mission to Mars.69

 With the aftermath of the first space launches 

in 1957 to 1958 and the frantic pace of Cold 

War posturing for national superiority via the 

number (versus the quality) of space launches, 

space became an ideological shuttlecock between 

the “free world” and the Soviet system. This 

clash of apparently irrevocable ideologies put 

space scientists in a difficult position because 

of America’s desire to use technology as a 

lever for prying neutral nations away from 

sympathies for the Communist/Socialist 

system and to bring them into the fold of free 

enterprise and democracy. Ironically, though, 

America’s ideological adversaries were trying 

to do exactly the opposite by claiming their 

own superior technology. Consequently, the 

space race afforded the U.S. Air Force myriad 

opportunities for state-of-the-art space research 

programs, a challenge the service accepted 

without hesitation but within the limits of 

peaceful exploration. These early years also 

established the dual paths of military and 

civilian approaches to the role that space would 

play in providing for the nation’s security 

while simultaneously promoting scientific 

breakthroughs for future system designs. The 

Air Force and other defense-related agencies 

would conduct their reconnaissance missions 

in a relative blackout mode, while NASA 

pursued free and open relations with other 

nations providing they restricted themselves 

to space science and released their data to all 

the world. This is how the United States first 

built its reputation as a fair and dependable 

provider of launch services for other nations.70

THE AIR FORCE ORGANIZES FOR 

SPACE AND MOVES AHEAD

 up to take the initiative in this transitional 

period in American space policy and history. 

This is not to say, though, that the road to the 

Air Force’s ultimately assuming responsibility 

for the military’s mission in space was smooth 

and straight. All three services made their 

own thrust for primacy in the space mission, 

but shortly after President John F. Kennedy 

entered office in January 1961 the Air Force 

reorganized and created the Air Force Systems 

Command and the Air Force Logistics 

Command. The former received responsibility 

for all research, development and acquisition 

of aerospace and missile systems, to include 

strategic missiles. The latter organization 

was established to handle maintenance and 

supply only. Without this type of overhaul, the 

Air Force could not have risen to the DoD’s 

challenge for the service to take over future 

military space development responsibilities. 

Even with this new charter for leading the 

DoD’s space efforts, the Air Force needed 

time to properly define its relationship with 

the other services and NASA and to reassure 

the public about the potential for a military 

presence, manned or unmanned, in space.71

 One of the ironies of the early space age was 

the perception of the need for a military role in 

space, but often a stumbling block to achieving 

this was the military itself. Because the nation’s 

strategic defense relied upon nuclear weapons 

(delivered from bombers, intercontinental 

ballistic missiles, and submarine-launched 

nuclear missiles) and the ability of the weapons 

to deter hostile nuclear action by other nations, 

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Over the years, Air Force reasearchers used a variety of balloons 

and aerostats from many different locations—including a ship 

from the United States Navy—and under various environmental conditions to collect data to support their state-of-the-art 

explorations of the atmosphere and ionosphere.

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atmospheric nuclear tests were not uncommon. 

Researchers understood these tests could have 

some impact on the few satellites on orbit 

or upon early astronauts circling the Earth, 

and due precautions were taken, but highaltitude tests continued. Two events in 1962 

demonstrated the dramatic changes within 

the radiation belts that these tests could 

produce. On 8 July 1962, the United States 

conducted a high-altitude nuclear test, and in 

October of that year, the Air Force announced 

special instruments on unidentified military 

test satellites had confirmed the danger that 

astronaut Walter M. Shirra, Jr., could have been 

killed if his...space flight [on 28 September] 

had taken him above a 400-mile altitude. The 

July blast caused an artificial radiation belt with 

peak intensities at least 100 times greater than 

normal.72 Two days after this same nuclear 

test, the world’s first communications satellite, 

Telstar, was launched. For six months, Telstar 

made history, speeding communications and 

making the world a smaller place by adding 

the phrase ‘live via satellite’ to the common 

vernacular.73 Telstar, though, was knocked 

out after six months by radiation from the 

Because Air Force systems operate at different altitudes, researchers have long looked for new and better ways to characterize the 

various operational environments of interest to ensure maximum performance of current and future Air Force and civilian systems.

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American high-altitude nuclear tests.74 The 1963 

Nuclear Test Ban Treaty banned future nuclear 

tests in the atmosphere and space, effectively 

eliminating this hazard to space operations for 

the United States and the rest of the world.

 Nevertheless, the Air Force continued its 

pioneering work in understanding the rigors of 

space. Air Force organizations such as the Air 

Force Weapons Laboratory (AFWL), located 

at Kirtland AFB, New Mexico, played a role 

in the evolution of the Air Force’s mission in 

space and researching the space environment. 

From its creation in 1963 through 1973, 

AFWL made major scientific and technical 

contributions to understanding natural and 

artificially created space radiations through a 

series of satellite flights and space probes. Much 

of this work focused on mapping the inner 

Van Allen belt more completely, measuring 

radiation levels and geomagnetic fields in both 

the inner and outer Van Allen Belts, and to 

compare measurements with theoretically 

predicted environments. Two other satellites 

carried AFWL instruments into space to 

study solar flares, cosmic radiation and the 

effects of solar storms on the Van Allen Belts. 

One of these satellites provided high precision 

measurements of polar cosmic radiation and 

recorded unique data on a major solar flare 

during May 1967 and had a significant role in 

defining the hazards for manned space missions 

during solar active periods. Later AFWL efforts 

helped to establish the limits on the length of 

time astronauts could operate in near-earth orbit 

behind various types of spacecraft shielding 

and collect data of considerable interest to both 

manned and unmanned operations in low- to 

mid-earth orbits.75 Over the years, AFWL 

and its successors, like the Phillips Laboratory 

and the Air Force Research Laboratory, used 

AFWL’s expertise in measuring radiation 

and developed it into world-class methods 

for radiation-hardening techniques that 

have helped to create and preserve America’s 

reputation as the leader in space operations.

 The most sustained contributions by an 

Air Force organization dedicated solely to 

geophysics research and development came 

from the AFCRL, which became the Air Force 

Geophysics Laboratory in January 1976.76 The 

nascent AFCRL began recruiting scientists in 

The Air Force Weapons Laboratory (AFWL) put its Fiber 

Optics Experiment aboard the Long Duration Exposure 

Facility (LDEF) satellite to study long-term effects of space 

background radiation. After four and a half years in space, 

the Space Shuttle retrieved the LDEF in January 1990, 

withAFWL’s experiment seen on the lower right hand corner 

of LDEF.

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September 1945, shortly after the Japanese 

surrender ended World War II. Many of the 

programs it initiated in the late 1940s made 

consistent contributions to state-of-the-art 

knowledge about space for years. For example, 

AFCRL pursued programs in theoretical 

and applied research in meteorology, upper 

atmosphere, and solar studies, and ionospheric 

and seismo-acoustic propagation. As science 

advanced, in the late 1950s AFCRL added 

programs in space physics and optical/infrared 

studies, followed shortly by geodesy and 

gravity. An engineering program that developed 

experimental meteorological equipment, 

sounding rockets and balloons, and instruments 

for satellites provided AFCRL the synergy and 

critical mass needed for successfully researching 

space weather and the space environment.77

 The discoveries made by Air Force and other 

researchers have constantly grown and changed 

our understanding of what to expect as we 

explore and exploit space. A look at the stateof-the-art technologies and breadth of scientific 

knowledge and data show both constantly 

expanding in absolute terms. Van Allen’s initial 

belief in 1958 that the belts extended to 8,000 

miles above Earth was just the start. Because of 

the work of AFWL and AFCRL, among others, 

scientists now know that the starting point for 

the inner belt ranges, depending upon latitude, 

from 250 to 750 miles, rises to approximately 

6,200 miles, and traps protons. The outer 

belt, though, traps electrons and extends from 

the top of the inner belt...up to 37,000 to 

52,000 miles depending on solar activity.78

THE AIR FORCE EXPLOITS THE 

SPACE ENVIRONMENT AND SPACE 

WEATHER

 The space environment and space weather, 

taken together, represent the major challenge 

facing Air Force researchers in their quest 

to field the best systems in support of the 

United States. According to one recent work,

Space weather starts inside the Sun 

and ends in the circuits of man-made 

technologies. Defined simply, space weather 

is a range of disturbances that are born on 

the Sun, rush across interplanetary space 

into Earth’s neighborhood, and disturb 

the environment around our planet and 

the various technologies-cell phones, 

satellites, electric power grids, radiosoperating in that environment. The key 

to space weather is the transformation of 

energy, a transformation from magnetic 

energy and intense heat on the Sun to 

plasma energy in interplanetary space 

to magnetic and electrical energy around 

the earth.79

Just as the study of weather on Earth often 

levied different methods on civilian and 

military meteorologists, Military and civilian 

space weather requirements are similar but 

often addressed independently. In addition, 

the lack of fundamental knowledge about 

the physics of space weather and its impact 

on technology makes it difficult to develop 

and evaluate techniques to compensate for 

space weather. This is something Air Force 

and other researchers are trying to conquer 

through extensive basic and advanced research 

into the space environment in the hope of 

ultimately being able to forecast space weather. 

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Space weather is difficult to understand 

because it isn’t tangible, like a thunderstorm or 

tornado.80 Rather, space weather and the space 

environment are dominated by a tenuous gas 

made up of charged atomic particles, including 

protons, electrons, and ions. Another factor is 

the solar wind, a very tenuous plasma, having 

a density of only a few protons or electrons 

per cubic centimeter. A paradox with the solar 

wind is that it could not be felt if it were to 

blow against your face, while its velocity greatly 

exceeds the velocity of any winds on Earth, being 

over a million miles per hour with an extremely 

high temperature in excess of 100,000 degrees.81

 Much of this knowledge about the space 

environment and space weather came from 

years of research and development by Air 

Force scientists and others receiving Air Force 

support, and ranged from advanced groundbased equipment to balloons to state-of-theart space experiments and systems. After all 

of the work accomplished by the Battlespace 

Environment Division, as the once-AFCRL 

is now called, there remains the challenge of 

developing state-of-the-art systems to collect 

data that supports creation of quality modeling 

and simulation tools for the warfighter.

 One such system is the Digital Ionospheric 

Sounding System, which brought together 

the expertise of the Air Force Air Weather 

Service (now the Air Force Weather Agency), 

the Air Force Space Forecast Center (now 

the Space Weather Operations Center), 

and the Geophysics Directorate of the Air 

Force Phillips Laboratory (now the Air Force 

Research Laboratory). The Research Laboratory 

developed this ionosonde, which sends out 

radio waves to sense the overhead ionosphere 

and measure the electron density profile. The 

Air Force Weather Agency currently operates 

the Digital Ionospheric Sounding System, 

which features 20 locations around the world, 

to gather global ionospheric data in real 

time. The Space Weather Operations Center 

ingests this collected data to create ionospheric 

specifications and forecasts for communications, 

surveillance and navigation systems.82

 Another ground-based system, the 

Ionospheric Measuring System, also developed 

by the Air Force Research Laboratory, measures 

the total electron content within a sampled 

volume. This system uses sophisticated 

coordination between a ground station and 

a Global Positioning Satellite (GPS) to 

measure integrated electron density content. 

By taking enough of these snapshot readings 

over a large area, researchers hope to be 

able to use the readings to model the local 

ionosphere. These snapshots play a role in 

devising new atmospheric models which 

can evolve over time as new readings are 

obtained or as new technology appears to 

more accurately measure the ionosphere.83

Ultimately, the hope is to create an accurate 

model of the ionosphere to support creating 

a space-weather forecasting system, just 

as extensive efforts to gather terrestrial 

weather data helped create today’s weather 

forecasting modeling and simulation tools.

 The Ionospheric Measuring System is 

also looking at the well-known problem of 

ionospheric scintillation, a phenomenon quite 

similar to atmospheric scintillation. Variations 

in the ionosphere’s density are known to cause 

variations in signals transmitted from on-orbit 

satellites, such as the GPS system. Scintillation 

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can cause satellites and ground stations to lose 

lock, losing messages. While current models 

are able to handle the effect of a GPS beam 

traveling through the ionosphere, extreme solar 

activity and scintillations that can contribute 

to signal degradation are not modeled.84

 The Air Force has also funded computerbased models in academia, such as the 

Magnetospheric Specification Model (MSM) 

at Rice University in the late 1980s. It took 

nearly ten years for a team of scientists and 

graduate students to design, build, and test 

the MSM, which computes the intensity of 

energetic electrons and ions in the equatorial 

plane of the earth. MSM can take real-time 

data from satellites and ground stations, or 

archived data from past storms, to create 

a continuous model output that gives the 

conditions of a storm as it is actually going on. 

Such nowcasting is useful because it provides a 

picture of where the most intense features...are 

at any time, and of how the storm is changing.85

 While nowcasting has a role to play in 

studying space weather events as they occur, Air 

Force and other researchers are greatly interested 

in developing an ability to forecast space weather 

and its potentially harmful effects on manmade systems. To use MSM for forecasting, 

researchers have incorporated artificial neural 

networks. These networks are an attempt to use 

the human brain’s ability to recall and associate 

past sights and sounds with current and, to a 

limited extent, future conditions. In computer 

terms, Inputs to mathematical neurons within 

a computer can be trained to recognize and 

associate combinations of inputs with certain 

outputs. This type of new work has many 

caveats, but the Magnetospheric Specification 

and Forecasting Model can already take this 

approach and provide good one-hour forecasts of 

Magnetospheric conditions. It can also generate 

longer forecasts, but the accuracy suffers.86

 A good example of how the Air Force works 

with industry to create new space-weather 

forecasting tools is the Parameterized Real-Time 

Ionospheric Specification Model (PRISM). 

The Battlespace Environment Division of the 

Air Force Research Laboratory has funded 

Computational Physics, Incorporated of 

Norwood, Massachusetts, to develop PRISM, 

the world standard model for High-Frequency 

communication and satellite surveillance. 

The 50th Space Wing at Schriever AFB, 

Colorado, used PRISM to provide timely 

reports on global ionospheric parameters to 

all DoD customers in the early 1990s, while 

Computational Physics indicates that more 

recently the 55th Space Weather Squadron 

(part of the Air Force Weather Agency 

collocated at Schriever AFB) also uses PRISM 

in support of military communications. The 

firm notes that a new version [of PRISM] 

incorporating the plasmasphere is currently 

under development.87 If you were to go to 

places like the Air Force Weather Agency, 

Dr. William Denig of the Battlespace 

Environment Division said, their ionospheric 

model, the one they use operationally, is 

PRISM,88 making PRISM an important 

Air Force contribution to the warfighter.

 The Air Force has been developing accurate 

and timely space-weather simulation models 

since the early 1960s. Recently, though, as 

data has become both more plentiful and 

detailed, the service has undertaken a new 

look at how to model the space environment 

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in support of developing the ability to forecast 

space weather. Changes in space weather are 

attributable to the highly variable, outward 

flow of hot ionized gas (a weakly magnetized 

‘plasma’ at a temperature of about 100,000 

degrees Kelvin, called the solar wind) from 

the Sun’s upper atmosphere. In addition, 

nonthermal, electromagnetic waves in the X-ray 

and radio portions of the spectrum also play 

a role in the conditions of space weather.89

 The Geophysics Directorate of the Air 

Force Phillips Laboratory realized that, for 

the most part, space weather forecasters 

have been essentially blind to impending 

interplanetary disturbances from the time they 

leave the Sun until the time they impact the 

magnetosphere. To fill this void, in late 1994 

the Directorate’s Solar Wind Interplanetary 

Measurements system, launched on NASA’s 

Wind spacecraft, went on-orbit and started to 

provide users at the 50th Weather Squadron, 

at NASA, and at the National Oceanic and 

Atmospheric Administration with advanced 

warning of about 1 hour related to the 

effects of geomagnetic storms. The Air Force 

Space and Missile Systems Center’s Space 

Test Program sponsored this innovative 

approach to forecasting space weather.90

 Because the solar wind carries energetic 

particles from the Sun, it could also cause 

damage to spacecraft as a result of electrical 

charging, much like the atmospheric electricity 

noted by aircraft pilots during World War II. 

Then, the sparks could cause communications 

problems and arc out of the aircraft through 

protuberances like engines. On modern 

spacecraft, however, with computers and other 

sensitive equipment onboard, a charge could 

cause a loss of communications or prevent 

the satellite from functioning, becoming 

little more than an orbiting brick.91

 Although space experts had known about 

spacecraft charging for some time, it became 

important to master this phenomenon as 

spacecraft began to include more sophisticated 

computers as their brains and electronics for 

performing their missions. In January 1979, the 

Geophysics Laboratory’s Spacecraft Charging 

at High Altitudes (SCATHA) satellite lifted 

off into space. Air Force Systems Command’s 

Space Division, through its DoD Space Test 

Program, managed the SCATHA satellite, 

with its thirteen experiments from the Air 

Force, Navy, NASA, Defense Nuclear Agency, 

industry, and university groups. SCATHA 

supplied data to support the development of 

The Air Force Geophysics Laboratory developed the primary 

experiments for the Spacecraft Charging at High Altitude 

(SCATHA) satellite launched in 1979. SCATHA demonstrated successfully for the first time a capability to discharge 

spacecraft at geosynchronous altitude by means of a low-energy 

plasma source.

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a comprehensive specification of the space 

environment at geosynchronous altitudes. 

SCATHA, a highly successful program, 

succeeded in its mission to obtain environmental 

and engineering data to allow the creation of 

design criteria, materials, techniques, tests 

and analytical methods to control charging of 

spacecraft surfaces and to collect scientific data 

about plasma wave interactions, substorms, 

and the energetic ring. In 1982, Geophysics 

Laboratory personnel closed out the SCATHA 

program when they delivered to Space Division 

the SCATHA Data Atlas, a statistical 

compilation of the environmental conditions 

experienced by SCATHA at geosynchronous 

earth orbit. They also delivered a computer 

code that was a charging design tool for 

calculating potentials on and about a threedimensional satellite composed of various 

materials. Finally, researchers also provided 

a report on the active control of spacecraft 

potential by the emission of plasma.92

 Moore’s Law, expounded in 1965 (three 

years before the creation of Intel), essentially 

says there will be a revolution in computer 

capabilities every eighteen months because 

engineers would be able to basically double the 

number of electronic devices onto microchips.93

The law seemed to be holding true throughout 

the 1970s and 1980s, so the sensitivity of 

electronics to the space environment and space 

weather continued to grow along with this 

sophistication. By 1990, the Air Force needed to 

evaluate the effects of the space environment on 

the latest generation of electronics equipment.

 The Air Force and NASA cooperated on the 

Combined Release/Radiation Effects Satellite 

(CRRES) that launched in July 1990. CRRES 

brought together the Air Force Space Radiation 

Effects program’s effort to seek better ways to 

shield microelectronics and NASA’s Chemical 

Release Program, which explored using 

chemical releases in space to explain the nearEarth space structure. During 1990 and 1991, 

CRRES collected data that revised the standard 

NASA...models of the radiation belts that are 

used by satellite designers. At the same time, 

CRRES also had the great fortune to record 

the creation of a long-lasting, third radiation 

belt (a second inner belt of protons) around 

the Earth following the major geomagnetic 

storm of March 1991. Scientists had long 

debated the possibility of this third belt but had 

never proved its existence before CRRES.94

 Air Force researchers developed innovative 

solutions to the problem of spacecraft charging 

in support of systems like the GPS that operate 

in a high-altitude or geosynchronous orbit. The 

charge control system launched in July 1995 and 

demonstrated that an autonomous, active system 

designed to prevent surface-charge buildup on 

deep-space satellites offered a way to avoid this 

potentially mission-ending problem. The charge 

control system featured a suite of charging 

sensors that could detect the start of, and source 

of, surface charging. A microprocessor, which 

communicated with the sensors, activated 

corrective measures when the sensors showed 

charging was underway. This system provided 

engineering design data for future operational 

systems while demonstrating and validating 

active charge control principles and technology.95

 Two significant programs at the Battlespace 

Environment Division address the complexities 

of ionospheric scintillation. Personnel there 

developed the Scintillation Network Decision 

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Aid (SCINDA), allowing the Air Force Space 

Command to predict satellite outages along 

the equator caused by naturally-occurring 

disruptions in the ionosphere. SCINDA collects 

data from a series of eight locations around the 

equator. Every 15 minutes the SCINDA system 

accesses the data from the worldwide network 

to create simple, three-color maps of areas on 

or within 20 degrees of the equator that might 

experience communications outages. These maps 

are automatically updated every 15 minutes. 

Because SCINDA also shows users areas that 

are not suffering from scintillation, operators 

may be able to maintain communications 

by easily adjusting an antenna.96

 The second system, the Communication/

Navigation Outage Forecasting System 

(C/NOFS) satellite, is a joint effort by the 

Air Force Research Laboratory and the DoD 

Space Test Program. Described by the Research 

Laboratory as the forecasting system of the 

future, C/NOFS (which should be ready for 

launch and operations within a few years) 

features three innovative core elements. First, 

The Combined Release/Radiation Effects Satellite was configured for a rocket-launched, single-orbit mission in 1987. Its solar 

panels have been drawn in to fit them to the fairing for the rocket.

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the satellite will carry a sensor suite into space 

to take in-situ and remote sensing ionospheric 

measurements. Second, ground sensors will 

be able to use C/NOFS data to augment 

theater coverage for scintillation specification. 

Third, models and other capabilities will 

be able to create tailored outage forecast 

maps for use by America’s warfighters.97

 Another solar weather event with importance 

for space- and ground-based systems is a coronal 

mass ejection (CME). Similar to a hurricane on 

Earth, a CME is the eruption of a huge bubble 

of plasma from the Sun’s outer atmosphere, 

its corona. CMEs are the principal ways that 

the Sun ejects material and energy into the 

solar system; they typically speed through the 

universe at about 1,000,000 mph. A single 

CME carries more than 10 billion tons of hot, 

electrically charged gas into the solar system. As 

a CME moves away from the sun with a force of 

billions of tons of TNT, it creates a shock wave 

as it hits the slower solar wind. The force caused 

by a wave of CMEs in 1998 pushed the leading 

edge of Earth’s magnetic field down to 15,300 

miles; it normally stretches about 45,000 miles 

from Earth toward the Sun. In effect, satellites 

normally protected by the magnetosphere in 

geosynchronous orbit at 22,300 feet suddenly 

found themselves twisting in the solar 

wind. The satellites didn’t move; their whole 

neighborhood in space moved away for a while.98

 The origins of such forces and their results are 

of obvious concern and interest to the Air Force 

and others who operate equipment in space and 

on the Earth. The Battlespace Environment 

Division currently has an experiment in 

space, launched as a secondary payload on 

the Coriolis mission on 6 January 2003 from 

Vandenberg AFB, California, called the Solar 

Mass Ejection Imager (SMEI). Scientists 

and engineers from the Air Force Research 

Laboratory, the University of California at 

San Diego, and the University of Birmingham, 

United Kingdom, worked together to design 

and fabricate the SMEI experiment and 

system. The SMEI has the capability to use 

its all-sky camera to take images that should 

help space-weather forecasters take a giant 

step forward in improving their forecasts. By 

detecting CMEs directed at the Earth, SMEI 

will help protect space assets and maintain 

stable communications, both of which are of 

immense importance to the warfighter. The 

all-sky images taken from SMEI will also 

benefit astronomers and astrophysicists in 

understanding solar processes and detecting 

astronomical phenomena.99 SMEI had already 

taken its first spectacular all-sky image 

of the sun within a month of liftoff.100

 SCINDA, C/NOFS, and SMEI represent 

ongoing efforts by the Air Force to create, 

refine, and distribute space-weather information 

to the warfighter. As these systems are 

updated and modified, they will become the 

basis for more advanced systems to provide 

timely and accurate information to the 

nation’s defenders. Advanced state-of-the-art 

systems may come from breakthroughs in 

computer technology, better instrumentation 

for measuring ionospheric scintillation, or 

some other event. The ongoing nature of this 

research underscores the constant contribution 

of scientific research and development to the 

growing importance of space to America.

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The Air Force Research Laboratory Space Vehicles Directorate’s Solar Mass Ejection Imager launched on 6 January 2003. The 

SMEI team at the Directorate’s Battlespace Environment Division shared its first all-sky image taken by the imager less than a 

month after launch (above). In March 2003, the team released an improved SMEI composite all-sky image (below).
SUMMARY AND CONCLUSION

 The year 1903 brought about several 

important events. Panama declared its 

independence from Colombia, allowing 

President Theodore Roosevelt to begin work on 

the Panama Canal the next year. The canal made 

navigation more convenient in terms of cost and 

time. It also allowed for quicker mobilization 

of the American fleet from the Pacific to the 

Atlantic in time of need, a lesson learned in 1898 

with the voyage of the USS Oregon from the 

Pacific coast to Cuba in support of the American 

fleet during the Spanish-American War. The 

first narrative silent movie, The Great Train 

Robbery, premiered, changing the motion picture 

by its use of jump cuts and crosscuts, outdoor 

locations, and camera placement. In Milwaukee, 

William Harley and the Davidson Brothers 

Arthur, Walter, and William, culminated their 

work on “taking the work out of bicycling,” 

and sold the first Harley-Davidson motorcycle. 

The motorcycle sported a one-cylinder gas 

combustion engine and was one of the three 

motorcycles the company manufactured that 

year and sold through its first dealership, 

located in Chicago. And Henry Ford and eleven 

other investors incorporated the Ford Motor 

Company and sold its first car, a Model A.101

 Arguably the single event that most 

revolutionized the world that year was the 

59-second, 852-foot first flight of a heavier-thanair machine at Kitty Hawk, North Carolina. 

Powered flight, and the aircraft and spacecraft 

we enjoy today, have come farther than any 

of the other technologies just mentioned. 

Motorcycles still carry only a few passengers, 

cars may get better mileage, and both may be 

more reliable than their 1903 counterparts. The 

Panama Canal still plays an important role in 

the global economy and America’s defense, and 

the Canal also has determined ship design for 

some time, for passage through it is important 

for large and small vessels. Just as the national 

economy was once built upon the railroad and 

personal mobility increased with the appearance 

of the automobile, so has air transport of people 

and cargo made the world a closer-knit place.

 Military operators, over the years, have 

come to rely on the tools created by Air Force 

scientists and engineers for understanding 

the space environment and space weather. 

Operational users have long enjoyed the benefits 

of state-of-the-art Air Force and Air Force–

sponsored research and development. From 

1971 through 1998, the Air Force operated 

the Defense Meteorological Satellite Program 

(DMSP), a series of satellites tasked “to 

generate terrestrial and space weather data for 

operational forces worldwide.” DMSP-generated 

data is also furnished to the civilian community 

through the Department of Commerce via 

NOAA [National Oceanic and Atmospheric 

Administration]. Air Force researchers played 

a major role in the development of a new class 

of remote atmospheric sensing systems and 

transferred these to DMSP. Among other 

functions, these sensors solved problems with 

previous generations of atmospheric sounders 

and allowed DMSP to provide continuous 

atmospheric soundings at altitudes ranging 

from the earth’s surface to 40 km [kilometers]. 

The Air Force Weather Agency uses the data 

collected in this manner to model the earth’s 

winds and cloud movements and provide timely, 

improved forecasts to all DoD forces and 

operating locations as well as to civil weather 

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forecasting agencies. In 1998, when the Air 

Force and the Department of Commerce 

agreed to transfer control of DMSP to a joint 

operational team, the Air Force contributed its 

scientific expertise directly to civilian users, a 

major contribution to the American people.102

 This is a fine example of how research 

and development experts, operators, and the 

American people have benefited from the stateof-the-art research the Air Force conducted 

on the space environment and space weather. 

Starting with lessons learned during World War 

II and using captured German V–2 rockets, 

Air Force science and technology has grown 

apart from terrestrial meteorology. Given the 

longer history of global weather data collection 

and dissemination, space-weather research 

is relatively well advanced after fifty years, in 

comparison with the work of early weather 

scientists like Benjamin Franklin in the 1750s.

 The Air Force has pursued space-related 

research from ground stations, aircraft, balloons, 

and outer space. Individually and collectively, 

these systems have quickly produced a series 

of unfolding and ever-changing definitions 

of what is state of the art in terms of our 

understanding of the space environment. As 

computing technology has matured since the 

1940s, so, too, has the Air Force’s ability to 

look into the vastness of space to discover what 

exactly faces the space systems of the future.

 Since the discovery of the Van Allen 

radiation belts in 1958, experts with the Air 

Force have dedicated themselves to the pursuit 

of knowledge in the belief that space holds the 

answers for many phenomena on earth. They 

have discovered myriad events related to the sun 

that create CMEs, atmospheric scintillation, 

and solar flares, and they have helped explain 

coronal holes, sunspots, and geomagnetic 

storms. All of these solar events can have 

dramatic impacts on man-made electronic 

systems on earth and in space. With the push 

of new technology pulling the development of 

new devices from black-and-white to color 

television to today’s high-definition television; 

from local broadcasts to satellite dishes; from 

the first hand-held calculators in the 1970s to 

the first affordable home computers in the 1980s 

to today’s cellular telephones, personal digital 

assistants, and Blackberry devices technology 

has been the hallmark of the post–World 

War II world. Military systems are likewise 

more dependent than ever upon consistent 

performance by electronics and computer 

hardware and software. Advanced work by the 

Air Force’s best and brightest is making sure 

that in the future, as they have in the past, 

Americans can enjoy the prosperity that comes 

from a world at peace, a world that can remain 

in touch, no matter the time or weather.

 The Air Force is well known for its 

advancements in air power and its important 

role in America’s wars in the last sixty years. 

But the Air Force has also created an impressive 

history in space-related accomplishments 

in conjunction with civilian counterparts 

at NASA, the Department of Commerce, 

and the National Oceanic and Atmospheric 

Administration. The same is also true of 

Air Force research and development efforts 

aimed at understanding and forecasting the 

space environment and the myriad events 

that constitute space weather. As the world 

becomes more attached to its electronic devices, 

as power grids continue to grow and carry 

Exploiting the High Ground

147
heavier burdens throughout the world, as 

satellites carry more and more of our economy, 

communications, and entertainment, and as 

space plays an increasingly more important role 

in our national security, an ability to predict 

the impacts of space weather on these systems 

is more important than ever. Space may be the 

next frontier, but without an understanding of 

the challenges in space and the impact of space 

weather on space- and ground-based systems, 

the promise of tomorrow cannot be attained.

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Space Flight:

Long-Range Missiles, Rocket Planes, and 

Lifting Bodies

Rick W. Sturdevant

John H. Darrah

Lieutenant General Forrest McCartney, USAF, Ret.
Abstract

 Almost from their inception, Air Force long-range ballistic 

missiles—Atlas, Titan, and Thor,—which were designed to project 

thermonuclear warheads toward targets thousands of miles distant, 

provided the nation with a significant space launch capability. These 

Intercontinental Ballistic Missiles (ICBM) and Intermediate Range 

Ballistic Missiles (ICBMs) were transformed in the late 1950s into 

dependable space launchers and eventually into today’s Evolved 

Expendable Launch Vehicles. The Air Force also contributed to 

the development of several powerful upper stages that significantly 

improved national space-launch capability.

 Moving into the realm of reusable launch vehicles, the Air 

Force led, or participated in, development and testing of several 

manned aerospace vehicles. Cooperation between the National 

Aeronautics and Space Administration and the U.S. Air Force has 

been key to the advancement of reusable launch vehicle technology: 

from the X–15 and Dyna-Soar to lifting bodies and the Space 

Shuttle. Pursuit of a National Aerospace Plane in the early 1990s 

highlighted the utility of a military space plane as part of a new 

generation of reusable launch vehicles to replace the shuttle.
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INTRODUCTION

 Rocketry—the science related to non-airbreathing pyrotechnic devices, that is, missiles, 

propelled by hot gases—led to a technology 

applied initially to advanced warfare. At least 

seven centuries of development preceded 

efforts in the mid-1900s to build missiles able 

to traverse thousands of miles and deliver 

thermonuclear warheads against enemy targets. 

Almost simultaneously, it became apparent that 

long-range military rockets also might serve 

astronautics, that is, manned or unmanned 

navigation, exploration, and utilization of 

outer space. As an integral part of astronautics, 

rockets function as boosters for spacecraft.

 Nearly sixty years ago, even before it 

became a separate service, the United States 

Air Force (USAF) undertook the design and 

acquisition of long-range missiles as weapon 

systems. By the 1960s, those missiles also 

had become the boosters that put American 

astronauts, satellites, and interplanetary 

probes into space. The vast majority of all 

American space launches from that time to 

the present, regardless of whether the payload 

belonged to National Aeronautics and Sapce 

Administration (NASA), a private company, a 

foreign nation, the USAF or another military 

service, or the once super-secret National 

Reconnaissance Office, have been achieved via 

USAF expendable boosters or their variants.

 In addition to expendable boosters derived 

from long-range ballistic missiles the 

intermediate-range Thor and intercontinental 

Atlas and Titan, the USAF has contributed 

significantly over the last half century to the 

development of powerful upper stages to propel 

spacecraft beyond low Earth orbit. The USAF 

also has worked extensively over many years on 

the design of hybrid (partially reusable) or fully 

reusable launch and powered-flight systems, even 

though these have been primarily under NASA’s 

purview for purposes of manned space flight. 

Unquestionably, America’s access to space has 

relied in large measure on launch capabilities 

provided in whole or part by the USAF.

LONG-RANGE MISSILES—

EXPENDABLE BOOSTERS

 American military interest in long-range 

missiles increased dramatically during the 

last years of World War II, when German 

V–2 rockets began raining down on London 

and other Allied targets. As early as 1944, 

the Jet Propulsion Laboratory in Pasadena, 

California, reported to the Army Air Forces 

on the feasibility of developing an American 

equivalent to the V–2 to deliver warheads over 

great distances. From that point through the 

early 1950s, however, military priorities and 

drastically diminished budgets prevented any 

sustained ballistic missile development program. 

Even a RAND report in early 1946 on the 

feasibility of an Earth-circling satellite, which 

suggested a secondary use for such missiles, 

failed to alter the situation. Not until the 

creation of smaller, thermonuclear warheads, 

combined with increasingly clear evidence 

of a long-range rocket program in the Soviet 

Union, did the USAF gain strong governmental 

backing for accelerated development of an 

intercontinental ballistic missile (ICBM). In 

1954, the service established the Western 

Development Division under the leadership 

of Brigadier General Bernard A. Schriever 

to oversee ICBM acquisition. In due course, 
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Figure 1. Thor IRBM.

primarily to ensure that nothing competed 

with the ICBM program and secondarily 

to leverage similarities in technology, the 

USAF space program was transferred to 

the Western Development Division.

THOR-DELTA

 Suspicious that the Russians were at 

least three years ahead of the United States 

in ballistic missile development and that 

accelerated procurement of an operational 

American ICBM involved considerable risk, 

the USAF opted through a 27 December 1955 

General Operational Requirement to acquire 

an intermediate-range missile capability within 

one year. Douglas Aircraft delivered the first 

Thor intermediate-range missile on 26 October 

1956. Powered by a single Rocketdyne MB–3 

Block II engine burning RJ–1 (kerosene) and 

liquid oxygen, the Thor, which measured 

56 feet high and 8 feet in diameter, boasted 

150,000 foot-pounds of thrust at sea level. 

Gimbaling of the main engine controlled pitch 

and yaw, while two vernier engines controlled 

roll and pitch adjustment for the main engine. 

As a space launcher, Thor could loft 1,570 

pounds. into low Earth orbit. When three 

Thiokol TX–33–52 (Sergeant) solid rocket 

boosters and an improved MB3 Block III main 

engine were installed in 1963 to produce the 

Thrust-Augmented Thor, it achieved 135,396 

foot-pounds of thrust at liftoff and could 

place approximately 2,200 pounds into a 100-

nautical mile orbit. Subsequent modifications 

to the original booster in the mid-1960s 

lengthened the tank by eleven feet to produce 

the Long-Tank Thrust-Augmented Thor.

 A tally of Thor space launches includes many 

noteworthy successes. Among the earliest were 

Discoverer I, the first polar-orbiting satellite, 

in February 1959; Explorer I, the first to 

photograph Earth from space, in August 1959; 

Pioneer 5, which entered solar orbit, in March 

1960; Transit 1B, the first navigational satellite, 

in April 1960; Discoverer XIV, the first mission 

to return reconnaissance photographs under 

the Corona program, in August 1960; Courier 

1B, the first active-repeater communication 

satellite, in October 1960; and Oscar 1, the first 

amateur radio operators’ satellite, in December 

1961. Thor became the mainstay for launching 
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Figure 2. Thor Space Launcher.

Corona reconnaissance satellites as well as 

associated Defense Meteorological Satellite 

Program (DMSP) payloads, during the 1960s. 

When the last Thor-Delta was launched on 

6 October 1981, the Thor booster had flown 

more than 500 times in various combinations.

 Under a NASA contract in 1959, Douglas 

Aircraft combined Thor components with U.S. 

Navy Vanguard elements to deliver, in only 

eighteen months, the Delta launch vehicle, 

which evolved over time to meet a variety of 

requirements. After a series of launch disasters 

during 1985–1987, the USAF, needing a 

launcher primarily for Global Positioning 

System (GPS) satellites, contracted with 

McDonnell Douglas to develop the Delta 

II. By 1998, Boeing had derived a Delta III 

from the Delta II to fulfill requirements 

for a higher capacity commercial launcher, 

one that could double the weight a Delta II 

could place in a geo-transfer orbit. While 

the Delta III added elements to increase 

performance, it shared a production line and 

many common systems (including the RS–27A 

first-stage main engine) with the Delta II.

 Like its Thor progenitor, Delta proved 

remarkably successful. Its first success came 

in August 1960 when Echo 1, the first passive 

communications relay satellite, entered 

orbit. Delta boosters also launched NASA 

Tiros weather satellites; the first Orbiting 

Solar Observatory in March 1962; AT&T’s 

Telstar satellites; and the first geosynchronous 

satellite, Syncom 2, in July 1963. In addition 

to being the workhorse for GPS launches, 

Delta II has launched NATO communications 

satellites and nonmilitary communications 

and scientific payloads for the United States 

and several foreign nations. One of its more 

recent achievements involved the extremely 

successful Near Earth Asteroid Rendezvous 

spacecraft launched in February 1996.

ATLAS

 Initiated by Convair as Project MX–774 for 

the Army Air Forces in 1945, the Atlas ICBM 

program received highest national priority in 

March 1955. In terms of production, testing, 

and construction, it soon became the largest 

and most complex program ever undertaken, 

surpassing even the Manhattan Project. Headed 

by Belgian-born Karel J. (Charlie) Bossart, 

Convair engineers used an innovative, weightsaving “balloon” construction in which the 

extremely thin, pressure-stabilized propellant 
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155

tanks were integral to the airframe itself. 

Although the first launch of a developmental 

Atlas A occurred in June 1957, the first 

operational Atlas D ICBM launch did not come 

until April 1959. The stage-and-a-half Atlas 

D, dubbed by one author the “granddaddy” 

of all versions over the next 40 years, evolved 

along two branches: one contained the E- and 

F-model ICBMs; the other focused on space 

launchers, beginning with the LV–3 series. 

Because tailoring each Atlas to a specific space 

mission lengthened lead times and increased 

cost, the USAF awarded the Convair Division 

of General Dynamics a contract in 1962 to 

develop a standardized launch vehicle. Twentyfive years later, after a national decision to 

remove commercial payloads from the Space 

Shuttle, the company opted on its own to build 

Atlas I. In May 1988, the USAF, needing 

a launcher primarily for Defense Satellite 

Communications System (DSCS) payloads, 

contracted with Convair to develop the Atlas 

II. Convair lengthened the Atlas I by nine 

feet to increase the amount of propellant the 

rocket could carry and employed an improved 

Rocketdyne MA–5A engine set that produced 

414,400 foot-pounds of thrust. Further 

modifications, which replaced the multiple 

Rocketdyne engines with a single Russian-built 

NPO Energomash RD180 and drastically 

Figure 3. Atlas ICBM. Figure 4. Atlas-Mercury Launcher.
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Figure 5. Titan II ICBM.

reduced the total part count to simplify 

construction, resulted in the Atlas IIAR. Later 

renamed the Atlas III, this launcher retained 

the pressure-stabilized structural concept of the 

original Atlas ICBM but dropped the stageand-a-half design in favor of a single stage.

 Atlas boosters achieved many prominent 

successes during the early years of space launch. 

First used in December 1958 for Project Score, 

the world’s first communications satellite, Atlas 

boosters also lofted USAF Midas and Samos 

payloads beginning in 1960 and Vela nuclear 

detection satellites beginning in 1963. As the 

1960s progressed, Atlas vehicles sent Ranger, 

Surveyor, and Lunar Orbiter spacecraft to the 

Moon in preparation for human expeditions. 

Mariner missions to Mercury, Venus, and 

Mars as well as Pioneer probes to Jupiter, 

Saturn, and Venus also employed the Atlas. 

NASA employed a man-rated version of 

the Atlas for every Mercury orbital flight 

beginning with John Glenn’s mission on 20 

February 1962. The last launch of an Atlas E 

placed a DMSP satellite in Sun-synchronous 

orbit on 24 March 1995. Atlas Is launched 

the Navy’s Ultrahigh Frequency Follow-On 

(UFO) satellites and the National Oceanic and 

Atmospheric Administration’s Geostationary 

Orbiting Environmental Satellites during the 

early 1990s. During the later 1990s, Atlas II 

took over the UFO launches, along with DSCS 

and various other kinds of communications 

payloads, both commercial and civil.

TITAN

 Considering the urgent requirement for an 

operational ICBM and recognizing the cuttingedge technological and manufacturing risks 

associated with Atlas development, the USAF 

opted in October 1955 to contract with the 

Martin Company for a two-stage Titan ICBM. 

This parallel development program stimulated 

industrial competition to produce a weapon 

system in the shortest time. To reduce the risk 

of failure even further, both the Titan and 

Atlas programs employed separate associate 

contractors for each major subsystem (e.g., 

airframe and assembly, propulsion, guidance, 

computers, and nose cones), thereby improving 

the odds that critical components might be 

interchangeable between the two missiles. 

Over the longer term, this approach ensured 

expansion of research and development (R&D) 

firms and, in turn, increased production 

capabilities relevant to missiles and space.
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157

 The Titan I ICBM, which first flew in 

February 1959, became the progenitor of a whole 

family of space launchers that culminated with 

the Titan IV heavy lifter, which first flew in June 

1989. Rather than rely on incremental changes 

to Titan I, the USAF chose to alter significantly 

the configuration of the Titan II ICBM. The 

latter had a self-contained, all-inertial guidance 

system that allowed a “salvo” launch of the 

entire force, and storable, hypergolic propellants 

instead of cryogenic fuels enabled a more rapid 

operational response. Each Titan II could 

be stored in and launched from a hardened, 

underground silo, and a system involving 

two main thrusters allowed for “steering” the 

missile in a novel fashion. A much greater 

“throw weight” permitted delivery of heavier 

thermonuclear payloads anywhere on the globe.

 Because problems and inefficiencies still 

existed in tailoring individual Titan IIs for 

specific space-launch missions, the USAF 

in 1961 initiated development of Titan III. 

A Titan II ICBM, structurally modified 

to handle increased payloads, served as the 

Titan III common core. Using that standard 

core in combination with solid-propellant, 

strap-on rockets, or in a stretched version, the 

USAF produced a variety of space launchers 

between 1965 and 1982: Titan IIIC, D, and 

E; 23B, C, D, and E; 24B; 33B; and 34B and 

D. From the Titan 34D, Martin Marietta 

derived a commercial Titan III that first flew 

in 1989. Meanwhile, deactivation of the Titan 

II ICBMs, which the USAF completed in 

1987, made them available for refurbishment 

as space launch vehicles with modification of 

Figure 6. Titan II SLV. Figure 7. Titan IVB.
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their guidance and attitude-control systems and 

addition of instrumentation and range safety 

destruct subsystems. The first Titan II space 

launch flight occurred in September 1988 from 

Vandenberg AFB, California. Finally, Titan IV 

assured access to space for heavy payloads in 

the wake of the 1986 Challenger disaster. Two 

seven-segment solid rocket motors attached 

alongside a stretched, strengthened version of 

the Titan III core vehicle enabled the USAF to 

place payloads of 31,000 pounds in polar orbit 

from the West Coast or 39,000 pounds into low 

Earth orbit from the East Coast. That capability 

meant the USAF, using a Centaur upper stage 

in conjunction with the Titan IV, could send as 

much as 10,000 pounds into geosynchronous 

orbit. With the successful emergence of Evolved 

Expendable Launch Vehicles (EELVs), however, 

Lockheed Martin staked its future on Atlas V 

and brought the Titan genealogy to an end. The 

last Titan IV is scheduled to launch a Defense 

Support Program satellite early in 2004.

 Like Atlas, Titan compiled an illustrious 

record of successful space missions. NASA 

employed man-rated Titan II boosters for 

every Gemini orbital mission during the 

1960s. During the same period, Titan IIIs 

launched Lincoln Experimental Satellites, 

as well as Initial Defense Communications 

Satellite Program payloads, Vela satellites, 

and reconnaissance platforms. In the wake of 

the Challenger disaster on 28 January 1986, 

Titan IV heavy lifters handled Milstar, Defense 

Support Program, and other defense-related 

payloads, while refurbished Titan II ICBMs 

furnished reliable space boosters for DMSP.

EVOLVED EXPENDABLE LAUNCH 

VEHICLE

 When exploration of alternative space-launch 

systems during the 1980s and early 1990s ended 

without a clear national consensus, Congress 

tasked the Department of Defense (DoD) 

with identifying the most appropriate way 

to remedy launch deficiencies and reduce the 

rising cost of launch services. A team headed 

by Lieutenant General Thomas Moorman, vice 

commander of Air Force Space Command, 

responded in April 1994 with the Space Launch 

Modernization Study, which considered four 

options: sustain existing launch systems; evolve 

current expendable launch systems; develop a 

new expendable launch system; and develop 

a new reusable launcher system. Based on the 

Moorman study’s recommendation, the National 

Space Transportation Policy, which President 

Clinton signed on 5 August 1994, directed the 

Secretary of Defense to implement the second 

option. There simply was not sufficient federal 

funding to develop a completely new expendable 

or reusable launch system, and high costs 

combined with inadequate flexibility weighed 

against simply sustaining the existing fleet. On 

25 October 1994, Deputy Secretary of Defense 

John Deutsch signed the implementation plan 

for evolution of the current expendable launch 

vehicle fleet. The USAF had management 

responsibility for the EELV program, 

but, unlike in earlier booster development 

programs, this time significant cost-sharing 

between the corporations and the government 

was involved. In October 1998, the USAF 

awarded contracts to both Lockheed Martin 

and Boeing for EELV development and initial 
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159

Figure 8. Atlas V.

launch services. Innovative management by the 

USAF resulted in trimming the traditional 

seven-year acquisition cycle to four years.

 The EELV fleet consists of two competing 

booster families - the Lockheed Martin Atlas 

V and the Boeing Delta IV - each blending 

new and mature technology, each based on a 

common booster core, and each deliverable in a 

variety of configurations (i.e., number and type 

of solid-propellant, strap-on boosters, as well as 

number of upper-stage engines and faring sizes) 

to meet military, civil, and commercial customer 

requirements through the year 2020. Atlas V 

is available in approximately fifteen mix-andmatch variants, all of which rely on a common 

core that incorporates a reinforced first-stage 

structure powered by a single, Russian-built 

RD180 engine. Depending on the variant, Atlas 

V can place more than 18,000 pounds into a 

geo-transfer orbit or 13,000 pounds directly 

into a geostationary orbit. Delta IV employs 

a common-core first stage powered by a single 

Rocketdyne RS–68 engine and appears in at 

least five variants employing Delta II or III 

second stages along with strap-on boosters—

either the solid-propellant, Graphite Epoxy 

Motor, or the liquid-propellant, common-core 

one. Depending on which variant is selected, 

the Delta IV can place between 9,000 and 

29,000 pounds into a geo-transfer orbit. The 

inaugural flight of an Atlas V, carrying a 

Eutelsat Hotbird 6 payload, occurred on 21 

August 2002, followed by the inaugural flight of 

a Delta IV, carrying a Eutelsat W5 payload, on 

20 November 2002. Another milestone came 

on 10 March 2003 when only the third EELV 

ever launched, another Delta IV, successfully 

placed USAF DSCS payload in its target orbit.

MINUTEMAN

 Unlike its predecessors, the Atlas and 

Titan, the solid-propellant Minuteman ICBM, 

which became operational in 1962, never 

evolved to a standard space-launch vehicle. 

Minuteman technology, nevertheless, enabled 

production of large, solid rocket boosters for 

Titan III and IV space-launch vehicles as 

well as even larger Solid Rocket Boosters for 

the Space Shuttle. Furthermore, Minuteman 

stages have been used in conjunction with 

commercial upper stages for satellite launches. 

Most of the credit for sustaining an interest 

in large, solid-propellant rockets during 
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Figure 9. Delta IV.

the mid-1950s belongs to USAF Colonel 

Edward N. Hall, who touted their simplicity 

compared to liquid-propellant systems. Even 

before the USAF gained DoD approval for 

the Minuteman program in February 1958, 

Hall’s efforts contributed substantially to the 

Navy’s Polaris Submarine Launched Ballistic 

Missile. Minuteman development prompted 

the use of aluminum as a fuel additive, the 

formulation of more powerful propellants such 

as polybutadiene–acrylic–acid–acrylonitrile 

for the Minuteman I first stage, and carboxy 

terminated polybutadiene for the Minuteman 

II second stage. Although carboxy terminated 

polybutadiene represented a significant advance 

in binder technology, it was very costly and was 

eclipsed in the late 1960s by an even better, 

less expensive polymer hydroxyl-terminated 

polybutadiene. Material and manufacturing 

innovations for nozzle throats, exit cones, 

and cases paved the way for later applications 

in large, solid-propellant space boosters.

 While the Minuteman did not become a 

standard space booster in its own right, it did 

provide two stages for the hybrid, four-stage 

Minotaur, which Orbital Sciences Corporation 

produced under a September 1997 USAF 

contract. Officially known as the Orbital 

Suborbital Program Space Launch Vehicle, 

the Minotaur combined Minuteman II first 

and second stages with the second and third 

stages of Orbital’s Pegasus XL small launch 
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161

vehicle. By using parts from 350 retired 

ICBMs, the USAF hoped to slash millions 

of dollars from the cost of launching military 

research satellites into low Earth orbit. The 

Minotaur could launch 1,400 pounds into low 

Earth orbit for an estimated cost per pound of 

$9,000 compared to $15,000 per pound using 

a Pegasus XL. In January 2000, the inaugural 

Minotaur launch successfully placed the Joint 

Air Force Academy–Weber State University 

Satellite (JAWSAT) in orbit. Also serving 

as a multi-payload adapter, JAWSAT carried 

four microsatellite payloads. One of the latter, 

OPAL, built by Stanford University students, 

subsequently released the smallest satellites 

ever placed in orbit. Built by The Aerospace 

Corporation, the Picosat 1A and 1B tethered 

satellites each measured approximately 4 inches 

by 3 inches by 1 inch. Another Minotaur 

launch in July 2000 successfully placed the 

USAF MightySat 2.1 experimental payload 

in Sun-synchronous orbit. Minotaur missions 

were restricted to government and university 

payloads on the basis of national need.

POWERFUL UPPER STAGES

 Although more attention generally has been 

given to large single or multistage boosters, 

some of the most advanced rocket research 

has focused on upper stages. Performing their 

tasks at relatively high altitudes, beyond the 

range of visible exhaust plumes, these relatively 

unsung heroes of the space age play a critical 

role in placing larger payloads into high Earth 

orbit or sending interplanetary spacecraft on 

their merry way across the heavenly expanse. 

Major upper stages generally depend little 

on booster or spacecraft subsystems for 

functions like navigation, telemetry, or control. 

Consequently, they represent a distinct category 

of propulsion systems, one to which USAFsponsored R&D has contributed significantly 

over many years. Some of these upper stages 

(e.g., Agena, Centaur, and Inertial Upper Stage) 

contributed to the success of numerous civil 

and commercial launches as well as military, 

while others (e.g., Burner II and Transtage) 

generally saw defense-related service.

AGENA

 Lockheed began working on the Agena, 

originally called Hustler because it used a 

Bell Aerospace engine by that name, in 1956. 

The USAF had contracted for such a vehicle 

to propel a WS–117 L satellite payload into 

orbit and, remaining attached, to supply the 

payload with power and directional pointing. 

Figure 10. Minotaur.
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Figure 12. Centaur Upper Stage.

All Agena upper stages relied on a single engine, 

and all except the very first one, which burned 

JP–4, used storable, hypergolic propellants: 

inhibited red fuming nitric acid/unsymmetrical 

dimethyl hydrazine. The first model, Agena 

A, became available in February 1959. Atop 

a Thor booster launched from Vandenberg 

AFB, the Agena A could place roughly 1,700 

pounds into low Earth, polar orbit. A structural 

redesign in October 1960 nearly doubled the 

propellant capacity, which allowed the Agena 

B version atop a Thor to place approximately 

2,500 pounds into a similar low Earth, polar 

orbit. Upgrades to improve producibility, 

versatility, guidance accuracy, and on-orbit 

longevity led to the Agena D in June 1962. The 

latter in combination with a Titan IIIB could 

place approximately 7,000 pounds in polar 

orbit from Vandenberg. Both the last Agena 

A and the last Agena B used Atlas boosters 

in January 1961 and June 1966, respectively. 

Production of the Agena D ceased in 1982, and 

the last flight occurred in February 1987 on a Titan 

IIIB. During its last two decades of operation, 

the Agena D registered a success record of 

100 percent during 131 missions. In every 

instance, the booster operated correctly, giving 

the upper stage an opportunity to perform.

CENTAUR

 Although NASA generally receives credit for 

developing the Centaur, this liquid-propellant, 

high-energy upper stage originated in 1956 

with Krafft Ehricke, an employee of Convair/

Astronautics Division of General Dynamics. 

That company wrote a detailed proposal in 

1957, which the USAF exhaustively reviewed. In 

January 1958, Air Research and Development 

Command proposed a program to the Air Staff 

to develop such an exploratory, experimental 

space vehicle. In August 1958, the Advanced 

Research Projects Agency formally established 

the Centaur program and assigned management 

responsibility to the USAF. The Centaur, 

powered by newly designed Pratt and Whitney 

RL–10 engines burning a liquid oxygen–liquid 

hydrogen mixture and flown atop Atlas or 

Titan boosters, would place heavy payloads into 

geosynchronous orbit. Relying on a balloon 

tank design similar to what Bossart used for the 

Atlas ICBM, Ehricke’s Centaur nevertheless 

featured an innovative, technically demanding 

double-walled integral bulkhead to provide 

insulation between fuel and oxidizer. Although 

Centaur was the first space vehicle to burn liquid 

hydrogen, one could trace USAF pursuit of 

Figure 11. Agena Upper Stage.
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163

liquid hydrogen as a rocket fuel to a July 1945 

contract with Ohio State University’s Cryogenic 

Laboratory. Despite this longstanding interest, 

development of the necessary technology 

proved extremely challenging. The USAF 

transferred the Centaur program to NASA on 

30 June 1959, but NASA continued to use the 

USAF contracts with General Dynamics until 

January 1962. Not until November 1963 did 

the first successful developmental flight occur, 

and it would be another three years beyond 

that before Centaur became operational.

BURNER II

 In September 1965, the USAF announced 

development under a Boeing Aerospace contract 

of a new, low-cost upper stage Burner II that 

would be adaptable to almost any standard 

USAF booster and would be the smallest 

maneuverable upper stage in its inventory. 

Relying on a Thiokol STAR 37B solidpropellant motor for its main propulsion, the 

Burner II first flew on a Thor in September 

1966. The Burner II permitted direct injection, 

Hohmann transfer perigee burns, and bi-elliptic 

transfer burns. When used with a Thor for 

direct ascent from Vandenberg, the Burner II 

could put a payload weighing approximately 

125 pounds into a 1,000-mile circular orbit. 

Desiring to add an apogee circularization 

capability, the USAF requested in June 1969 

that Boeing modify the Burner II. By adding a 

second stage powered by a Thiokol STAR 26B 

solid-propellant motor, the Burner IIA nearly 

doubled the on-orbit capability of Burner II, 

thereby improving the ability to circularize 

payloads in operational orbits and allowing 

changes in the orbital plane. Placement of flightproven Burner II equipment and subsystems 

(e.g., guidance and flight control, reaction 

control, electrical and telemetry subsystems) in 

the apogee kick stage allowed jettisoning of the 

larger, first-stage motor after burnout, which 

enhanced overall performance of the upper 

stage. Atop an Atlas 3A, the Burner IIA could 

put roughly 500 pounds into geosynchronous 

orbit. The first Burner IIA flew in October 

1971. Used primarily to launch DMSP 

satellites, the last successful Burner II flight 

occurred in June 1979, after which the USAF 

launched those satellites on higher-performance 

boosters that did not require an upper stage.

INERTIAL UPPER STAGE

 When Vice President Spiro Agnew’s Space 

Task Group learned in 1969 that NASA was 

projecting another 15 years before its space tug 

would be operational, the group favored rapid 

development of an Interim Upper Stage (IUS) 

to bridge the gap. Despite the perceived urgency 

for producing an operational upper stage, 

official records reflect little progress until the 

USAF assumed, in a May 1973 memorandum 

on the DoD use of the Space Shuttle, military 

development of the IUS. In October 1973, 

NASA agreed that the USAF should oversee 

IUS development, and in September 1976 

Boeing Aerospace received the validation-phase 

contract for a new two-stage, solid-propellant 

IUS, one that would be compatible with Space 

Shuttle designs and pose less danger to the 

flight crew than a cryogenic system would. 

Introduction of a USAF requirement that 

the IUS also be compatible with the Titan 

34D booster, the largest expendable booster 

then available, compelled Boeing to abandon 
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Figure 13. Inertial Upper Stage.

its original intention of simply designing a 

“growth” version of the existing Burner II. 

Cancellation of the NASA space tug program 

at the end of 1977 further refocused the 

IUS program and resulted in its name being 

changed to Inertial Upper Stage, a reference 

to its guidance-control technique. As fullscale development proceeded after April 

1978, numerous technical difficulties in the 

propulsion subsystem, software, and avionics, 

as well as programmatic changes, shifting 

specifications, and a weight-growth problem, 

threatened to scuttle the entire program.

 The resulting operational IUS, which first 

flew in October 1982, proved to be unique in 

several ways. It had a first-stage motor that could 

maintain continuous thrust longer than any 

other solid-propellant upper stage (up to 2.5 

minutes); it was more functionally redundant 

than any other upper stage; and it was the only 

one that ground controllers could command 

during flight. Although its structure could 

support an 8,000-pound payload, Boeing studies 

suggested that modifications would allow it to 

handle as much as 16,000 pounds The IUS 

provided the first upper-stage guidance for the 

Titan 34D, and it also became the first upper 

stage used on both the Titan IVA and B.

TRANSTAGE

 Martin Marietta, working under a USAF 

contract in the early 1960s, developed the 

Transtage for the Titan III. This particular 

upper stage underwent its first developmental 

flight test on a Titan IIIA in September 1964, 

graduating to a Titan IIIC on its fifth R&D 

flight in June 1965. In November 1970, the 

Titan 23C became the booster of choice for 

Transtage, and it remained so through another 

twenty-one missions over twelve years. From 

January 1984 to its final flight in September 

1989, the Transtage rode atop Titan 34D 

boosters. Relying on twin Aerojet AJ10–138 or 

AJ101–38A engines capable of multiple starts 

in space, the Transtage atop a Titan 34D could 

deliver more than two tons to geosynchronous 

orbit. Its control module, which used an inertial 

guidance system to handle the entire Titan 

vehicle during flight, could be modified to 

separate from the propulsion module and remain 

with the spacecraft to meet attitude-control and 
Long-Range Missiles, Rocket Planes, and Lifting Bodies

165

maneuvering requirements during the lifetime 

of the payload. The ability of a single Transtage 

to place several satellites in different orbits also 

proved valuable and made this upper stage a 

direct predecessor of the Multiple Independently 

Targetable Reentry Vehicle “bus” for propelling 

multiple small, thermonuclear weapons 

launched on a single ICBM to various targets.

REUSABLE LAUNCH SYSTEMS: 

ROCKET PLANES AND LIFTING 

BODIES

 The USAF quest for reusable launch vehicles, 

manned or unmanned, began at the same time 

as its pursuit of long-range, surface-to-surface 

strategic missiles. As early as April 1946, 

the Army Air Forces guided missile program 

included Project MX–770, which involved 

a one-year contract with North American 

Aviation (NAA) for the study and design of a 

supersonic, winged rocket, the Navaho, having 

a range of 175 to 500 miles. Engine testing 

began with a surplus, liquid-propellant unit 

from Aerojet General that developed only 1,000 

pounds of thrust. By June 1946, however, NAA 

proposed a two-phase engine development 

plan that involved refurbishing and testing a 

complete German V–2 propulsion system and 

subsequently redesigning it to meet American 

engineering standards and production methods. 

The company, drawing on the V–2 design 

but incorporating a number of improvements, 

added a third phase in early 1947 to produce a 

new engine. Even as the USAF was achieving 

independence in September 1947, NAA was 

Figure 14. Transtage.

Figure 15. Navaho.
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Figure 16. X–15 Research Plane.

beginning preliminary design work on the 

Phase III engine. A major simplification, which 

translated into significant weight reduction 

without loss of thrust, was the replacement of 

multiple liquid-oxygen lines, each line feeding 

an individual injector, with a single injector 

plate that resembled a showerhead. This feature, 

applicable to larger engines with greater thrust 

than the 56,000 pounds produced by the V–2, 

became especially important when the USAF 

instructed NAA, in February 1948, to stretch 

the Navaho’s range beyond 1,000 miles.

 When the USAF doubled the range 

requirement, the original boost–glide approach 

to trajectory proved inadequate. The USAF 

proposed adding ramjet propulsion to the 

initial rocket boost to lengthen the time of 

supersonic cruise. The twin engines mounted 

on vertical tailfins, along with the necessary 

fuel supply, increased the total weight of the 

Navaho, which compelled modifying the 

Phase III rocket engine’s thrust from 56,000 

pounds to 75,000 pounds. Testing began in 

November 1949 and continued into March 

1951, when engineers solved the vexing problem 

of combustion instabilities in the engine’s thrust 

chamber. By then, progression of the Cold War 

and the Korean conflict had driven the USAF 

to extend the high-speed, pilotless aircraft’s 

ultimate range requirement to 5,500 nautical 

miles. This, in turn, led to a fundamental 

design change that placed the rocket engines 

and ramjets in separate vehicles, making the 

Navaho a two-stage cruise missile. The ramjetpowered second stage, with its nuclear payload, 

would ride piggyback on the rocket-powered 

first stage to an altitude of 58,000 feet and 

a velocity of Mach 3, when the first stage 

would separate and return to base for reuse.

 Although canceled by the USAF in 1957, 

the Navaho program contributed substantially 

to the future of American spaceflight. The 

missile’s inertial guidance system found its 

way into nuclear submarines and Navy attack 

aircraft as well as into Hound Dog and 

Minuteman missiles. More importantly, the 

Navaho Phase III engine produced by the 

Rocketdyne division of NAA, along with those 
Long-Range Missiles, Rocket Planes, and Lifting Bodies

167

built in parallel by Aerojet General, became 

the basis for the propulsion systems in the 

Atlas, Titan, and Thor launchers, as well as 

in the Army’s Jupiter. Further improvements 

increased the thrust of this basic engine design 

to 205,000 pounds. NASA clustered eight of 

these engines to produce the 1,600,000 pounds 

of thrust in the Saturn I and I-B boosters 

used so successfully in the Apollo and Skylab 

programs. In addition to hardware, the Navaho 

program enriched the aerospace research and 

production capabilities of NAA. The same 

NAA engineers who oversaw pioneering 

breakthroughs for the Navaho presided over 

such production triumphs as the Saturn V’s 

main engines and the hydrogen-fueled engine 

that powered the Moon rocket’s upper stages.

X–15

 Not surprisingly, the USAF found the 

concept of an aerospace plane very attractive 

at an early date. If the Bell X–1 and X–2 

programs were not direct precursors, they were 

at least harbingers of the X–15 program. The 

latter originated with the National Advisory 

Committee for Aeronautics (NACA), which 

decided in June 1952 that it should explore 

flight characteristics of atmospheric and exoatmospheric designs capable of achieving 

velocities of Mach 4 to 10 and altitudes of 12 

to 50 miles. In December 1954, the USAF 

and the Navy had joined NACA in forming 

a Research Airplane Committee, which 

oversaw the lengthy, complicated process of 

selecting a prime contractor, NAA, to build 

the experimental aerospace craft. Flights of the 

X–15 commenced in 1959 and ended in October 

1968, after a total of 199 missions, 89 with 

USAF pilots. During that decade of testing, 

USAF Captain Robert M. White accomplished 

the first astronaut wings flight by piloting the 

craft to an altitude of 314,750 feet in July 1962, 

and USAF Captain Joseph H. Engle became 

the only pilot to qualify for astronaut wings 

three times when he took the X–15 to 266,500 

feet in October 1965. Another USAF pilot, 

Captain William J. Knight, set an unofficial 

world absolute speed record of Mach 6.70 in 

the X–15 in October 1967. Captain White 

was also at the controls in May 1960 when 

the U.S. received and recorded physiological 

data onboard an aircraft for the first time.

 The contributions and spinoffs from the X–15 

program were enormous. In October 1968, 

NASA engineer John Becker compiled an abbreviated list of 22 accomplishments that included 

the development of the first large, restartable, 

man-rated, throttleable rocket engine; first application of hypersonic theory and wind-tunnel 

work to an actual flight vehicle; first use of reaction controls in space, with successful transition 

from aerodynamic controls to reaction controls 

and a return to aerodynamic control; first reusable superalloy structure capable of withstanding 

hypersonic reentry temperatures and thermal 

gradients; first application of energy-management techniques; development of practical 

boostglide pilot displays; development of the first 

practical, single-piece, full-pressure suit for pilot 

protection in space; demonstration of a pilot’s 

ability to function in a weightless environment 

and control a rocket-boosted aerospace craft 

during exo-atmospheric flight; and the first demonstration of piloted, lifting atmospheric reentry. 

Becker also mentioned that engineers studied 

hypersonic acoustic measurements from the 
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168

X–15 flights to define insulation and structural 

design requirements for the Mercury spacecraft.

 A later listing of X–15 program accomplishments by Captain Ronald Boston of the USAF 

Academy History Department expanded Becker’s assessment of the flight research program 

by discussing follow-on experiments that began 

around 1963 in the physical sciences, space navigation, reconnaissance, and advanced aerodynamics. Carrying instruments above the attenuating effects of Earth’s atmosphere, the X–15 

contributed to the physical sciences by achievements in photometric analysis of the ultraviolet 

brightness of several stars to determine their 

material composition; measurement of the atmospheric density to profile seasonal variations; 

and the first direct measurement of the Sun’s 

irradiance from above the atmosphere, resulting 

in a revaluation of the solar constant of radiation 

that, in consequence, proved useful for designing thermal protection for spacecraft. The space 

navigation experiments aboard the X–15 furnished information about Earth’s infrared horizon-radiance profile, which was used in attitudereferencing systems for orbiting spacecraft, and 

they collected data on the radiation characteristics of the daytime sky, which was applied in an 

automatic, electro-optical star trackingî system 

used on high-altitude reconnaissance aircraft 

and in satellite-positioning systems. Ultraviolet 

and infrared sensors aboard the X–15 tested 

the feasibility and relative efficacy of using those 

parts of the spectrum to detect and characterize the exhaust plumes of long-range missiles, 

which aided the development of satellite systems 

for missile-warning. Finally, the X–15 program 

spawned an enduring Mach 8 hypersonic ramjet 

engine project, even though X–15 flights ended 

before a prototype hypersonic ramjet engine 

could be delivered for actual flight tests.

X–20 DYNA-SOAR

 Advocacy for USAF development of a fully 

reusable space vehicle based on the boostglide 

principle began with Walter Dornberger, a 

former general who headed Germany’s military 

rocket program during World War II. During 

that period, he had become familiar with the 

work of Eugen Sänger and Irene Bredt, who 

collaborated on designing an antipodal bomber 

that would be boosted to orbital velocity, skip 

on the atmosphere, deliver its payload to the 

opposite side of the globe, and glide back to a 

friendly base for reuse. After the war, he had 

worked on missiles for the USAF at WrightPatterson AFB, Ohio, before becoming a 

consultant to Bell Aircraft, where he and Kraft 

Ehricke, another German rocket scientist who 

had been brought to the United States through 

Project Paperclip, rejuvenated the Sänger-Bredt 

design study. In April 1952, Bell and Wright 

Air Development Center undertook joint 

Figure 17. Preparing scale model of Dyna-Soar for wind tunnel 

test at Arnold Engineering Development Center. 
Long-Range Missiles, Rocket Planes, and Lifting Bodies

169

development of a manned bomber and space 

reconnaissance vehicle called BoMi, which would 

be launched by a two-stage rocket to altitudes of 

100,000 feet or higher and operate at velocities 

exceeding Mach 4. Through a series of USAF 

contracts with Bell, the BoMi project continued 

for another four years. During March 1956, 

however, the USAF channeled the development 

effort specifically toward a piloted, high-altitude 

reconnaissance system code-named Brass Bell. 

Before year’s end, the contractor had designed a 

two-stage system powered by Atlas-type rocket 

engines and capable of reaching an altitude of 

170,000 feet at a velocity of more than 13,200 

mph with a range of 5,500 nautical miles.

 Meanwhile, the USAF continued its pursuit 

of a manned, hypersonic, boostglide bomber 

by issuing study contracts to six aerospace 

companies Boeing, Republic, McDonnell, 

Convair, Douglas, and NAA for what became 

known in June 1956 as RoBo, a vehicle 

capable of reaching an orbital altitude of 

300,000 feet and a velocity of 15,000 mph. In 

November, the USAF established a manned, 

glide-rocket research program known as 

HYWARDS (Hypersonic Weapons Research 

and Development System) to collect data on 

problems ranging from aerodynamics and 

structure to components and human factors. 

Faced with funding difficulties and the challenge 

posed by the Soviet Union’s launch of Sputnik, 

the USAF opted in early October 1957 to 

consolidate HYWARDS, Brass Bell, and RoBo 

into a single Dyna-Soar (Dynamic Soaring) 

development program. Joined by the newly 

created NASA, the USAF contracted with 

Boeing in November 1959 to build Dyna-Soar 

based on a single-orbit operational principle. 

By autumn 1961, however, a USAF decision 

to make Dyna-Soar a multiorbit vehicle forced 

Boeing to add a more sophisticated guidance 

system, improve the reliability of various 

subsystems, and add a retro-fire system for 

deorbiting the craft. Given the increasingly 

obvious experimental character of Dyna-Soar, 

it received the designation X–20 in June 1962. 

Plagued sporadically by less than wholehearted 

support from both within and outside USAF 

circles, as well as by perceptions of redundancy 

once NASA defined its Gemini program, the 

X–20 effort finally was canceled by Secretary of 

Defense Robert McNamara in December 1963.

 Although Dyna-Soar never actually flew, 

its service as a testbed for numerous advanced 

technologies contributed much to the science of 

high-Mach flight. Advances in guidance-system 

technology proved important to the X–15 and 

later programs. Progress in aerodynamics, 

structures, and materials technology, much of 

it based on more than 14,000 hours of windtunnel tests, had significant worth for nearly 

two decades of subsequent lifting-body research. 

Figure 18. X–20 Dyna-Soar.
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When Rockwell International began design 

work leading to the Space Shuttle, the single 

most important U.S. database on fundamental 

reentry heating-dynamics technology came 

from the X–20 program. The Ren 41 hightemperature nickel alloy developed for X–20 

heat shielding reappeared during the 1970s 

in Boeing’s Reusable Aerodynamic Space 

Vehicle, a project in which the USAF invested 

several million dollars for development of a 

rocket-powered spacecraft that would have 

operated much like an aircraft in terms of 

takeoff and landing. Two classified, followon industrial studies of single-stage-to-orbit 

technologies, both sponsored by the USAF 

during the 1980s, suggested the feasibility of the 

reusable space vehicle for a variety of military 

applications, such as reconnaissance, rapid 

satellite replacement, and general space defense, 

but the USAF opted to drop the project and, 

instead, supported development of a National 

Aerospace Plane with air-breathing jet engines.

LIFTING BODIES—WINGLESS AND 

WINGED ROCKETS

 During the late 1950s, NACA (and its 

successor NASA) as well as the USAF 

undertook research into lifting bodies—

wingless, blunt-bodied craft that could 

maneuver at hypersonic velocities and reenter 

Earth’s atmosphere as gliders. In 1959, the 

USAF initiated the minimal-cost ASSET 

(Aerothermodynamic/elastic Structural Systems 

Environmental Tests) project, which launched 

heavily instrumented, hypersonic glider models 

from Cape Canaveral on Thor and Thor-Delta 

boosters to investigate reentry from space at 

near-orbital speeds. ASSET added significantly 

to the technology base for future manned 

reentry systems, especially regarding such issues 

as practical fabrication of refractory metals, 

coating processes, reaction-control system 

design, and the phenomenon of communications 

blackout during reentry. Furthermore, ASSET 

paved the way by early 1964 for an expanded 

Spacecraft Technology and Advanced Reentry 

Tests program with two parts: PRIME 

(Precision Recovery Including Maneuvering 

Entry), involving hypersonic boostglide tests 

using the SV–5D/X–23A unpiloted lifting body 

built by Martin Marietta; and Piloted Lowspeed Tests, using the SV–5P/X–24A manned, 

rocket-powered lifting body, also built by Martin 

Marietta. Launched from Vandenberg AFB on 

Atlas boosters during 1966–1967, three X–23A 

PRIME flights entailed pioneering work in 

ablative materials and internal steam-cooling, 

accomplished the first cross-range maneuvering 

Figure 19. X–24A (above) and X–24B (below)

Lifting Bodies.
Long-Range Missiles, Rocket Planes, and Lifting Bodies

171

of a spacecraft, demonstrated accurate guidance 

to a selected recovery point, and supported the 

concept of a reusable spacecraft.

 Jointly sponsored by the USAF and NASA, 

the X–24A/B project gained momentum with 

USAF approval for Martin Marietta to begin 

construction of the first and only X–24A, 

powered by a single Thiokol XLR11–RM13 

rocket engine, in March 1966. Between April 

1969 and June 1971, two USAF pilots and 

one NASA pilot completed 28 flights (9 were 

glides, 18 were powered, and 1 was a glide in 

middle of a powered flight) in the X–24A, which 

was dropped from a B52. A flight in October 

1970 provided the first demonstration that an 

unpowered spacecraft could perform a shuttletype approach and land on a conventional 

runway. In 1972, the USAF directed Martin 

Marietta in Denver, Colorado, to modify the 

X–24A shell to a more streamlined X–24B 

(basically giving it a new, pointed nose), 

which would allow testing of an aerodynamic 

configuration providing better maneuvering 

capability during reentry. Pilots flew the X24B 

thirty-six times between August 1973 and 

November 1975, twice landing successfully on 

a concrete, strip-type runway at Edwards AFB, 

California. This gave NASA engineers the 

confidence they needed to plan similar landings 

for the Space Shuttle, which was by then well 

into the design phase. Not surprisingly, that 

design owed much to the hypersonic flight 

research conducted by the USAF and NASA.

NATIONAL AEROSPACE PLANE

 An aerospace plane—one powered by an 

air-breathing engine, capable of horizontal 

takeoff from a conventional runway, achieving 

orbital velocity, maneuvering in space, reentering 

the atmosphere, and landing conventionally —

 appealed to USAF officers. Indeed, the USAF 

had begun pursuing this concept in the late 

1950s and, before funding ceased in the early 

1960s, had shifted from a single-stage-to-orbit 

design toward a two-stage-to-orbit concept 

not unlike the later Space Shuttle. Before it 

died, however, this initial effort to develop an 

aerospace plane spawned potentially useful 

research on air collection enrichment systems, 

Mach 8 subsonic combustion ramjets, the Liquid 

Air Collection Engine System, scramjets, and 

advanced turbo-ramjets or turbo-accelerators. 

When the USAF Trans-Atmospheric Vehicle 

program began studying shuttle replacement 

in 1982, both air-breathing jet engines and 

rockets received serious consideration. Because 

several other organizations were pursuing 

similar work, it seemed efficacious by late 1985 

to form a single National Aerospace Plane 

Program jointly sponsored and funded by the 

USAF, Navy, NASA, Advanced Research 

Projects Agency, and Strategic Defense Initiative 

Organization, with the USAF responsible 

for overall management. Despite the obvious 

military leadership and potential defense-related 

applications of the National Aerospace Plane, 

the Reagan administration touted its peaceful 

uses and envisioned the National Aerospace 

Plane as pioneering hypersonic commercial 

flights. Enthusiasts viewed it as the potential 

progenitor of all manned space transportation 

systems after the Space Shuttle.

 Plans called for building the National 

Aerospace Plane flight-test vehicle, which 

received the designation X–30A, after 

validation of the high-risk technology associated 
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with a Mach 25 aerospace craft capable of 

taking off and landing like a conventional 

aircraft. Development of airframes, materials, 

subsystems, and powerplants suitable for 

repetitive hypersonic flights posed a daunting 

challenge, but participating government agencies 

and private companies made significant technical 

progress before budget difficulties and the end of 

the Cold War led to cancellation of the National 

Aerospace Plane program in 1994. With respect 

to propulsion, the program registered several 

noteworthy accomplishments: thrust above 

Mach 8 was directly measured for the first time; 

large-scale ramjets were tested to Mach 8,

large-scale scramjets were tested to Mach 16, 

and small-scale scramjets were tested to Mach 18; 

the inlet and combustor were tested to Mach 

18 for the first time; the production, transfer, 

storage, and transportation of slush hydrogen 

were demonstrated; and the newly developed, 

cryogenic 2D integrated fuel tank 

was tested. Exceptional progress 

also occurred regarding coated 

carbon-carbon composites, titanium 

aluminides, advanced metal matrix 

composites, copper niobium, and 

beryllium fiber material. Fabrication 

of advanced composite materials 

substantiated the capability 

to develop leading edges that 

could survive under near-flight 

conditions. Finally, the program 

yielded designs for integration of 

engine and airframe applicable to 

future spaceplane work, including 

a rounded-nose lifting-body 

concept. Some of the most valuable 

knowledge gained from the National Aerospace 

Plane program involved discovery of what 

would not work, in terms of both management 

structure and hardware.

 With the National Aerospace Plane program 

scrapped, NASA sought to regain momentum 

through a cooperative agreement with 

Boeing to produce an X–37 reusable, orbital 

spaceplane. The unmanned, autonomously 

operated X–37 would provide a testbed for 

30 to 40 airframe, propulsion, and operating 

technologies that might significantly reduce 

the cost of space transportation. Concurrently, 

the USAF financed a subscale version the 

X–40A Space Maneuver Vehicle to test the 

low-speed atmospheric flight dynamics of 

the X–37. Unveiled in September 1997, the 

graphite-epoxy and aluminum maneuver vehicle 

successfully completed a series of drop tests 

beginning in August 1998. Using an integrated 

GPS and inertial guidance system, the test 

Figure 20. National Aerospace Plane.
Long-Range Missiles, Rocket Planes, and Lifting Bodies

173

vehicle autonomously acquired the runway in a 

simulated return-from-orbit and landed under 

its own power, similar to how a conventional 

aircraft would, thereby clearing the way for 

drop-testing the unpowered, full-scale X–37. A 

large portion of funding for the Space Maneuver 

Vehicle went into propulsion technology, with 

Aerojet receiving more than $10 million in 

May 2001 to develop a nontoxic, hydrogen 

peroxidebased system. By April 2002, the 

company had designed a revolutionary tri-fluid 

propellant injector for the Advanced Reusable 

Rocket Engine, and it was making progress in 

other risk areas, for example, in catalyst beds, 

thrust-chamber design, and turbine materials. 

As a reusable upper stage, the Space Maneuver 

Vehicle could be launched on several different 

boosters, but it was designed primarily as a key 

component of the Space Operations Vehicle 

system architecture, which relies on a reusable 

first stage and orbital maneuvering capability 

to accomplish a variety of military missions.

SUMMARY

 Even as the nation contemplated the recent 

Columbia disaster and the implications for space 

flight, it continued to rely largely on expendable 

launch vehicles that originated from USAFsponsored R&D programs in the late 1940s 

and 1950s. As requirements for more powerful 

launchers, more often than not defense-related, 

emerged during the 1960s and 1970s, the USAF 

contracted with industry to upgrade the existing 

Thor, Atlas, and Titan technology. When the 

Challenger accident compelled the United States 

to rethink its designation of the Space Shuttle 

as its sole means of space launch, USAF officials 

had already been considering how to revitalize 

the production lines for expendable booster. 

To meet defense-related demands for medium 

and heavy lift, respectively, the USAF procured 

the Delta II and the Titan IV. With the end 

of the Cold War and the imposition of fiscal 

constraints on military spending, the USAF 

initiated acquisition of a launch vehicle to reduce 

significantly the cost of sending into orbit small, 

experimental payloads of national interest. 

The same fiscal constraints led to a national 

decision to continue the evolution of existing, 

highly reliable, expendable launchers rather 

than to embark on development of something 

entirely new at the beginning of the twentyfirst century. Responsibility for managing that 

evolution fell squarely upon the USAF, which 

devised innovative partnering arrangements with 

industry to share the cost of acquiring EELVs.

 As for reusable launch systems, USAF 

scientists and engineers considered them even 

before the establishment of the USAF as a 

separate military department. Working with 

the NACA and its successor, NASA, the 

USAF contributed extensively to the nation’s 

understanding of the dynamics of hypersonic 

flight and to its technological base for producing 

the actual materials and subsystems needed 

for a space plane. Competing concepts of 

manned versus unmanned reusable vehicles 

generated reams of design studies over more 

than five decades and sparked countless hours of 

discussion about the relative advantages of one 

approach over the other. From the X–15, DynaSoar, and lifting bodies through Space Shuttle 

development and National Aerospace Plane, 

the USAF and NASA partnered to promote 

piloted, reusable systems for military, civil, and 

commercial purposes. Over time, however, the 
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174

USAF found itself reverting to the original 

notion of an unpiloted, reusable space plane, 

equipped with propulsion systems allowing it to 

operate efficiently through the atmosphere, into 

space, and, on its return, be capable of landing 

autonomously, like an aircraft, on a conventional, 

concrete runway. While NASA held primary 

managerial responsibility for reusable launch 

systems, the USAF and NASA worked 

diligently at the end of the twentieth century 

to improve their partnering arrangements and, 

thereby, avoid costly duplication of R&D efforts.
Military Satellite Communications:

From Concept to Reality

Harry L. Van Trees

Lieutenant General Harry D. Raduege, USAF

Rick W. Sturdevant

Ronald E. Thompson 
Abstract

 Military satellite communications have had a major impact 

on the success of recent military operations, such as Iraqi Freedom. 

Following a brief review of basic satellite characteristics—including 

orbital locations, frequency bands, bandwidth considerations, and 

terminal characteristics—the evolution of military satellite systems 

from a paper concept in 1945 to the sophisticated systems today.

 Also discussed are technological developments that enabled 

the implementation of the Defense Satellite Communications 

System, Milstar, and Ultrahigh Frequency Follow-on systems, and 

various commercial adjuncts. Although some specific elements, 

such as multiple-beam antennas, phased arrays, signal design, 

and onboard switching are discussed, the technology focus is at the 

systems level. Specific operational successes that relied on military 

satellite communications are described. The technology developments 

required to support the evolving operational concepts are outlined.
INTRODUCTION

 Military satellite communications have 

played a major role in the success of recent 

military operations. From Operations 

Desert Shield and Desert Storm to Iraqi 

Freedom, the precise coordination of assets 

would have been impossible without satellite 

communications (SATCOM). The ability 

to implement the sensor-to-shooter loops in 

near real time relied heavily on satellites.

 This paper has three intertwined discussions: 

history, technology, and operations. We examine 

the history of SATCOM from a paper concept, 

appearing in science fiction articles in 1945, 

to the sophisticated, reliable systems of today. 

We focus on the key historical events that 

helped determine the evolution of SATCOM. 

In parallel, we discuss the key technology 

developments that have enabled the growth from 

the small (INTELSAT) I, Early Bird, launched 

in 1965, which carried 240 voice circuits, to 

the current large satellites, which carry massive 

amounts of voice and data traffic. The third goal 

of the paper is to demonstrate how SATCOM 

have affected military operations. Most of the 

new military operational capabilities in the 

information age rely heavily on SATCOM.

 It is important to note that we use the 

term “military satellite communications,” 

or MILSATCOM, to mean satellite 

communications for military purposes. The 

emphasis is on military satellite systems, but we 

will also discuss the usage of commercial satellite 

systems for military applications. The current 

Department of Defense (DoD) MILSATCOM 

system consists of five subsystems:

■ Defense Satellite Communications 

System (DSCS)

■ Milstar

■ Ultrahigh frequency (UHF)

■ Global Broadcast System (GBS)

■ Commercial adjuncts

 The evolution of each of these subsystems 

is described, including their configuration and 

their impact on recent military operations.

 In an appendix to this paper, we review 

several satellite system fundamentals that 

will be helpful in understanding some of the 

information presented here. Readers not 

familiar with satellites may want to read this 

material before continuing with the paper

EARLY HISTORY OF SATCOM

 The concept of using artificial, Earth-circling 

satellites for worldwide communications 

emerged near the end of World War II, a 

conflict that demonstrated the fundamental 

need for electronically transmitting military 

information over longer distances, in greater 

quantities, with more reliability and higher 

security than had ever been required before. 

In the February 1945 issue of the British 

technical journal Wireless World, science-fiction 

writer Arthur C. Clarke published a letter 

speculating on how three satellites positioned 

120 degrees apart in geosynchronous orbit 

could relay television and microwave signals 

worldwide. Although theorists like Konstantin 

Tsiolkovsky (1911), Hermann Oberth (1923), 

and Hermann Potocnik (1929; pseudonym 

Hermann Noordung) wrote about space stations 

in geostationary orbits, and the latter two 

even speculated on the use of such stations as 

communication platforms, Clarke was the first 

to spell out essentially all the technical details 

for modern geosynchronous communications 

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178
satellites. After circulating his ideas privately 

in a paper titled “The Space Station: Its Radio 

Applications,” Clarke presented a more refined 

technical analysis of the orbital geometry and 

communications links in the October 1945

Wireless World article, “Extra-Terrestrial Relays.”

 Others soon echoed Clarke’s basic notion. In 

a May 1946 report titled “Preliminary Design 

of an Experimental World-Circling Spaceship,” 

Project RAND engineers at the Douglas 

Aircraft Company plant in Santa Monica, 

California, told the U.S. Army Air Forces 

that satellites could significantly improve the 

reliability of long-range communications and 

might spawn a multibillion-dollar commercial 

market. Subsequent RAND studies by James E. 

Lipp, in February 1947, and Richard S. Wehner, 

in July 1949, further developed the concept 

of geostationary communications satellites 

located above the equator. Eric Burgess further 

analyzed the possibility of using geosynchronous 

orbits for SATCOM and described in detail 

a potential satellite configuration in the 

September 1949 issue of Aeronautics. Writing 

under the pseudonym J.J. Coupling in Amazing 

Science Fiction, John R. Pierce of AT&T’s 

Bell Telephone Laboratories suggested a 

communications satellite system in March 

1952. He became one of the first people outside 

defense-related circles to evaluate, systematically, 

technical options and financial prospects for 

SATCOM. In a 1954 speech and 1955 article, 

Pierce assessed the utility of passive “reflector” 

and active “repeater” satellites at various orbital 

altitudes. If Arthur Clarke developed the theory 

of geostationary SATCOM, John Pierce and 

his team at Bell Labs pioneered and improved 

much of the hardware, for example, travelingwave tubes and low-noise amplifiers that 

transformed theory into actual working systems.

 The USSR’s launch in 1957 of Sputnik I, 

which transmitted an electronic signal back to 

Earth simply for tracking purposes, sparked 

serious efforts by the United States to develop 

SATCOM for military, civil, and commercial 

use. SCORE (Signal Communication by 

Orbiting Relay Equipment), developed by 

the Advanced Research Projects Agency 

(ARPA) and launched by the Air Force in 

December 1958, became the world’s first active 

communications satellite. During its twelve-day 

operational lifespan, which terminated when 

the battery failed, SCORE received messages 

from a ground station and stored them on a 

tape recorder for transmission back to Earth. 

The U.S. Army’s Courier satellite, launched 

in October 1960, operated on much the same 

principles as SCORE, that is, store-and-dump 

with the use of onboard tape recorders, but 

Courier carried solar cells and rechargeable 

batteries to extend its potential lifetime to one 

year. Unfortunately, a command system failure 

terminated Courier after only seventeen days.

 In addition to these early experiments with 

active repeater satellites, various organizations 

studied the efficacy of passive reflector satellites. 

Under Project West Ford, for example, the 

Air Force contracted with the Massachusetts 

Institute of Technology’s Lincoln Laboratory 

to disperse 480 million copper dipoles, each 

0.72-inch long and 0.0007-inch in diameter, in a 

nearly circular, nearly polar orbit in May 1963. 

This and other experiments led researchers 

to conclude that the passive systems were 

impractical when compared to repeaters.

 Several active communications satellites 

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launched during 1962–65 revealed great 

technological strides. Two Telstar satellites, 

developed by Bell Telephone Laboratories for 

AT&T, established that multichannel telephone, 

telegraph, facsimile, and television signals could 

be transmitted across the Atlantic. The capacity 

of each Telstar included 600 one-way voice 

circuits or one television channel and 60 twoway voice circuits.

 Two relay satellites, developed by the RCA 

Corporation for the National Aeronautics and 

Space Administration (NASA), had a more 

complex communications subsystem (two 

identical redundant repeaters) than Telstar 

did. These experimental systems demonstrated 

that existing technology could produce useful, 

medium-altitude communications satellites at 

a time when a more desirable geosynchronous 

altitude posed a somewhat daunting launch 

challenge.

 Meanwhile, Hughes Aircraft Company 

supplied NASA with three Syncom satellites, 

which became the world’s first geosynchronous 

communications platforms and, in the case of 

Syncom 3, the first geostationary satellite. The 

orbit- and attitude-control system developed by 

Harold Rosen and his team at Hughes Aircraft 

made simple, lightweight, geosynchronous 

satellites possible. This was, undoubtedly the 

single most important advancement in early 

SATCOM.

 While the U.S. military has relied heavily on 

commercial SATCOM over the years, it also 

developed and launched dedicated systems to 

satisfy unique national security requirements. 

In 1958, ARPA had directed the Army and 

Air Force to plan for a strategic SATCOM 

system, with the Air Force responsible for 

the booster and spacecraft, and the Army for 

actual communications elements aboard the 

satellite as well as on the ground. Primary 

management responsibility for this geostationary 

system, dubbed Advent, resided with the Army. 

High costs, inadequate payload capacity, and 

an excessive satellite-to-booster weight ratio 

soon plagued this technologically ambitious 

undertaking, which someone described as a “not 

quite possible dream.” To make matters worse, 

management problems obscured many technical 

issues and prevented a coherent resolution of 

them. Consequently, Secretary of Defense 

Robert McNamara canceled Advent in May 

1962 and, pending a decision on whether the 

defense establishment could lease commercial 

satellite capacity to satisfy its requirements at 

lesser cost, delayed authorization of another 

dedicated military communications satellite 

program until July 1964.

 The U.S. Air Force spearheaded the 

new effort, dubbed the Initial Defense 

Communications Satellite Program (IDCSP), 

and became responsible for procurement of 

all future military communications satellite 

systems. Intended for strategic communications, 

the IDCSP furnished the basic design 

for British Skynet and NATO satellites. 

Recognizing the advantages of a geostationary 

orbit for communications, the Air Force quickly 

evolved the sub-synchronous prototype IDCSP 

system of 1966 into the geostationary DSCS 

II of the 1970s and the jam-resistant DSCS 

III of the 1980s. The DSCS satellites basically 

provided service between large fixed terminals 

and transportable terminals with 20- and 8-foot 

diameter parabolic antennas.

 Over time, another group of satellites 

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constituted the mobile-and-tactical segment 

of the MILSATCOM architecture. The 

first, Tacsat and its Lincoln Experimental 

Satellite, LES6, predecessor, were used 

experimentally to investigate various aspects 

of tactical communications on land, sea, and 

air. Developed by Hughes Aircraft Company, 

launched in February 1969, and operated by 

the Air Force Communications Service, Tacsat 

supported Apollo recovery operations by 

connecting aircraft with their carrier and ground 

stations. Because Tacsat failed in December 

1972 and Fleet Satellite Communications 

(FLTSATCOM) capability was not expected 

before 1978, the Navy leased gap-filler UHF 

service from COMSAT General Corporation. 

Between 1978 and 1989, the Air Force procured 

from TRW Systems eight FLTSATCOM 

satellites and successfully launched six into 

geostationary orbits. In addition to sharing the 

FLTSATCOM satellites, the Air Force Satellite 

Communications system relied on packages 

aboard several satellites in high-inclination orbits 

to provide coverage of the northern polar region.

 Based on congressional direction during 

1976–77 to increase its use of leased commercial 

satellite services, DoD implemented the leased 

satellite program. It contracted with Hughes 

Communication Services in September 1978 

for at least five years of service at each of four 

orbital locations. Five leased satellite launches 

occurred during 1984–90, and leases on three 

were extended into 1996.

 The five subsystems that currently constitute 

the DoD MILSATCOM system, DSCS, 

Milstar, UHF, GBS, and the commercial 

adjuncts, will be discussed. We will look at how 

each of these subsystems evolved, describe their 

current configuration, and give examples of their 

impact on recent military operations.

DSCS

 One can trace the roots of the DSCS back 

to cancellation of the U.S. Army’s Advent 

program in May 1962. At that time, officials 

recommended two approaches: an IDCSP, 

which would use proven technology to develop 

simple satellites for placement, seven at a 

time, in random polar orbits at an altitude of 

approximately 5,000 miles using the proven 

Atlas-Agena launcher; and, somewhat later, an 

Advanced Defense Communications Satellite 

Program to place station-keeping satellites in 

synchronous orbits. A successful Titan IIIC 

launch in June 1965 led to that vehicle’s selection 

for placing IDCSP satellites developed by Philco 

(later Ford Aerospace and Communications 

Corporation) into random, subsynchronous, 

equatorial orbits, three to eight at a time, 

between June 1966 and June 1968. Weighing 

only 100 pounds, these spin-stabilized satellites 

contained no moveable parts, lacked command 

and control capabilities, and had only a basic 

telemetry capability for monitoring purposes.

 Under Project Compass Link in 1967, 

IDCSP provided pathways for transmission of 

high-resolution photographs between Saigon 

and Washington, D.C. As a result of this 

revolutionary development, analysts could 

conduct near-real-time battlefield intelligence 

from afar. By June 1968, IDCSP had been 

declared operational and its name changed 

to Initial Defense Satellite Communications 

System (IDSCS).

 The follow-on DSCS II program aimed to 

overcome several deficiencies limited channel 

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capacity, user access, and coverage in IDSCS. 

In March 1969, TRW Systems received an 

Air Force contract to produce a qualification 

model and six flightworthy DSCS II satellites. 

Unlike the IDSCS satellites, DSCS II would 

have a command subsystem, attitude control 

and station-keeping capabilities, and multiple 

communication channels with multiple-access 

capability, and would occupy synchronous, 

equatorial orbits. It was dual-spin- stabilized and 

weighed approximately 1,300 pounds. Several 

design modifications extended the five-year 

design life to as much as twenty years. The Air 

Force launched the last DSCS II in 1989.

 In 1974, the Air Force began design of 

an improved DSCS III satellite to meet the 

need for greater communications capacity, 

especially for mobile terminal users, and for 

better survivability. General Electric’s DSCS 

III was three-axis-stabilized, weighed 2,475 

pounds, and had a ten-year design life. The 

first DSCS III launch to geostationary orbit 

occurred in October 1982. The Service Life 

Enhancement Program (SLEP) added highpower amplifiers to the last four DSCS III 

satellites to better support the warfighters. The 

last of these improved satellites was launched 

in 1989. One measure of the confidence the 

Air Force placed in the Jam Resistant Secure 

Communications capability afforded by DSCS 

III satellites is that, since December 1990, they 

have been the primary means for transmitting 

missile warning data from key sensor sites 

worldwide to correlation and command centers 

at Cheyenne Mountain, and elsewhere.

THE CURRENT DSCS

 The DSCS space segment primary 

constellation consists of five DSCS III satellites 

in geostationary orbits as shown in Figure 1. Six 

residual satellites provide additional capacity for 

training, testing, and contingency operations.

Figure 1. DSCS Space Segment.

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 The first DSCS III was launched in 1982. A 

total of fourteen have been launched, last one in 

2003. A DSCS III satellite is shown in Figure 2.

 The multiple-beam antennas (MBA) provide 

an important capability. The receive MBA has 

61 beams. By suitably weighting these beams, 

the system can provide enhanced gain in the 

direction of friendly terminals and place nulls 

in the direction of interfering signals. The 

terminal segment includes:

■ Fixed small, medium, and large terminals

■ Transportable tactical terminals

■ Mobile shipboard and airborne terminals

■ Suitcase terminals

Example terminal types are shown in Figures 3 

through 6.

 The system operates in superhigh frequency 

(SHF) band in the vicinity of 8 GHz and uses 

500 MHz of bandwidth. The major DSCS user 

communities include:

■ Intelligence Organizations

■ Combatant Commands (COCOMs) and 

their components

■ Ground Mobile Forces

■ Defense Information Systems Network 

(DISN)

■ USAF Satellite Control Network

■ Diplomatic Telecommunications Service

Figure 2. DSCS III Satellite.

 The DSCS system provides two types of 

capability. It provides high capacity in an 

unstressed environment (the absence of jamming 

and nuclear scintillation). In the current world 

situation, this is the dominant mode of operation. 

The system carries wideband traffic, high-speed 

computer-to-computer links, and interswitched 

trunks. The nominal DSCS satellite capability is 

about 75 Mbps between fixed sites, with an 

equivalent amount dedicated toward tactical 

sites. Capacity varies depending on the actual 

network requirements as changes occur in such 

factors as terminal performance, network 

topology, and satellite health.

 The system can also operate in the presence of 

jamming by utilizing an antijam signal and the 

nulling capabilities of the MBA. In this mode, it 

provides secure voice and low-rate data services.

 The basic DSCS III segment uses technology 

developed in the 1970s. However, the last four 

DSCS III satellites were upgraded as part of a 

Satellite Life Enhancement Program (SLEP). 

Technology upgrades included more transmit 

power in each channel, more sensitive receivers, 

improved solar cells to provide more power, and 

various processing changes. These upgrades 

improved the capacity by over 200 percent, 

improved support to small terminals, and 

provided greater flexibility in system usage.

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Figure 3. Fixed Terminals DSCS AN/FSC–78 terminal (left) and AN/GSC–52 (right).

Figure 4. Transport Terminals - 20 foot AN/TSC–85 (left), 8 foot AN/TSC–93 (middle), and 2.4 meter triband (right).

Figure 5. Shipboard and Airborne Terminals —WSC–6 shipboard (left) and ASC–24 airborne on the E4B aircraft (right).

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 The DSCS terminal segment has had 

continuing technology upgrades over the years. 

The most dramatic was the introduction of Light 

Multi-band Satellite Terminals. These terminals 

are packaged in transit cases and provide a 

rapid deployment capability that is important 

in support of current operational concepts. The 

first terminal of this type, the LST8000, was 

built by M/ACOM under USAF guidance and 

deployed in 1984 to support the White House 

Communications Agency. The devices have 

evolved into multiband terminals that provide 

SHF, C-band (46 GHz), and Ka-band (30/20 

GHz) frequencies so they can operate over 

different satellite systems. The number of transit 

cases has been significantly reduced.

 The requirements for wideband SATCOM 

have continued to grow rapidly. Warfighting 

requirements that contribute to this growth 

include:

■ Situational awareness

- imagery and intelligence, surveillance, and 

reconnaissance (ISR) products

- environmental and map data

■ Battle management

- collaborative planning

- video teleconferencing

- simulation and wargaming

■ Sensor-to-shooter

- target sensing and tracking

- target-weapon pairing

- rapid target engagement

■ Support

- interactive data networks

- telemedicine

- reachback

 Some specific examples of how DSCS has 

satisfied these warfighting requirements are 

provided in the next section.

OPERATIONAL IMPACT OF THE DSCS

 Over the years, the DSCS has evolved into 

a highly successful system providing rapid, 

critical Command, Control, Communications, 

Computers, Intelligence, Surveillance, and 

Reconnaissance (C4ISR) communications for 

warfighters to execute military operations. 

Within hours, the system can provide highcapacity communications worldwide. The 

constellation is prepositioned and configured 

to handle large-scale operations. During 

peacetime operations, DSCS planners leverage 

the flexibility of DSCS and its ability to surge 

bandwidth toward quickly satisfying dynamic 

and robust user requirements. The historical 

support required for major contingencies has 

Figure 6. DSCS Suitcase terminals 

- USC–60A triband terminals (left) 

and LST–8000VT tri-band terminal (right).

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shaped the way MILSATCOM is managed 

today. Summaries of recent major conflicts that 

have changed the way DSCS is managed follow.

Operations DESERT SHIELD and 

DESERT STORM

 The reaction to the invasion of Kuwait in 

1990 triggered one of the most massive and 

rapid deployments of forces of that period. This 

rapid deployment produced a great dependence 

on MILSATCOM. The DSCS constellation 

serving the United States Central Command 

(USCENTCOM) area of responsibility 

(AOR) at the time consisted of a DSCS II over 

the Indian Ocean and a DSCS III over the 

Atlantic. Before the invasion, USCENTCOM 

employed four terminals in the region operating 

at aggregate of 4.5 Mbps. Within a month, 

forty-eight terminals were active at 38.3 Mbps, 

which equated to approximately 600 voice 

circuits. When President George H.W. Bush 

announced a 100,000-troop buildup, DSCS 

planners realized their overall capacity would 

be inadequate. As a result, the Joint Staff 

sanctioned the movement of another DSCS II 

from the western Pacific to the Indian Ocean 

region. In aggregate, the three satellites provided 

68 Mbps of tactical communications using 110 

SHF satellite Earth terminals. This provided 

critical Command, Control, Communications, 

and Intelligence (C3I) capability from 

USCENTCOM networks to the National 

Command Authorities via DISN services 

(secure voice, data, imagery, etc). The intelligence 

community also expanded its requirements from 

23 Mbps to 36 Mbps. This put total DSCS 

support at 104 Mbps, a significant capacity 

during this timeframe. To augment DSCS 

support, two British Skynet satellites adding 11 

Mbps were also used. USCENTCOM thus had 

a total SHF throughput of 115 Mbps to conduct 

a successful operation.

 During this era, SATCOM provided most 

of the communications to the battlefield, 

networking commanders with their components 

and bringing information back to the Pentagon. 

The tactical extension to the field primarily 

consisted of secure voice and data messaging 

services that were essential for communications. 

The typical SATCOM network consisted 

of intratheater mesh networks connecting 

tactical terminals with 256 Kbps data rates 

between sites. A few intratheater tactical trunks 

connecting the networks back to the DSCS 

Gateways provided DISN services to the field.

 SHF capabilities supporting the Navy 

were very limited during this time. The Navymounted AN/WSC6 SHF terminal was limited 

to only a few ships, so the Navy obtained Air 

Force AN/TSC93B Ground Mobile Forces 

SHF SATCOM vans for aircraft carriers and 

amphibious flagships deployed to the Persian 

Gulf. This operation drove the need to accelerate 

installation of SHF capability onboard the largedeck ships for future operations.

Operation NOBLE ANVIL

 During the 1999 crisis in Kosovo, 

requirements were developed quickly, and 

planning was intense. A clear need for 

communications had grown quickly since 

Operation Desert Storm. Within a very short 

timeframe, United States European Command 

(USEUCOM) had submitted requirements that 

quickly absorbed all available DSCS resources. 

Not only were the satellite resources a limiting 

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186
factor, but the ground services were falling short 

as well. Because deployed tactical terminals 

were pulling DISN services from the Standard 

Tactical Entry Point sites, expectations were 

greatly exceeded. In the past, only a few 

links with small data rates were required to 

support an entire network on the battlefield. 

A major change was the increase in bandwidth 

required to support video applications. Video 

teleconferencing was used extensively during 

the conflict so that commanders could interface 

directly by video with their subordinate field 

commanders. Intelligence dissemination on 

the front line in support of the shooters also 

significantly increased video applications. 

The same 256 Kbps link used in Operation 

Desert Storm now needed to be 2 Mbps or 

more. In response, the Defense Information 

Systems Agency (DISA) performed a rapid 

upgrade to all European Standard Tactical 

Entry Point sites. The final USEUCOM 

requirement totaled 64 Mbps, in addition to 

the 20 Mbps supporting USCENTCOM 

Operation Southern Watch and existing fixed 

requirements, which totaled approximately 100 

Mbps. The same amount of throughput used 

in Operation Desert Storm that supported 

more than 120 deployed terminals now only 

satisfied the requirements for 20 deployed 

terminals. This was adequate for a small-scale 

operation, but it provided a perfect example of 

where SATCOM requirements were heading. 

Wideband SATCOM Support

Figure 7. Wideband SATCOM Increased significantly during the four major conflicts requiring less troop deployments.

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In addition, DSCS III satellites provided this 

support and were a huge improvement over 

the primarily DSCS II capability used during 

Desert Storm, since the DSCS III payload 

could be reconfigured more quickly and easily

Operation ENDURING FREEDOM

 Hours after the attacks on the World Trade 

Center and Pentagon, DSCS support was 

critical for the immediate deployment of Navy 

ships along U.S. coastlines and en route to the 

Mediterranean. The Indian Ocean satellites 

were reconfigured immediately to provide added 

bandwidth and margin toward Afghanistan, 

with the expectation that deployment orders 

would soon follow. The satellite configurations 

were continuously updated as the operation 

developed. Over the coming months, tactical 

requirements increased to 120 Mbps in an 

area where existing coverage was already 

fully employed. DSCS provided the required 

bandwidth to support most of this operation, 

but the MILSATCOM resources were quickly 

running low. This would impact the follow-on 

operations for other operation plans (OPLANS) 

in the USCENTCOM and USEUCOM AOR.

Operation IRAQI FREEDOM

 In April 2002, the Joint Staff assembled 

a team of experts to visit USCENTCOM 

to assist with potential conflicts. In addition 

to Operation Enduring Freedom, they 

were exploring options for an invasion of 

Iraq. Among their recommendations for 

overcoming shortfalls were upgrading deployed 

tactical terminals, improving capabilities 

at Standard Tactical Entry Point sites, 

relocating a DSCS satellite, and augmenting 

DSCS satellites with commercial ones. 

DSCS support of warfighter requirements 

surged to 350 Mbps tactical and 150 Mbps 

fixed. These requirements were supported 

with one DSCS SLEP and three DSCS III 

satellites. The total capability provided for this 

operation far exceeded anything to date and 

set a precedence for the way OPLANS are 

developed and communications are provided.

 Requirements for SHF Earth terminals 

were unprecedented. In an era when military 

planners were talking about megabits per 

second, gigabits per second were now required. 

With the introduction of unmanned aerial 

vehicles (UAVs) and huge amounts of digital 

imagery and data, large communications pipes 

were required to get the information to the 

shooters in real time. During Operation Desert 

Storm, air-support operations were required to 

have target data available before takeoff. The 

Iraqi military would often move targets before 

the actual attack. With modern technology, 

pilots would be getting updated coordinates 

while in flight, just minutes before impact on 

the target. Real-time information feeds and 

targeting resulted in a greater success rate of 

precision munitions and ordinance hitting 

their targets. SHF MILSATCOM support 

provided data such as this to win the battle.

MILSTAR

The Milstar system was initiated in April 

1981. At that time, Cold War tensions were 

high and the system was designed to ensure 

essential communications during a major nuclear 

exchange. It was designed to survive an antisatellite attack using nuclear weapons, counter 

the projected Soviet jamming threat, and operate 

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autonomously for an extended period. The 

consequence of these requirements was a Milstar 

system that provided only low data rate (LDR) 

service. However, it is important to realize that 

Milstar guaranteed the necessary service in any 

anticipated environment.

 President Ronald Reagan assigned Milstar 

“Highest National Priority” status in 1983, 

which allowed the program to proceed with few 

funding restrictions and led to the addition of 

numerous technical requirements to meet more 

varied missions.

 Milstar marked a major change in the role of 

satellites. All of the communications satellites 

prior to Milstar acted as relays in space. The 

Milstar constellation, with its crosslinks and 

onboard signal processing, provided a network 

in space that allowed communications around 

the globe without intermediate ground stations.

 Initially designed to provide LDRenhanced extremely high-frequency (EHF) 

communications, Milstar offered crosslink 

capabilities and extensive hardening against 

radiation. Four satellites would be placed in polar 

orbits, and four others, in geostationary orbits. 

Because the primary objective was survivability, 

not high capacity, the first two satellites (Milstar 

I) carried payloads capable of transmitting voice 

and data at the LDR rate of 752,400 bps. Each 

satellite supports 192 channels of service.

 The end of the Cold War prompted a Milstar 

restructure referred to as Milstar II. The revised 

system provides medium data rates (MDR) of 

4,800 bps to 1.544 Mbps. Additionally, the 

program underwent significant downsizing based 

on congressional demands and DoD reviews.

 By early 1994, the Milstar program included 

only six satellites without the vast array of 

survivability features and with fewer ground 

control stations. The first block of two satellites, 

designated Milstar I and built by Lockheed 

Martin, would retain the limited-use LDR 

capability, but the subsequent Milstar II 

satellites would be equipped with an MDR 

package to better support tactical users. On 

7 February 1994, the first Milstar satellite 

went into orbit. Even before it had completed 

its on-orbit checkout, the 10,000-pound 

satellite contributed operationally to Uphold 

Democracy, the U.S. intervention in Haiti. 

Each Milstar satellite serves as a space-based 

“smart switchboard” by actually processing 

communications signals, crosslinking with 

other Milstar satellites, and directing traffic 

from terminal to terminal anywhere on Earth. 

The need for intermediate ground relays under 

normal conditions is thus virtually eliminated. 

The last of six Milstar satellites went into 

geostationary orbit in April 2003.

Current Milstar System

 The Milstar system operates in the EHF/

SHF band (44 GHz uplinks and 20 GHz 

downlinks) and utilizes 2 GHz of bandwidth 

on the uplink and 1 GHz of bandwidth on 

the downlink. The EHF band allows the use 

of narrow beams, so less transmitted power 

and smaller antennas are allowed. Jammers 

must be physically closer to be in the satellite’s 

beam. In a nuclear environment, outage 

times are much lower at EHF. However, 

EHF signals are affected by rain and foliage, 

so large link margins are required.

Important Milstar system features include:

■ Robust signal waveform to provide 

antijamming and nuclear protection

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189
■ Onboard signal processing (a switchboard 

in space)

■ Intersatellite crosslinks at 60 GHz

■ Cross-banding between EHF/SHF and 

UHF

■ Flexible networking

■ A sophisticated antenna farm

The Milstar II satellite shown in Figure 8 has 

an LDR wing and an MDR wing. The spacecraft 

is 78 feet long, 116 feet wide, and weighs 10,100 

pounds. The picture shows the extensive antenna 

farm, one of Milstar’s most impressive features. 

The transition from Telstar to Milstar is an 

outstanding technological accomplishment.

 The terminal segment includes:

■ The Air Force command-post terminals 

which support LDR and are nuclearhardened

■ The Navy terminals which support both 

LDR and MDR

■ The Army Secure Mobile Antijam Reliable 

Tactical Terminal (SMART-T)

 which supports LDR and MDR

■ The Single Channel Antijam Man-Portable 

(SCAMP) II terminal which supports LDR

 Because the EHF frequency is significantly 

higher than the SHF, the antennas can be much 

smaller. A picture of a SMART-T terminal is 

Figure 8. Milstar II Satellite. Figure 10. Milstar SCAMP II terminal.

Figure 9. Milstar SMART-T terminal.

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shown in Figure 9, and a picture of the SCAMP II 

terminal is shown in Figure 10.

 Milstar serves strategic-level, theater-level, 

and tactical-level users. At the strategic level 

the system provides tactical warning/attack 

assessment data relay, nuclear command and 

control (C2) conferencing, emergency action 

message dissemination, and force managements 

and reportback. At the theater/tactical level 

it provides C2 communications for joint task 

forces and Army Corps, and below, units, 

tactical intelligence dissemination, range 

extension for the Army mobile subscriber 

equipment, dissemination of ATOs, Tomahawk 

cruise missile updates, and Navy task force 

connectivity.

Operational Impact of Milstar

 Milstar, as a communications system, 

has the flexibility to be reconfigured to 

meet changing operational requirements. 

The system supports a wide range of 

strategic and tactical missions, including:

■ Connectivity for C2

 of tactical forces.

■ Connectivity for deployed Special 

Operations Forces.

■ Connectivity for deployed naval battle 

groups to support rapid deployments of 

land, air, and naval forces anywhere in the 

world.

■ Missile threat conferences.

■ Nuclear force execution orders.

■ Air Expeditionary Force en route planning

■ Reportback information from strategic and 

nonstrategic nuclear forces.

■ C2

 connectivity between COCOMs and 

their components.

 Because of its inherent design features, 

Milstar can support these missions despite 

enemy jamming and can, if necessary, withstand 

nuclear effects.

Operation DESERT STORM

 EHF only provided experimental service 

during Operation Desert Storm using the 

EHF package on the UHF Follow-On (UFO). 

Although EHF terminals were just being fielded, 

the EHF package on the Navy’s FLTSATCOM 

satellite was used to provide a secure 

communications link between the Chairman of 

the Joint Chiefs of Staff and the Commander of 

USCENTCOM. Contingency plans existed to 

bring transportable EHF terminals to the theater 

if our MILSATCOM systems were jammed.

Operation NOBLE ANVIL

By the time of Noble Anvil, enough EHF 

terminals had been delivered to the military 

Services so that EHF was integrated into the 

warfighters’ communications plans. Milstar 

support to operations in Kosovo began in 

June 1999 and continues today. In particular, 

the Navy had installed EHF LDR terminals 

in the Battle Groups. In general, LDR was 

used for Naval tactical communications, 

including ATO dissemination. Figure 13 

depicts transmission times for ATOs and other 

information exchanges at different data rates. 

Communications support was also provided to 

deployed Kosovo ground forces.

Operations ENDURING FREEDOM and IRAQI 

FREEDOM

 Now that the MDR constellation was 

nearly complete and substantial numbers 

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191
of EHF terminals were deployed, EHF saw 

more extensive use during these conflicts. The 

Navy and Marine Corps both used MDR 

extensively for a variety of applications.

 The Milstar system has been critical 

for secure communications, Global Hawk 

surveillance, and “net-centric” operations. 

Critical U.S. intelligence, such as National 

Reconnaissance Office and Central Intelligence 

Agency data, is similarly routed from the 

United States to the theater. The system’s 

space-to-space relay capability avoids the 

need to bounce this secret communications 

traffic through multiple ground stations.

 In addition to operations involving Global 

Hawk surveillance and Special Forces 

missions, the Marine Expeditionary Forces 

in Iraq have been exploiting Milstar’s secure 

communications, antijamming capabilities for 

tactical ground operations. The Army’s 4th 

Infantry Division, moving northward from 

southern Iraq, also is heavily equipped with 

Milstar terminals, sources said. According to 

the commander of 124th Signal Battalion,

The SMART-T is an incredible force 

multiplier and it has performed remarkably 

well. My CG’s [Commanding General’s] 

Assault Command Post (ACP) had a 

Battle Command on the Move Bradley 

equipped with ABCS [Army Battle 

Command System] systems. We put Line 

of Sight (LOS) and SMART-T teams 

with him as he deployed into Iraq. His 

SMART-T crew was able to establish voice 

and data communications whenever he 

decided to halt for over 30 minutes. They 

averaged 15 minutes to get the link in and 

were able to do it as fast as 9 minutes.

 We put the same packages with the 

1st Battalion, 44th Air Defense Artillery 

(ADA) Tactical Operation Center 

(TOC), 1st Brigade Combat Team (BCT) 

Commander, 1st Squadron, 10th Cavalry 

TOC and had similar results. At one point 

we had a BCT in Iraq; a BCT doing 

Reception, Staging, Onward movement, 

and Integration (RSOI) in Camp New 

York; and a BCT at the port off-loading 

equipment. We would not have been able 

to accomplish the mission without the 

SMART-T.

 The 124th Signal Battalion (assisted by 

other units) was able to install, operate, and 

maintain the largest division communications 

network in the history of the Army consisting 

of eleven Node Centers, more than forty-five 

Small Extension Nodes, four Node Center 

Support Elements, and fourteen SMART-Ts 

dispersed over a 90,000 square kilometer area 

of operations in Iraq. Again, it would have 

been impossible to do this mission without the 

SMART-Ts.

Milstar Technologies

The Milstar system was designed to 

emphasize robustness and flexibility, which 

resulted in many significant technological 

enhancements. Robustness is the ability to 

operate under adverse conditions, including 

direct jamming, interception, and nuclear attack; 

flexibility is the ability to provide worldwide, 

unscheduled access and worldwide connectivity 

to terminals on all types of platforms. Satellite 

features to support system robustness include 

frequency-hopped uplinks and downlinks, 

extensive onboard processing, 60 GHz 

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192
crosslinks, and nuclear hardening. Satellite 

features to support flexibility include multiple 

uplink and downlink channels at various rates, 

in-band control channels for service requests, 

multiple uplink and downlink beams (including 

agile beams that can switch on a hop-by-hop 

basis), and routing of individual signals between 

uplinks, downlinks, and crosslinks. To achieve 

robustness and flexibility, Milstar 1 technology 

developments included broadband multichannel 

demodulators, hardened general-purpose 

processors, advanced piece-parts, and crosslink 

technologies.

 Access control messages are processed by 

onboard processors, which have been hardened 

using special piece-parts and shielding. Access 

control responses and other control data are 

generated by the onboard processors and sent 

back to the user terminals on the downlink. 

Through access control messages, Milstar users 

may request various communication services 

such as joining an existing network, establishing 

a new network, making point-to-point calls, 

moving a spot beam antenna, and requesting 

information about the status of the Milstar 

constellation.

 The Milstar Spacecraft Processor was a 

general-purpose, radiation-hardened Mil 1750A 

computer developed specifically for Milstar I. 

One computer was used to control the spacecraft 

bus; another, to control the payload. The 

Milstar Spacecraft Processor uses a 2-micron 

Complimentary Metal-Oxide Semiconductor 

(CMOS) radiation-insensitive digital processor 

chip set developed and manufactured for Milstar 

by the Sandia Corporation, and radiationinsensitive volatile Static Random Access 

Memory memory manufactured by Harris 

Corporation, using Sandia-licensed designs. 

All of the Milstar satellites nonvolatile digital 

memory employs magnetic bubble-memory 

technology. The demodulation processing 

implemented for Milstar I used an acoustoelectric array of processor technology that at the 

time was the only known way to demodulate 

the approximately 200 Frequency Shift Keying 

channels in a package with sufficiently low 

weight and power requirements to be applicable 

to spaceborne operations. The antenna suite 

includes an agile antenna, which is capable of 

switching between coverage areas across the 

field of view in nanosecond timescales. This 

required development of fast ferrite switches 

and a radio-frequency (RF) lens structure. The 

satellite design included crosslinks at 60 GHz, 

which required the development of 60-GHz 

sources, receivers, and antenna manufacturing 

technologies to allow the construction of large 

reflectors with the required surface smoothness 

and suitability for space operation. Any one of 

these technologies would have been considered a 

major advancement; Milstar I tackled them all.

 The MDR payload has eight narrow spotbeam antennas designed to meet Army and 

Navy requirements. Two of the MDR spotbeam antennas have onboard adaptive nulling 

capability to negate the effects of both in-beam 

and out-of-beam jammers. The six other small 

spot-beam antennas without nulling are called 

Distributed User Coverage Antennas. The 

onboard autonomous nulling antenna design 

was a significant technology development for 

the Milstar II program. The nulling antenna is 

a complete feedback-control system designed 

to continuously maximize desired signals while 

processing-out jamming signals. Nulling antenna 

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193
technology combined with spread-spectrum 

processing can provide antijam protection 

against both in-beam and out-of-beam jammers, 

even when the desired user is operating a lowpower terminal at a relatively high data rate.

 While the Milstar LDR and MDR payloads 

share many architectural features, the MDR 

payload developed in 1991–92 incorporates 

many of the technological advances made since 

the mid-1980s. Technology advances occurred in 

both digital and microwave integrated circuits. 

These new integrated circuits are key to the 

implementation of the MDR payload within the 

weight and power constraints of Milstar II. The 

LDR payload digital processing subsystem is 

based on 1.5-micron CMOS custom large-scale 

integrated circuits. The maximum number of 

digital gates per device is approximately 5,000. 

The LDR processor chip sets, excluding the 

primary onboard computer, contain 35 custom 

large-scale circuit designs, which are reused in 

multiple processor applications. Each Milstar 

LDR payload has 630 of these custom integrated 

circuits. The processors in the MDR digital 

processing subsystem are based on radiationhard 0.8-micron CMOS application-specific 

integrated circuits. The 0.8-micron CMOS 

application-specific circuits can accommodate up 

to 100,000 gates per device. The MDR digital 

subsystem, excluding the primary onboard 

processor, has only fourteen unique applicationspecific integrated circuit designs. The total 

number of large-scale integrated circuit devices 

required for the MDR processors is 397.

 The MDR RF equipment took advantage 

of advances in Gallium Arsenide (GaAs) 

Monolithic Microwave Integrated Circuit 

technology. As an example, the nulling antenna 

low-noise amplifiers are fully integrated, fourstage High Electron Mobility Transistor 

amplifiers, all on a single chip. These advances 

in piece-parts and circuit design result in 

significant weight and power savings. The 

LDR payload equipment totals approximately 

2,400 pounds and 1,500 watts, while the MDR 

payload equipment is approximately 1,000 

pounds and 1,000 watts. Much of the reduced 

weight and power of MDR is due to the use 

of advanced RF and digital technologies.

UHF SYSTEM

Evolution of UHF Communications

 The early history of UHF SATCOM was 

described above. By 1988, the UHF system had 

evolved from the early mixture of FLTSATCOM 

and leased satellites into a fourth-generation 

capability called the UFO system.

 This UFO system continues to operate today 

and consists of eight satellites plus an on-orbit 

spare. It was designed to replace the Navy’s aging 

FLTSATCOM and leased satellites as well as 

accommodate a national growing requirement 

for UHF capacity. In July 1988, the Navy 

awarded Hughes Space and Communications 

Company (now Boeing Satellite Systems, Inc.) an 

innovative, fixed-price acquisition contract giving 

it the latitude to select commercial-off-the-shelf 

components for the UFO satellite and procure 

commercial launch vehicles for putting UFO 

capability on orbit. Following an initial launch 

failure, Boeing Satellite Systems successfully 

launched the next nine UFO satellites between 

1993 and 1999. The first three satellites 

supported mobile communications and fleet 

broadcast services with UHF and SHF payloads. 

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The next four satellites carried an additional EHF 

capability to provide protected communications 

support using Milstar terminals.

Current UHF System

 The UHF system operates in the 225400 

MHz frequency band, coexisting with lineof-sight UHF requirements. It is the primary 

system employed for mobile SATCOM 

user communications. The associated small 

and inexpensive terminals routinely use 

nondirectional antennas. The available UHF 

bandwidth is limited by both the frequency 

and propagation characteristics of the system. 

User demand exceeds the available capacity. 

UHF communications are fundamentally 

unobstructed by weather or foliage, but 

unfortunately the UHF band provides virtually 

no antijamming capability. Communications 

can be degraded by changing propagation 

characteristics dominated by ionospheric 

scintillation, multipath, or other unintentional 

user interference sources.

 The current UHF space segment consists 

of eight UFO satellites in six inclined 

geosynchronous orbits. Two satellites are 

located in each of four coverage areas. The 

system provides 39 channels on each satellite, 

17 of which are 25 KHz, and the remaining 

21, 5 KHz. An additional service is provided 

by a fleet broadcast channel consisting of a 

jam-resistant SHF/EHF uplink and associated 

UHF downlink. All UHF channels operate 

as “bent pipes” through a simple, transponded 

satellite. The most recent four enhanced UHF 

satellites provide an EHF payload that operates 

with Milstar terminals as well as a Ka-band (20 

GHz) broadcast package that supports the GBS 

(described later).

 The Army, Navy, and Air Force all employ 

UHF terminals to fulfill a portion of their 

communications needs. Efficient system use 

is achieved through implementing demandassigned multiple-access techniques to allow 

resource sharing. The development of a workable 

demand-assigned, multiple-access system was 

an important technical accomplishment. A 

representative terminal, the Army PSC5, or 

Spitfire terminal, is shown in Figure 11.

 Typically, Army users include early-entry 

forces and a variety of mobile communication 

users. Air Force airborne and manpack 

tactical communications, Airborne Warning 

and Control System, and Take Charge and 

Move Out operations also take place over 

this UHF system. The Navy’s Fleet Satellite 

Broadcast subsytem, secure voice networks, and 

information exchange systems operate on UHF 

as well.

 The key technical challenge in the UHF 

system continues to be improving the 

effectiveness of the demand-assigned, multipleFigure 11. Army UHF Spitfire.

Military Satellite Communications

195
access implementation to increase capacity even 

further.

Operational Impact of the UHF System

 The operational history of UHF spans 

many years. The numerous uses of this critical 

system stem directly from the advantageous 

propagation characteristics of communicating 

at these frequencies. While frequencies higher 

than UHF perform as effectively in clear 

weather when the view of the distant end 

is unobstructed, reduced capability can be 

expected when rain, jungle foliage, or other 

impediments that cause signal degradation 

are present. UHF, on the contrary, is more 

robust and likely to be less expensive under 

these types of conditions. Such communication 

links routinely operate with higher availability 

and reliability and under a more varied set 

of conditions. It is this characteristic of 

UHF that makes it particularly well suited 

to tactical communications as well as to 

other specialized missions. UHF satellites 

provide military planners with a reliable 

transmission medium for sending critical 

intelligence, operations, and logistics data.

 UHF communications over the last decade 

have played an important role in all our military 

operations. This medium has been critical in 

every conflict: Desert Shield, Desert Storm, 

Bosnia, Kosovo, Afghanistan, as well as the push 

to Baghdad. It will continue to be of vital use as 

our forces work nation-rebuilding issues in Iraq.

 UHF SATCOM routinely allows 

commanders to overcome many of the 

distance and terrain restrictions that face 

similar broadcast radio networks operating 

at higher frequencies. At the tactical level, 

this enables units to operate informal voice 

nets over wide areas without deploying 

VHF FM rebroadcast stations. The small 

portable terminals provide maneuver 

commanders the ability to maintain control 

over subunits under adverse circumstances.

 In both Bosnia and Kosovo, battlefield 

commanders routinely used UAVs operating 

over secure UHF SATCOM paths to assist 

in assessing the local operational situation. 

Deployed worldwide, these systems support 

joint combatant forces in peacetime, wartime, 

and antiterrorism operations. High-mobility 

vehicles and their accompanying ground-based 

system components transport information 

and imagery to assist in identifying targets 

and in other intelligence-gathering activities.

 In Operations Desert Shield and Desert 

Storm, these UHF capabilities were used to 

provide strategic, operational, and tactical 

communications support to U.S. Navy battle 

groups. In particular, it facilitates command 

and control of guided missiles, like Tomahawks 

and other cruise missiles, from ships and 

submarines. It provides a path for updating 

cruise-missile missions from bases ashore. 

UHF capability is also used in disseminating 

ATOs to B52 bombers and providing a medium 

for effective mobile-user communications 

for national and coalition forces.

 A very heavy demand and subsequent 

dependence on these communications has 

developed more recently as a result of our 

efforts in Afghanistan. To provide for the 

additional required capacity, the U.S. military 

reassigned a nine-year-old Navy spacecraft, the 

UFO F2, to the USCENTCOM theater of 

operations to assist in satisfying the increased 

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196
demand for vital battlefield communications. 

In addition to combat missions, UHF radios 

are routinely used in communications for 

air traffic control coordination and in secure 

communications via the Secure Telephone 

Unit III, and tactical commanders can send 

Secret Internet Protocol Router Network 

e-mail over UHF communications paths 

for entry into large terrestrial networks.

 On 7 April 2003, during Operation Iraqi 

Freedom, the United States executed an air 

strike against the Iraqi leader Saddam Hussein. 

Tipped off by someone on the ground, the 

information regarding Saddam Hussein’s 

location was relayed through a UFO satellite to 

a B–1B bomber already in the air. The B–1B 

hit the target with four Global Positioning 

System guided Joint Direct Attack Munitions. 

This demonstration of flexible response was 

made possible because of the UFO system.

Evolution of GBS

 One can trace the origins of GBS back to 

an April 1992 final report to Congress on 

the conduct of the Persian Gulf War. That 

report highlighted the limited capability 

of existing military and civilian SATCOM 

systems to provide responsive, high-capacity 

links of the kind needed for imagery and video 

transmission to deployed, mobile tactical 

users with small antennas. In early 1993, the 

National Information Display Laboratory, 

hosted by Sarnoff Corporation, began briefing 

government officials on the value of direct 

broadcast satellite (DBS) technology. An 

industry team led by Hughes Aircraft Company 

had been developing this technology for several 

years with the intention of marketing a new 

commercial broadcast service Direct Television. 

Through a series of detailed briefings, laboratory 

personnel convinced key DoD decision makers 

that this technology had significant potential 

for overcoming the communications shortfall 

identified in the Persian Gulf War report.

 The next steps toward GBS involved a series 

of demonstrations. In a project designated 

Radiant Storm, the National Information 

Display Laboratory helped the Navy accomplish 

the first transmission of encrypted intelligence 

data via a DBS system. Next, with the 

laboratory’s support, the Air Force undertook a 

more ambitious program that yielded several key 

results:

■ Use of commercial Ku-band satellites to 

achieve worldwide coverage

■ Use of commercial, mobile uplinks for 

theater injection

■ Linking to a UAV ground station intheater for live video dissemination

■ Development of a high-speed data interface 

unit for the commercial encoder

■ Development of asynchronous transfer 

modecompatible interfaces at both the 

encoder and receiving stations

■ Use of standard telephone links combined 

with DBS service to provide two-way, 

interactive capabilities

 Successful application of these results 

during the 1995 Joint Warrior Interoperability 

Demonstration was termed as one of the 

demonstration’s “golden nuggets.” Based on this 

experience, the National Information Display 

Laboratory proposed using this same DBS 

technology to disseminate UAV video in support 

of Bosnian operations during the summer of 1995.

Military Satellite Communications

197
Current GBS

 The GBS is a combined space and C3I 

system that provides one-way, high-volume 

information flow (data files, imagery, and 

voice) to garrisoned, deployed, or on-themove forces. It is the successor to the Joint 

Broadcast Service (JBS) that played an 

important role in the Bosnian operations. 

It consists of three subsystems:

■ A broadcast management and 

signal injection subsystem

■ A space segment which broadcasts 

information to the users

■ User terminals

 The signal injection subsystem consists of a 

primary injection point in Norfolk, Virginia, 

which can uplink 94 Mbps to the space 

segment, and theater injection points which 

can uplink 6 Mbps to the space segment. 

The uplink is at Ka-band (30 GHz).

 In March 1996, the Navy ordered a highpower, high-speed, Ka-band GBS payload to be 

added to UFO satellites 8, 9, and 10. Derived 

from Hughes’s experience with commercial 

Ku-band satellite broadcast systems in Bosnian 

operations and elsewhere, the GBS package 

supplied data delivery rates vastly superior to 

any prior MILSATCOM capability. The first 

GBS payload went into service aboard UFO 

Flight 8 in June 1998, and the launch of UFO 

Flight 10 in late November 1999 completed 

a three-satellite constellation providing DoD 

near-global broadcast coverage. Transmitting 

to small, mobile, tactical terminals, the 

GBS package revolutionizes the full range 

of DoD’s high-capacity communications 

requirements, which ranged from intelligence 

dissemination to quality-of-life programming.

 The current space segment consists of 

Ka-band payloads on the last three UFO 

satellites. However, because only a few UFO 

satellites hosted the Ka-band GBS payload, it 

became necessary to continue leasing Ku-band 

commercial satellite services to augment UFO 

where gaps in coverage existed and, if necessary, 

to complement the limited number and size 

of the downlink beams from UFO GBS.

 The payload has two uplink antennas: 

one is fixed and the other is steerable. It has 

three steerable downlink antennas: two are 

narrow-beam (500 nm) and one is widebeam (2,000 nm). Four transmitters operate 

in the 20-GHz range. The use of narrow 

beams allows high transmission rates (23 

Mbps) to reasonably small terminals.

 The user terminal subsystem consists of landbased fixed and transportable terminals with 

1-meter antennas and ship-based terminals.

 The entire system is depicted as 

a block diagram in Figure 12.

 The GBS concept of operations includes 

two types of information management 

referred to as “smart push” and “user pull.” 

Smart push information is that which can 

be predetermined on the basis of a user’s 

mission. User pull information is that 

requested by a user via a low-capacity feedback 

link and is broadcast at a high data rate.

Typical information that can be 

provided over GBS includes:

■ Integrated Broadcast Services

■ National Imagery (National Imagery and 

Mapping Agency)

■ Theater Data (COCOMs)

■ ATO (Joint Forces Air Component

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198
 Command)

■ Fleet Broadcast (Navy)

■ UAV Target Video (airborne link 

segment)

■ Joint Deployable Intelligence Support 

System products (multisource)

■ Weather Reporting (multisource)

■ Tomahawk Mission Data (Navy)

■ Situation Awareness (services)

■ Logistics (services)

■ Training (services)

■ Army Forces Radio and Television 

System

■ Television Receive-Only, Cable News 

Network, Movies

 To illustrate the advantage of the GBS 

23 Mbps data rate, Figure 13 shows the 

transmission time for representative products. 

One of the key warfighting advantages of GBS is 

that it allows near-real-time targeting based on 

sensor inputs (e.g., Predator video). In a typical 

application, an encrypted Predator video is 

downlinked to a terminal, injected into the GBS 

payload, and broadcast to the appropriate users.

Operational Impact of GBS

 The GBS concept provides the correct 

information to the user at the required time 

and place. The fundamental approach addresses 

the standard push-and-pull GBS architecture 

capable of multiple security levels, and tailors 

the information to a specific user’s needs by 

sensor-to-shooter couplings. The GBS has 

met with resounding success over the last ten 

or so years in revolutionizing military use of 

information. This is reflected in an increased 

understanding of battlefield events and an 

improved ability to apply destructive force when 

and where it is necessary. GBS expands the use 

of battlespace dominance through improved 

information use. In the pre-GBS environment, 

serious bandwidth problems arose with the 

use of UHF circuits during Operation Desert 

Storm when transmission of a 500-page ATO 

and its associated imagery could take hours. 

More recently, with the use of direct broadcast 

Figure 12. GBS System.

Military Satellite Communications

199
transponders, the same data is transmitted 

within seconds. Th is capability makes it possible 

for combat leaders to be keenly aware of the 

situation confronting them. Th e information 

they receive helps them assess the enemy’s size, 

location, and activity. Th is instant situational 

awareness now available to troops and pilots 

is achieved by integrating satellite intelligence, 

UAV fl ights, and ground-signals intelligence 

stations into a common picture.

Figure 13. Transmission Time for Representative Products.

SATCOM 2.4 Kbps 64 Kbps 512 Kbps 1.544 Mbps 23 Mbps

Th roughput ( for example, on) ( for example, to) ( for example, to) ( for example, on) GBS

Example Milstar & UFO Navy’s IT-21 SIPRNet Milstar MDR

Information

Air Tasking 1.02 hr 2.61 min 17.19 sec 5.7 sec .38 sec

Order (DESERT STORM)

1.1Mb

Tomahawk 100 sec 4.29 sec .47 sec .16 sec .01 sec

Mission Data Update

0.03 MB

Imagery 22.2 hr 57 min 6.25 min 2.07 min 8.4 sec

8x10

Annotated

25 Mb

Desert Shield Time 9.65 day 9.92 hr 1.09 hr 21.59 min 1.45 min

Deployment Data

(log support)

250 Mb

Operation NOBLE ANVIL

 Originally implemented as the Bosnia JBS, 

the fi rst phase of the GBS became operational 

to support immediate operations in Bosnia. It 

provided a tactical network allowing virtually 

instantaneous communications among all U.S. 

forces. In large part, this technology provided 

for dissemination of UAV video in support of 

Bosnia operations during the summer of 1995. 

Th is represented a signifi cant improvement 

Th e Limitless Sky

200
over the Gulf War situation when only a 

limited use of in-theater video, and then, only 

to commanders at high levels, was available. 

In Bosnia, surveillance and reconnaissance 

assets plus live video feeds from intelligence 

assisted in conducting operations and gathering 

intelligence. The video feeds were provided at 

the division level. The trend to push information 

to lower command levels continues as battlefield 

video-teleconferencing becomes available down 

to brigade and now, in some cases, battalion 

level. UAVs are proliferating in the battlespace. 

Predator UAVs that became operational in 

Bosnia around 1995 used this system and flew 

more than 600 missions in support of NATO, 

UN, and U.S. operations. JBS commercial 

SATCOM service used commercial television 

DBS technology modified for military functions. 

JBS was implemented as an element of the 

Predator UAV communications architecture 

specifically for the dissemination of electrooptical and infrared video sensor information. 

The processed video information was relayed 

from the UAV ground station via transoceanic 

cable to the JBS injection site at the Naval 

Research Laboratory in Washington, D.C., 

where it was retransmitted to the Atlantic 

Ocean Region and then JBS receivers. The 

system was called the Bosnia Command & 

Control Augmentation (BC2

A) Program’s JBS.

Operations ENDURING FREEDOM and IRAQI 

FREEDOM

 The GBS system now “pushes” weather and 

a variety of data, imagery, other high-volume 

intelligence, as well as other information, to 

a widely dispersed user community through 

relatively low-cost receive terminals. The 

system includes the capability for users to 

request, or “pull,” specific pieces of information. 

The GBS distributes many high-bandwidth 

products directly from the United States to 

the lowest levels of command. GBS traffic 

runs the gamut from video and large data 

files to Internet Protocol traffic. GBS collects 

real-time intelligence from ground-based and 

space-based sources, collates that intelligence, 

and sends it immediately to fighter jet cockpits 

and mobile Army support vehicles. This 

connectivity provides more than enhanced 

situational awareness. It has changed the roles 

of the warfighter and the weapons platform. 

Predator follows a conventional launch sequence 

from a semiprepared surface under direct lineof-sight control. Takeoff and landing typically 

require 2,000 feet. Mission control is achieved 

through Ku-band satellite links or line-ofsight data links to produce continuous video. 

Video signals received at the Ground Control 

Station are passed to the Trojan Spirit van for 

worldwide intelligence distribution or directly 

to operational users via a commercial GBS. 

Command users can task the payload operator 

in real-time for still images or real-time video. 

The local commander has excellent visibility 

of his battlespace, enhanced largely by the 

communications capability of GBS.

 Critical GBS mission-traffic continues 

to support operations in both Afghanistan 

and Iraq. In support of Operation Iraqi 

Freedom, available bandwidth has been 

doubled throughout the duration of the 

conflict. The future of GBS likely includes 

netted Joint Service Command, Control, 

Communications, Computers, and Intelligence 

(C4

I) systems operating over the GBS.

Military Satellite Communications

201
COMMERCIAL ADJUNCTS TO 

MILSATCOM

 Over the past forty years, numerous 

U.S. military organizations have relied on 

commercial SATCOM to meet specific, ad 

hoc requirements or to supplement dedicated 

military capabilities. Officials have reasoned 

that leased commercial channels provide 

cost-effective voice and data communications 

and meet the growing demand for long-haul, 

wideband services such as computer-to-computer 

nets, video conferencing, high-speed facsimile, 

and electronic document transfer. Despite the 

obvious advantages of tapping into commercial 

SATCOM capabilities, the ongoing challenge 

remains to make the most efficient use of them. 

That depends, in turn, on effectively integrating 

them with MILSATCOM capabilities to 

form a relatively seamless architecture.

 Next, we describe several commercial adjuncts 

and their operational usage. Before we begin our 

general discussion however, it is important to 

understand that during the most recent periods 

of conflict—Operation Enduring Freedom and 

Operation Iraqi Freedom—DoD for the first 

time put commercial bandwidth in place ahead 

of the warfighter and weapons systems relying on 

it. In doing so, DISA took risk in anticipation of 

requirements by using a combination of contract 

vehicles and vendors to develop an architecture 

flexible and agile in its design that ultimately 

satisfied the myriad of requirements asked for 

by USCENTCOM and its components.

Commercial Adjuncts

 Three types of commercial satellite service are 

used to augment the military satellite systems.

 The first is the fixed satellite service provided 

by INTELSAT and other carriers. The space 

segment consists of geostationary satellites 

operating at C-band (6 and 4 GHz) and Kuband (12 and 14 GHz). The service provided 

is similar to the DSCS system operating in an 

unstressed mode. The system provides high 

throughput for imagery and video and gives 

a surge capability during crises and wars. A 

technical development enhancing the utility 

of the system is the tri-band (C, SHF, and 

Ku) transportable transit-case terminal. This 

provides the user with a terminal that can be 

used with either the DSCS or INTELSAT 

system.

 The second type is the mobile satellite 

service that uses geostationary satellites. The 

International Maritime Satellite (INMARSAT) 

system operates at L-band (1.5 GHz) and 

provides voice and video service to very small 

terminals. The system is widely used by 

reporters accompanying military operations. 

It is also used to provide quality-of-life 

communications for deployed forces.

 The third type is the mobile satellite service 

that uses satellites in low Earth orbit. The 

smaller range to the satellite allows the use of 

handheld terminals only somewhat larger than a 

cell phone.

Operational Impact: DESERT SHIELD

 AND DESERT STORM

 During Operations Desert Shield and 

Desert Storm, Commercial T1 circuits 

were leased over two INTELSAT satellites. 

Fourteen commercial satellite terminals were 

used providing 3 Mbps of data (simplex). This 

equated to 25 percent of the SATCOM used 

in the theater. Additionally, INMARSAT was 

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202
used to supplement UHF SATCOM. For the 

first time, MILSATCOM (DSCS, allied, and 

commercial) was the bread-and-butter source 

of communications connectivity, both long-haul 

and tactical.

 One lesson learned was that DoD should 

procure through the military departments 

commercially available satellite terminals 

and bandwidth. On-call arrangements for 

commercial transponders should also exist. 

In 1994, DISA was funded to develop and 

implement a commercial SATCOM program, 

then known as the Commercial SATCOM 

Communications Initiative. On 1 October 1998, 

the initiative was transitioned to the Defense 

Working Capital Fund. This transition made 

customers responsible to pay for the bandwidth 

leased to support their requirements. Without 

central funding, DoD was unable (through 

DISA) to preposition commercial satellite 

bandwidth and to pay for on-call arrangements 

for additional bandwidth. The result was that 

during Operations Noble Anvil, Enduring 

Freedom, and Iraqi Freedom DISA again was 

forced to lease bandwidth as funding was made 

available. Fortunately, sufficient bandwidth was 

found to support all three operations.

Operational Impact: NOBLE ANVIL

 In Bosnia and Kosovo, the use of commercial 

augmentation to MILSATCOM provided 

critical extension of DISN services (Secret 

Internet Protocol Router Network, Nonclassified 

Internet Protocol Router Network, Defense Red 

Switch Network, Defense Switched Network, 

video teleconferencing, etc). This was the first 

time that commercial SATCOM was the 

dominant provider of SATCOM. Transponders 

leased during this conflict supported DISN 

extension into the Balkans; UAV control and 

video; C2 networks, Kosovo forces intratheater 

communications; situational awareness tools 

(Blue Force Tracking); and Joint Task Force 

requirements. In January 1996, USEUCOM 

requested an extension of the DISN into the 

Balkans to help free up tactical assets. The 

DISA-Europe field office installed DISN pointsof-presence consisting of Integrated Digital 

Network Exchange multiplexers and routers in 

Bosnia, Croatia, and Hungary. These points-ofpresence provide long-haul connectivity back to 

three locations in the central region of Germany. 

During Operation Allied Force, USEUCOM 

again requested DISA to extend the DISN into 

Kosovo and Macedonia. DISA now had pointsof-presence in Skopje, Macedonia, and Pristina, 

Kosovo. USEUCOM has used over forty-four 

European leased circuits at 2.048 Mbps (E1) 

for the Bosnia operations and fifty E1s for 

the Kosovo operations, totaling 225 Mbps of 

commercially leased bandwidth.

Operational Impact: ENDURING FREEDOM 

and IRAQI FREEDOM

 In the aftermath of September 11, 2001, 

commercial SATCOM was used to augment 

MILSATCOM in USCENTCOM operations 

throughout Southwest Asia. Composite 

totals for the theater show that forty-two 

deployable Ku-band Earth terminals were 

used in support of warfighters amounting to 

more than 3.2 GHz of bandwidth on fiftyone different transponders. The significance 

of this bandwidth is reflected in the success 

commanders enjoyed in Afghanistan and the 

rapid advance of warfighters through Iraq. This 

Military Satellite Communications

203
commercial augmentation enabled forward 

units to communicate from day one with their 

headquarters, providing an overwhelming 

advantage to the U.S.-led coalition. One specific 

mission enabled by commercially provided 

bandwidth was the UAV reconnaissance of 

enemy positions. For the first time, real-time 

UAV video was available via multiple feeds: 

from the UAV to the ground station; from the 

ground station to the processing station; and 

from the processing station to forward planners. 

This synergistic capability allowed for real-time 

collaboration among warfighters, intelligence 

analysts, and the Pentagon, thereby establishing 

a new benchmark for the situational awareness, 

decision-making, and feedback loops. As 

Secretary of Defense Donald Rumsfeld noted,

“linkages between UAVs, combat aircraft and 

bombers, and people on the ground, and the 

value that is created by those linkages...creates 

a very powerful effect.”

 Commercial SATCOM constituted more 

than 68 percent of the MILSATCOM 

used during Operation Iraqi Freedom. The 

dramatic growth in commercial SATCOM 

augmentation for deployed forces can be easily 

seen by comparing the relative amounts of 

military and commercial SATCOM used 

during Desert Shield and Desert Storm (75 

percent military, 25 percent commercial) and 

during Operation Iraqi Freedom (32 percent 

military, 68 percent commercial). The growth 

in commercial SATCOM is not the result of 

a corresponding decrease in MILSATCOM. 

Rather, the use of both military and commercial 

SATCOM increased, further demonstrating 

the increased demand warfighters have for 

satellite bandwidth and the way commercial 

SATCOM was able to meet those demands.

 The low Earth-orbit satellite system, 

Iridium, made a different kind of contribution 

by providing communications with the 

use of handheld terminals from difficult 

environments. Iridium use grew from 17,255 

calls of 54,755 minutes in September 2001 

to 812,689 calls of 4,536,410 minutes in 

July 2003. During Operations Enduring 

Freedom and Iraqi Freedom, Iridium proved 

to be an excellent addition to the warfighters’ 

communications tool kit. Its compact size 

and weight, secure capability, operational 

simplicity, and global coverage favorably 

positioned Iridium to supplement other 

tactical communications systems. These 

Iridium testimonials are also useful:

■ “In this fast paced war, if a communications 

system was not functioning quickly, 

alternative methods were employed...

The only systems consistently praised by 

the Marines were the Blue Force Tracker 

(SATCOM- though unsecure) and Iridium 

Phones (SATCOM). These systems provided 

reliable communications at all times. In many 

instances these systems were the sole means 

of communication.” Marine Corps Systems 

Command Liaison Team, Central Iraq, 

May 2003

■ “Only RELIABLE Communications 

out of the Valley (During Operation 

ANACONDA)”

75th Rangers

■ “Without Enhanced Mobile Satellite Services 

(EMSS) we would have been unable to 

support the Air Mission in Afghanistan”

USAF

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204
■ “Iridium handheld satellite telephones with 

secure sleeves also proved to be invaluable for 

diverse SOF units conducting split operations 

in the rugged mountainous terrain. SOF 

liaison teams carried Iridium units during all 

operations with the Northern Alliance.”

BG (P) James W. Parker, USA, Director, 

Center for Intelligence and Information 

Operations, SOCOM. (Signal Magazine, 

March 2003)

■ “We could go in there naked with flip-flops 

and as long as we have good radios, we could 

do our job.”

Captain Jason Amerine, USA, 5th Special 

Forces Group. (Washington Post, 

11 December 2001)

SUMMARY

 In this paper, we have discussed the 

evolution of communications satellites from 

a paper concept in 1945 to the sophisticated 

systems currently in operation. The emphasis 

was on MILSATCOM, but many of the 

technological achievements were common to 

both commercial and military applications.

 Most of the early commercial satellites 

served as relays between large, fixed Earth 

terminals that provided an alternative to 

submarine cables and landlines. The military 

required communications to be transportable 

or to be supported by mobile terminals. 

The UHF frequency band provided mobile 

services, but the data rates were very limited. 

The SHF band provided moderate data rates 

to vehicular and nontransportable terminals. 

Finally, as the technology became available at 

the EHF range, significant data rates became 

available to terminals mounted on High 

Mobility Multipurpose Wheeled Vehicles. 

Milstar changed the role of satellites from 

space-based relays to a space-based network. 

This evolution will continue in the future.

 The implementation of these systems has 

required an enormous amount of technological 

development, from basic research to advanced 

development. Funding came from both 

government and commercial sources. The launch 

schedule for a particular satellite type may 

span a decade or more. Thus, delays may be 

significant as new technology is incorporated.

 MILSATCOM played a vital role in all 

recent military operations. This paper provided 

some representative examples. This dependence 

on SATCOM will continue to grow.

APPENDIX: SATELLITE SYSTEM 

FUNDAMENTALS

 Several basic ideas are fundamental 

to any discussion of satellites. A brief 

review of these ideas appears here.

Orbits

 Most satellite communication systems use 

satellites in a geostationary orbit, as shown in 

Figure A.1. The basic idea is straightforward. 

The satellite is placed in an orbit that lies in 

the equatorial plane and is 35,786 kilometers 

above the surface of the Earth. The satellite is 

inserted into this orbit with a linear velocity 

such that its angular velocity is identical to 

the angular velocity of the Earth. At this 

altitude and velocity, the gravitational force 

and satellite’s momentum are balanced so 

that the satellite remains in this orbit. In 

practice, other effects (e.g., eccentricity of 

the Earth, gravitational forces from the Sun 

Military Satellite Communications

205
and Moon) must be considered, so a process 

called station-keeping is required to maintain 

the satellite in this desired orbit. This orbit 

has the advantage that to an observer on 

Earth the satellite appears to be stationary.

 In addition, the altitude is sufficiently high 

that messages can be exchanged by terminals 

separated by about one-third of the Earth’s 

circumference. Thus, three satellites separated 

by 120 ̊ could provide global coverage between 

the latitudes of ±70 ̊. Earth coverage contours 

for a geostationary satellite located above the 

equator in the middle of the Atlantic Ocean 

are shown in Figure A.2. The various curves 

correspond to the minimum elevation angles 

of the Earth terminals in the coverage area.

 The disadvantage of the geostationary orbit 

is that the range causes significant signal 

attenuation (proportional to the square of the 

range) and a delay of about 300 milliseconds.

SATCOM Frequencies

 A number of different frequency bands are 

allocated for SATCOM. Their characteristics 

are an important factor in the design of a 

particular satellite system. The allocations 

and usage for both commercial and military 

satellites are shown in Figure A.3.

 In this paper we focus our attention on four

 frequency bands:

■ UHF: 225–400 MHz

■ SHF: 7.25–7.75 GHz, 7.9–8.4 GHz,

20.2–21.2 GHz

■ Ku and Ka: 12–14 GHz, 30–31 GHz

■ EHF: 43–45 GHz, 60 GHz

 Two important factors are the location of the 

band in the frequency spectrum and the amount 

of bandwidth allocated. We discuss these factors 

for the above bands.

 The UHF band has a wavelength of about 

1 meter (exactly 1 meter at 300 MHz). This 

results in a propagation that is resistant to 

atmospheric effects, such as rain, and is able 

penetrate foliage cover. However, it is generally 

not practical to use antennas that focus the 

transmitted energy in a given direction. Thus, 

most UHF systems use antennas with modest 

gain and reasonably wide beams. This restricts 

the data rates that can be sent in UHF systems, 

but the small antennas make mobile and manportable terminals feasible.

 The bandwidth available at UHF is relatively 

small. This bandwidth limit has two effects. 

First, it restricts the data rates that can be 

sent through the system (typically, a digitized 

voice channel is 2,400 bps). The second effect 

is the inability to resist enemy jamming. 

Antijam techniques rely on either spreading 

the information over a large bandwidth to 

force the jammer to spread its power, or using 

a sophisticated antenna that can place a null in 

the direction of the jammer. Neither of these 

techniques are feasible at UHF.

 The SHF band has wavelengths that vary Figure A.1. Geostationary Equatorial Orbit.

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206
from 10 centimeters at the lower end (3 GHz) to 

1 centimeter at the upper end (30 GHz). SHF 

systems can utilize parabolic antennas where gain 

is proportional to the square of their diameter 

in wavelengths. Large antennas (40 feet to 60 

feet in fixed systems, and 8 feet to 20 feet in 

transportable systems) can focus the energy in the 

desired directions and allow significant data rates.

Figure A.2. Earth coverage contours for a geostationary satellite.

Figure A.3. SATCOM Frequency Usage.

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207
 The larger bandwidth allocated allows the use 

of antijamming techniques such as spreading the 

information across a 500 MHz bandwidth. In 

addition, it is feasible to utilize antennas on the 

satellites that can place nulls on jammers. The 

disadvantages of the SHF band are increased 

atmospheric effects, inability to penetrate 

foliage, and the size of the terminals.

 The Ku and Ka bands are subsets of the 

SHF band and have similar characteristics. 

The portion of the EHF band of interest in 

SATCOM has wavelengths ranging from 0.67 

centimeter to 0.5 centimeter. These wavelengths 

allow the usage of very small (1 to 2 foot) 

terminals that provide high gain. The bandwidth 

available allows for significant antijam 

protection.

 The disadvantage of EHF is that atmospheric 

effects, such as rain, can cause significance 

attenuation of the signal, and the system design 

must take this possibility into account.

 One characteristic of the different frequency 

bands that has become less important in the 

post Cold War era is the time it takes a system 

to restore adequate propagation after a nuclear 

explosion. These times range from days at UHF 

to minutes at EHF.

 The characteristics of the various frequency 

bands are summarized in Figure A.4.

A.3. Technology Challenge

Some of the technologies that had to be 

developed to transition SATCOM from concept 

to reality are:

i. Launch vehicles to deliver the satellites into 

orbit

ii Satellite bus

- Lightweight structure

- Power generation (solar cells, batteries)

- Orbit maintenance (thrusters)

- Satellite stabilization

- Thermal control

- Telemetry, command, and control

iii. Communications payload

- Antennas for receive and transmit

- Low-noise amplifiers

- On-board signal processing

ii. High-power transmitters (traveling-wave 

tube amplifiers)

iv. Earth Terminals

- Antennas

- High-power amplifiers

- Low-noise amplifiers

All of these areas required significant research and 

development. Specific examples are highlighted in 

various sections of this paper.

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Frequency

Band

Ultra High

Frequency

(UHF)

Super High

Frequency

(SHF)

Extremely

High Freq.

(EHF)

Information

Transmission

Capacity

Low

Moderate

High

High

Bandwidth

Low

Moderate

High

Atmospheric

Eff ects

Low

Moderate

High

Scintillation

Eff ects

High

Moderate

Low

Susceptibility

To Jamming

High

Moderate

Low

Mobility

Mobile

Transportable

Man

Transportable

Figure A.4. Characteristics of Frequency bands.

Military Satellite Communications

209
Directed Energy:

The Wave of the Future

Robert W. Duffner

Robert R. Butts

J. Douglas Beason

General Ronald R. Fogleman, USAF, Ret.
Abstract

 In many ways the wave of the future for directed energy 

technologies began with the discovery of the laser in May 1960. A 

beam of energy that travels at the speed of light immediately appealed 

to the military community, which envisioned high-power lasers as a 

new class of weapons, destined to revolutionize the science and art of 

warfare in the twenty-first century. To turn that concept into reality, 

the Air Force laboratory system took the lead and maintained it in 

the development of an operational airborne laser system.

 The focus of this paper is on the development and 

transformation of the airborne laser, covering nearly four decades as 

it evolved from a “laboratory in the sky” to a full-scale, operational 

weapons platform capable of unleashing deadly beams of light to 

disable or destroy ground- and air-launched missiles. Unmistakably, 

the Airborne Laser Laboratory ranks as the Wright Flyer of the laser 

world and has served as the technological bridge between laboratory 

research and the current Airborne Laser. Along the way, new and 

improved technologies emerged from the Air Force laboratories, such 

as the chemical oxygen iodine laser and sophisticated adaptive optics, 

which, combined, have enabled the propagation of a high-quality, 

high-powered beam through a turbulent atmosphere to ensure the 

long-range delivery of sufficient energy to engage and disable enemy 

weapons systems.
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214

INTRODUCTION

 At the height of the Roman Empire, Roman 

Legions armed with arrows, spears, swords, 

and shields devastated the more numerous 

but ill-equipped barbarian hordes. From the 

ancient world of Rome to the twentieth century, 

the means to wage war shifted dramatically 

from reliance on the physical prowess of the 

individual soldier to the modern weapons of 

warfare that depend on the scientific principles 

of physics, optics, chemistry, and other related 

disciplines. As the historical timeline of weapon 

development progressed over the ages, so did the 

level of precision and lethality of the emerging 

weapons. On 9 August 1945, a lone B–29 

aircraft flying over Nagasaki, Japan, dropped 

a single atomic bomb that ultimately ended 

World War II. In February 1991, precisionguided smart bombs, ground-hugging cruise 

missiles, and invisible Stealth fighters forced 

the massively equipped Iraqi army to its knees.

 Although decades apart, these overwhelming 

victories had one thing in common. They 

exploited technology to incur a revolution 

in military affairs that was so dramatic, so 

disruptive, and so profound that it changed not 

only the way wars were fought, but how nations 

interacted. Today, the next revolution in military 

affairs is about to begin. This revolution is not 

built on bombs or bullets, or anything you 

can hold in your hands. It is made of ordinary 

light in the same spectrum of energy found 

in your microwave, your light bulb, or in your 

television remote control; it’s called directed 

energy. With recent advances in one form of 

directed energy called the chemical oxygen 

iodine laser (COIL), invented by Air Force 

researchers at what is now the Directed Energy 

Directorate (DE) of the Air Force Research 

Laboratory (AFRL), and supporting beamcontrol technology such as adaptive optics, also 

advanced by Air Force researchers, the Airborne 

Laser (ABL) may constitute the key arsenal 

in this next revolution in military affairs.

 The wave of the future for directed energy 

weapon technologies in many ways began with 

the discovery of the laser in May 1960. It was 

this unpredicted and unprecedented event 

that radically changed the thinking of how the 

U.S. military would apply this groundbreaking 

concept of directed energy to the development 

of operational weapon systems. The laser—he 

term derives from light amplification by 

stimulated emission of radiation—would move 

forward over the next forty-three years as one 

of the most promising technologies in the 

field of directed energy. Moreover, the United 

States made a substantial commitment to 

laser research because a beam of energy that 

could travel at the speed of light immediately 

appealed to the military community that 

envisioned high-power lasers as a new class of 

weapons destined to revolutionize the science 

and art of warfare in the twenty-first century.

HISTORICAL PERSPECTIVE

 One of the first conceptual directed energy 

systems that emerged in the 1960s was the ABL. 

To turn that concept into reality, the Air Force 

laboratory system took the lead and maintained 

it as the most prominent Department of Defense 

(DoD) player that steadily pursued an extensive 

ABL research and development program. That 

work focused on the transformation of the 

ABL and its associated technologies for more 

than four decades. During that time, the ABL 
Wave of the Future

215

evolved from an experimental laboratory in the 

sky‘ to a full-scale, operational weapon platform 

capable of unleashing deadly beams of light to 

disable ground- and air-launched missiles.

 The Airborne Laser Laboratory (ALL), a 

highly modified NKC–135 research aircraft 

(the equivalent of the commercial Boeing 

707), was the first aerial platform to integrate 

a high-energy laser with a precision pointing 

and tracking system. Unmistakably, the ALL 

ranks as the Wright Flyer of the laser world; 

it is the technological bridge from early lasers 

and field demonstrations of lasers and beamcontrol components to the next-generation 

ABL, currently under development. Along the 

way, new and improved technologies emerged 

from the Air Force laboratories, such as the 

COIL and sophisticated adaptive optics that 

would become critical components of the ABL 

system. These technological advances proved 

invaluable in giving the ABL the capability to 

propagate a quality, high-power laser beam 

through a turbulent atmosphere to ensure 

the long-range delivery of sufficient energy to 

engage and disable enemy weapon systems.

 In assessing the evolution of the ABL, one 

must keep in mind a number of important 

historical themes. To start with, the 

development and testing of the first ABL 

represented a significant turning point in the 

history of military science and technology. 

The ALL was truly revolutionary because of 

the results it achieved, which were completely 

beyond the capabilities of any other type 

of weapon system in existence. In 1983 the 

ALL projected a coherent beam of light 

from a moving aircraft to shoot down five 

supersonic AIM–9B “Sidewinder” air-to-air 

missiles. This historical first was an event 

of major proportions that had far-reaching 

consequences on the future development of 

advanced laser weapons and directed energy.

 A second theme is directly linked to the first. 

A distinguishing feature of the ALL was that 

it was a revolutionary weapon development 

program intended to radically change how 

people “thought about” fighting future wars. 

The ALL was not simply a first-of-a-kind event 

that occurred and then disappeared. Rather, the 

first ABL opened the door for DoD to make 

some risky decisions to move ahead to invest in a 

completely new class of directed energy weapons. 

The proof of that change in thinking is the 

second-generation ABL currently being built and 

scheduled to be deployed into the operational 

Air Force around 2008. Until recently, the 

ABL was the second-highest priority weapons 

acquisition program in the Air Force until the 

program transferred on 1 November 2001 to the 

Ballistic Missile Defense Organization, a joint 

service organization under DoD. (The F/A–22 

tactical fighter is the number-one program.) To 

underscore the importance of the reality of lasers 

and their implications for the future, in July 

1998 former Air Force Chief of Staff Ronald 

Fogleman confidently predicted, “Directedenergy weapons are going to be the centerpiece 

of the twenty-first century Air Force.”1

 The third theme has to do with people. 

No doubt, the ALL succeeded because of the 

joint effort among the military, civil servants, 

and contractors. What is unique about this 

particular program is that the military was 

truly a critical “hands-on player.” Traditionally, 

the military manages weapons development 

programs. But in the case of the ALL, a 
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216

highly educated and talented military group 

of scientists and engineers served as the 

grunts in the trenches and were intimately 

involved in working the day-to-day solutions 

to difficult scientific and technical problems.

 Finally, it must be remembered, strong 

and steady leadership made a difference in 

the success of the ABL to elicit the best from 

a talented, but very diversified, workforce. 

Colonel Don Lamberson, working from the 

Air Force Weapons Laboratory (AFWL) at 

Kirtland AFB in Albuquerque, New Mexico, 

was the indisputable leader of the ALL 

program. Lamberson was a unique individual 

who possessed the rare combination of highly 

competent technical expertise coupled with 

extraordinary leadership and people skills. 

He was the one who conceptualized, sold, 

and led the ALL program. Motivating people 

and instilling in them a sense of urgency were 

two of his strongest traits. Lamberson was 

fond of saying in the early years of the ABL, 

“No one knew where the research would 

take us.” In the end, it led to success.2

 Dr. Petras Avizonis, Lamberson’s chief 

scientist over the years, described his boss as 

simply different. “Lamberson was able to convey 

in his briefings his vision from a technical 

point of view, and his ability to articulate 

that technically in a way senior officers and 

DoD officials could understand it. He didn’t 

talk down to them technically. So he had a 

fantastic combination of abilities, which was 

in large part the reason the Air Force for 

some ten years stood solidly behind the ALL 

demonstration.” Lamberson had all the wrong 

credentials for making general. He never flew an 

airplane and he never commanded operational 

troops, yet he rose to become a major general 

primarily on the basis of his scientific talents 

and outstanding leadership record. As former 

Secretary of the Air Force Hans Mark put it 

in describing the success of the ABL, “Above 

all, leadership, persistence, and dedication 

prevailed and made the difference.” The lesson 

learned was that people made a tremendous 

difference in revolutionizing science.3

ORIGINS

 Although the Air Force would become the 

military leader in exploring the possibilities 

of using lasers on aircraft in the 1970s, the 

roots of the ALL program stretched back 

to research conducted by private industry a 

decade earlier. On 15 May 1960, Dr. Theodore 

Maiman, a senior scientist at Hughes Research 

Laboratory in Malibu, California, generated 

the world’s first laser beam. Despite measuring 

only a few watts of power, the discovery of the 

ruby laser signified a revolution in the science 

of light that brought with it both confusion 

and promise for future applications. Maiman 

was one of the first to realize this and was 

cautiously optimistic about the significance of 

his groundbreaking research when he remarked, 

“The laser is a solution looking for a problem.”4

 However, the identification of problems 

and the applications of solutions proceeded 

at an extremely rapid pace. In the medical 

community lasers were used for delicate 

eye surgery to remove cataracts or to repair 

detached retinas. Commercially, lasers read 

bar codes on grocery items at the supermarket 

checkout counter and are just as capable of 

cutting through steel or drilling precision 

holes in the nipples of baby bottles.5
Wave of the Future

217

 Maiman’s invention quickly whetted 

the appetite of the defense community 

that envisioned high-power lasers not as a 

moneymaking enterprise, but as a new class 

of weapons that in the future would tip the 

strategic balance of power in favor of the United 

States in the ever-changing environment of 

the Cold War. The Pentagon wanted to build 

on Maiman’s seminal work to develop a highpower laser, later defined as having a power 

output greater than 20 kilowatts, which would 

eventually be the unbeatable operational 

weapon. Ballistic missile defense and antisatellite 

and antiaircraft missions led the list of the 

military’s applications for laser weapons.6

 Military visionaries looked at lasers operating 

at the speed of light as a radical departure 

from the traditional kinetic energy type of 

weapon that relies on a projectile colliding with 

a target as the kill mechanism. In simplest 

terms, three conditions are necessary for lasing. 

First, some type of substance (gas, liquid, or 

solid) is needed to produce a beam, even Jell-O 

and bourbon whiskey can lase! Second, an 

intense energy source (electricity, a chemical 

reaction, a pulse-discharge lamp, etc.) is 

required to excite and alter the condition of the 

selected material. Third, a device commonly 

referred to as a resonator with mirrors at 

each end is required to extract the precise 

optical energy in the form of a beam.7

 Although it was a complex process to generate 

a laser beam and to accurately direct it to a 

target, the military believed that in the long 

run the potential advantages outweighed the 

disadvantages of building a laser system. One 

major benefit is that light emitted by a laser is 

highly directional because its photons, or packets 

of light, are ““in step,” precisely aligned in the 

same direction, accounting for the brightness of 

the beam. This allows the energy of the beam 

to be highly concentrated and focused on one 

spot so the beam penetrates the target quickly.8

 Two other important factors convinced 

DoD officials that lasers were ideally suited 

as the ultimate weapon. Perhaps the most 

attractive feature of a laser beam is that it 

travels over long distances at the speed of light, 

about 186,230 miles per second. It takes only 

6 millionths of a second (6 microseconds) for 

a laser beam to travel 1 mile. This means an 

operator does not need to lead the target because 

large amounts of energy can be delivered to 

a target nearly instantaneously. In addition, 

the lightning speed of the laser gives the 

operator more time between shots to identify 

and select other targets before committing 

to refiring the laser. Consequently, the target 

has virtually no time to evade the beam.9

 Once it hits its target, the laser inflicts 

damage by rapidly heating and burning a hole 

in the target’s surface, melting structural and 

electronic components, blinding sensors and 

detectors, and, in some cases, igniting on-board 

flammable materials. Lasers fired in short 

bursts (pulses) can also inflict damage from 

the explosive shock waves created by rapid 

heating of the target material by the beam.10

 Besides the technical advantages, a second 

attractive feature of lasers was driven by political 

considerations. Lasers are not weapons of mass 

destruction like nuclear bombs and missiles. 

Rather, they are highly selective because all their 

destructive power is concentrated on one small 

area, which reduces the potential for civilian 

casualties as well as produces less collateral 
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218

damage to structures around the target. The 

notion that a laser could be used as a “surgical 

scalpel” was very attractive to many of the 

top decision makers at DoD and was one of 

the main reasons for increased congressional 

funding for laser research in the 1970s.11

 Recognizing the potential military payoffs 

for lasers, DoD’s Advanced Research Projects 

Agency (ARPA) was the first government 

organization to sponsor laser research and 

development work. The decision to create 

ARPA on 7 February 1958 was a direct 

response to the Soviet launch of Sputnik on 

4 October 1957. ARPA recruited the best 

scientific and engineering minds in the country 

to conduct high-risk research that would 

lead to rapid technological breakthroughs 

of a “revolutionary nature,” in contrast to 

the slower, more traditional “evolutionary” 

approach to weapon development.12

 At Kirtland AFB, the Air Force Special 

Weapons Center (AFSWC) was able to secure 

$800,000 from ARPA on 26 February 1962, 

which was the Air Force’s first shaky step into 

the world of laser exploration. This money 

and follow-on funding were used primarily to 

conduct vulnerability studies to measure how 

much damage a laser could inflict on various 

materials. By the late 1960s, the AFWL, which 

had been carved out of AFSWC in 1963, 

had earned the reputation as the center of 

excellence for laser research in the Air Force.13

 In July 1963 the AFSWC presented its 

findings from its investigation of glass ruby 

lasers. Results from this work were very 

disappointing because enormous devices would 

be needed to reach high power, and heat buildup 

with glass lasers severely distorted the beam. 

As a young captain, Don Lamberson was 

working on this project and explained, “We 

showed conclusively that you really just couldn’t 

get there.” However, the Air Force refused 

to give up on perfecting a working laser.14

 Two pivotal technical advances changed 

the outlook for the future of lasers in a very 

positive way. A Bell Telephone scientist, 

Dr. Charles Kumar N. Patel, discovered in 

April 1964 that molecular gas carbon dioxide 

(CO2

), through electrical pumping, could be 

used as a laser medium. This was the first 

continuous-wave CO2

 laser. His breakthrough 

touched off widespread interest in CO2

lasers, mainly because of their promise to 

attain higher power levels and efficiency.15

 A second major milestone occurred in 1966 

when Dr. Edward Gerry of AVCOEverett 

Research Laboratory demonstrated a new 

pumping technique to stimulate population 

inversion (the phenomenon that produces a laser 

beam) by rapid expansion of a hot equilibrium 

gas mixture through a bank of supersonic 

nozzles. This was the first gas dynamic laser. 

AVCO continued to refine its gas dynamic laser 

and produced 168 kilowatts in March 1968. 

This represented tremendous progress. Until 

1964, power levels of lasers were so low that 

“Gillettes” defined as the number of razor 

blades a laser could penetrate in .05 second 

were used as the standard unit for measuring 

power. All these events—AFWL’s initial laser 

research, invention of the gas dynamic laser, 

and AVCO’s advances in achieving higher 

power levels—hastened the Air Force’s interest 

in the military applications of gas dynamic 

lasers. That interest turned into a practical 

research and development program in 1968 
Wave of the Future

219

when Headquarters, Air Force, authorized 

AFWL to proceed with building and testing 

a ground-based gas dynamic laser.16

AIR FORCE LEADS THE WAY

 Once given the green light, AFWL’s first 

priority was to design, build, and fire a CO2

 gas 

dynamic ground-based laser capable of engaging 

static and moving targets. AFWL vigorously 

pursued this goal using the tri-service laser 

(DoD gave each service an identical AVCObuilt CO2

 laser for research purposes) at 

Sandia Optical Range (Sandia’s name changed 

to Starfire Optical Range in the late 1980s) 

located on the southeast section of Kirtland 

AFB. Looking toward the future, AFWL 

recommended placing a laser on an aircraft 

to be tested as a possible tactical or strategic 

weapon. The Air Force had thus planted the 

seed that would grow into the development of 

the ALL, perfecting the physics and engineering 

requirements to enable firing a laser from 

an airborne platform. But it was clear to 

everyone that the laser would first have to be 

demonstrated on the ground before it could be 

integrated and tested on an airborne platform.17

 The ground-based laser experiments at the 

Sandia Optical Range were part of Eighth 

Card, the code name of a highly classified 

DoD program to advance laser technology 

quickly. The name Eighth Card originated 

from seven-card stud poker, implying the 

advantage went to the player who held the extra 

eighth card. Translated to the political arena, 

this suggested that if the United States held 

the eighth laser card, it would hold a distinct 

advantage over the Soviets in the Cold War 

or in any future military confrontation.18

 The first step to prove the feasibility of a 

ground-based laser occurred in October 1971 

when the field-test telescope (built by Hughes 

Aircraft) was combined with a CO2 laser and 

referred to as Air Force Laser I. Mating of these 

two critical system components resulted in 

the telescope’s focusing the low-power

(1,000 watts) laser on a target pod mounted 

on a T39 aircraft flying downrange. Although 

the T39 suffered no damage because of the low 

power of the beam, this was a tremendously 

important event because it was the first time 

a laser beam had hit an aircraft in flight. In 

December 1972, the Air Force reached a second 

major technical milestone when it successfully 

directed and focused a high-power laser beam 

(150 kilowatts) on a rotoplane located 1,760 

meters downrange from the laser device. 

Resembling a windmill contraption, the 30-

foot-long arm of the rotoplane rotated a small 

target, the size of a postcard, 360 degrees along 

its vertical plane at 25 revolutions per minute.19

 Project DELTA (Drone Experiment Laser 

Test and Assessment) served as the final climax 

to the ground-based program. On 14 November 

1973, AFWL used a CO2 laser to shoot down 

a radio-controlled aerial target (drone) as 

it flew a racetrack pattern between Sandia 

Optical Range and the Manzano Mountains. 

This was the first time in the history of the 

world that a high-energy laser had disabled 

an aerial target, an enormously important 

technical accomplishment, considering that 

lasers had been on the scene a mere thirteen 

years. Equally important, this historic event 

served as a political rallying point to sustain 

laser work in general. More specifically, 

DELTA helped persuade the purse-string 
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220

holders and the doubters, unfamiliar with 

the new technology of lasers, of the urgency 

to move forward with the ABL program.20

 In January 1973, General Dynamics had 

extensively modified the NKC–135 research 

aircraft to serve as the first ABL testbed. 

This ALL was intended not to be a prototype 

but rather a science laboratory in the sky for 

proving the physics of lasers by conducting a 

three-stage research and test program. Cycle I 

was to demonstrate that the airborne pointing 

and tracking system could accurately track a 

maneuvering target when the ALL was airborne. 

This was accomplished through a series of 

flight tests that ended in November 1973, with 

no laser in the airplane, over White Sands 

Missile Range in southern New Mexico.21

 Cycle II mated a low-power electric discharge 

laser with the airborne pointer and tracker to 

determine if the beam could be directed from 

the turret of the ALL aircraft to intercept an 

aerial target. By 1976, after more than 100 

flight tests, the ALL proved it could track a 

diagnostic NC–135 aircraft that flew alongside 

the ALL and, at the same time, aim a beam 

from the ALL with sufficient precision to send 

it through a small window on the side of the 

diagnostic aircraft. This was a milestone of 

major proportions because it was the first time 

in history a laser beam had been fired from an 

airborne platform to intercept a flying target.22

 Although armed with a high degree 

of confidence derived from the success of 

Cycles I and II, the ALL team realized Cycle 

III would be an ambitious undertaking. A 

diverse group of workers now had to face 

an enormously complex engineering project 

to design, build, and integrate a vastly more 

powerful laser with a water-cooled, optical 

beam-control system. Integrating and perfecting 

the laser system during Cycle III was both 

frustrating and rewarding for those who 

worked on the ALL. However, after more 

than seven years of extensive ground-testing 

and flight-testing—plain hard work marked 

by numerous failures for every success—the 

ALL was ready to face its greatest challenge.23

 On 26 May 1983, the ALL made history 

again when it completed its first successful 

engagement of an aerial target and destroyed an 

AIM9B Sidewinder air-to-air missile over the 

Naval Weapons Center Test Range at China 

Lake, California. The beam remained on the 

nose of the missile long enough (4.8 seconds) to 

heat up and damage the sensitive components 

of the guidance system, causing the missile to 

break lock. Colonel John Otten, the ALL test 

director, described that history-making first 

shootdown as “if someone wrote the textbook. 

Tracking was rock solid, the beam remained 

on the nose of the missile to cause significant 

damage causing the missile to veer off course 

and crash.” On four other airborne tests that 

followed, the ALL’s precision pointer and tracker 

succeeded in disabling all four Sidewinder 

missiles. Hailed in the scientific community 

as an exceptional step forward in the world of 

directed energy, these demonstrations proved 

for the first time that a high-power ABL could 

intercept and destroy an air-to-air missile.24

 Four months later in the fall of 1983, the 

beam intercepted three Navy BQM–34A 

drones over the Pacific near Point Mugu, 

California. For the first drone, the beam 

slightly missed the fuel tank aim point and 

did not cause the tank to rupture. On the 
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second drone experiment, the beam deposited 

sufficient energy to cause structural damage 

to the wing root, but the drone continued 

flying. For the third and final drone, the beam 

burned through the flight control box and 

melted numerous wires, which caused multiple 

circuit failures. As the electrical system failed, 

the drone went out of control, making a hard 

90-degree roll to the right. It abruptly made 

a sharp pitch-down maneuver and crashed 

into the ocean. That was a confirmed kill.25

 The ALL was a prime example of advanced 

science and technology that served to strengthen 

this nation’s overall military strategy during 

the Cold War. Although it never became 

an operational weapon, the ALL certainly 

made substantial progress in developing 

new technology that offered to revolutionize 

the art and science of war. U.S. and Soviet 

nuclear deterrence based on the delivery of 

nuclear warheads launched from long-range 

bombers, submarines, and land-based missile 

silos provided the foundation of deterrence. 

The Soviets and Americans both realized the 

development of laser weapons was a very real 

threat that could easily disrupt the delicate 

balance of power in an unstable world. They 

also knew whoever could harness and apply 

the new technology of lasers first would be 

in a much stronger bargaining position to tip 

the scales of strategic power in their favor. 

Looking toward the future, the scientific 

and technical bricks and mortar of the ALL 

doubtlessly laid the foundation for the secondgeneration ABL currently under development.

ADAPTIVE OPTICS

 As work progressed on the ALL, scientists 

at the AFWL pursued laser research programs 

independent of the ALL program. Results 

from those scientific investigations led to 

groundbreaking technological advances in two 

extremely important areas. One was the growth 

of adaptive optics; the other, the discovery and 

development of COIL. These technologies 

would become the two critical components 

of the new ABL system designed to shoot 

down enemy missiles in their boost phase.

 The Air Force has a rich heritage spanning 

three decades in advancing adaptive optics 

technology, one of the essential enabling 

technologies for the ABL. One of the reasons 

attention turned to adaptive optics research 

in the 1970s was because the ALL mirrors 

were unsuitable for use on the next-generation 

ABL. The ALL water-cooled mirrors were 

not optimally efficient, were not reliable for 

transmitting a quality beam through the 

atmosphere, and were subject to corrosion that 

could damage their surface. Indeed, adaptive 

optics research at the AFRL and at its follow-on 

organization, Phillips Laboratory, led to many of 

the most important breakthroughs in the field.

 Laser beams are electromagnetic waves, and 

an electromagnetic wave can be described in 

terms of its amplitude and phase, or wavefront. 

Just as a distorted wavefront can degrade the 

performance of an imaging system (think of a 

picture taken with a camera that is out of focus), 

a distorted wavefront can limit the intensity 

of a high-energy laser (HEL) at the target 

and prevent the desired target destruction.

 By altering the wavefront of the HEL, an 

adaptive optics system can correct or compensate 

for the deleterious effects of beam aberrations 

to enable an intense and lethal concentration 
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222

of laser energy at the target. The ABL uses 

two types of active optics to correct the HEL 

wavefront: fast-steering mirrors (FSMs) and 

deformable mirrors (DMs). An FSM is just 

a flat mirror that can be tilted rapidly about 

two axes to adjust the direction in which the 

HEL is pointed. Coarse pointing of the HEL is 

accomplished by directing a 1.5 meter telescope, 

but compensation for high-bandwidth tilt errors, 

such as those induced by acoustic disturbances 

within the aircraft, requires more agility than 

can be achieved by pointing the telescope. A 

DM is just what the name suggests: a mirror 

whose reflective surface can be deformed. The 

DM used by the ABL has hundreds of actuators 

attached to the backside of the mirror which 

can be electronically commanded to adjust 

the shape of the mirror’s front surface and 

thereby adjust the wavefront of the HEL that 

reflects from it. Figure 1 illustrates the use of 

a DM to correct an aberrated wavefront.

 The requirement for adaptive optics for 

the ABL arises from two sources: distortions 

imparted to the HEL onboard the ABL aircraft, 

and aberrations acquired by the beam along 

the propagation path through the atmosphere 

from the ABL to the target. The ABL COIL 

gain medium consists of gases flowing at 

supersonic velocities. Inhomogeneities within 

the medium can warp the wavefront of the 

beam that the gain medium produces. Also, 

even though the ABL optics absorb only a 

tiny fraction of the laser energy, the HEL is so 

powerful that the optics will still heat up and 

deform. The resulting changes in the surface 

figure of the optics are small, but uncorrected 

optics deformations of even a fraction of a 

micrometer can have a devastating impact on 

system performance. Therefore, there must be 

a “local loop” compensation system onboard 

the ABL to correct these aberrations.

 After the beam exits the nose of the ABL, it 

initially encounters airflow around the aircraft 

as well as turbulence that exists in the free 

atmosphere between the aircraft and the target. 

Light propagated through the atmosphere is 

always affected by turbulence, the term used 

to denote random localized fluctuations in 

the temperature and density of the air. The 

twinkling of starlight is perhaps the most 

widely known manifestation of the effects of 

atmospheric turbulence on light propagation. 

The laws of physics dictate that turbulence can 

severely impact the performance of imaging 

systems and HEL weapon systems. For 

example, astronomical telescopes must be large 

enough to collect sufficient light to detect dim 

objects. Without adaptive optics, atmospheric 

turbulence limits the resolution of an image 

produced by a large telescope—the ability to 

distinguish the stars in a binary pair—to a 

level of quality no better than that of a small 

Figure 1. A deformable mirror is used to correct an aberrated 

wavefront.
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amateur backyard telescope. Figure 2 illustrates 

the impact of turbulence on astronomical 

imagery and the capability of adaptive optics 

to dramatically improve image quality.

 A highly simplified depiction of the ABL 

adaptive optics system is shown in Figure 3. 

This system has two separate adaptive optics 

subsystems: a local loop system and a target 

loop system. The local loop system is used to 

correct the aberrations imparted to the beam in 

its generation and propagation inside the ABL 

aircraft up to the aperture-sharing element, 

which in the case of the ABL is a simple beam 

splitter. The target loop system corrects the 

aberrations imparted to the beam on its journey 

from the aperture-sharing element to the target.

 In 1953, Horace Babcock first proposed using 

adaptive optics26 for real-time compensation 

of astronomical imaging to create higher 

resolution by using large telescopes to their full 

potential. However, the approach he proposed 

was never implemented. A few years later R.B. 

Leighton27 used the simplest form of real-time 

adaptive optics consisting of simple tip-tilt 

correction with an FSM to stabilize the images 

of planets during camera exposures and to 

improve image sharpness. Deformable mirrors, 

the critical element of any adaptive optics 

system, would not be developed for many more 

years. National defense requirements drove 

much of the progress on deformable mirrors 

in the late 1960s and into the 1970s. DoD 

Figure 2. Binary star images taken with the AFRL Starfire Optical Range 3.5m telescope and adaptive optics system at Kirtland 

Air Force Base in New Mexico.
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224

became interested in adaptive optics for their 

potential to improve the performance of imaging 

systems and of possible future laser weapons.

 Rome Air Development Center and 

its contractors from Itek Corporation 

accomplished the first real-time, higher-order 

compensation of atmospheric turbulence 

using a deformable mirror in 1974.28 (Rome 

Air Development Center later became Rome 

Laboratory and is now a part of the Information 

Technology Directorate of AFRL.) Rome 

personnel developed the real-time atmospheric 

compensation system and demonstrated the 

correction of a 632.8-nanometer laser beam 

propagating over a 300-meter horizontal path to 

a 30-centimeter receiving aperture. Their system 

used a monolithic piezoelectric mirror with 

twenty-one actuators, a white-light shearing 

interferometer wavefront sensor (WFS) with 

sixteen subapertures (areas within the aperture 

over which the local wavefront tilt is measured), 

and a high-speed controller based on an analog 

computer. Both the monolithic piezoelectric 

mirror and the shearing interferometer 

represented breakthrough advances in the 

state of the art in adaptive optics hardware.

 The first real-time compensation (beyond 

tilt) of astronomical images was reported in 

the literature in 1977.29 The apparatus had a 

30-centimeter receiver and adjustment was 

accomplished with six movable mirrors. Also in 

1977, compensated images of artificial satellites 

were collected at Maui with an adaptive optics 

system mounted on a 1.6-meter telescope by 

the Advanced Radiation Technology Office 

of the AFWL which later became part of the 

Air Force Phillips Laboratory and then part of 

the Directed Energy Directorate. The system 

used a 37-actuator mirror driven modally to 

correct for focus and astigmatism while an 

Figure 3. The ABL adaptive optics system compensates for both on board and atmospheric disturbances.
Wave of the Future

225

FSM compensated wavefront tilt. Both tilt and 

higher-order aberrations were measured by a sixsubaperture WFS. For classification reasons, the 

results were not reported in the open literature, 

but details of the digital control architecture 

can be found in Corsetti et al.30 Unfortunately, 

the poor sensitivity of the system limited its 

application to only the brightest space objects.

 Rome Laboratory installed the first practical 

adaptive optics system, the compensated imaging 

system, on the 1.6-meter telescope on Mt. 

Haleakala at the Defense Advanced Research 

Projects Agency (DARPA) (ARPA’s name 

changed to DARPA in 1972) Maui Optical Site 

in 1982.31 The system pictured in Figure 4 used a 

DM with more than 100 actuators. A workhorse 

system, it provided compensated images of space 

objects continuously until the early 1990s.

 During the 1980s, work continued to improve 

the technology for DMs. John Kenemuth 

and his group at AFWL sponsored DM 

development at Hughes, Itek, Perkin Elmer, 

and United Technologies. Much of the effort 

was devoted to improvements in linearity of 

response and reliability and to work on cooled 

DMs for HEL applications. The cooled DM 

technology has since been somewhat overtaken 

by events as dramatic improvements in ultralowabsorption coatings have largely eliminated 

the need for cooled optics. All ABL optics are 

uncooled. Advantages of uncooled optics include 

reduced weight, elimination of potential damage 

from coolant leaks, and, most importantly, the 

elimination of the HEL jitter caused by coolant 

flow and the coupling of pumps through the 

plumbing into the optics. AFRL developed 

many of the advances in optical coatings.

 Development of artificial beacon technology 

was another important AFWL contribution to 

adaptive optics. Early adaptive optics systems, 

such as the compensated imaging system, relied 

on light from the object to provide the reference 

for the WFS. Usually, most of the available light 

was required for the adaptive optics system, 

leaving little signal for forming the image, and 

dim objects provided insufficient signal for 

effective compensation. Artificial guidestars 

created by backscatter of pulsed beacon lasers 

from the atmosphere were proposed as a solution 

to this problem. An AFWL team led by Dr. 

Robert Fugate and the Massachusetts Institute 

of Technology’s Lincoln Laboratory performed 

the seminal experiments that proved the viability 

of this technique.32 DoD’s artificial beacon 

research was classified until May 1991 when 

DoD decided to declassify its artificial guidestar Figure 4. Compensated Imaging System mounted on 1.6 meter 

telescope on Mt. Haleakala.
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226

research, which was revealed at the American 

Astronomical Society’s annual meeting in 

Seattle. Transfer of this technology to the 

astronomical community has had a revolutionary 

impact on the subsequent development of 

large ground-based observatories. Today, 

every large astronomical telescope being built 

incorporates adaptive optics in its design.

 When the ABL was proposed in the early 

1990s, it was understood that the problem of 

compensation of turbulence effects would be 

substantially different than it would be for 

ground-based imaging and laser transmission 

systems for which light propagation through 

the turbulence is nearly vertical. For groundbased systems, turbulence is concentrated 

within a few kilometers of the receiving or 

transmitting aperture. The ABL HEL, however, 

must propagate for hundreds of kilometers 

horizontally to destroy its target. Furthermore, 

because ground-based applications were 

dominated by turbulence at low altitudes, 

there had been less attention paid to the nature 

of turbulence at ABL operational altitudes 

at 40,000 feet. One of the key questions 

at the inception of the ABL program was 

whether or not the turbulence at high altitude 

would allow the concentration of lethal 

levels of laser energy on the target, even with 

adaptive optics. The Air Force laboratories 

performed research to answer that question 

and to better understand the fundamental 

phenomenology of high-altitude turbulence.

 The strength of the optical effects of 

turbulence can be related to the magnitude of 

the temperature fluctuations in the atmosphere. 

The Air Force Geophysics Laboratory, now 

part of the AFRL Space Vehicles Directorate, 

pioneered balloon-borne high-bandwidthsensitive temperature probes that could be used 

to measure turbulence at altitudes up to 30 

kilometers. Techniques they developed were 

used to characterize turbulence at several sites 

including Maui and White Sands Missile Range. 

The Geophysics Laboratory developed models of 

turbulence from these data, including the Clear1 

model33 that was adopted as the basis for the 

turbulence requirements for the ABL program. 

The balloon probes provided vertical slices 

through the turbulence profile. To obtain highresolution data on the horizontal structure of 

turbulence, AFWL’s DE developed techniques 

to measure the strength of turbulence using 

temperature probes mounted on aircraft.34

 Efforts to characterize high-altitude 

turbulence for the ABL program culminated in 

the ABLSTAR experimental campaigns in 1999 

and 2000.35 DE conducted three deployments in 

three different seasons in the Middle East and 

the Korean peninsula and collected atmospheric 

turbulence data using balloons and a specially 

instrumented C–135 aircraft (dubbed Argus) 

that served as a flying laboratory. In addition to 

the in situ temperature measurements, a stellar 

scintillometer was also flown on Argus to sense 

the integrated effects of turbulence along slant 

paths similar to those of some ABL engagement 

scenarios. These experiments provided further 

validation of the models of turbulence used 

to specify ABL system requirements.

 AFRL also conducted a number of 

propagation experiments to determine 

the efficacy of adaptive optics for the ABL 

application. In 1993, AFRL/DE conducted 

the Airborne Laser Experiment (ABLEX) 

that propagated a laser from one aircraft to 
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another at separations up to 200 kilometers 

and at ABL operational altitudes. By measuring 

the irradiance distribution of the beam across 

an 80-centimeter aperture on the receiving 

aircraft, the performance with perfect phase 

compensation (perfect adaptive optics) could 

be calculated without making any assumptions 

regarding the structure of turbulence.36 Real 

adaptive optics systems do not achieve perfect 

compensation, of course, but the experiment 

established that the physics limit of phase 

compensation with high-altitude turbulence 

was as expected. The physics limit for phaseonly compensation was determined to yield 

Strehl ratios from 0.7 to 0.8. Those were 

extremely good measurements, considering 

a Strehl ratio of 1.0 represents perfection.

 ABLEX was followed by the ABL 

Extended Atmospheric Characterization 

Experiment (ABLE ACE) in 1995.37 ABLE 

ACE was another set of experiments that used 

measurements of a laser beam propagated 

between two aircraft flying at high altitudes, but 

it included a much richer suite of instruments 

than ABLEX. High-resolution temporal 

and spatial measurements of the laser beam’s 

amplitude and phase were recorded on flights 

in the continental United States and in Korea. 

ABLE ACE was designed to be sensitive 

to every turbulence effect that was thought 

to be important for ABL performance. It 

replicated, at higher fidelity, the measurements 

taken in ABLEX and added high-bandwidth 

scintillometry, measurements of the phase 

difference between two beams propagated 

between the transmitting and receiving aircraft, 

as well as WFS data, full aperture wavefront tilt, 

and far-field imagery. After an extensive effort 

to understand all the experiment noise sources, 

all the data presented a consistent picture that 

provided even stronger validation of the models 

used to predict ABL system performance.

 Parallel to the efforts to better understand 

high-altitude turbulence, DE conducted 

propagation experiments to determine the 

performance of adaptive optics compensation 

for turbulence distributed along the entire 

propagation path. Those experiments used 

a combination of range, laser wavelength, 

aperture size, and turbulence strength so that 

they were scaled to ABL scenarios, that is, the 

turbulence effects were identical to those that 

would be expected for the ABL. The Horizontal 

Propagation Experiment (HOPE), performed at 

the Starfire Optical Range in 1992, successfully 

used adaptive optics to compensate a visible 

wavelength laser propagating over a two-mile 

path. The experiment showed that adaptive 

optics significantly improved performance, 

but as understanding of compensation of 

distributed turbulence improved, much better 

performance was achieved later in similar 

experiments at the Lincoln Laboratory 

Firepond facility and at North Oscura Peak, 

located on the White Sands Missile Range.

 Some of the early propagation experiments 

used a point-source beacon as the reference for 

tracking and adaptive optics. Of course, the 

ABL cannot rely on that degree of cooperation 

from potential adversaries who will not put 

beacons on their targets. The ABL must 

provide its own beacons, which it does by 

illuminating the missile target with separate 

illuminator lasers for tracking and adaptive 

optics (called the TILL and BILL, respectively). 

The ABL tracks the reflected TILL light and 
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228

sends the reflected BILL light to the WFS. 

This approach is illustrated in Figure 5.

 In 1999, DE performed an important series 

of tests identified as the Dynamic Compensation 

Experiment (DyCE) at North Oscura Peak. A 

compensated surrogate HEL, a low-power laser 

used to score the experiments, was propagated 

to a diagnostic target board on an aircraft in 

flight at ranges of 30 to 50 kilometers. A laser 

beacon on the aircraft provided the reference for 

the tracking and adaptive optics. Although the 

target was cooperative, the tests used a dynamic 

target. In 2000, the Non-cooperative Dynamic 

Compensation Experiment (NoDyCE) followed 

DyCE. In NoDyCE, the important features 

of the ABL compensation architecture were 

replicated at the North Oscura Peak site. 

The tracking and adaptive optics performed 

used reflected light from an illuminated target 

board on a Cessna aircraft. Performance of the 

system met all expectations. Figure 6 shows a 

comparison between the performance with the 

high-bandwidth tracking and closed adaptive 

optics loops, and performance with only lowbandwidth tracking and no adaptive optics.

CHEMICAL OXYGEN IODINE LASER

 Shortly after the invention of the laser, 

DARPA recognized the potential utility 

of using lasers on the battlefield. As speedof-light weapons, lasers are able to deliver 

focused, coherent energy at near-instantaneous 

velocities of over 186,000 miles a second 

(around Mach 88,000). Furthermore, 

Figure 5. The Airborne Laser must illuminate the target with illuminator lasers, separate from the COIL high-energy laser, to 

provide signal for tracking and adaptive optics sensors.
Wave of the Future

229

lasers are not constrained by ballistics, 

allowing warfighters the unprecedented 

opportunity to deliver effect on demand.

 DARPA’s early investments in advancing 

laser technology resulted in the hydrogen 

fluoride (HF) and deuterium fluoride (DF) 

lasers, the first high-power systems apart from 

the “traditional” CO2

 chemical laser. Although 

these various lasers worked well, they lased 

in relatively long wavelengths, requiring large 

optics and enormous infrastructure to store the 

energy necessary for their operation. And even 

though the CO2

 laser had been used in the ALL, 

the dream of one day putting an operational 

high-power laser onboard a plane, perhaps 

ultimately in space, would never be achieved 

unless a more efficient, shorter wavelength laser 

could be found. Also, chemical lasers promised 

significant weight savings, an important 

consideration if the device were to be sent aloft.38

 In the mid-1960s, Jerome V.V. Kasper 

and George Pimentel demonstrated the first 

successful chemical laser and the first iodine 

laser in experiments performed at the University 

of California, Berkeley. Unlike lasers that 

require electricity or flash lamps to generate 

a reaction, chemical lasers rely on chemical 

reactions to excite the molecules for light 

amplification (the la of laser) to create a beam 

of light.39 Operated at a wavelength of 1.315 

microns (a micron is equivalent to a millionth 

of a meter, a distance a thousand times smaller 

than a millimeter), the iodine laser appeared to 

be an ideal wavelength for airborne applications. 

Figure 6. Average scoring laser profiles at the aircraft mounted target board recorded during one of the NoDyCE tests. The profile 

in the front was recorded without the adaptive optics loop closed, but with a low bandwidth (12 Hz) track loop using a cooperative 

beacon. The more intense profile was recorded with the adaptive optics and high bandwidth track loops closed. Loops were closed 

using reflected illuminator laser light from the non-cooperative target.
The Limitless Sky

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Specifically, it was not readily absorbed into 

the atmosphere, and its short wavelength 

would allow the use of smaller optics and 

lighter supporting infrastructure. If a highpower, continuous beam iodine laser could be 

invented, it would solve most of the problems 

associated with other high-power laser systems.

 However, the Berkeley iodine laser operated 

only in short, single pulses and had nowhere 

near the power to use as a weapon. If this 

tantalizing iodine wavelength was to be used 

in the real world, it had to be generated by 

an entirely different method. In addition, it 

had to have the ability to “scale,” that is, have 

the potential to increase in power by over a 

billion times, and it had to be a continuous 

beam instead of a short pulse. An analogy 

is that although the Wright Flyer and the 

F/A–22 Raptor both fly in air, they are 

worlds apart in performance capabilities. 

The same advancements were needed if the 

iodine laser was ever going to be a serious 

contender as a directed energy weapon.

 Around the same time that the shortpulse iodine laser was invented, the Air Force 

introduced extremely high-flying reconnaissance 

aircraft such as the U–2 and the SR–71 into 

the operational force structure. These and 

other high-flyers flew in the stratosphere, where 

knowledge regarding the chemical properties

of the air was wanting. Consequently, there 

were concerns about the possibility of the 

effects of air pollution and corrosion on aircraft 

at those altitudes. As a result, the Air Force 

Office of Scientific Research (AFOSR) in 1965 

awarded a contract to Dr. Elmer A. Ogryzlo 

at the University of British Columbia to study 

the reactions of a particular chemical state of 

the oxygen molecule, the singlet delta oxygen, 

which was present in the upper atmosphere. 

With his graduate student S.J. Arnold, Ogryzlo 

noted a strange chemiluminescence when 

mixing singlet delta oxygen and iodine.40

 During a sabbatical at Cambridge in the late 

1960s, Ogryzlo worked with collaborator Brian 

Thrush. It would be Thrush’s graduate student 

R.G. Derwent who first noted the emission of 

1.315-micron light from the iodine atom while 

studying the spectroscopy of an oxygen iodine 

system. Derwent and his colleagues published 

a series of three landmark papers detailing the 

dissociation, or breakup, of elemental iodine (I2) 

by the excited state of oxygen known as singlet 

delta oxygen. They thus discovered a chemical 

excitation mechanism of the iodine atom. 

Although Derwent and Thrush first suggested 

the inversion or alteration of iodine if enough 

singlet delta oxygen could be produced (which 

became the central problem), it is generally 

agreed Ogryzlo first observed the phenomena 

that established the theoretical groundwork 

for Kasper and Pimentel’s invention of the 

chemical excitation of the iodine laser.41

 The publication of Derwent’s work in 1971 

provided the initial impetus for researchers at 

the AFWL, where senior scientists Dr. Petras 

Avizonas and Lieutenant Colonel Mel Bina 

took an avid interest in Derwent’s work. In 

1973, Dr. Alan McKnight began working on 

the oxygen iodine laser at AFWL with the lab’s 

first direct funding. McKnight’s initial work 

consisted of conducting a literature search for 

developing the kinetic rate constants necessary 

to computationally model an oxygen iodine 

laser. Before an attempt was made to build 

this laser, a massive effort was undertaken to 
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231

verify the kinetics involved in the production 

of inverted or altered iodine. Plus, McKnight 

sought to locate a source to generate the 

critical singlet delta oxygen, first unsuccessfully 

trying microwave-excited oxygen.42

 In-house AFWL researchers, consisting of 

military and civilian scientists, worked with 

collaborators to optimize the production 

of singlet delta oxygen. In 1973, McKnight 

approached Major Bill McDermott, a Ph.D. 

chemist then stationed at the Frank J. Seiler 

Research Laboratory, a basic research lab run 

by AFOSR at the United States Air Force 

Academy, who had decided to investigate 

chemical lasers. McDermott enlisted another 

Seiler researcher, Major John Viola, previously at 

the AFWL, to work on the singlet delta oxygen 

production problem, and the AFOSR initially 

funded McDermott’s work with $10,000. 

Major Dave Thomas, a physics professor at the 

United States Air Force Academy, recruited 

additional personnel from the academy’s physics 

department to further support this effort, 

including addressing the dilemma of how to 

accurately measure singlet delta oxygen. During 

this time, McDermott became convinced 

from his literature studies and other efforts 

that a liquid-phase reaction between chlorine 

and basic hydrogen peroxide could generate 

sufficient amounts of singlet delta oxygen. Their 

successes, along with the efforts of Major Ben 

Loving and Lieutenant Colonel Dana Brabson, 

convinced the then-head of AFOSR, Dr. Bill 

Lehmann, to support the growing oxygen iodine 

laser effort at the Frank J. Seiler Research 

Laboratory with an additional $50,000, along 

with another $20,000 contribution from 

AFWL, all of which provided much-needed 

equipment and funded travel that permitted 

collaboration with other key scientists.43

 Major McDermott transferred to AFWL in 

1977, about the same time that Dr. McKnight 

departed, and he worked with Major Ron 

Bousek, who ran the COIL program there. 

Newly arrived Dr. Dave Benard and his team 

made a site visit to scientists at Rockwell 

Science in California, the contractor selected 

to develop the singlet delta oxygen generator. 

Rockwell had been experiencing some technical 

difficulties. Perhaps in haste, Benard took over 

a Rockwell experiment working with both 

oxygen and iodine in the contractor’s lab, and he 

determined that an inversion of iodine had in 

fact occurred. This discovery squelched threats 

to shut down the program, and AFWL received 

Rockwell’s generator. After briefly heading down 

what was the wrong path, the team reoriented 

itself by reexamining earlier work done by 

academic scientists as well as earlier work 

done at the Academy. AFWL’s Captain Nick 

Pchelkin continued to improve on McDermott’s 

generator design, significantly increasing the 

amount of singlet delta oxygen for lasing, while 

Benard prepared detectors that would record 

the lasing. Supporting these scientists were 

AFWL’s machine shop, a glass blower, and 

several Air Force enlisted technicians. Finally, 

on 30 November 1977, a small spike in light 

intensity was observed. It was possible that 

lasing had occurred, but it wasn’t until the next 

day when the experimental team realigned 

the mirrors that lasing occurred every time 

the fledgling laser device was turned on.44

 The laser consisted of four basic parts. 

First, a generator was required to produce the 

excited singlet delta oxygen, resulting from a 
The Limitless Sky

232

chemical reaction between chlorine gas and 

basic hydrogen peroxide. Second, a trap removed 

undesirable chlorine, oxygen, and water vapor 

that would interfere with the laser’s gas kinetics. 

Third, a spray bar, or nozzle, injected iodine into 

the oxygen flow the excited oxygen dissociated 

the iodine transferring energy. Finally, an 

optical resonator, or mirrors at the ends of a 

laser cavity, extracted energy from the inverted 

iodine; in a later version, the residual chlorine 

and iodine were removed at this stage.45

 With this exciting advance in 1977, the 

world’s first chemical oxygen iodine laser, 

COIL, had been invented, yielding a power 

output of only 4 milliwatts, a mere 0.004 

watt. This proof-of-concept demonstration, 

however, was a continuous wave laser, unlike 

the pulsed iodine laser invented a decade before, 

meaning that all the advantages of continuous 

wave lasers might now be exploited with the 

use of chemical fuels. Majors McDermott and 

Bousek, Captain Pchelkin, and Dr. Benard, 

all of whom were Air Force personnel (threequarters blue-suiters), authored the Air 

Force’s patent on COIL awarded in 1981.46

 Once AFWL proved that COIL worked, 

a race commenced to dramatically increase 

its power. A second COIL device failed to 

withstand the required changes and did 

not lase, but in an almost apocryphal event, 

Captain Pchelkin and Dr. Benard had already 

designed the successful COIL III device on 

the back of a placemat in a local restaurant. By 

28 July 1978, less than a year after achieving 

“first light,” its successful first operation, the 

power jumped to 100 watts in this new version 

of COIL, an increase nearly 100,000-fold. 

New collaborators were pulled in, and the 

AFWL team tapped the nation’s science and 

technology contractor base to exploit a scheme 

to generate lasing in a supersonic flow. This 

effort paid high dividends, as year after year, 

COIL reached record power levels. By 1982, 

COIL IV incorporated significant advances and 

had produced over 4 kilowatts of power. This 

effort was overtaken in June 1984 when AFWL 

scientists led by Dr. Gordon Hager created the 

first supersonic COIL device, called RECOIL, 

with a power output of 1.5 kilowatts; a second 

device quickly reached over 4 kilowatts. Also 

in 1984, Rockwell Corporation (under Air 

Force contract) developed a supersonic mixingnozzle array. Supersonic COIL devices, named 

so because they moved gas supersonically 

through the cavity, were vastly improved over 

the subsonic COILs (I through IV). Supersonic 

devices reduced the size of the laser, reduced 

the cavity operating temperature, reduced 

water vapor to increase efficiency, improved 

the beam quality, and provided greater power 

output. By 1987, an AFWL COIL device known 

as ROTOCOIL, using TRW Corporation’s 

rotating disk oxygen generator and Rocketdyne’s 

scalable mixing-nozzle arrays, achieved 25 

and then 35 kilowatts of power. Oxygen 

generator improvements increased efficiency, 

since COIL efficiency was directly related to 

the amount of excited oxygen created. Just 

as important, a COIL device using a high-Q 

ring resonator produced a near pristine laserbeam quality. These supersonic COIL devices 

showed that COIL lasers could be scaled to 

increase their power for weapon applications.47

 Almost from the beginning, COIL attracted 

high-level attention. Laboratory commanders 

and directors, notably Dr. Lehmann (director 
Wave of the Future

233

of AFWL, 19781981) shepherded the program 

along with generous funding. Air Force Chief 

of Staff General Lew Allen, a former AFWL 

officer, visited and encouraged the original 

COIL device team. When its laser-beam 

quality reached even higher levels, Secretary 

of the Air Force E.C. Aldridge, Jr., lauded its 

potential. Although the Air Force’s original 

intent had been to use COIL as a ground-based 

laser, General Donald Lamberson, a strong 

proponent of directed energy technology, quickly 

became interested in COIL as a potential 

candidate for the next-generation ABL.48

 Barely twenty-five years after this 

groundbreaking discovery by a nearly all-officer 

team of in-house Air Force scientists, the ABL is 

on the verge of powering a COIL in the range of 

several megawatts of power, an increase of nine 

orders of magnitude roughly a billion times 

more powerful than the first small laboratory 

device. As early as 1990–91, when the ABL 

program began its emergence from its ALL 

origins, COIL was immediately considered the 

leading candidate for the ABL’s weapon system. 

Its initial advantages included its continuous 

short wavelength for better beam propagation 

through the atmosphere and more energy on 

target. By the early 1990s, COIL technology 

had matured to permit a reliable, stable, and 

safe device offering substantial savings in 

weight and a relatively minor cost of operation 

in comparison with other chemical lasers. Its 

scalability to weapon-system power levels made 

it the system of choice. When compared to 

the original and antiquated ALL CO2

 laser, 

COIL was considerably less bulky and was 

lighter and able to generate considerably more 

power, resulting in longer effective ranges.49

 During the 1990s, significant improvements 

occurred with COIL. In 1993, power operations 

were sustained for more than two minutes, and 

the following year the Phillips Laboratory’s 

VertiCOIL was able to continuously lase for 

more than ten minutes, and its closed-loop 

system permitted chemicals to be extracted and 

reused. Because COIL operates in relatively 

low temperatures, plastic parts replaced 

metal ones to increase weight savings and 

decrease cost. In 1995, Phillips Laboratory 

scientists built the RADICL, the research 

assessment device improvement chemical 

laser. A 10- to 20-kilowatt supersonic COIL, 

RADICL, tested new laser nozzles designed 

to permit lower temperatures and improved 

efficiency. RADICL’s laser beam could be 

transmitted via fiber optics, and a shift from 

costly helium buffer gas used in the supersonic 

flow to less expensive nitrogen provided 

another advancement.50 In addition, Air Force 

researchers determined that the high-power 

laser had significant commercial applications 

including cutting thick metals under hazardous 

conditions, for example, in dismantling 

contaminated nuclear power plants.51

 AFRL’s DE scientists who supported the ABL 

System Program Office continued to advance 

the laser to its development as a weapon system. 

Under the November 1996 ABL contract, the 

Air Force gave Northrop Grumman the task 

of developing a megawatt-class COIL weapon. 

Northrop Grumman had already demonstrated 

the COIL Baseline Demonstration Laser 

module the previous August, and it now 

proceeded to develop the Flight-Weighted 

Laser Module (FLM), which served as the 

basic building block for the laser weapon (with 
The Limitless Sky

234

several FLMs linked to achieve the necessary 

power levels). The FLM passed its critical design 

review in March 1997, and Northrop Grumman 

proceeded with production. That September, 

Team ABL proved the critical singlet oxygen 

generator achieved its necessary production 

levels, and the FLM reached first light in June 

1998. In September 1998, the FLM produced 

110 percent of its design power. By March 

2002, Northrop Grumman had completed its 

testing of the first FLM, or LM1, which had 

reached 118 percent of the laser’s design power 

levels. The contractor proceeded to disassemble 

the module and send it to Edwards AFB in 

California for integration into the ABL’s flight 

system. The next step was to build and integrate 

the final five modules into the demonstrator.52

 In sum, COIL showed what an Air Force 

laboratory could do best. Creative Air Force 

minds had invented the first COIL laser at 

AFWL. As an in-house program, COIL 

provided practical experience for more than two 

decades to Air Force scientists and technicians, 

both blue-suiters and civilians. The Air Force 

laboratory system, with additional funding 

from the AFOSR, had steadily nurtured 

and developed the technology. As Air Force 

researchers discovered more innovations and 

breakthroughs for COIL, new applications 

for its use were likewise identified. COIL had 

begun as a candidate for a ground-based laser 

system, but, because of the inventiveness of 

laboratory researchers, it evolved as the prime 

laser for airborne applications, potentially 

for use in space. On top of these noteworthy 

events, COIL was even ready to transfer 

to the civilian commercial market, with 

potential to revolutionize the industrial use 

of lasers. Undeniably, over these more than 

25 years, COIL set an impressive standard for 

military research and development efforts.53

AIRBORNE LASER

 The development and success of adaptive 

optics and COIL accounted in large part for 

the Air Force’s decision to move forward with 

the ABL program. A concerted push for ABL 

began in 1992 when the Air Force began 

assessing what type of aircraft was the best 

aerial platform suited to accommodate a new 

high-energy ABL. In November 1996, the 

Air Force awarded a $1.1 billion contract to 

Boeing, Northrop Grumman, and Lockheed 

Martin to produce a prototype attack laser 

aircraft using a commercial 747–400 (freighter) 

airframe. The purpose of the ABL is to detect, 

track, and shoot down Scud missiles in their 

boost stage. This second-generation ABL uses 

a powerful COIL working in conjunction 

with a nose-mounted pointer and tracker that 

incorporates advanced adaptive optics.54

 The justification and military value of the 

new ABL is to protect the United States from 

hostile nations who have in their possession 

or are in the process of developing ballistic 

missiles capable of carrying nuclear, biological, 

or chemical payloads. (More than thirty 

nations possess ballistic missiles, and the list 

is growing in an unstable world susceptible 

to unpredictable terrorist attacks.) Although 

based in the United States, the ABL will be 

capable of deploying to any region of the world 

within twenty-four hours. Once on-station 

and operating in a standoff mode over friendly 

territory, the ABL will use three low-power 

lasers to track enemy missiles from launch 
Wave of the Future

235

through their boost stage. (In its boost phase 

a missile is most vulnerable because it emits a 

distinctive infrared signature that is trackable 

and its travel is at a relatively slow rate of speed 

along a predicted flight path.) In addition, the 

three lasers will measure distortions caused 

by turbulence in the atmosphere between the 

ABL and its target. That critical information 

is passed on to the ABL’s adaptive optics 

portion of the fire-control system that directs 

and sharply focuses a high-power beam (in 

the megawatt range) on the target at a range 

of up to several hundred of kilometers.55

 The beam travels at the speed of light, 

destroying the missile and dispersing its deadly 

payload over the enemy’s own territory, thereby 

protecting friendly positions on the ground at 

the intended target site. Because each missile 

is destroyed almost as soon as the laser is fired, 

the ABL operator is afforded the opportunity 

and flexibility to quickly select and destroy 

other missile threats in the same area. Another 

advantage of the ABL is that when it detects 

a missile launch, it also can pinpoint the 

location of the launch pad on the ground. That 

information can then be passed on to tactical 

fighter aircraft to destroy missile launch sites.56

 ABL has progressed beyond the conceptual 

phase and is on the verge of moving into the 

operational Air Force within the next few years. 

The Air Force ordered the first ABL aircraft 

from Boeing in January 1998 to initiate the 

program’s prototype hardware development 

stage. Two years later, on 22 January 2000, the 

ABL rolled off the Boeing assembly line and was 

delivered to the company’s aircraft modification 

facility in Wichita, Kansas. The plane remained 

there to undergo extensive modifications so it 

would be able to accept the laser, beam-control 

system, nose turret, and other components that 

constitute the total, integrated system. After the 

modifications were completion in May 2002, 

the ABL flew to Edwards AFB to begin work 

on on the integration and installation of all 

components and subsystems on the aircraft. The 

ABL is currently going through a comprehensive 

set of ground tests to validate the design and 

performance of the entire laser system. Once 

that phase is completed, ABL flight-testing 

will take place against a variety of aerial 

targets. We must keep in mind that the ABL 

would not be at the point it is today without 

the laboratory development and technological 

breakthroughs associated with COIL and 

adaptive optics over the past forty years.57

CONCLUSION: 

THOUGHTS ON REVOLUTIONARY 

WEAPONS

 Throughout history, epochs and nations 

have been defined by their ability to visualize 

the connection between emerging technologies 

and the security needs of the times. In 

ancient Greece the phalanx–a close-order 

fighting formation of heavily armed infantry 

spearmen troops–with its discipline and 

speed of maneuver allowed Greek warriors to 

dominate their part of the world for centuries. 

Roman Legions–a coherent army combat unit 

of foot soldiers and cavalry capable of speed 

and agility–used the Roman short sword as a 

thrusting weapon at close range, which provided 

Rome the basis to conquer the world as it was 

then known. Introduction of the stirrup in 

the sixth century allowed a horse and rider to 

go from a means of transportation to a lethal 
The Limitless Sky

236

shock weapon, combining the mass and speed 

of the horse with the thrust of a lance or saber. 

The armor-mounted knight of Europe was 

neutralized by the standoff firepower of the 

long bows of the English yeomen. Over time, 

long bows and massive fortifications were 

neutralized by the invention of gunpowder and 

siege cannons. During the age of discovery, 

empires were built on the range and firepower 

of sailing ships, only to be superseded by ships 

powered by steam. With the invention of rifled 

barrels and rapid-fire weapons, land warfare 

later came to be dominated by trench warfare.

In the twentieth century, trench warfare was 

replaced by maneuver with the adaptation of 

the internal combustion engine to machines of 

war. Aircraft emerged to provide the ultimate 

high ground combined with speed, range, and 

lethality. Later in the century missiles made 

it possible to strike any place on the globe 

within minutes. This same technology made it 

possible to lift highly effective reconnaissance 

and communications payloads into space. 

Combined with air-breathing intelligence, 

surveillance, and reconnaissance assets, these 

space assets began to pave the way for a new era 

in warfare, one in which it would be possible 

to find, fix, track, target, and engage anything 

of consequence that moved on the face of the 

earth or through the atmosphere. Incredibly, all 

this would be accomplished in near real time!

 As we enter the twenty-first century, we find 

ourselves on the verge of a new breakthrough in 

warfare with the application of directed energy 

technology to the battlefield. As advanced 

sensors and kill mechanisms, directed energy 

applications in the laser and high-power 

microwave areas will become the centerpiece of 

twenty-first century arsenals. We are in an era in 

which precision and the lack of collateral damage 

are determinants in the acceptability of weapons. 

Directed energy weapons with their ability to 

generate both lethal and nonlethal effects at 

the speed of light will gain greater acceptance. 

The nation with the vision to embrace these 

weapons will dominate the battlefield for the 

foreseeable future. When combined with 

near real-time intelligence, surveillance, and 

reconnaissance assets, the ability to strike 

quickly with air- and space-based directed 

energy weapons will revolutionize warfare for 

surface forces. For an aggressor, sanctuaries 

will be few and retribution swift when faced 

with such revolutionary systems as the ABL.
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Notes: Tightening the Circle

1. Polybius, Universal History, www.mcsdrexel.edu/

~crorres/Archimedes/Seige/Ploybius.html, pp. 1-4. 2. Robert White, A Foundation for the Future: Celebrating 

50 Years of Basic Research, Air Force Office of Scientific 

Research, Arlington, VA, 2002, pp. 7-27, passim. 3. Hugh McDaid and David Oliver, Smart Weapons , 

Welcome Rain Publishers, NY, 1997. p. 10. 4. http://www.aerofiles.com/ostfriesland.html; R. Cargill 

Hall, ed., Case Studies in Strategic Bombardment, Air 

Force History and Museums Program, Washington,. 

DC, 1998, p. 13. 5. Case Studies in Strategic Bombardment, p. 13. 6. Ibid. 7. Ibid. 8. Daniel R. Mortensen, “The Air Service in the Great 

War,” in Bernard C. Nalty, Winged Shield, Winged 

Sword, A History of the United States Air Force, Vol. I, 

Air Force History and Museums Program, Washington, DC, 1997, p. 68; Donald I. Blackwelder, The Long 

Road to Desert Storm and Beyond: The Development of 

Precision Guided Bombs, Air University Press, Maxwell 

Air Force Base, AL, 1992, p. 4 . 9. Blackwelder, p. 3. 10. David R. Mets, The Quest for a Surgical Strike: The 

United States Air Force and Laser Guided Bombs, Office 

of History, Armament Division, Air Force Systems 

Command, 1987, p. 1. 11. Ibid. 12. David R. Mets, Evolution of Air to Ground Weapons: 

The USAF Quest for a Precision Strike, 1903-Present, 

SAAS, undated, briefing in author’s files, slides 3,6. 13. Daniel R. Mortensen, “The Air Service in the Great 

War,” in Bernard C. Nalty, Winged Shield, Winged 

Sword, A History of the United States Air Force, Vol. 

I, Air Force History and Museums Program, Washington, DC, 1997, p. 69. 14. David R. Mets, The Long Search for a Surgical Strike: 

Precision Munitions and the Revolution in Military 

Affairs, Air University Press, Maxwell Air Force Base, 

AL, 2001, p. 5. 15. Ibid. 16. Ibid. 17. Ibid. 18. Richard P. Hallion, “Precision Guided Munitions and 

the New Era of Warfare,” Air Power Studies Centre 

Paper Number 53, APSC, RAAF Base, Fairburn ACT, 

The Limitless Sky

238
Australia, ND, p. 3. Available online at: http://www.

fas.org/man/dod-101/sys/smart/docs/paper53.htm. 19. Ibid.; Website, World War II Airpower: Bombs, Weapons, Rockets, Aircraft Ordnance, http://danshistory.

com/ww2/bombs.shtml., pp. 13-14. 20. Hallion, “Precision Guided Munitions and the New 

Era of Warfare,” p. 4. 21. Dik Alan Daso, Hap Arnold and the Evolution of American Airpower, Smithsonian Institution Press, Washington, DC, 2000, pp. 151, 158-160. 22. Ibid., p. 156; Wesley F. Craven and James L. Cate, eds., 

The Army Air Forces in World War II, Vol. 6, Chicago, 

University of Chicago Press, Chicago, IL 1955, Office 

of Air Force History reprint, 1985, pp. 178-80. 23. Daso, p. 158. 24. Ibid. p. 179. 25. Blackwelder, p. 9. 26. Daso, p. 179. . 27. Daso, pp. 185-86; David R. Mets, The Quest for a Surgical Strike: The United States Air Force and Laser Guided 

Bombs, Office of History, Armament Division, Air 

Force Systems Command, Eglin AFB, FL. 1987, p. 13. 28. Blackwelder, p. 9. 29. Mets, The Quest for a Surgical Strike, p. 13. 30. Blackwelder, p. 10. 31. Hallion, “Precision Guided Munitions and the New 

Era of Warfare,” p. 7. 32. Ibid., p. 14; Website, http://www.vectorsite.net/

twbomb3.html, World War II Glide Bombs, p. 8. 33. Blackwelder, p. 10. 34. Ibid., pp. 9-10. 35. Hallion, .p. 9. 36. Mets, The Quest for a Surgical Strike, p. 11. 37. Blackwelder, p. 15. 38. Wesley F. Craven and James L. Cate, Men and Planes,vol.

6 of, The Army Air Forces in World War II, Office of 

Aor Force History, Washington, DC., 1955, p. 253, as 

cited by Blackwelder, p. 15. 39. Blackwelder, p. 15. 40. Website, http://www.vectorsite.net/twbomb3.html, 

World War II Glide Bombs, p. 7 41. Mets, Evolution of Air to Ground Weapons: The USAF 

Quest for a Precision Strike, 1903-Present, p. 17. 42. Mets, The Quest for a Surgical Strike, pp. 15, 21. 43. Mets, The Quest for a Surgical Strike, p. 26; Hallion, 

“Precision Guided Munitions and the New Era of Warfare,” p. 8. 44. Mets, The Quest for a Surgical Strike, p. 28. 45. Ibid., p. 31. 46. Blackwelder, p. 21. 47. Hallion, “Precision Guided Munitions and the New 

Era of Warfare,” p. 4. 48. Mets, The Quest for a Surgical Strike, p. 31. 49. Ibid., p. 34. 50. Ibid., p. 35. 51. Ibid., p. 40. 52. Ibid., pp. 43-47. 53. Eduard Mark, Aerial Interdiction in Three Wars, Center 

for Air Force History, Washington, DC, 1994, p. 387. 54. Ibid 55. Mets, The Quest for a Surgical Strike, pp. 47-48. 56. Ibid., p. 52. 57. Ibid., p.53. 58. Ibid., p. 55; Vernon Loeb, “Bursts of Brilliance,” The 

Washington Post Magazine, December 15, 2002, p. 8. 59. Mets, The Quest for a Surgical Strike, p. 56. 60. Vernon Loeb, “Bursts of Brilliance,” The Washington 

Post Magazine, December 15, 2002, p. 8. 61. Ibid. 62. Mets, The Quest for a Surgical Strike, p. 71. 63. Ibid., p. 83. 64. While the U.S. Navy employed the electro-optically 

guided Walleye at this time, but none of their strike 

aircraft were certified for LGBs. See: Email, Dave 

Mets/SAAS to Robert White/AFOSR/PIC, 17 July 

2003, subj.: PGM Draft. 65. Ibid. 66. Mets, The Quest for a Surgical Strike, pp. 86-87; 

Mark, Aerial Interdiction in Three Wars, p. 387; Wayne 

Thompson, To Hanoi and Back, The USAF and North 

Vietnam, 1966-1973, Air Force History and Museums 

Program, Washington, DC, 2000, pp. 234-35. 67. Mark, p. 387. Also see: Major Donald L. Ockerman, 

Tactical Analysis Division, Headquarters, 7th Air Force, 

Thailand, “An Analysis of Laser Guided Bombs in 

SEA,” 28 June 1973, Air Force Historical Research 

Agency, K740.041-4. 68. Hallion, “Precision Guided Munitions and the New Era 

of Warfare,” p. 4. 69. Donald I. Blackwelder, The Long Road to Desert Storm 

and Beyond: The Development of Precision Guided 

Bombs, School of Advanced Airpower Studies, Air 

University, Maxwell Air Force Base, AL, 1992, p. 30; 

Michael Rip and James Hasik, The Precision Revolution: 

GPS and the Furure of Aerial Warfare, Naval Institute 

Press, Annapolis, MD, 2002, p. 224; John A. Tirpak, 

Deliberate Force, Air Force Magazine Online, at: http://

www.afa.org/magazine/oct1997/1097deli.asp, pp. 4-5, 

citing Air Force Secretary Sheila E. Widnall address 

to the 1996 AFA Air Warfare Symposium; Kenneth 

P. Werrell, “Did USAF Technology Fail in Vietnam?” 

Aerospace Power Journal, Spring 1998, available at: 

239

Notes and References, Pages 28–39
http://www.airpower.maxwell.af.mil/airchronicles/

apj/apj98/spr98/werrell.html, p. 7; CEP of 447 feet 

based on F-105 Rolling Thunder campaign employment of unguided munitions and CEP of 23 feet is for 

F-105 employment of LGB munitions between February 1972 through February 1973; Wayne Thompson, 

To Hanoi and Back: The USAF and North Vietnam, 

1966-1973, Air Force History and Museums Program, 

USAF, Washington, DC, 2000, p. 306. Approximately 

8,000,000 tons of air munitions were dropped in SEA 

by US forces, 6,162,000 figure reflects total tonnage 

minus B-52 tonnage, both in North and South Vietnam. Also see: Reaching Globally, Reaching Powerfully: 

The Uniited States Air Force in the Gulf War, A Report 

September 1991, p. 15, at: http://www.fas.org/man/

dod-101/ops/docs/desstorm.htm. A consolidated CEP 

for the 26,000+ PGMs dropped in Vietnam could not 

be found, but several periodic CEP measurements exist. 

Blackwelder notes: “In 1969, 1612 LGBs were dropped 

with 923 (57%) direct hits, an additional 1114 damaged targets...between 1 February 1972 and 28 February 1973, 10,651 laser guided bombs were dropped in 

SEA...[n]early 50% (5,107) of the bombs were direct 

hits...,” pp. 26-7. Blackwelder continues: “...during the 

1972 Easter Offensive, the Air Force dropped 6000 

LGBs...with 64% achieving direct hits.” (p. 28). Hallion 

in Storm Over Iraq, notes that “CEPs within six feet [of 

the target]” were seen during the Linebacker campaign. 

P. 283. Werrell notes (page 12): “Electro-optical glide 

bombs (EOGBs) were primarily used in low threat 

areas. During 1972, 329 were launched, and 53.5% 

of these achieved direct hits. By comparison, 9,094 

LGBs were dropped, and 47.5% achieved direct hits.” 

Blackwalelder (pp. 29-30) also notes: Target acquisition and lock-on with the EO (Walleye), as employed 

in Vietnam, required a long, stable final approach from 

12-14,000 feet AGL at 450 knots. “In low threat areas 

the crews could make individual passes, but in high 

threat areas like route Package 6, they had to maintain 

four-ship pod (to enhance defensive electronic countermeasures) formations...the Walleye was used much 

less extensively than the laser guided bomb. Weather 

and restrictive target requirements were the primary 

limitations. Only 898 Walleye Is, 79 Walleye IIs, and 

3 Walleye IIs (with data link) were dropped in SEA 

through the combined eforts of the Air Force and 

the Navy...68% of all Walleyes dropped were direct 

hits.” Also see: General Eggers, USAF, “The Employment Effectiveness of Missiles and Guided Weapons,” 

briefing presented to JCS in 1973, Air Force Historical Research Agency, Maxwell AFB, AL, (call no. 

K712.153-1), p. 56. 70. Hallion, Storm Over Iraq, p. 305. 71. Ibid.

72. Interview, Robert White with Robert Seirakowski and 

Al Weimorts, Eglin AFB, FL, 17 June 2003. 73. Ibid.

74. Ibid.

75. Ibid; Email, Dave Mets, SAAS to Robert White, 

AFOSR/PIC, 17 July 2003, subj.: PGM Draft. 76. E-mail, Martin (Ric) Wehling to Robert White, subj.: 

Meeting at AFRL/MN Next Week, Atch.: “Tightening 

the Circle,” p. 1. 77. Website article, “Guided Bomb Unit-28 (GBU-28),” 

www.globalsecurity.org/military/systems/munitions/

gbu-28.htm 78. Website, “The Art of Bunker Busting,” http://danshistory.com/lgb.shtml, p. 2. 79. For the most detailed study of the GBU-28 evolution, 

see: Barry R. Barlow, The GBU-28, February 1991,

Office of History, Air Force Development Test Center, 

Eglin Air Force Base, FL, 1996. 80. E-mail, Martin Wehling to Robert White, 18 June 

2003, subj: GBU-28 Story. 81. Ibid. 82. Eric Schmitt and James Dao, “A Nation Challenged: 

The Air Campaign, Use of Pinpoint Air Power Comes 

of Age in New War,” New York Times, 24 December, 

2001, p. 3. 83. E-mail, Martin (Ric) Wehling to Robert White, subj.: 

Meeting at AFRL/MN Next Week, Atch.: “Tightening 

the Circle,” p. 2. 84. “A Nation Challenged,” pp.3-4. 85. Ibid., p. 4. 86. E-mail, Maurice Lourdes, AFRL/AFOSR to Robert 

White AFRL/AFOSR, 30 August 2003, subj.: FW: 

S&T Historical Map. 87. INS historical data provided by: Email, AFRL/MN 

to Robert White/AFRL/AFOSR, subj.: INS Data; 1 

August 2003. 88. Michael Rip and James Haslik, The Precision Revolution, Naval Institute Press, Annapolis, MD, 2002, p. 

224; John A. Tirpak, “Deliberate Force,” Air Force 

Magazine Online, Air Force Association, http://www.

afa.org/magazine/oct1997/1097deli.asp 89. See: Adam J. Hebert, “Compressing the Kill Chain,” Air 

Force Magazine, March 2003, p. 52. 90. AFOSR/PIP, Briefing, “Anectodal Success Stories,” 10 

July 2003, slide. 39. 91. Interview, Dr. Robert Sierakowski and Fred Davis, 

AFRL/MN, 16 June 2003. 92. E-mail, Martin (Ric) Wehling to Robert White, subj.: 

The Limitless Sky

240
Meeting at AFRL/MN Next Week, Atch.: “Tightening 

the Circle,” p. 2; Interview, Dr. Robert Sierakowski and 

Fred Davis, AFRL/MN, 16 June 2003; John A. Tirpak, “Long Arm of the Air Force,” Air Force Magazine, 

October 2002, p. 32. 93. John A. Tirpak, “Long Arm of the Air Force,” Air Force 

Magazine, October 2002, p. 32. 94. E-mail, Laurice Lourdes, AFRL/AFOSR to Robert 

White, AFRL/AFOSR, 16 August 2003, subj.: FW: 

ST Historical Map.ppt. 95. Robert L. Sierakowski, “Meet the Chief Scientist,” 

Technology Horizons, June 2002, p. 12. 96. Ibid. 97. Interview, Dr. Robert Sierakowski, AFRL/MN, 16 

June 2003. 98. Ibid. 99. Martin F. (Ric) Wehling, AFRL/MN, Briefing, “Tara98: Guidance and Control Technology Overview,” 10 

February 1998, slides 83-88. 100. AFRL/MN, Briefing, “Micro-Air Delivered Munitions, Advanced Research Program,” June 2003, Eglin 

AFB, FL, passim. 101. Martin F. (Ric) Wehling, AFRL/MN, Briefing, “Tara98: Guidance and Control Technology Overview,” 10 

February 1998, slides 89. 102. Interview, Robert White with Robert Seirakowski, Al 

Weimorts, and Fred Davis, Eglin AFB, FL, 17 June 

2003; “Lattice Fin Technology,” talking paper, AFRL/

MN, undated. 103. See: Buster C. Glosson, “Impact of Precision Weapons 

on Air Combat Operations,” Airpower Journal, Summer 1993, http://www.airpower.au.af.mil/airchronicles/apj/glosson.html, p. 1; Hallion, “Precision Guided 

Munitions and the New Era of Warfare,” passim; 

Michael Rip and James Haslik, The Precision Revolution, passim; Hallion, “Precision Guided Munitions and 

the New Era of Warfare,” passim. 104. Buster C. Glosson, “Impact of Precision Weapons on 

Air Combat Operations,” Airpower Journal, Summer 

1993, http://www.airpower.au.af.mil/airchronicles/

apj/glosson.html, p. 4.

Footnotes: Enlisting the Spectrum for Air 

Force Advantage

1.

 Gen H. H. Arnold, Memo for Dr. Von Karman, 

7 November 1994, in Prophecy Fulfilled: “Toward 

New Horizons” and Its Legacy, M. Gorn ed., Air Force 

History and Museums Program, Washington, DC,1994.

2. Ibid.

3. Research sites at Wright-Patterson AFB, OH, also 

at Hanscom AFB, MA and Kirtland AFB, NM, have 

been major players in this area. 4. Programs for space-based applications of infrared sensors, not addressed in this paper, fall under Air Force 

Research Laboratory’s Space Vehicles Directorate. 5. U.S. Air Force Fact Sheet, AIM–9 Sidewinder, Public 

Affairs Office, Air Combat Command , March 2003. 6. James Aldridge, USAF Research and Development: 

The Legacy of the Wright Laboratory Science and 

Engineering Community, 1917–1997, Wright-Patterson Air Force Base, Aeronautical Systems Center History Office, OH, 1997, pp.89–96. 7. U.S. Air Force Fact Sheet, LANTIRN, Public Affairs 

Office, Air Combat Command (as of August 1999); 

“Martin-Marietta ‘LANTIRN’ Navigation and Targeting System, Online.. Available: www.wpafb.af.mil/

museum 8. Silverman, Mooney, and Shepherd, Infrared Video 

Cameras, pp. 80–81; Communication from F.D. Shepherd, Aug 03. 9. Silverman, Mooney, and Shepherd, Infrared Video 

Cameras, 10. R. C. Hardie, K. J. Barnard, J. G. Bognar, E. E. Armstrong, and E. A. Watson, “High-resolution image 

reconstruction from a sequence of rotated and translated frames and its application to an infrared imaging 

system,” Opt. Eng. 37(1) 247–260, 1998. 11. U.S. Air Force Fact Sheet, B–52 Stratofortress, Public Affairs Office, Air Combat Command (as of July 

2001); U.S. Air Force Fact Sheet, Global Hawk, Public 

Affairs Office, Aeronautical Systems Center, December 

2002. 12. D.A. Fulghum, “Advanced Sensors Expand JSF Role,” 

Aviation Week and Space Technology, September 11, 

2000, pp.58–59. 13. U.S. Air Force Fact Sheet, RQ–1 Predator UAV, Public 

Affairs Office, Air Combat Command, May 2002. 14. E. A. Watson, M. P. Dierking, and R. D. Richmond, 

“Laser Radar Systems for Multi-Dimensional Imaging 

and Information Gathering,” presented at the Annual 

Meeting of the Lasers and Electro-Optics Society, 

Orlando, FL,1998. 15. R. Liebowitz, “Atmospheric Propagation Codes for 

DoD Systems,” ERIM Newsletter, 1990. 16. G. Thompson, “Infrared Target-Scene Simulation Software employed in OIF,” Hansconian, June 13, 2003. 17. Silverman, Mooney, and Shepherd, Infrared Video 

Cameras, p. 82. 18. S.G. Burnay, T.L. Williams, C.H Jones, Applications 

of Thermal Imaging, Bristol and Philadelphia: Adam 

241

Notes and References, Pages 40–75
Hilger, 1988, passim. 19. Systems described in this section are from Jane’s Electro-Optic Systems, 4th Edition, K. Atkin ed., Butler 

and Tanner Limited, London, 1999. 20. U.S. Air Force Fact Sheet, AIM–9 Sidewinder. 21. E.H. Tilford, Jr, USAF Search and Rescue in Southeast 

Asia, Washington, DC: Center for Air Force History, 

1992, pp. 93, 136. 22. T. Thompson, History of Rome Laboratory, Griffiss 

AFB, NY: RADC History Office,1997, AF 50th Anniversary Publication, pp. 16–18. 23. History of the Aeronautical Systems Division, January–December 1991, ASC History Office, WrightPatterson AFB, pp. 336–340. 24. U.S. Air Force Fact Sheet, Global Hawk, Public Affairs 

Office, Aeronautical Systems Center, December 2002. 25. “Back to Bosnia,” Aviation Week and Space Technology, 

October 14, 1996; R.J. Newman, “The Little Predator That Could,”Air Force Magazine, March 2002, pp. 

48–53. 26. Maj Gen Stephen G. Wood, Commander, Air Warfare 

Center, Nellis AFB, Nevada

Footnotes: From the Air

1. Niccolo Machiavelli, The Prince and the Discourses. 

 New York: Modern Library, 1950, p. 523.

2. Airborne remote sensing collects and analyzes information of an area or thing from a distance using different 

kinds of sensors operating from a variety of aircraft. 3. Invented at Stanford University in 1939, the klystron 

was a high-frequency electron tube. The klystron produced higher power levels than the magnetron, another 

electron tube used in many types of radar. 4. Maurice Long, ed., Airborne Early Warning System 

Concepts. Boston: Artech House, 1992, p. 3. 5. Alfred Goldberg, ed., A History of the United Sates 

Air Force, 1907–1957. Princeton, New Jersey: D. Van 

Nostrand Company, Inc., p.136. 6. Kenneth Schaffel, The Emerging Shield: The Air Force 

and the Evolution of Continental Air Defense. Washington, D.C., Office of Air Force History, p. 221. 7. Harry A. Pearce. “AWACS to Bridge the Technological 

Gap,” Air University Review vol. 23, p. 56, May–June 

1972. 8. Lori A. McClelland and David M. Russell, (September 1984). “AEW Market Soars: Interest in Airborne 

Early Warning Aircraft Runs High Following Combat 

Demonstrations,” Defense Electronics. vol.16, p.127, 

September 1984. 9. Tom Kaminski and Mel Williams, The United States 

Military Aviation Directory. Norwalk, Connecticut: 

AIRtime Publishing Inc., 2000, p. 50. 10. “Boeing Company Selected to Build AWACS Aircraft,” 

Department of Defense News Release, July 8, 1970. 11. “Boeing Gets Big Radar Plane Contract,” New York 

Times, July 9, 1970. 12. What is today Air Force Research Laboratory, Information Directorate (AFRL/IF), was known as Rome Air 

Development Center (RADC) until 1990 and Rome 

Laboratory until 1997. To avoid confusion, “Rome 

Laboratory” will be used to designate all research conducted at that location. 13. “AF Demonstrates Pave Mover System,” The Hansconian. November 18, 1982. 14. Thomas Robillard, The Joint STARS Platform Decision. Washington, D.C.: Department of the Air Force, 

1997, passim. 15. “Pave Mover/Assault Breaker,” Rome Research Site 

History File, n.d. 16. “Joint STARS Flies High in April,” Hansconian, June 

10, 1988. 17. “Joint STARS Earns Initial Operational Capability,” 

Air Force Materiel Command (AFMC) News Release, 

December 14, 1999. 18. Kaminski and Williams, The United States Military 

Aviation Directory, p. 54. 19. James Aldridge, ed., USAF Research & Development: 

The Legacy of the Wright Laboratory Science and 

Engineering Community, 1917–1997. Wright-Patterson Air Force Base: Aeronautical Systems Division 

History Office, n.d., p. 90. 20. “Affordable Moving Surface Target Engagement 

Enters Second Phase,” AFRL News Release, Sep 29, 

2000. 21. Rich Tuttle, “Northrop Grumman Beats Ratheon 

in AMSTE Competition,” Aerospace Daily, Sep 20, 

2001. 22. Jon Jones, Steven Southwell, Stephen Scott, Stephen 

Welby, and Charles Taylor, “Affordable Moving Surface 

Target Engagement,” AIAA Missiles and Science Conference, Nov 2002. 23. David Fulghum, “Bull’s-Eye Concludes Moving Target 

Test,” Aviation Week & Space Technology. vol 155, pp. 

33–34, September 10, 2001 24. Mark Pronobis, “Battlespace Awareness Through Information Fusion,” AFRL Technology Horizons. vol. 2, p. 

14, Jun 2001. 25. Jim Coghlan, “Countering the Cruise Missile: The Air 

Defense Initiative Seeks Multispectral Space-based 

Sensors, Defense Electronics. vol. 19, pp. 77, September 1987.

The Limitless Sky

242
26. Jeffrey Brandstadt and Mark Kozak, “Multi-Platform 

Tracking Exploitation,” National Symposium and Sensor Fusion Conference, June 2001. 27. Jon Jones and Martin Liggins, “Off-Board Augmented 

Theater Surveillance,” National Symposium and Sensor Fusion Conference, April 1996. 28. “Sensors, Electronics, and Battlespace Environment,” 

Defense Technology Area Plan. Washington D.C.: 

Department of Defense, 1997, chap. 7, p. 18. 29. Allen A. Boraiko, “The Chip: Electronic Mini-Marvel 

That Is Changing Your Life,” National Geographic. vol. 

162, p. 421, October 1982. 30. Aldridge, USAF Research & Development, p. 90. 31. Air Force avionics research at Wright-Patterson Air 

Force Base is a long one, characterized by frequent 

organizational changes and redesignations. To avoid 

confusion, “Avionics Laboratory” is used throughout 

this paper to identify research carried out at that location. 32. J.F. Rippin, Jr., “Survey of Airborne Phased Array 

Antennas,” Phased Array Antennas, Proceedings of the 

1970 Phased Array Antenna Symposium, 2–5 June 

1970, Dedham, Massachusetts: Artech House Inc., 

1977, pp. 275–87. 33. T.E. Harwell, “Airborne Solid State Radar Technology,” 

E. Brookner, ed., Radar Technology, Dedham, Massachusetts: Artech House Inc., 1977, pp. 275–287. 34. Aldridge, USAF Research & Development, pp. 97–

99. 35. H.E. Schrank, “Some Notable Firsts in Array Antenna 

History,” Antenna Applications Symposium, 19–21 

September 2001, pp. 231–49. 36. John Clarke, “Airborne Early Warning Radar,” Proceedings of the IEEE, vol. 73, pp. 320, February 1985. 37. S. Silver, ed., Microwave Antenna Theory and Design, 

Vol 12, Radiation Laboratory Series, New York: 

McGraw Hill Publishing Co., 1949, pp. 286–301. 38. A.F. Kay and A.J. Simmons, “Mutual Coupling of Shunt 

Slots,” IRE Transactions on Antennas and Propagation, 

vol. 8, pp. 389–400, July 1960. 39. A. Oliner, “The Impedance Properties of Narrow Radiating Slots in the Broadface of Regular Waveguide,” 

Parts I and II, IRE Transactions on Antennas and 

Propagation, vol. 5, pp. 4–20, January 1957. 40. MITRE and AWACS: A Systems, Engineering Perspective. Bedford, Massachusetts: MITRE Corporation, 1990, passim. 41. “Air Force Completes AWACS Fleet,” Air Force Systems Command Newsreview, vol. 28, p. 6, July 1984. 42. McClelland and Russell, “AEW Market Soars,” Defense 

Electronics , p.130.

43. H. Schnitkin, “Unique Joint STARS Phased Array 

Antenna,” Proceedings of the 1989 Antenna Applications Symposium, University of Illinois, 1989. 44. “Early Delivery for Seventh Consecutive Joint STARS,” 

Leading Edge, October 2001. 45. Jon Jones, Steve Scott, and John Cotton, “Advanced 

Developments for Joint STARS Enhancements,” TriService Radar Symposium, April 1997. 46. “Technology: Key to Progress,” Commanders Digest, 

October 30, 1975. 47. “Air Force Gears for AI Buy,” Advanced Military Computing. vol. 5, p.3, January 30,1989. 48. Bernard C. Nalty, ed., Wing Shield, Winged Sword: 

A History of the United States Air Force, Vol II, 

1950–1997, Washington D.C.: Air Force History and 

Museum Program, 1997, p. 287. 49. Jack Robertson, “Viet ‘Wall’ Will Sense Enemy, Flash 

Warning to Main HQ,” Electronic News, October 30, 

1967. 50. Jacob Van Staarveren, Interdiction in Southern Laos, 

1960–1968, Washington, D.C.: Center for Air Force 

History, 1993, p. 271. 51. Edwin Armistead, AWACS and Hawkeyes: The Complete History of Airborne Early Warning Aircraft, St. 

Paul, Minnesota: MBI Publishing Company, 2002, p. 

80. 52. McClelland and Russell, “AEW Market Soars,” p. 127. 53. Alexander Levis, AF/ST, to Ruth Liebowitz, Electronic 

Systems Center/History Office, “Bruce Brown,” e-mail, 

August 5, 2003. 54. Ibid. 55. Ibid. 56. Nalty, Wing Shield, Winged Sword: A History of the 

United States Air Force, Vol II, 1950–1997, p. 487. 57. Ibid., p. 499. 58. Armistead, AWACS and Hawkeyes, p. 181. 59. Thomas A. Keaney and Eliot A. Cohen, Gulf War Air 

Power Survey Summary Report, Washington D.C.: 

Government Printing Office, 1993, p. 109. 60. “Joint STARS Earns Initial Operational Capability,” 

AFMC News Release, February 1998. 61. Benjamin Lanbeth, “Kosovo and the Continuing SEAD 

Challenge,” Aerospace Power Journal, vol.16, p. 14, 

Summer 2002. 62. David Fulghum, “New Bag of Tricks,” Aviation Week & 

Space Technology, vol. 158, p. 23, 21 April 2003. 63. “RQ–1 Predator Unmanned Aerial Vehicle,” News 

Release Fact Sheet, ACC/PA, May 2002. 64. Nalty, Winged Shield, Winged Sword: A History of 

the United States Air Force, p.527. 65. Kenneth Munson, ed., Jane’s Unmanned Aerial Vehi243

Notes and References, Pages 76–82
cles and Targets, Alexandria, Virginia: Directory & 

Database Publishers Assciation, 2001, p. 283. 66. Chuck Roberts, “Operation Iraqi Freedom,” Airman, 

vol. 47, p. 23, May 2003. 67. Fulghum, “New Bag of Tricks,” p. 23. 68. David Fulghum, “Battlefield Buzz,” Aviation Week & 

Space Technology, vol. 158, p. 27, March 24, 2003. 69. Maj Gen. Joseph P. Stein, ACC/DO, to Thomas W. 

Thompson, AFRL/IFOI, “AF Centennial of Flight 

Paper,” e-mail, August 8, 2003. 70. Brig Gen. Kelvin R. Coppock, ACC/IN, “ISR Reachback: An OIF Success Story,” Briefing, 19 June 19, 

2003. 71. Ibid. 72. Stein to Thompson, e-mail, August 8, 2003. 73. Bistatic radars operated with their transmitters and 

receivers in different locations. This configuration 

afforded several advantages, including more angles 

from which to observe targets, better electronic counter 

counter measures (ECCM) capability, and advantages 

attendant with dispersal generally.

References: Pilots in Extreme Environments

1. “Aerospace Medicine”, H. G. Armstrong, ed., The Williams and Wilkins Co., Baltimore, 1961. 2. Carey, C. T. “A Brief History of US Military Aviation Oxygen Breathing Systems” http://webs.lanset.

com/aeolusaero/Article/Oxygen%Systems%20history 

— Pt1.htm. 3. “A History of Mitchel Field — The Cradle of Aviation 

Museum” http://www.cradleofaviation.org/history/

airfields/mitchel.html. 4. Payton, G., “Fifty Years of Aerospace Medicine”, AFSC 

Historical Publications, Series No. 67–180, 1968. 5. Dempsey, C. A., “50 Years of Research on Man in 

Flight”, Aerospace Medical Research Laboratory, Published by the United States Air Force, 1985. 6. Heim, J. W., “Aerospace Medicine — The Early Years”, 

unpublished memoirs, 1966. 7. “Oral History Interview: Major General Harry G. 

Armstrong (Ret), US Air Force Medical Corps, Aerospace Medical Division, Air Force Systems Command, 

Brooks Air Force Base, United States Air Force, 1981. 8. “Major General Otis O. Benson, Jr. Biography”, http://

www. Af.mil/bios/bio_4669.shtml, 1981. 9. History of Research in Space Biology and Biodynamics” http://www.hq nasa.gov/office/pao/History/afspbio/illustr.htm. 10. Ernsting, J., “Operational and Physiological Requirements for Aircraft Oxygen Systems”, AGARD Report 

No. 697. 7th Advanced Operational Aviation Medicine 

Course. RAFIAM, Farnborough, Hants, UK. Nov 

1983. 11. Ernsting, J. “Minimal Protection for Aircrew Exposed 

to Altitudes above 50,000 feet”. Joint Airworthiness 

Committee Paper No. 1014, Issue 2, Jan 1983. 12. Sears, William J., “High-Altitude Pressure Protective 

Equipment: A Historical Perspective”, Pages 121–132 

in “Raising the Operational Ceiling: A Workshop on 

the Life Support and Physiological Issues of Flight 

at 60,000 feet and Above”, AL/CF–SR–1995–0021, 

Edited by Pilmanis, Andrew A. and Sears, William J. 

December 1995. 13. Webb, J. T. and Pilmanis, A. A, (1995) Altitude 

decompression sickness: Operational significance. In 

Pilmanis, A. A. and Sears, W. J, eds. Raising the 

operational ceiling: A workshop on the life support and 

physiological issues of flight at 60,000 feet and above. 

AL/CF–SR–1995–0021. Brooks AFB, TX 14. Sears W. J. “Vaporization of Tissue Fluids at Extreme 

Altitudes — A Review”, SAFE Annual Meetings 

1989. 15. King, Kenneth R. and Griswold, Harrison R., “Air 

Force High Altitude Advanced Flight Suit Study”, 

USAFSAM–TR–83–49 December 1983 16. Byrnes, Donn A. and Hurley, Kenneth D., “Blackbird 

Rising — Birth of an Aviation Legend”, published by 

Sage Mesa Publications, Los Lunas N.M. 1999 17. Barry, Daniel M., Bassick, John W., “ NASA Space 

Shuttle Advanced Escape Suit Development” SAE 

Technical Paper #951545, 25th International Conference on Environmental Systems, San Diego, California, 

July 1995. 18. Shaffstall, Robert M., Morgan, Thomas R. and Travis, 

Thomas W., “Development of USAF Pressure Breathing Systems”, in “Raising the Operational Ceiling: A 

Workshop on the Life Support and Physiological 

Issues of Flight at 60,000 feet and Above”, AL/CF–

SR–1995–0021, Edited by Pilmanis, Andrew A. and 

Sears, William J. December 1995. 19. Self, B, W. Sears and A. Pilmanis, “Development of 

the Sustained High Altitude Respiratory Protection 

and Enhanced Design G Ensemble (SHARP EDGE), 

AFRL–HE–BR–TR–2001–0175, Feb 2001 

Footnotes: Exploiting the High Ground

1.

 Eileen Shea, compiler, A History Of NOAA, Being 

A Compilation of Facts And Figures Regarding 

The Life And Times of The Original Whole Earth 

Agency, (Washington, D.C.: National Oceanic and 

Atmospheric Administration, 1987), p. 9, available 

The Limitless Sky

244
on the Internet at http://www.lib.noaa.gov/edocs/

noaahistory.html as of 25 June 2003. [Hereinafter 

cited as Shea, History of NOAA.]

2. National Weather Service Forecast Office Los Angeles/

Oxnard, “Cooperative Weather Program,” last updated 

17 February 2002, available on the Internet at http://

www.nwsla.noaa.gov/coop/index.html as of 25 June 

2003. This site also describes the prestigious Thomas 

Jefferson Award, presented annually “to honor cooperative weather observers for unusual and outstanding 

achievements in the field of meteorological observations. 

It is the highest award the NWS [National Weather 

Service] presents to volunteer [weather] observers.” 3. Anonymous, “Benjamin Franklin as a Scientist,” n.d., 

available on the Internet at http://sln.fi.edu/franklin/

scientist/scientst.html as of 25 June 2003; Keith C. 

Heidorn, Ph.D., ACM, “Benjamin Franklin: The First 

American Storm Chaser,” 14 July 1998, available on the 

Internet at http://www.islandnet.com/~see/weather/

history/bfrank1.htm as of 25 June 2003. This source 

marks Franklin as “perhaps America’s first meteorological scientist. Others before him had been weather 

observers, but few set out to observe and then explain 

weather phenomena.” This site also presents Franklin’s 

account of his encounter with the whirlwind. Rita M. 

Markus, et al., Air Weather Service: Our Heritage, 

1937–1987 (Scott Air Force Base, Illinois: USAF Military Airlift Command, 1987), p. 1. [Hereinafter cited as 

Markus, et al., Air Weather Service.] 4. Shea, History of NOAA, p. 9. 5. Markus, et al., Air Weather Service, p. 1. 6. Markus, et al., Air Weather Service, p. 1. 7. Markus, et al., Air Weather Service, pp. 1–2. John F. 

Fuller, Thor’s Legions: Weather Support to the U.S. 

Air Force and Army, 1937–1987 (Boston: American 

Meteorological Society, 1990), pp. 1–7. [Hereinafter 

cited as Fuller, Thor’s Legions.] This source offers 

greater detail on the early contributions of the U.S. 

Army in the nation’s weather service and notes that “the 

magnitude of the transfer” of weather-related duties 

from the Army Signal Corps to the U.S. Weather 

Bureau “was illustrated by the fact that the Signal 

Corps budget for meteorology fell from $753,284.70 in 

1891 to $31,687.62 in 1892” (p. 7). 8. V. E. Tarrant, Jutland: The German Perspective 

(Annapolis, MD: Naval Institute Press, 1995), pp. 

229–233 covers the role of German airships at the 

battle. 9. R. Ernest Dupuy and Trevor N. Dupuy, The Encyclopedia of Military History, From 3500 B.C. to the Present, second revised edition (New York: Harper & Row, 

Publishers, 1986), p.950. 10. Fuller, Thor’s Legions, pp. 13, 15. For more on the 

weather’s impact on American plans and operations see 

pp. 9–15 of this source.

11. Dr. Helmut E. Landsberg, Geophysics and Warfare 

[Washington, D.C.: Research and Development Coordinating Committee on General Sciences, Office of the 

Assistant Secretary of Defense (Research and Development, 1954), p. 4. [Hereinafter cited as Landsberg, 

Geophysics and Warfare.] 12. Fuller, Thor’s Legions, pp. 17–18. 13. Major Scott D. West, USAF, “Warden and the Air 

Corps Tactical School: Déjà vu?,” thesis submitted to 

the faculty of the School of Advanced Airpower Studies, and published by the Air University Press, Maxwell 

Air Force Base, AL, October 1999, p. 23. 14. For a recent biography of Mitchell see James J. Cooke, 

Billy Mitchell (Boulder, CO: Lynne Rienner Publishers, 2002). 15. Jeffrey C. Benton, They Served Here: Thirty-Three 

Maxwell Men (Montgomery, AL: Air University Press, 

1999), pp. 2–3, available on the Internet via the Air 

University home page at http://www.au.af.mil/au/

aul/aupress/Books/Benton/Benton.pdf as of 30 June 

2003. 16. Markus, et al., Air Weather Service, p. 4. 17. Fuller, Thor’s Legions, p. 20. 18. For details on Appleton’s work, see his 12 December 

1947 lecture on the ionosphere on the occasion of 

winning the 1947 Nobel Prize for Physics, available 

on the Internet at http://www.nobel.se/physics/laureates/1947/appleton-lecture.pdf as of 30 May 2003. 

For short biographies of Appleton and Kennelly visit 

the IEEE History Center at http://www.ieee.org/organizations/history_center/legacies/Appleton.html and 

http://www. ieee.org/organizations/history_center/

legacies/kennelly.html, respectively. A short biography 

of Heaviside can be found on the Internet at http://

www-history.mcs.st-and.ac.uk/history/Mathematicians/Heaviside.html. 19. Landsberg, Geophysics and Warfare, pp. 4–5. 20. Landsberg, Geophysics and Warfare, pp. 4, 18; J. M 

Stagg, Forecast For Overlord: June 6, 1944 (London: 

Ian Allan Ltd., 1971), p. 5. This source offers a complete 

account of the meteorology personnel and skills that 

supported General Dwight D. Eisenhower’s decision to 

postpone the invasion from 5 June to the next day, and 

“Why then did the weathermen not foresee the rough 

conditions on the following days and advise General 

Eisenhower accordingly?” Fuller, Thor’s Legions, pp. 

245

Notes and References, Pages 93–120
35–212 covers meteorological support during World 

War II on the home front, Europe (including North 

Africa, the Italian campaign, the strategic bombing 

effort, and D-Day), the Pacific, and the China, Burma, 

India theater in some detail. 21. Michael J. Carlowicz and Ramon E. Lopez, Storms 

From The Sun: The Emerging Science of Space Weather (Washington DC: The Joseph Henry Press, 2002), 

pp. 114–115. 22. Anonymous, “Boeing B–17 ‘Flying Fortress,’” available 

on the Internet at http://www.wpafb.af.mil/museum/

air_power/ap16.htm as of 27 June 03; “Anonymous, 

“Boeing B–29 ‘Superfortress,’” available on the Internet 

at http://www.afmuseum.com/ aircraft/b29.html as of 

27 June 03. 23. Landsberg, Geophysics and Warfare, pp. 9, 11. For 

more on Atmospheric Electricity see C. F. Campen, 

Jr., et al. (eds.), Handbook of Geophysics for Air Force 

Designers (Hanscom AFB, MA: Air Force Cambridge 

Research Center, 1957), pp. 9-1 to 9-35. 24. Anonymous, “B–36 Fleet Destroyed by Tornado,” 

updated 14 June 2003, available on the Internet at 

http://www.cowtown.net/proweb/tornado/tornado.

htm as of 2 July 2003. 25. Landsberg, Geophysics and Warfare, pp. 8–13. 26. This equated to being a “5-star general,” a rank awarded 

to only four other American Army leaders during the 

War: Generals George C. Marshall, Dwight D. Eisenhower, Douglas A. MacArthur, and Omar N. Bradley. 

According to a brief biography of him at the Arlington 

National Cemetery web site (at http://www.arlingtoncemetery.net/ hharnold.htm) Arnold retired in 1946, 

but “was honored in 1949 by the rank of General of 

the Air Force,” making him “the first (and only) officer 

to attain five-star rank in both the United States Army 

and United States Air Force.” According to a U.S. Navy 

web page (http://www.history.navy.mil/faqs/faq36-

1.htm) the U.S. Navy named three Fleet Admirals, or 

“5-star admirals,” during the War: Admirals William D. 

Leahy, Chester W. Nimitz, and Ernest J. King. Admiral 

William F. Halsey, Jr., became Admiral of the Fleet in 

December 1945. 27. Vannevar Bush, Endless Horizons (reprint, NY: Arno 

Press, 1975) p. iii. For a biography of Vannevar Bush 

(11 March 1890–30 June 1974) see G. Pascal Zachary, Endless Frontier: Vannevar Bush, Engineer of 

the American Century (NY: Free Press, 1997). Many 

credit Bush with establishing the research teaming 

of the military and academia that ultimately created 

ARPANET, the precursor to today’s Internet. He is 

also renowned for his visionary article “As We May 

Think” in the July 1945 issue of Atlantic Monthly, in 

which “Bush described a futuristic machine called the 

‘memex’ that promised to ‘give man access to and command the inherited knowledge of the ages.’ He imagined the memex as a work desk with viewing screens, 

a keyboard and sets of buttons and levers. Printed and 

written material, even personal notes, would be stored 

on microfilm, retrieved rapidly and display on screen by 

a high-speed ‘selector.’” (Zachary, Endless Frontier, pp. 

261–262.) 28. David N. Spire, Beyond Horizons: A Half Century 

of Air Force Space Leadership (Washington, DC: Air 

Force Space Command in Association with Air University Press and available from the U.S. Government 

Printing Office, 1998) p. 11. For a narrative of the work 

of two Air Force science and technology visionaries 

see Dik Daso (Major, USAF), Architects of American 

Air Supremacy: General Hap Arnold and Dr. Theodore von Kármán (Maxwell Air Force Base, AL: Air 

University Press, 1997). General Arnold supported 

Dr. von Kármán’s work on the seminal studies on the 

interrelationships between dominant air power and 

science and technology, Where We Stand: First Report 

to General of the Army H. H. Arnold on Long Range 

Research Problems of the Air Forces with a Review of 

German Plans and Developments (22 August 1945) 

and Toward New Horizons (15 December 1945). The 

first volume of this multivolume publication predicted 

simply and directly the high-technology skills of the 

future United States Air Force: Science: The Key to 

Air Supremacy. On 15 December 1995, the 50th anniversary of the release of Toward New Horizons, the Air 

Force Scientific Advisory Board released a vision for a 

potential future for the service, New World Vistas: Air 

and Space Power for the 21st Century, a multivolume 

work about the Air Force, technology, and ideas and 

their roles in providing for the nation’s defense. 29. The designation of the Air Force research and development unit at Hanscom AFB changed many times over 

the years: Cambridge Field Station (1945–1949); Air 

Force Cambridge Research Laboratories (1949–1951); 

Air Force Cambridge Research Center (1951–1960); 

Air Force Cambridge Research Laboratories (1960–

1976); Air Force Geophysics Laboratory (1976–1989); 

Geophysics Laboratory (Air Force Systems Command) 

(1989–1990); Geophysics Directorate, Air Force Phillips Laboratory (1990–1997); and Battlespace Environment Division, Space Vehicles Directorate, Air 

Force Research Laboratory (1997–present). For consistency in this paper, references to events between 1945 

and 1975 will be listed as AFCRL; between 1976 and 

The Limitless Sky

246
1990 as the Geophysics Laboratory; between 1990 and 

1997 as the Geophysics Directorate; and since 1998 to 

the Battlespace Environment Division. 30. Dr. Ruth P. Liebowitz, “The Air Force’s Geophysics 

Directorate: A 50th Anniversary Retrospective,” Eos, 

Transactions, American Geophysical Union, (Vol. 76, 

No. 38), September 19, 1995, pp. 371, 381–382. 

[Hereinafter cited as Liebowitz, “50th Anniversary.”] 

Anonymous, “Alfred Lee Loomis, the legend, ultrasonics 

and the radar,” available on the Internet at http://www.

ob-ultrasound.net/loomis.html as of 13 July 2003. 

Also see Jennet Conant, Tuxedo Park: A Wall Street 

Tycoon and the Secret Palace of Science That changed 

the Course of World War II (NY: Simon and Schuster, 

2002) for an interesting look at one of America’s more 

unusual laboratories, “hidden in a massive stone castle,” 

where scientists such as Albert Einstein, James Frank, 

Niels Bohr, and Enrico Fermi could meet. 31. RAND Corporation, Preliminary Design of An Experimental World-Circling Spaceship, Special Anniversary 

Edition, (Santa Monica, CA: Rand, 1998), inside cover. 

[Hereinafter cited as RAND, Preliminary Design.] 32. RAND, Preliminary Design, pp. ii, viii, 2. 33. RAND, Preliminary Design, p. 1. 34. William R. Corliss, NASA Sounding Rockets, 1958–

1968; A Historical Summary (Washington, DC: Scientific and Technical Information Office, NASA, for 

sale by the U.S. Government Printing Office, 1971), p. 

11–12, also available on the Internet at http://history.

nasa.gov/SP–4401/sp4401.htm as of 7 July 2003. This 

source notes that 300 boxcars full of V–2 parts notwithstanding, “at best only two complete V–2s could 

be assembled from the original components. Gyros 

were in especially short supply and 140 more had to be 

built by American industry.” In addition, “many repairs 

were required” for the parts confiscated in Germany, 

“and industry had to turn to and manufacture a great 

variety of missing pieces.” This was especially true for 

the “entirely new scientific ‘warheads’” used on the V–2’s 

at WSPG (p. 13). [Hereinafter cited as Corliss, NASA 

Sounding Rockets.] 35. For a comprehensive overview to the space race see 

Walter A. McDougall, The Heavens and The Earth: A 

Political History of the Space Age (NY: Basic Books, 

1985). For a description of the V–2 see Gregory P. 

Kennedy, Vengeance Weapon 2: The V–2 Guided 

Missile, (Washington DC: Smithsonian Institution 

Press for the National Air and Space Museum, 1983) 

and Michael J. Neufeld, The Rocket and the Reich: 

Peenemünde and the coming of the Ballistic Missile Era 

(NY: Free Press, 1995). For a look at the competition 

between the U.S. and Russia for Nazi Germany’s rocket 

scientists see two widely diverse works: Dieter K. 

Huzel, Peenemünde to Canaveral (Englewood Cliffs, 

NJ: Prentice-Hall, Inc., 1962, a memoir of working on 

V–2s in Nazi Germany and escape to American lines 

and relocation to the U.S. and Linda Hunt, Secret 

Agenda: The United States Government, Nazi Scientists, and Project Paperclip, 1945 to 1990 NY: St. 

Martin’s Press, 1991), an account by a former Cable 

News Network investigative reporter. 36. Corliss, NASA Sounding Rockets, p. 13. 37. A. McIntyre, Summary of AFCRL Rocket and Satellite Experiments (1946–1966) (Hanscom AFB, MA: 

Headquarters Air Force Cambridge Research Laboratories Office of Aerospace Research, AFCRL 66–868, 

Special Reports, No. 54, December 1966), p. 4; Corliss, 

NASA Sounding Rockets, p. 15. 38. McIntyre, Summary of AFCRL, pp. 4–7, Corliss, 

NASA Sounding Rockets, pp. 13, 15. McIntyre lists a 

total of 67 V–2 launches with entries for 14 AFCRL 

V–2 launches while Dr. Ruth P. Liebowitz, “Contributions to Space Science and Technology By the Geophysics Directorate, Phillips Laboratory and its Predecessor Organizations,” Hanscom AFB, 1992, p.1, in the 

Phillips Research Site Historical Information Office 

archives, cites a total of 13 AFCRL V–2 launches. 

[Hereinafter cited as Liebowitz, “Contributions.”] 39. Liebowitz, “Contributions,” p. 1; Interview, Dr. Barron 

K. Oder, Air Force Research Laboratory Space Vehicles 

Directorate Historical Information Office with Dr. 

William Denig, Air Force Research Laboratory Space 

Vehicles Directorate Space Weather Center of Excellence, 20 June 2003. 40. Corliss, NASA Sounding Rockets, p. 15. Note that 

this source and McIntyre show different dates for the 

end of V–2 tests; the former indicates on p. 13, “the 

final V–2 flight on 28 June 1951,” while the latter, p. 

7, shows an AFCRL V–2 experiment at WSPG on 22 

August 1952. A V–2 chronology, located on the Internet at http://www.astro nautix.com/lvs/v2.htm as of 

7 July 2003 shows its last entry for a V–2 flight on 19 

September 1952. Also see Willy Ley, Rockets, Missiles, 

and Space Travel, revised and enlarged edition (NY: 

The Viking Press, 1959), pp. 458–459 for another list 

of V–2 launches. This list, based on General Electric’s 

Project Hermes Final Report, shows a total of 67 V–2 

firings in all configurations, with the last coming on 28 

June 1951. 41. Lewis Zarem, New Dimensions of Flight, (NY: E.P. 

Dutton & Co., Inc, 1959), pp. 151–152. According to 

Eugene M. Emme, Aeronautics and Astronautics: An 

247

Notes and References, Pages 120–126
American Chronology of Science and Technology in 

the Exploration of Space 1915–1960 (Washington: 

NASA, 1961) p. 70, on 26 July 1952, an “Aerobee 

fired capsule containing two monkeys and two mice 

to approximately 200,000 feet at Holloman AFB, all 

recovered unharmed.” This followed what Haley, Rocketry and Space Exploration, p. 242, called an “historic 

flight” on 20 September 1951. Emme, Aeronautics and 

Astronautics, p. 68 notes on that day “USAF made 

first successful recovery of animals from a rocket flight 

when an instrumented monkey and 11 mice survived 

an Aerobee flight to an altitude of 236,000 feet from 

Holloman AFB.” 42. McIntye, Summary of AFCRL, pp. 5–6; James Van 

Allen, John W. Townsend, Jr., and Eleanor C. Pressly, 

“The Aerobee Rocket,” in Homer E. Newell, Jr., ed., 

Sounding Rockets (NY: McGraw-Hill, 1959), pp. 

54–70; see especially the Aerobee specifications and 

sketch on pp. 60–63 and the table summarizing Aerobee firings through 1956 on pp. 64–69. Also see pp. 

71–95 for a description of the Aerobee-Hi rocket, and 

pp. 96–104 and 190–219 for more on the Nike-Deacon and Nike-Cajun rockets. 43. Andrew G. Haley, Rocketry and Space Exploration: 

The International Story (Princeton, NJ: D. Van Nostrand Company, Inc., 1958) p. 121. For a good background study of how rockets such as the V–2, Aerobee, 

and others became the instruments of choice for military researchers interested in the upper atmosphere and 

ionosphere, see David H. DeVorkin, Science With A 

Vengeance: How the Military Created the US Space 

Sciences After World War II (NY: Springer-Verlag, 

1992). 44. McIntyre, Summary of AFCRL, pp. 5–12; Corliss, 

NASA Sounding Rockets, pp. 18–21. 45. Liebowitz, “Contributions,” p. 1. 46. Captain Robert C. Truax, U.S. Navy, “The Use of 

Sounding Rockets for Military Research,” in Newell, 

ed., Sounding Rockets, pp. 45–53. 47. Tina D. Thompson, ed., Space Log 1996 (Redondo 

Beach, CA: TRW Space & Electronics Group, 1997), 

p. 65. For the impact of Sputnik on Americans see Paul 

Dickson, Sputnik: The Shock of the Century (NY: 

Walter & Co., 2001), which weaves personnel recollections of the launch from average individuals into the 

history of the first years of the space race. Anonymous, 

“Explorer-I and Jupiter-C: The First United States 

Satellite and Space Launch Vehicle,” available on the 

Internet at http://history.nasa.gov/ sputnik/expinfo.

html as of 9 July 2003. James R. Killian, Jr., Sputnik, 

Scientists, and Eisenhower: A Memoir of the First Special Assistant to the President for Science and Technology (Cambridge, MA: The MIT Press, 1977) provides 

an “insider’s” look at the American response to Sputnik 

and some of the options facing the nation. 48. Anonymous, “International GeoPhysical Year (IGY),” 

updated on 11 August 1999, available on the Internet 

at http://www.hq.nasa.gov/office/pao/History/sputnik/igy.html as of 9 July 2003. 49. Anonymous, “International Geophysical Year,” available 

on the Internet at http:// www.infoplease.com/ce6/

sci/A0825345.html as of 9 July 2003. Many books 

on IGY have appeared over the years, including two 

references at this site: Sydney Chapman, IGY: Year of 

Discovery; the story of the International Geophysical 

Year (Ann Arbor, MI: University of Michigan Press, 

1959), and Walter Sullivan, Assault on the Unknown; 

the International Geophysical Year (NY: McGrawHill, 1961). See also Arthur C. Clarke, The Making of 

a Moon, the Story of the Earth Satellite Program (NY: 

Harper, 1958) for a contemporaneous look at both the 

IGY and the first man-made satellites. 50. Walter A. McDougall, The Heavens and the Earth (NY: 

Basic Books, 1985), p. 168. This page also recounts a 

central irony of the early space race: the Army and Navy 

were in serious competition with each other as much as 

the Soviet Union for the prestige associated with the 

first space flight. An added irony came later, when the 

Air Force became the service most closely associated 

with space technologies and breakthroughs. 51. Emme, Aeronautics and Astronautics, p. 98, also contains quote from Van Allen. 52. Dr. James L. Green, “The Magnetosphere,” n.d., available on the Internet at http:// ssdoo.gsfc.nasa.gov/

education/lectures/magnetosphere.html as of 12 July 

2003. 53. Dr. David P. Stern and Dr. Mauricio Peredo, “Some 

Dates in the Exploration of the Magnetosphere,” updated 25 November 2001, available on the Internet at 

http://www-spof.gsfc.nasa.gov/Education/whchron.

html as of 12 July 2003. 54. Dr. David P. Stern and Dr. Mauricio Peredo, “#12a. The 

Inner Radiation Belt,” updated 25 November 2001, 

available on the Internet at http:// www-spof.gsfc.nasa.

gov/ Education/winbelt.html as of 12 July 2003; Dr. 

David P. Stern and Dr. Mauricio Peredo, “#12b. The 

Outer Radiation Belt,” updated 25 November 2001, 

available on the Internet at http:// www-spof.gsfc.nasa.

gov/ Education/woutbelt.html as of 12 July 2003. 55. William E. Burrows, This New Ocean: The Story of 

the First Space Age (NY: Modern Library, 1998) pp. 

211–212 [Hereinafter cited as Burrows, New Ocean]; 

The Limitless Sky

248
Michael J. Carlowicz and Ramon E. Lopez, Storms 

From The Sun: The Emerging Science of Space Weather (Washington DC: The Joseph Henry Press, 2002), 

pp. 66–71. [Hereinafter cited as Carlowicz and Lopez, 

Storms.] David P. Stern, “A Brief History of Magnetospheric Physics During the Space Age,” last updated on 

25 November 2001, available on the Internet at http://

www-spof.gsfc.nasa.gov/Education/bh2_1.html. Note 

that this is an electronic of the original article that 

appeared in Reviews of Geophysics, 34 (1996) pp. 

1–31. 56. Burrows, New Ocean, p. 212, which also notes that Van 

Allen “would be awarded the Crafoord Prize, comparable to the Nobel Prize, by the Royal Swedish Academy 

of Sciences in 1989.” 57. Philip Taubman, Secret Empire: Eisenhower, The CIA, 

and the Hidden Story of America’s Space Espionage 

(NY: Simon and Schuster, 2003) pp. 3–34 provides a 

good overview to President Eisenhower’s conundrum 

about authorizing spy flights and the need to know 

what “the other side” was up to in terms of military 

readiness and basing. 58. Spires, Beyond Horizons, pp. 51–53; Burrows, New 

Ocean, pp. 166–170 provides some of the behind-thescenes planning by U.S. advisors and lawyers prior to 

the launch of any satellite as a means of establishing 

America’s right to fly reconnaissance satellites for intelligence purposes. 59. Killian, Sputnik, Scientists, and Eisenhower, pp. 119–

144 provides an inside look at how President Eisenhower and his advisors shaped the creation and mission 

of NASA, and the Department of Defense’s position 

that it must be able to maintain “the latitude to pursue 

those things that are clearly associated with defense 

objectives.” (p. 136). 60. According to T. M. Pearce (ed.) New Mexico Place 

Names: A Geographical Dictionary (Albuquerque: 

University of New Mexico Press, 1990), p. 161, Sunspot is 18 miles south of Cloudcroft, and was so named 

because of the observatory’s mission “to predict suninduced disturbances in earth’s atmosphere and in outer 

space.” 61. Liebowitz, “50th Anniversary,” p. 381. 62. Dr. Ruth P. Liebowitz, “Air Force Geophysics 1945–

1995: Contributions to Defense and to the Nation,” 

April 1996, pp. 39–40, copy in the archives of the 

Phillips Research Site Historical Information Office, 

Kirtland AFB, NM. [Hereinafter cited as Liebowitz, 

“Air Force Geophysics.”] 63. Dr. David H. Hathaway, “Solar Flares,” 6 January 03, 

available on the Internet at http:// science.msfc.nasa.

gov/ssl/pad/solar/flares.htm as of 14 July 2003. 64. Anonymous, “Solar flares produce quakes deep inside 

the sun,” 27 May 1998, available on the Internet at 

http://www.cnn.com/TECH/space/9805/27/sun.

quakes as of 14 July 2003. 65. Anonymous, “Thanksgiving Solar Flares Trigger Large 

Weekend Space Storm,” 25 November 2000, available 

on the Internet at http://www.space.com/spacewatch/

space_ weather_001125.html as of 14 July 2003. 66. Dr. Donald Neidig, “New Optical System Automatically Monitors Solar Activity,” in AFRL Technology 

Horizons, June 2001, pp. 29–30, also available on 

the Internet at http://www.afrlhorizons.com/ Briefs/

June01/VS0009.html as of 14 July 2003. 67. Liebowitz, “Air Force Geophysics 1945–1995,”

p. 37. 68. Liebowitz, “Air Force Geophysics,” pp. 41, 48; Liebowitz, “Contributions,” p. 5. 69. Liebowitz, “Contributions,” p. 5. 70. McDougall, The Heavens and the Earth, pp. 344–360, 

in a chapter cal “Benign Hypocrisy: American Space 

Diplomacy” provides a good overview to the evolution 

of U.S. military and civilian paths in space science; 

quotes from sidebar on p. 353. Spires, Beyond Horizons, pp. 53–80 provides another look at the development of military and civilian roles in space. 71. Spires, Beyond Horizons, pp. 86–112. 72. James M. Grimwood, Project Mercury: A Chronology, NASA Special Publication 4001, available on the 

Internet at http://history.nasa.gov/SP-4001/contents.

htm as of 11 July 03. This source also indicates that on 

7 September “The results of a joint study by the Atomic 

Energy Commission, the Department of Defense, and 

NASA concerning the possible harmful effects of the 

artificial radiation belt created by Operation Dominic 

on Project Mercury’s flight MA–8 were announced. 

The study predicted that radiation on outside of capsule during astronaut Walter M. Schirra’s six-orbit 

flight would be about 500 roentgens but that shielding, 

vehicle structures, and flight suit would reduce this dosage down to about 8 roentgens on the astronaut’s skin. 

This exposure, well below the tolerance limits previously established, would not necessitate any change of 

plans for the MA–8 flight.” The July nuclear test was 

Operation Dominic. 73. Anonymous, “40 Years of Telstar,” n.d., available on the 

Internet at http://www. lucent.com/minds/telstar/fit.

html as of 11 July 2003. 74. McDougall, Heavens and the Earth, p. 358. 75. Anonymous, “The Air Force Weapons Laboratory’s 

Measurements of the Space Environment,” n.d., in the 

249

Notes and References, Pages 126–137
archives of the Air Force Research Laboratory Phillips 

Research Site Historical Information Office, 11 July 

2003. 76. Dr. Ruth P. Liebowitz, Chronology: From the Cambridge Field Station to the Air Force Geophysics 

Laboratory, 1945–1985 (Hanscom AFB: Air Force 

Geophysics Laboratory, 1985), p. 66. 77. Liebowitz, “50th Anniversary,” p. 371. 78. Thomas D. Damon, Introduction to Space: The Science of Spaceflight, 2nd ed., (Malabar, FL: Krieger 

Publishing Company, 1995), p. 60. 79. Carlowicz and Lopez, Storms, p. 75. 80. Carlowicz and Lopez, Storms, pp. 129–130; and Chris 

Tschan (USAF, Ret), as quoted on p. 131. 81. John W. Freeman, Storms in Space (Cambridge, UK: 

Cambridge University Press, 2001), pp. 14–15. [Hereinafter cited as Freeman, Storms.] 82. Jurgen Buchau, et al., “The Digital Ionospheric Sounding System Network of the US Air Force Air Weather 

Service,” presented at XXIIVth General Assembly of 

the International Union of Radio Science, Kyoto, Japan, 

25 August – 2 September 1993, available on the Internet at http://www.ips.gov.au/IPSHosted/INAG/uag104/index.html as of 14 July 2003. 83. Interview, Oder with Dr. Denig, 20 June 2003. 84. Interview Oder with Dr. Denig, 20 June 2003; Marcio 

H. O. Aquino, et al., “GPS Based Ionospheric Scintillation Monitoring,” available on the Internet at http:// 

www.estec.esa.nl/wmwww/wma/spweather/workshops/SPW_W3/PROCEEDINGS_W3/Aquino.

pdf as of 14 July 2003. 85. Freeman, Storms, pp. 61–62. 86. Freeman, Storms, pp. 63–64. See also J. Freeman, et 

al., “The Magnetospheric Specification and Forecast 

Model,” available on the Internet at http://hydra.rice.

edu/ ~freeman/ding/www/ msfm95/msfm.html as 

of 15 July 2003 provides a thorough background and 

description of the forecasting system, as well as details 

on many aspects of the model. 87. Anonymous, “Point Paper: The Geophysics Directorate,” Solar News, July 1994, available on the Internet at 

http://gong.nso.edu/SolarNews/07_94.html as of 12 

July 2003. 88. Interview, Oder with Dr. Denig, 20 June 2003. 89. Carlowicz and Lopez, Storms from the Sun, p. x. 90. Anonymous, “Solar Wind Interplanatary [sic] Measurements (SWIM) Help Forecast Space Weather,” 

in Phillips Laboratory Success Stories 1995 (Kirtland 

AFB, NM: Phillips Laboratory, 1996), p. 71; Air Force 

Research Laboratory Space Vehicles Directorate Fact 

Sheet, “Solar Wind Interplanetary Measurements,” current as of January 1998, available on the Internet at 

http://www.vs.afrl.af.mil/Factsheets/swim.html as of 

13 July 2003. 91. Anonymous, “Mitigation of Spacecraft Charging,” in 

Phillips Laboratory Success Stories 1995 (Kirtland 

AFB, NM: Phillips Laboratory, 1996), p. 33; Dr. Keith 

E. Holbert, “Spacecraft Charging,” updated 20 February 2003, available on the Internet at http://www.eas.

asu.edu/~holbert/eee460/spc-chrg.html as of 13 July 

2003. This last reference provides a link to an informative spacecraft charging flash animation. 92. Alice B. McGinty (ed.), “Air Force Geophysics Laboratory Report on Research For the Period January 1979–

December 1980,” April 1982, AFGL–TR–82–0132, 

pp. 101–102; Mark Wade, “SCATHA,” updated on 

26 June 2002, available on the Internet at http://www.

astronautix.com/craft/scatha.htm as of 13 July 2003. 

Also see data on SCATHA’s payload at the Jet Propulsion Laboratory Mission and Spacecraft Library at 

http://msl.jpl.nasa.gov/QuickLooks/scathaQL.html 

available at of 13 July 2003. Alice B. McGinty (ed.), 

“Air Force Geophysics Laboratory Report on Research 

For the Period January 1981–December 1982,” August 

1983, AFGL–TR–83–0198, p. 83 93. Charles C. Mann, “The End of Moore’s Law?”, n.d., 

available on the Internet at http://www.uow.edu.

au/~hasan/buss951/The_future_of_Moores_Law.

pdf as of 15 July 2003. 94. Liebowitz, “Air Force Geophysics,” p. 33; M. H. Johnson 

and John Kierein Ball, “Combined Release and Radiation 

Effects Satellite (CRRES): Spacecraft and Mission,” available on the Internet at http://tide1.space.swri.edu/CRRESpaper.html as of 15 July 2003. For the full story on SPACERAD and CRRES see Ruth P. Liebowitz, “A History 

of the Space Radiation Effects (SPACERAD) Program 

for the Joint USAF/NASA CREES Mission, Part I: 

From the Origins Through the Launch, 1981–1990,” 

16 March 1992, Phillips Laboratory Technical Report 

PL–TR–92–2071, Special Reports, No. 269. 95. Anonymous, “Mitigation of Spacecraft Charging,” in 

Phillips Laboratory Success Stories 1995 (Kirtland 

AFB, NM: Phillips Laboratory, 1996), p. 33. 96. U.S. Air Force Fact Sheet, “Scintillation Network Decision Aid,” current as of June 2002, available on the Internet 

at http://www.vs.afrl.af.mil/Factsheets/scinda.html as of 

14 July 2003. 97. U.S. Air Force Fact Sheet, “Communication/Navigation Outage Forecasting System,” current as of April 

2002, available on the Internet at http://www.vs.afrl.

af.mil/ Factsheets/cnofs.html as of 14 July 2003. 98. Carlowicz and Lopez, Storms from the Sun, pp. 13–16.

The Limitless Sky

250
99. Air Force Research Laboratory Space Vehicles Directorate Fact Sheet, “Solar Mass Ejection Imager,” current as of November 2002, available on the Internet 

at http://www. vs.afrl.af.mil/Factsheets/SMEI.html 

as of 13 July 2003; Lockheed Martin Corporation 

Press Release, “Titan II Successfully Launches Coriolis 

Mission from Vandenberg Air Force Base,” 6 January 

2003, available on the Internet at http://www.spaceref.

ca/news/ viewpr.html?pid=10319 as of 15 July 2003. 100. E-mail message, Janet C. Johnston, Air Force Research 

Laboratory Space Vehicles Directorate Battlespace 

Environment Division to Barron K. Oder, AFRL Space 

Vehicles Directorate Historical Information Office, 

“RE: History Tasker,” 6 February 2003.

101. Anonymous, “Timeline of the Twentieth Century: 

1900–1909, n.d., available on the Internet at http://

history1900s.about.com/library/time/bltime1900.

htm; Tim Dirks, “The Great Train Robbery,” available on the Internet at http://www.filmsite.org/grea.

html; Anonymous, “Harley-Davidson Motorcycles: 

The American Legend,” n.d., available on the Internet 

at http://www.carpartsplaza.com/harley_story/htm; 

Anonymous, “From a Dream to a Legacy,” n.d., available on the Internet at http://www.spartanburghog.

com/ hdhistory html; and Anonymous, “Ford Motor 

Company history timeline,” n.d., available on the 

Internet at http://wwwautomuseum.com/forddate.

html, all available as of 14 July 2003. 102. Air Force Space and Missile Systems Center Fact 

Sheet, “Defense Meteorological Satellite Program, “ 

current as of June 2003, available on the Internet at 

http://www. losangeles.af.mil/SMC/PA/Fact_Sheets/

dmsp_fs.htm as of 15 July 2003; Anonymous, “DMSP 

transferring control of satellites to NOAA,” 15 July 

1998, available on the Internet at http://www.af.mil/

revised/n19980715_981032.txt as of 23 May 2003; 

Neal Peck, “Historical S&T,” n.d. [Dec 99], in the 

archives of the Phillips Research Site Historical Information Office as of 15 July 2003. For an in-depth look 

at the Air Force Geophysics Laboratory’s role in DMSP 

see Dr. Ruth P. Liebowitz, “Historical Brief: AFGL 

Support to the Defense Meteorological Satellite Program, 1971–1988,” August 1988, in the archives of the 

Phillips Research Site Historical Information Office as 

of 15 July 2003.

Bibliography: Military Satellite Communications

Armacost, Michael H. The Politics of Weapons Innovation: The Thor-Jupiter Controversy. New York: 

Columbia University Press, 1969.

Beard, Edmund. Developing the ICBM: A Study in 

Bureaucratic Politics. New York: Columbia University Press, 1976.

Chapman, John L. Atlas: The Story of a Missile. New 

York: Harper & Brothers, 1960.

Dyson, George. Project Orion: The True Story of the 

Atomic Spaceship. New York: Henry Holt, 2002.

Hallion, Richard P., ed. The Hypersonic Revolution: 

Case Studies in the History of Hypersonic Flight. 

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Footnotes: Directed Energy

1. Greg Caires, “Fogleman: Energy Weapons Will Be 

Centerpiece Of Future AF,” Defense Daily, July 23, 

1998, p. 3. 2. Interview, Robert W. Duffner with Dr. Petras Avizonis, 

December 15, 1988; Interview, Duffner with Major 

General Donald L. Lamberson, January 12 1989.

251

Notes and References, Pages 137–215
3. Interview, Duffner with Dr. Hans Mark (former Secretary of the Air Force), September 29, 1992. 4. T.H. Maiman, “Stimulated Optical Radiation in 

Ruby,” Nature, August 6, 1960, pp. 493–494; John A. 

Osmundsen, “Light Amplification Claimed by Scientist,” New York Times, July 8, 1960, pp. 1, 7. 5. Arthur L. Schawlow, “Lasers: The Practical and the 

Possible,” The Stanford Magazine, Spring/Summer, 

1979, pp.24–29. 6. Interview, Duffner with Lamberson, January 12, 1989; 

Jeff Hetch, Beam Weapons: The Next Arms Race, New 

York: Plenum Press, 1984, pp. 1–13. 7. Rpt, “Laser Research and Applications,” prepared at 

the request of the Honorable Howard W. Cannon, 

Chairman, Committee on Commerce, Science, and 

Transportation, U.S. Senate, Washington, D.C., U.S. 

Government Printing Office, 1980; Rpt, Colonel John 

C. Scholtz, Jr., “The Air Force High-Energy Laser Program,” Air War College Professional Study No. 4229, 

November 1970, pp. 1–6. 8. Interview, Duffner with Demos T. Kyrazis, (Director of 

ALL), August 8, 1985; Phillip J. Klass, “Special Report: 

Laser Weapons,” Aviation Week & Space Technology, 

August 18, 1975, pp. 34–39. 9. Statement by Hans Mark, Secretary of the Air Force, 

Before the Subcommittee on Science, Technology, and 

Space, Albuquerque, New Mexico, January 12, 1980; 

Rpt, U.S. Senate, “Laser Research and Applications,” 

1980. 10. Ibid. 11. Interview, Duffner with Kyrazis, 8 August 1985; Interview, Duffner with Russ Parsons (Colonel, USAF, 

Retired), December 15, 1988; Anthony Ripley, “Laser 

is Stirring Imagination of Weapon Scientists,” New 

York Times, October 16, 1971, p. 15. 12. George Heilmeir, “Contributions to Science and Technology by the Advanced Research Projects Agency 

(ARPA) 1957–1970,” Commanders Digest, October 7, 

1976; Interview, Duffner with David R. Jones (former 

AFWL Commander), September 19, 1988. 13. Interview, Duffner with Jones, September 19, 1988; 

Ltr, J.P. Ruina, Director ARPA, to Commander, Office 

of Aerospace Research, “ARPA Order 313–62,” February 26, 1962. 14. Interview, Duffner with Lamberson, January 12, 1989; 

Rpt, RTD-TDR-63–3070, Marvin C. Atkins et al. 

“AFWL Progress on PROJECT SEASIDE as of July 

20, 1963,” November 1963, pp. iii, 1, 41–44. 15. Interview, Duffner with Lamberson, January 12, 1989; 

C. Kumar N. Patel, “Selective Excitation Through 

Vibrational Energy Transfer and Optical Laser Action 

in N2-CO2,” Physical Review Letters, Vol 13, 1964, pp. 

617–619. 16. Paper, Air Force Weapons Laboratory, “A Thumbnail 

Sketch of the US HEL Weapons Program,” n.d., p. 1; 

Rpt, WLREL–69–025, “Advanced Development Program: High-Energy Laser Program, Program 644A–

Task II,” February 24, 1969, pp. A1–A3. 17. Letter Contract, F29601–69–C–0058, Air Force Special Weapons Center with Hughes Aircraft Company for “Optics For High Power Systems,” February 

3, 1969; Rpt, AFWL, Colonel David R. Jones, “The 

Air Force Weapons Laboratory Management Plan: 

EIGHTH CARD Program,” February 13, 1969, p. 5. 18. Interview, Duffner with Kyrazis, June 20, 1985. 19. Rpt, ARTO–73–1, Lamberson, “Program Management Plan: Advanced Radiation Technology Office,” 

June 1973, pp. 2–3; Briefing Chart, AFWL/ARTO, 

“TSL Milestones,” September 7, 1972. 20. Ltr, Colonel Allison, Chief, Office of Security Review, 

Office of Public Affairs, HQ USAF, to AFSC/PAS, 

“Fact Sheet and Film — DELTA,” August 29, 1980. 21. Interview, Duffner with Lamberson, January 12, 1989; 

Rpt, AFWL–TR–86–01, Vol I, Raymond V. Wick, 

“Airborne Laser Laboratory Cycle III: Systems and 

Test Descriptions,” May 1988, p. v. 22. Briefing, Lamberson, “Milestone Review of Cycle II,” 

June 8,1976 23. Rpt, AFWL, “Airborne Laser Laboratory Cycle III Test 

Plan (Executive),” October 31, 1977, pp. 3–5, 93–94; 

John C. Rich, “Air Force Overview,” in Proceedings of 

the Third DoD High-Energy Laser Conference, July 

1979, pp. 47, 52–53; John W. Dettmer and Demos T. 

Kyrazis, “Overview of the Airborne Laser Program,” 

in Proceedings of the Third DoD High-Energy Laser 

Conference, July 1979, pp. 379–396. 24. Interview, Duffner with Colonel John Otten (former 

Test Director ALL), May 26, 1994; Interview, Duffner 

with Colonel Jerry Janicke (former Chief, AFWL’s Laser 

Development Division), October 4, 1988; Ltr, Major 

General Jasper A. Welch, Jr., Asst DCS/Research, 

Development and Acquisition, HQ USAF, to AF/CC 

et al., “Item of Interest,” May 26, 1983. 25. Interview, Duffner with Lieutenant Colonel Denny 

Boesen (former Test Director for ALL), August 12, 

1994; Interview, Duffner with Lieutenant Colonel 

Steve Coulombe, February 6, 1995; Interview, Duffner with General Robert T. Marsh (former Air Force 

Systems Command Commander), August 13, 1990; 

Rpt, AFWL–TR–86–01, p. 94; USAF News Release 

(AFSC #83–130), November 29,1993; Video, “Airborne Laser Laboratory Laser Flight,” March 1, 1985.

The Limitless Sky

252
26. H. W. Babcock, “The possibility of compensating astronomical seeing,”: Publ. Astron. Soc. Pac., Vol. 65, pp 

229–236, 1953. 27. R. B. Leighton, “Concerning the problem of making 

sharper photographs of the planets,” Scientific American. vol. 194, June 1956, pp 157–166, 28. J. W. Hardy, J. Feinlieb, and J. C. Wyant, “Real-time 

phase correction of optical imaging systems,” Dig. Technical Reports, Topical Meeting on Optical Propagation 

Through Turbulence, sponsored by OSA, Boulder, 

CO, July 1974. 29. A. Buffington, F. S. Crawford, R. A. Muller, and C. D. 

Orth, “First observatory results with an image sharpening system,” J. Opt. Soc. Amer., Vol. 67, 1977. pp. 

304–305. 30. Charles D. Corsetti, Stephen B. Talley, and Charles 

W. Martin, “Design of a digital control system for an 

advanced optical tracker,” Midwest Symposium on Circuits and Systems, June 1981. 31. John W. Hardy, “Adaptive Optics,” Scientific American, 

June 1994, pp 60–65. 32. R. Q. Fugate, et al, “Two generations of laser-guide-star 

adaptive-optics experiments at the Starfire Optical 

Range,” JOSA, Vol. 11, No. 1, 1994, pp. 310–324. 33. Robert R. Beland, “Propagation through Atmospheric 

Optical Turbulence,” The Infrared & Electro-Optical 

Systems Handbook, Vol. 2, Chapter 2, SPIE Press, 

Bellingham WA, 1993. 34. Ronald J Hugo, et al, “Acoustic noise-source identification in aircraft-based atmospheric temperature measurements,” AIAA Journal, Vol. 40, No. 7, July 2002. 35. AFRL–DE–TR–2002–1024, Lawrence D. Weaver, et 

al., “ABLSTAR,” 2002. 36. Russell Butts and Lawrence D. Weaver, “ABLEX: High 

Altitude Laser Propagation Experiment,” Proceeding of 

the NASA–UCLA Workshop on Laser Propagation 

in Atmospheric Turbulence, edited by A. V. Balakrishnan and Russell Butts, February 1994. 37. D. C. Washburn, et al, “Airborne Laser Extended 

Atmospheric Characterization Experiment (ABLE 

ACE),” PL–TR–96–1084, 1996. 38. Rpt, AFWL/AR, “Advanced Radiation Technology: 

PE 63605F,” September 1985. 39. Glen P. Perram, Chemical Lasers, Air Force Institute 

of Technology; “What’s a Chemical Laser?” [Online] 

Available: http://www.aae.uiuc.edu/~detweile/chemlase.htm; Rpt, William McDermott, A History of the 

Oxygen Iodine Chemical Laser, n.d., 1979, pp. 5, 7. 40. McDermott, A History, pp. 1–2. 41. Ibid., pp. 2–3; William E. McDermott, “Historical 

Perspective of COIL” in Steven J. Davis and Michael C. 

Heaven, editors, Gas and Chemical Lasers and Intensive Beam Applications III, SPIE Proceedings Volume 

4631, 2002, p.1. 42. McDermott, A History, pp. 3–4; McDermott, “Historical Perspective,” p.2, 5. 43. McDermott, A History, pp. 10–14; McDermott, “Historical Perspective,” p.2, 3. 44. McDermott, A History, pp.17–25; McDermott, “Historical Perspective,” pp.4–5; Interview, Duffner with 

Nicholas Pchelkin, August 24, 1999; Ltr, Edward G. 

Clements, Tech Advisor, Programs and Requirements 

Office, to AFSC/DLZ, subj: Outstanding Technical 

Achievements, January 3, 1978; W. E. McDermott, et 

al., “An electronic transition chemical laser,” Applied 

Physics Letters, April 15, 1978, pp. 469–470. 45. Rpt, AFWL Oxygen-iodine Chemical Laser, n.d.; 

Briefing to AFSC/XTW, Lt Col Hasen, AFWL/

ARDI, “Chemical Oxygen Iodine Lasers (COIL), May 

17, 1989; AFRL/DE Fact Sheet, “Chemical Oxygen 

Iodine Laser, “ January 1998. 46. McDermott, A History, p.25; Interview, Duffner with 

Pchelkin; United States Patent, McDermott et al, 

Continuous Wave Chemically Pumped Atomic Iodine 

Laser (No. 4,267,526), May 12, 1981; United States 

Patent, McDermott et al., Gas Generating System for 

Chemical Lasers (No. 4,246,252), January 20, 1981. 47. McDermott, A History, pp.25–29; McDermott, “Historical Perspective,” pp. 5–6; K.A. Truesdell, C.A. 

Helms, and G.D. Hager, “COIL Development in the 

USA,” AIAA Paper 94–2421 presented at the 25th 

AIAA Plasmadynamics and Lasers Conference, Colorado Springs, CO, June 1994, p.5; Ltr, AFWL/CC to 

AFSC/DL, “COIL Beam Quality Milestone,” July 23, 

1987; AFWL TR–85–43, Vol I, J.O. Berg, et al., “Oxygen Iodine Supersonic Technology,” October 1985, 

pp. 35–40; Ltr, Maj Gerald Hasen, AFWL/ARDA 

to AFWL/AR, “Nomination for AFWL Technical 

Achievement Award,” January 30, 1985. 48. Ltr, Secretary of the Air Force E. C. Aldridge, Jr., to 

General Bernard P. Randolph, AFSC/CC, subj: COIL, 

August 5, 1987. 49. McDermott, “Historical Perspective,” Briefing, Colonel 

John Otten, PL/LI, “Airborne Laser,” April 27, 1992; 

Ltr, PL/SX to SMC/CC. et al., “Airborne Laser Program” October 22, 1992; “Airborne Laser: History” 

[Online]. Available: http://www.airbornelaser.com/

history, July 25, 2003. 50. Air Force Research Laboratory, Air Force Research 

Laboratory Success Stories, 1997/98, “Chemical Oxygen-Iodine Laser Sets World Record for Laser Power 

Delivered Through a Fiber Optic,” p. 14; Major John 

253

Notes and References, Pages 216–233
DelBarga, et al., “Advances in Chemical Oxygen-Iodine 

Laser Technology, “ in AFRL Technology Horizons,” 

December 2001, pp. 22–23; “Application of HighPower Chemical Oxygen-Iodine Laser Technology,” in 

Phillips Laboratory Success Stories, 1995, p. 61. 51. K.A. Truesdell, C.A. Helms, and G.D. Hager, “A History of COIL Development in the USA,” in Proceedings, Tenth International Symposium on Gas Flow and 

Chemical Lasers, SPIE Volume 2502, p. 230. 52. “Airborne Laser: Program Milestones” [Online]. Available: HYPERLINK “http://www.airbornelaser.com/

schedules/milestones.html” http://www.airbornelaser.com/schedules/milestones.html, July 25, 2003; 

“Team ABL Proposes Airborne Laser Weapon System’ 

[Online]. Available: http://www.airbornelaser.com/

news/1996/070996.html, July 28, 2003; “Boeing, Lockheed Martin, Northrop Grumman win Airborne Laser 

Contract” [Online]. Available: HYPERLINK “http://

www.airbornelaser.com/news/1996/111296.html” 

http://www.airbornelaser.com/news/1996/111296.

html, July 28, 2003; “Northrop Grumman Approved 

to Begin Manufacturing First Laser Hardware for 

Airborne Laser System” [Online]. Available: http://

www.airbornelaser.com/news/1997/031097/html, 

July 28, 2003; “‘First Light’ Produced for Airborne 

Laser” [Online]. Available: http://www.airbornelaser.

com/news/1998/061598b.html, July 28, 2003; “Airborne Laser Produces 110 Percent Power” [Online] 

http://www.airbornelaser.com/news/1998/091698.

html, July 28, 2003; “Airborne Laser Team Completes 

Successful Tests of High-Power Laser, Prepares to 

Deliver First Flight Laser Module” [Online]. Available: HYPERLINK “http://www.airbornelaser.com/

news/2002/032902.html” http://www.airbornelaser.

com/news/2002/032902.html, July 31, 2003. 53. McDermott, “Historical Perspective,” 4; Briefing, Major 

Hasen, AFWL/ARBI, “Chemical Oxygen-Iodine 

Lasers (COIL),” May 22, 1986; Briefing, Major Hasen, 

AFWL/ARBI, “COIL Technology Status,” February 

13, 1987. 54. “Laser aircraft contract goes to Boeing,” Kirtland Focus, 

November 15, 1996, pp. 1–4; “Airborne Laser: Program Milestones,” [Online]. Available: http://www.

airbornelaser.com, July 10, 2003. 55. Video, produced by Boeing, “Airborne Laser: Missile 

Defense For A Global Threat,” n.d. 56. Ibid. 57. Ibid.; “Overview: Airborne Laser,” [Online]. Available: HYPERLINK “http://www.airbornelaser.com” 

http://www.airbornelaser.com, July 10, 2003.

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255

Acronyms

ABCS - Army Battle Command System

ACC - Air Combat Command

ACP - Assault Command Post

ACTD - Advanced Concept Technology 

Demonstration

ADA - Air Defense Artillery

ADCSP - Advanced Defense Communications 

Satellite Program

AEF - Air Expeditionary Force

AFATL - Air Force Armament Laboratory

AFCRL - Air Force Cambridge Research 

Laboratories

AFLC - Air Force Logistics Command

AFRL - Air Force Research Laboratory

AFOSR - Air Force Office of Scientific 

Research

AFSATCOM - Air Force Satellite 

Communications

AFSC - Air Force Systems Command

AFSCN - Air Force Satellite Control Network

AFWL - Air Force Weapons Laboratory

AJ - Anti-Jamming

ALSS - Advanced Location Strike System

AMSTE - Affordable Moving Surface Target 

Engagement

AMTI - Airborne Moving Target Indicator

AOR - Area of Responsibility

APL - Applied Physics Laboratory

ARPA - Advance Research Projects Agency

ASC - Aeronautical Systems Center

ASIC - Application Specific Integrated Circuit

ATM - Asynchronous Transfer Mode

ATO - Air Tasking Order

ATR - Automatic Target Recognition

AWACS - Airborne Warning and Control 

System

BC2A - Bosnia Command & Control 

Augmentation

BCT - Brigade Combat Team

BDA - Battle Damage Assessment

BG - Battle Group

C3I - Command, Control, Communications, 

and Intelligence

C4I - Command, Control, Communications, 

Computers and Intelligence

C4ISR - Command, Control, Communications, 

Computers, Intelligence, Surveillance, and

Reconnaissance

C/NOFS - Communication/Navigation Outage 

Forecasting System

CAOC - Combined Air Operations Center

CCS - Charge Control System

CFACC - Combined Force Air Component 

Commander

CFD - Computational Fluid Dynamics

CIA - Central Intelligence Agency

CME - Coronal Mass Ejection

CMOS - Complimentary Metal Oxide 

Semiconductor
256

COCOMS - Combatant Commands

COMSAT - Communications Satellite

CRRES - Combined Release/Radiation Effects 

Satellite

CSCI - Commercial SATCOM 

Communications Initiative

CSEL - Combat Survivor/Evader Locator

DAMA - Demand Assigned Multiple Access

DARPA - Defense Advanced Research Projects 

Agency

DBS - Direct Broadcast Satellite

DCS - Decompression Sickness

DISA - Defense Information Systems Agency

DISN - Defense Information Systems Network

DISS - Digital Ionospheric Sounding System

DMSP - Defense Meteorological Satellite 

Program

DNSS - Defense Navigation Satellite System

DSARC - Defense Systems Acquisition Review 

Council

DSCS - Defense Satellite Communications 

System

DSP - Defense Support Program

DTS - Diplomatic Telecommunications Service

DUCA - Distributed User Coverage Antenna

EAR - Electronically Agile Radar

ECM - Electronic Counter Measures

EELV - Evolved Expendable Launch Vehicle

EHF - Enhanced High Frequency

EMSS - Enhanced Mobile Satellite Services

EO/IR - Electro-Optical/Infra-Red

ESC - Electronic Systems Center

ESD - Electronic Systems Division

FAA - Federal Aviation Administration

FUR - Forward Looking Infrared System

FLTSATCOM - Fleet Satellite Communications

FSK - Frequency Shift Keying

GBS - Global Broadcast System

GBU - Guided Bomb Unit

GMF - Ground Mobile Forces

GMTI - Ground Moving Target Indicator

GOES - Geostationary Orbiting Environmental 

Satellite

GPS - Global Positioning System

HEMT - High Electron Mobility Transistor

HMMWV - High Mobility Multipurpose 

Wheeled Vehicle

IBS - Integrated Broadcast Services

ICBM - Inter-Continental Ballistic Missile

IDCSP - Initial Defense Communication 

Satellite Program

IDNX - Integrated Digital Network Exchange

IGTD - Inertial Guided Technology 

Demonstration

IGY - International Geophysical Year

IMS - Ionospheric Measurement System

IMU - Inertial Measurement Units

INMARSAT - International Maritime Satellite

INS - Inertial Navigation System

INTELSAT - Intelligence Satellite

IOC - Initial Operational Capability

IP - Internet Protocol

IRBM - Intermediate Range Ballistic Missile

IRTSS - Infrared Target-Scene Simulation 

Software

ISOON - Improved Solar Optical Observing 

Network

ISR - Intelligence, Surveillance, and 

Reconnaissance

IUS - Interim Upper Stage

JASSM - Joint Air-to-Surface Standoff Missile

JBS - Joint Broadcast Service
257

JDAM - Joint Direct Attack Munitions

JRSC - Jam Resistant Secure Communications

JSOW - Joint Stand-Off Weapon

JSTARS - Joint Surveillance Target and Attack 

Radar System

JTIDS - Joint Tactical Information Distribution 

System

JWID - Joint Warrior Interoperability 

Demonstration

LAAS - Local Area Augmentation System

LAN - Local Area Network

LANTIRN - Low Altitude Navigation and 

Targeting Infrared for Night

LDR - Low Data Rate

LEASAT - Leased Satellite

LEO - Low Earth Orbit

LES - Lincoln Experimental Satellites

LGB - Laser Guided Bomb

LMST - Light Multi-band Satellite Terminals

LNA - Low-Noise Amplifier

LORAN - Long Range navigation

LOS - Line of Sight

LSI - Large Scale Integrated

MBA - Multiple-Beam Antennas

MCS - Master Control System

MDR - Medium Data Rate

MEF - Marine Expeditionary Forces

MEMS - Micro Electro Mechanical Systems

MERA - Molecular Electronics for Radar 

Applications

MILDEP - Military Department

MILSATCOM - Military Satellite 

Communications

MMIC - Monolithic Microwave Integrated 

Circuit

MSM - Magnetospheric Specification Model

MSP - Milstar Spacecraft Processor

MTBF - Mean Time Between Failures

MTE - Moving Target Exploitation

MTI - Moving Target Indicator

NACA - National Advisory Committee for 

Aeronautics

NASA - National Aeronautics and Space 

Administration

NASP - National Aero-Space Plane

NAVSPASUIR - Naval Space Surveillance 

System

NCSE - Node Center Support Element

NDGPS - National Differential GPS

NEAR - Near Earth Asteroid Rendevouz

NIDL - National Information Display 

Laboratory

NIMS - Navy Ionosphere Monitoring System

NOAA - National Oceanic and Atmospheric 

Administration

NORAD - North American Air Defense 

Command

NRL - Naval Research Laboratory

NRO - National Reconnaissance Office

OCD - Operational Concept Demonstration

OPLANS - Operation Plans

ORT - Overland Radar Technology

OSO - Orbiting Solar Observatory

OTH - Over-The -Horizon

PDM - Presidential Decision Memorandum

PGM - Precision Guided Munitions

PoP - Points-of-Presence

PPB - Positive Pressure Breathing

PPS - Partial Pressure Suit

PRISM - Parameterized Real-Time Ionospheric 

Specification Model

PRN - Pseudo Random Noise
258

RADC - Rome Air Development Center

RASSR - Reliable Advanced Solid State Radar

RF - Radio Frequency

RLV - Reusable Launch Vehicle

RSO - Reconnaissance Systems Officer

RSOI - Reception, Staging, Onward movement, 

and Integration

RSTN - Radio Solar Telescope Network

SAC - Strategic Air Command

SAM - Surface-to-Air Missile

SAMSO - (Air Force) Space and Missile 

Systems Organization

SAR - Synthetic Aperture Radar

SAS - Space Aggressor Squadron

SATCOM - Satellite Communications

SCAMP - Single Channel Anti-Jam Man 

Portable

SCATHA - Spacecraft Charging at High 

Altitudes

SCINDA - Scintillation Network Decision Aid

SCORE - Signal Communication by Orbiting 

Relay Equipment

SDB - Small Diameter Bomb

SEN - Small Extension Node

SEON - Solar Electro Optical Network

SHF - Super-High Frequency

SIPRNET - Secret Internet Protocol Router 

Network

SLEP - Satellite Life Enhancement Program

SLV - Space Launch Vehicle

SMART-T - Secure Mobile Anti-Jam Reliable 

Tactical Terminal

SMEI - Solar Mass Ejection Imager

SMV - Space Maneuver Vehicle

SOF - Special Operations Forces

SOON - Solar Optical Observing Network

SRAM - Static Random Access Memory

SSPA - Solid State Phased Array

STEP - Standard Tactical Entry Point

SWA - Southwest Asia

TAC - Tactical Air Command

TACAMO - Take Charge and Move Out

TAV - Trans-Atmospheric Vehicle

TCC - Time Critical Target

TOC - Tactical Operation Center

TVRO - Television Receive Only

TWT - Traveling-Waves Tube

UAV - Unmanned Aerial Vehicle

UFO - UHF Follow-On

USAFE - United States Air Forces in Europe

USCENTCOM - United States Central 

Command

USCG - United States Coast Guard

USEUCOM - United States European 

Command

VTC - Video Teleconferencing

WAAS - Wide Area Augmentation System

WDD - Western Development Division

WSPG - White Sands Proving Grounds
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Dr. J. Douglas Beason is Director of Proliferation Detection and Monitoring, Los Alamos 

National Laboratory, responsible for all space, intelligence, remote sensing and directed 

energy. A Fellow of the American Physical Society, he has served on the White House staff 

under the President’s Science Advisor, and has experience ranging from designing nuclear 

weapons to commanding the USAF’s Phillips Research Site. A USAF Academy graduate, 

he has authored 12 books, over 10 publications, is a distinguished graduate of ICAF and

is a Nebula Award finalist.

Maj Gen Robert F. Behler, USAF, Ret. is the Business Area Executive for Strike Warfare, 

Johns Hopkins University, Applied Physics Laboratory. He has commanded the 31st Test and 

Evaluation Squadron, the 9th Operations Group, the 9th Reconnaissance Wing, and the Air 

Force Command and Control, and Intelligence, Surveillance and Reconnaissance Center. The 

general is a command pilot and experimental test pilot with more than 5,000 flying hours in 

65 types of aircraft, including the SR–71 and U–2.

George W. Bradley III is the Command Historian at Headquarters Air Force Space 

Command, Peterson AFB, Colorado, a position he assumed in April 1992. He graduated 

from Canisius College, Buffalo, New York, with a B.A. in History in 1972 and in 1975 was 

awarded an M.A. in American Military History by The Ohio State University, Columbus, 

Ohio. The author of a number of published works on Air Force history, he began his career

as a civilian Air Force historian in 1979 and has held a variety of positions.

Lt Gen Bruce K. Brown, USAF, Ret., is former Commander, Alaskan Air Command. He 

holds a Bachelor of Science Degree from the United States Naval Academy and Masters 

Degree in International Relations from George Washington University, Washington, D.C. 

He is a command pilot with more than 5,000 flying hours. He retired from active duty on 

1 September 1985.

Dr. Russell R. Burton is a retired member of the scientific and professional cadre of senior 

executives as a chief and senior scientist of the School of Aerospace Medicine, Armstrong 

Laboratory, and Air Force Research Laboratory. His is research expertise is acceleration 

physiology focused on the development of anti-G protective methods/systems for fighter 

pilots. He has authorednumerous scientific publications and received many awards and medals 

for his contributionsto the scientific and Air Force communities.

Authors
260

Dr. Robert R. Butts received his PhD in mathematics in 1969, he began his career at the 

Laser Division of the Air Force Weapons Laboratory (now part of the AFRL). He has 

specialized in the areas of laser beam propagation through the atmosphere and adaptive 

optics. For the past ten years, he has been the technical lead of AFRL’s ABL Technology 

Program for which he received the Department of Defense Distinguished Civilian Service 

Award in 2001.

Major William B. Cade entered the Air Force through the ROTC program at Texas A&M 

University (B.S. in physics) in 1987. Since then he has provided space weather support to 

NORAD and US Space Command missions, worked at the Air Force Space Command 

Headquarters, and served as an Air Force ROTC instructor. The Air Force sponsored him 

in obtaining a Master’s Degree and then Ph.D. in physics from Utah State University. He 

is currently assigned to the Air Force Weather Agency Chief of the Applied Technology 

Division.

Brig Gen Daniel J. Darnell is Commander, Space Warfare Center, Air Force Space 

Command, Schriever Air Force Base, Colo. The mission of the Space Warfare Center 

(SWC) is to advance Air Force, joint and combined space warfare through innovation, 

testing, tactics development and training. General Darnell has served on the Joint Staff in 

Washington, D.C., and has commanded the “Thunderbirds.” He is a command pilot with 

more than 4,500 flying hours.

John H. Darrah retired from the federal government as a member of the Senior Executive 

Service and Chief Scientist of Space Command in the fall of 1999. He continues to consult 

at a high level of government. John is nationally recognized in the many missions and 

systems of the Space Commands and has been a principle contributor from the cold war’s 

missile warning and space surveillance to creating today’s many new space capabilities. His 

work to make survivable the United State Strategic Forces and their command and control 

has been recognized nationally and internationally. Mr. Darrah has advised many government agencies on nuclear weapons, their effects and alternative systems designs. John served 

as an advisor on the Strategic Arms Limitation Talks, and was loaned to the Reagan administration during its transition period in 1980-81 to, among other things, work on developing 

the national security budget for the new administration. Mr. Darrah is an Adjunct Staff 

Member Institute for Defense Analysis (IDA) Washington D.C. (2000-to the Present) IDA 

is a Federally Funded Research and Development Center (FFRDC). Mr. Darrah Supports 

the Commander in Chief (CINC) North; Commander of Air Force Command Command, 

Asst. Sec. for Defense OSD/C3I, and other DOD and Government Offices and Agencies at 

a high level. Mr. Darrah holds a Bachelor of Arts and a Master of Science degree in Physics 

University of Nevada, Reno
261

W. Denig is a space physicist within the Battlespace Environment Division, Space Vehicles 

Directorate, Air Force Research Laboratory. He is the author of numerous articles dealing 

with the space environment and the effect of space on military systems. He holds a Masters 

Degree in Nuclear Science and a PhD in space physics from Utah State University. 

Robert W. Duffner is a historian at the Air Force Research Laboratory’s Historical

Information Office at Kirtland Air Force Base, New Mexico He received his PhD from 

the University of Missouri and is the author of Airborne Laser: Bullets of Light (1997) and 

Science and Technology: The Making of the Air Force Research Laboratory (2000). He is 

currently working on a book on the history of adaptive optics in the Air Force.

General Ronald R. Fogleman, USAF, Retired, is currently the President and Chief 

Operating Officer of Durango Aerospace Incorporated. General Fogleman is the formerChief 

of Staff of the United States Air Force. Prior to that, he managed the Air Mobility Command 

and served as Commander and Chief, US Transportation command. He is currently a 

member of the NASA Advisory Council, NASA’s Return to Flight Task Force and Defense.

Dr. Ivan A. Getting, a founding member of the Air Force Scientific Advisory Board in 

1946,contributed extensively to the development of radar and military systems for command 

and control during the 1950s. From 1960-1977 he served as the first president of the 

Aerospace Corporation. His conceptual work on a space-based guidance system for rail-mobile 

ICBMs and subsequent advocacy of space-based navigation were critical to the development of 

the Global Positioning System. This was his last paper. He died on October 11, 2003.

Jon S. Jones is Senior Scientist, Air Force Research Laboratory (AFRL), Rome Research Site, 

Rome, New York. He holds Bachelors of Science and Masters of Science Degrees in Electrical 

Engineering from the State University of New York at Buffalo and Syracuse University 

respectively. His field of research is data fusion for Ground Moving Target Indicator (GMTI), 

in particular its application to Joint STARS.

Lt Gen Daniel P. Leaf, a native of Shawano, Wisconsin, is Vice Commander of Air Force 

Space Command. He has commanded a flight, two squadrons, an operations group, and two 

fighter wings, and has directed joint operations. He commanded the 31st Air Expeditionary 

Wing comprised of F–16, F–15, F–117, A–10, and EC–130 aircraft during Operation 

Allied Force. During Operation Iraqi Freedom, he served as the Director, Air Component 

Commander in Kuwait including Allied Force, Joint forge, Northern Watch and Southern 

Watch combat missions.
262

Dr. Alexander H. Levis is University Professor of Electrical, Computer and Systems 

Engineering currently on leave from George Mason University serving as the Chief Scientist of 

the Air Force. He joined GMU in 1990 and served twice as chair of the Systems Engineering 

department. He is Fellow of IEEE, AAAS, and an Associate Fellow of AIAA and has served 

as president of the IEEE Control Systems Society. He was educated at MIT where he also 

worked for eleven years as a senior research scientist. 

Dr. Ruth P. Liebowitz is currently Chief of the History Office at the Electronic Systems Center, 

Hanscom Air Force Base, Massachusetts. Her research interests include the history of radar and 

reconnaissance since World War I, and also military sponsorship of science and technology.She 

holds a doctorate in History and a master’s in History of Science from Harvard University.

Dr. Robert J. Mailloux is Senior Scientist, Sensors Directorate, Air Force Research 

Laboratory, Hanscom Air Force Base, Massachusetts. He is the author or co-author of 

numerous journal articles. Mailloux holds a B.S. Degree from Northeastern University and 

M.S. and Ph.D. degrees from Harvard University.

Lt Gen Forrest McCartney retired from the Air Force in 1987. During his Air Force career, 

he held positions as Program Director for several major satellite programs, Commander of 

the Ballistic Missile Organization and Commander of Space Division. In late 1986 he was 

assigned as the Director of Kennedy Space Center, a post he held until his retirement from the 

Air Force in 1987. He remained with NASA as a civilian and continued as Director of KSC 

until 1991. In 1994 he joined Lockheed Martin as the Astronautics Vice President for Launch 

Operations. He retired from Lockheed Martin in 2001.

Dr. George C Mohr, a Chief Flight Surgeon, served 39 years with the USAF in a variety of 

clinical, command and scientific posts. Dr. Mohr, a Rhodes Scholar, received his M.D. degree 

from Harvard. He is board certified in Aerospace Medicine, has authored 55 scientific papers 

and has received numerous awards and decorations from the USAF and civilian institutions. 

He currently resides with his wife, Annabel, in San Antonio, TX.

Bradford W. Parkinson is Edward C. Wells Professor of Aeronautics and Astronautics 

(Emeritus) at Stanford University. As an Air Force colonel, he was the first Program Manager 

of GPS, credited with selling the concept, synthesizing the design and building the phase one 

system. He flew combat missions in Laos during the Vietnam War, was an instructor at the 

USAF Test Pilot, School, and head of the Astronautics Department at USAFA. Later he was 

a Vice President at Rockwell International. As a tenured Professor at Stanford, he pioneered 

many civil applications of GPS. He is the winner of the prestigious Draper Prize of the 

National Academy of Engineering.
263

Lt Gen Harry D. Raduege, Jr., is director, Defense Information Systems Agency, Arlington, 

Virginia. As director, he leads a worldwide organization of over 8,200 military and civilian 

personnel. This organization plans, develops, and provides interoperable command, control, 

communications computers (C4), and information systems to serve the needs of the President, 

Secretary of Defense, Joint Chiefs of Staff, the combatant commanders, and other Department of Defense components under all conditions ranging from peace through war. He has 

worked his entire career in the areas of C4 space, and information operations serving in 

command, operations, maintenance, engineering, plans, budgeting and readiness positions. 

Prior to assuming his current position, he was the director of command control systems, 

Headquarters North American aerospace Defense Command and US Space Command, and 

director of communications and information, Headquarters Air Force Space Command. He 

also served as the Chief Information Officer for all three commands.

Dr. William Sears is an internationally recognized authority in the field of Aerospace 

Physiology and Aircrew Life Support Systems. For the fourteen years prior to his retirement 

from the USAF in 1981, he was intimately involved in research and development activities at 

the USAF School of Aerospace Medicine and as an exchange officer at the Royal Air Force 

Institute of Aviation Medicine. Following retirement he has consulted with over 25 Life 

Support and Airframer Companies during the development of the life support systems for 

several new aircraft.

Dr. Robert Sierakowski is chief scientist, Munitions Directorate, Air Force Research Laboratory, Eglin Air Force Base, Fla. In this capacity he provides scientific guidance and advice 

to the director of the Munitions Directorate as well as the commander, Air Force Research 

Laboratory, on research plans and programs in conventional weapon system and armament 

basic research.

Maj Gen Joseph P. Stein is Director of Aerospace Operations, Headquarters Air Combat 

Command. As such he directs operations, planning, and command and control. General Stein 

holds a Bachelor of Science Degree from the United States Air force Academy and is a master 

navigator with more than 3,200 flying hours in the B–52G, T–43, B–1B, and E–8C.

Dr. Rick W. Sturdevant is Deputy Command Historian at HQ, Air Force Space Command; 

he joined the Air Force History Program in 1984. He has authored numerous reviews, articles 

and papers on military space history that have appeared in various scholarly journals and 

books. He has also presented papers on military space history at numerous conferences and 

symposia. An active member of the American Astronautical Association, he is also a member 

of a number of other professional historical organizations.
264

Dr. Thomas W. Thompson heads the Office of History, Air force Research laboratory 

(AFRL), Rome Research Site, Rome, New York. Dr. Thompson is an Air Force veteran, 

having served as a radar weapons controller from 1967 until 1971. He holds a Ph.D. 

in history from Miami University, Oxford, Ohio, and has studied the history of science

 at Cornell University.

Ronald E. Thompson retired from the Aerospace Corporation in July 2002 after spending 

43 years in the aerospace industry; the last 38 years at the Aerospace Corporation. Mr. 

Thompson joined Aerospace in 1964 as a member of the Gemini Launch Vehicle program 

Office and participated in all the Gemini launches as part of a joint Air Force/NASA launch 

team. After several years as a member of the Manned Orbiting Laboratory Program he held 

various management positions working to integrate military satellites for flight on NASA’s 

Space Shuttle. In 1991, Mr. Thompson added the Military Space Test Program to his 

responsibilities. From 1993 to his retirement in 2002 Mr. Thompson was a member of the 

Milsatcom organization and was responsible for supporting the Air Force as a member of the 

management team for the DSCS and Milstar programs. When he retired Mr. Thompson had 

participated directly in 22 successful military space missions.

Dr. Van Trees is a graduate of West Point and M.I.T.. He served on the M.I.T. faculty 

as a Professor of Electrical Engineering. While at M.I.T., he wrote the 3-volume series on 

Detection and Estimation Theory, which is a classic in the field. He has been involved with 

satellite communications for over 30 years. As Chief Scientist at DCA, he formed the first 

Military Satellite Office, which generated the first comprehensive milsatcom architecture. 

He directed the Advanced Planning group at Comsat for 3 years and edited a comprehensive 

book on Satellite Communications. As ASD(C3I), he imitated the Milstar program . At 

M/A-COM, he built the first set of transportable SHF terminals for the Air Force. He taught 

a classified course on Military Satellite Communications for AFCEA for over 20 years. He 

is currently a Professor of Electrical Engineering and Director of the C3I Center at George 

Mason University. He recently finished a comprehensive book on Optimum Array Processing 

which is Part IV of the DEMT series.

Dr. Edward A. Watson is the Technical Advisor, Electro-Optical Technology Division, Air 

Force Research Laboratory and has been involved in research in active and passive electro-optic 

sensors. He is also an Adjunct Assistant Professor of Electrical Engineering at the Air Force 

Institute of Technology. He has a Ph. D. in Optics (University of Rochester), and an M. S. in 

Optical Sciences and a B. S. in Physics (University of Arizona). He is a Fellow of the SPIE.

Dr. Billy E. Welch. Prior to his retirement from Federal Civilian Service, Dr. Welch was 

thefounding Director of the Air Force’s Armstrong Laboratory. Earlier assignments were 

in the USAF School of Aerospace Medicine, in the Human Systems Division as Chief 

Scientist and in the Office of the Secretary of the Air Force as the first Special Assistant for 

Environmental Quality. He currently is involved in S & T consulting and is affiliated with the 

Los Alamos National Laboratory.
265

Dr. Robert P. White is retired from the U. S. Air Force, where he served for ten years 

as a Signals Intelligence Officer in positions that included squadron operations officer 

and squadron commander. Following graduation from Ohio State University with an 

Air Force sponsored degree in military history, he served as an Air Force historian and 

Chief of Air Staff History. His biography on Maj Gen Mason Patrick was published 

by the Smithsonian Institution Press in 2001. He is currently the historian for the Air 

Force Office of Scientific Research in Arlington, Virginia.

Maj Gen Stephen G. Wood is Commander, Air Warfare Center, Nellis AFB, Nevada. 

A command pilot with over 3,400 hours, he leads the Air Force’s premier training 

and testing center, including the Air Force’s only operational remotely piloted aircraft 

squadrons. He served as Commander, Combined Air Operations Center, Prince 

Sultan AB, Saudi Arabia, providing critical command and control during Operation 

ENDURING FREEDOM.

Dr. Michael I. Yarymovych is President of the International Academy of Astronautics 

since 1996. Until 2000 he was the Chairman of the NATO Research and Technology 

Board, and prior to that was Chairman of AGARD. In February 1998 Dr. Yarymovych 

retired from Boeing, and its predecessor Rockwell International, where he held various 

positions as Vice President responsible for engineering and technology on Missile 

Defense, GPS, Space Shuttle, B1 aircraft and classified programs. He was Chief 

Scientist of the U. S. Air Force, Deputy for Requirements to the Assistant Secretary of 

the USAF for R&D and Technical Director of the USAF Manned Orbital Laboratory.