bluuebunny/crossref_metadata_2025 huggingface dataset:
Space Life Sciences
Authors: Grigoriev Anatoly I. , Malashenkov Dmitry C.
Published: October 2003

The term space life sciences refers to the set of sciences that study the biology of living things under conditions of spaceflight. The synonymous term, space biology, coined in 1920 by K. Tsiolkovsky, is more common in Russia (USSR) and will be used in this article. The origin and development of space life sciences as a discipline are the result of certain advancements in modern science and technology and are associated with the development of jet propelled flight vehicles that can overcome the force of gravity to ascend beyond the bounds of Earth's atmosphere.

Space Biology arose at the intersection of many scientific disciplines. It is indissolubly bound up with cosmonautics and space medicine.

Space medicine is the area of general medicine that studies what happens to human physiological processes under the unique conditions of space flight to develop means and methods for maintaining the health and performance capacity of crews of spacecraft and space station pre‐, in‐ and postflight. As one of the branches of occupational medicine, space medicine attempts to provide the answers to a number of questions confronting humanity as a result of scientific and technological progress. These answers are derived from a very large medical knowledge base relating to various areas of theoretical and clinical medicine such as space physiology and psychophysiology, space hygiene, space radiobiology, and medical expertise.

Major phases in the evolution of space life sciences are discussed. Understanding how living things react to extreme environments and tolerance to the extremes is key to developing an artificial closed system for space exploration. The main results of scientific studies conducted are provided.
U.S.
Manned Space Flight: Mercury to the Shuttle
Authors: Faget Maxime A. , Silveira Milton A.
Published: October 2003

There are many publications relating to Mercury, Gemini, Apollo, Skylab, Apollo‐Soyuz Test Project, and the Space Shuttle. This article presents an objective review of some of the technical considerations of the design, development, and operation of these spacecraft. Although there were many triumphs, a number of surprises, and not a few setbacks during the 39‐year period covered, such incidents will be mentioned only in the context of technical significance. A little more than 19 years elapsed between 20 February 1962, when John Glenn first rode Mercury into orbit, and 12 April 1981, when John Young and Robert Crippen inaugurated orbital flight for the Space Transportation System, or the Space Shuttle as it is commonly called. A comparison of the Mercury capsule and the spaceship Columbia reviews the extent of progress made during these first years of manned flight.

During the early 1920s after approximately 19 years of development, the aviation industry was also entering the transportation phase. But there is a significant difference between the development of airplanes and the development of manned spacecraft. Early airplanes were relatively cheap and easy to build. A great number of airplanes was built and flown. This led to a rapid evolutionary process for both the design and the operation of aircraft, and a number of accidents and fatalities provided a strong cooperative influence on any misdirection. The philosophical basis for the design and operation of spacecraft has had to progress without this impartial and unerring guidance of “survival of the fittest.” As a substitute, we have had to rely on intensive analysis, extensive testing, imperfect simulations, and the judgment and experience of the hundreds of key people working on these programs.

American manned spacecraft by type together with a number of weights, dimensions, and features that characterize them are listed. Mercury was a first of a kind design, and the Gemini and Apollo command and service module (CSM) followed in an evolutionary trend. The Apollo lunar module (LM) and the Space Shuttle, on the other hand, represent new and distinctive designs and have unique features for which no prior art existed.
Weather Satellites
Authors: Singer S. Fred , Rao P. Krishna
Published: October 2003

The world's first meteorological satellite, a polar‐orbiting satellite, was launched from Cape Canaveral on 1 April 1960. Named TIROS for Television Infrared Observation Satellite, it demonstrated the advantage of mapping Earth's cloud cover from satellite altitudes. TIROS showed clouds banded and clustered in unexpected ways. Sightings from the surface had not prepared meteorologists for the interpretation of the cloud patterns that the view from an orbiting satellite would show.

The spacecraft, the sensors, the communication links, the data, and the data uses of weather satellites today bear little resemblance to what they were at the time of that pioneering effort. In the decades that have elapsed, satellite weight has grown from about 100 kg to nearly a metric ton; vidicon cameras have given way to scanning radiometers; hand‐drawn analyses of the data have been replaced by computer‐generated products; what was analog has become digital; and capabilities have expanded to include atmospheric profiling, ocean sensing, and collecting and relaying environmental data recorded by remote reporting platforms. In addition, weather satellites now measure the space environment in which they operate. Just as their technology and uses have evolved, so have weather satellites proliferated internationally. Meteorological spacecraft in polar orbit and geostationary orbits are operated by the United States, the European Space Agency, Japan, India, Russia, and the People's Republic of China.

This article gives the history of the development of weather satellites from 1960 to the present. International cooperation in monitoring Earth and its environment is discussed.

Satellites by their nature rely on remote sensing. Fundamental topics include: reflection and scattering of solar radiation, thermal emission for the surface and the atmosphere, active probing using radar and lidar. Other topics include applications, climate studies, and the continuity and future of operational satellite programs.
Muscle Loss in Space: Physiological Consequences
Authors: Baldwin Kenneth M. , Reggie Edgerton V. , Roy Roland R.
Published: October 2003

Recent findings clearly suggest that one of the hallmarks of exposing humans and animals to the environment of spaceflight involves the process of muscle atrophy and associated deficits in one's performance capability. This article describes the effects of spaceflight and/or states of muscle unloading on (1) the intrinsic structural and functional properties of skeletal muscle, (2) the performance of muscular activities associated with locomotion and other motor tasks both during and after exposure to spaceflight, and (3) theoretical concepts for enhancing our current understanding of the effectiveness of countermeasures routinely used either to maintain or prevent observed muscle loss and corresponding deficits in musculoskeletal function. Data from both human and animal models from in‐flight and ground‐based experiments are examined.
First Flight of Man in Space
Authors: Klimuk Petr I. , Vorobyov G.I.
Published: October 2003

The twentieth century was one of rampant technological development, of unprecedented flourishing of science, a century in which grandiose, fantastic ideas became reality, and when the dreams of many generations of people who lived and now live on Earth came true.

There were a great many ideas, discoveries, projects, and accomplishments in the century just past. But among all the numerous outstanding human achievements in the twentieth century that captured the contemporary imagination, the most thrilling were the launch of the first artificial satellite and, especially, the flight of the planet's first cosmonaut, Yuriy Alekseyevich Gagarin on the Vostok spacecraft.

The launch of the first artificial satellite into orbit around Earth took place on 4 October 1957 at 22:28 Moscow time marking the start of the Space Era in human history. Yuriy Gagarin's spaceflight, launched on 12 April 1961 at 09:07 Moscow time, lasted for 108 minutes, during which the spacecraft carrying the first cosmonaut completed a full orbit around Earth and then landed safely in the scheduled recovery area. This flight marked the start of the Era of Human Presence in Space.

These two events are directly linked; without the first, the second could never have occurred. The first became a momentous milestone in the history of technological progress; the second was the embodiment of a centuries‐old dream of humankind.

This article details the preparations for the first flight and how Yu. A. Gagarin was chosen for the mission, Biographical information on Gagarin is given.
Exploration of Mars by theUSSR
Authors: Zakharov Alexander V. , Moroz V.I.
Published: October 2003

Mars research began long before the Space Age. Ground‐based astronomical observations using photometry polarimetry, and infrared spectrometry were performed in the Soviet Union throughout the 1950s and 1960s. G.A. Tikhov attempted to find evidence of life on Mars using spectroscopic techniques. Theoretical models for the internal structure of the planet began to be developed.

Early Soviet planetary spacecraft were developed by Special Design Bureau 1. One of the primary motivations for the development of long‐term Martian research programs was a desire to find life on the planet. It was generally understood that this project had to begin elsewhere—learning more about the planet Mars itself. Nevertheless, early Soviet spacecraft carried a spectrophotometer for observations of the so‐called Sinton bands, which were, at that time, presumed to indicate the presence of organic material on Mars.

Eight attempts were made to launch a spacecraft to Mars, starting in 1962. Only the fourth spacecraft, the Mars‐1 (1962) executed a flyby, but communications were lost prior to the flyby. Jet Propulsion Laboratory made two attempts (1964) during this period, one of which was successful: Mariner‐4 performed a Mars flyby and transmitted an image of the planet.

In 1965, S.P. Korolev transferred all unmanned interplanetary space flight projects to another facility, the Design Bureau and Plant named after S.A. Lavochkin.

This article gives details on the Mars 2–7 spacecraft. The phobos spacecraft was launched to study phobos and not Mars.
Spacelab
Authors: Hoffmann Hans E.W.
Published: October 2003

Spacelab is the European contribution to the Post Apollo Program. Spacelab is a reusable, multipurpose, modular laboratory and in the first 10 years of Space Shuttle operation, became its major payload. This payload remained attached to the Orbiter during the whole flight and maintained certain dependences. Spacelab was not a habitat, so that the Mission and Payload Specialists stayed in the Orbiter during take‐off and landing and used it also as living quarters.

Spacelab was designed for a 10‐year lifetime and/or 50 missions. Inside the laboratory, called the module, a shirtsleeve atmosphere for the astronauts was required; experiments on the outside had to be conducted in the open space on a pallet. Both module and pallet were accommodated inside the Shuttle payload bay and remained attached to the Shuttle during the mission. This fact limited the time of a Spacelab mission to the time of a Shuttle flight.

This article gives details on the various components of the Spacelab (module, pallet instrument painting, environmental control, command systems, electrical power systems).

On 4 June 1974, the contract to design and build Spacelab was given by the European Space Agency (ESA) to an industrial consortium of companies from eight European countries.

For most of the time from 1974 to 1983, the Spacelab development ran parallel to the Shuttle development on a no exchange of funds basis to use common hardware and subsystems as much as possible.

The flight hardware, schedule and cost are described. Missions are listed and the lessons learned from this cooperative program are presented.
Communication Satellite Development in Russia
Authors: Kozlov A.G. , Bartenev V.A.
Published: October 2003

Work on the practical applications of artificial Earth satellites began in Russia (USSR) in 1961. The first of these satellites, the small low‐altitude Strela series spacecraft of the “electronic mail” type, were developed by the Scientific Production Association for Applied Mechanics (NPO PM) and placed in orbit in 1964. One year later, the Experimental Design Bureau‐1 (OKB‐1), (currently S.P Korolev Energia Rocket and Space Corporation) inserted the active relay satellite Molniya‐1 into a highly elliptical orbit. In 1965, work on this spacecraft was transferred to NPO PM and, for the next 30 years, this organization was the only one in the country developing telecommunication satellites. The first geostationary satellite was inserted into orbit in 1975.

It was not until 1997 that a communication satellite, Kupon, developed by another organization, the S.A. Lavochkin NPO, was placed in orbit, and in 1999, the communication satellite Yamal developed by Energia was launched. At present, work to design communication satellites is being conducted by the Machine Building NPO and the M.V. Khrunichev State Space Scientific Production Center.

The spacecraft that were and are being developed in Russia may be divided into three categories on the basis of the types of orbit:

satellites in low circular orbits, primarily at an altitude of 1500 km (such satellites are used to form multisatellite communications systems);

Molniya
type satellites in highly elliptical orbit;

satellites in geostationary orbit.

These three categories are discussed in detail in this article.
International Space Station
Authors: Michael Hawes W.
Published: October 2003

The establishment of a long‐term, low Earth orbiting outpost has long been a goal of space exploration advocates. A variety of orbiting space stations, envisioned by writers, engineers, and scientists for years, have been developed, launched, and deorbited. The Soviet Union and Russia have flown several Salyut stations and only recently terminated operations of the Mir Space Station. The United State flew three missions on the Skylab Space Station that was launched in 1975.

The long developmental history of the International Space Station (ISS) includes many lessons and are discussed. The huge scale of the project offers many engineering, policy, and management lessons for our future endeavors in space. Despite the many challenges and the long development period, the project is now demonstrating great success an overview of the configuration of the ISSW given. The segments contributed by the U.S., Russia, Canada, Europe, and Japan are detailed. These partners have formulated a share agreement to allocate all of the critical ISS resources. In November 2000, the first permanent crew docked with and entered the International Space Station. Since then, the International team has continued to outfit and augment the ISS. At this time, the fifth expedition crew is well into their stay on board the ISS. The results of many years of painstaking work are evident as the ISS flies overhead.
Plasma Thrusters
Authors: Morozov Alexey I. , Balebanov Vyacheslav M.
Published: October 2003

Plasma thrusters are a class of electric propulsion in which the working medium has the form of plasma in the acceleration zone. The presence of plasma, both positive ions and negatively charged electrons, in the acceleration gap distinguishes plasma thrusters from ion thrusters where the acceleration gaps contain only positively charged ions. In ion propulsion, the space charge field restricts the emissions of ions from the emitter (ion generator), and thus ion thrusters have a relatively low thrust density and require a high acceleration voltage. As a result, they can be efficient only with an acceleration voltage >1 kV and exhaust velocities of ≥30 km/s.

Because the acceleration gaps in a plasma thruster contain both positive ions and electrons, no space charge is needed. For this reason, there are no limitations in theory on the thrust density in plasma thrusters, and the exhaust velocity may range from a few km/s to hundreds or more km/s. Of course, different plasma thruster designs are optimal for each range of exhaust velocities and power levels.

Plasma thrusters, like other electric propulsion thrusters, are of interest for space technology primarily because of their capacity to reach high exhaust velocities, greater than those attained by thermochemical (liquid or solid) fuel rocket engines. In a number of instances, other features of such thrusters may also be of interest.

The chemical energy contained in the working medium is not sufficient to attain high velocities. For this reason, plasma thrusters, like other rocket engines, require special sources of energy. Today, these sources may be either the Sun or nuclear processes of one kind or another (fission, radioactive decay). For each specific flight, optimal velocity parameters exist, defined with respect to minimum total mass of propellant and power source. The optimal exhaust velocities for the majority of purposes are currently within the range of approximately 15–30 km/s.

These thrusters are classified primarily on the basis of the mechanism for accelerating the plasma. Three basic types of plasma thrusters are identified: Thermal plasma thrusters; electromagnetic (Ampere's force) plasma thrusters; and the third class encompasses plasma thrusters in which acceleration is achieved through both kinetic gas pressure and Ampere's force.

The division of plasma thrusters into three groups on the basis of the acceleration mechanism is very general. However, detailed classification of all possible plasma thrusters on the basis of their physical or design features is virtually impossible, This article describes only representatives of the three types of plasma thrusters that have already functioned in space.
Skylab
Authors: Kerwin Joseph
Published: October 2003

A space station has been an obvious part of space exploration since people began to think seriously about space travel. Skylab was a program that was being designed and trained for simultaneously, and the design and training were taking place in parallel with the Gemini, and later, the Apollo manned flights. Thus, the problems and experiences of those flights shaped the Skylab design.

As spacecraft and boosters for Project Apollo, NASA's lunar landing program, were defined, space station concepts derived their specifics from them. Modifications of the Command Module, the Lunar Module, and various configurations of the Apollo booster series, were studied. NASA wanted to use its hardware for programs beyond Apollo. In 1965, the concept of Apollo Extension Systems was formalized at NASA Headquarters and very soon became the Apollo Applications Program (AAP). The concept later named Skylab was just one of the missions proposed by AAP.

This article details the development of Skylab and discusses the first, second, and third missions. Skylab's goals were to discover whether humans could live safely in weightlessness and uncover any problems with design. Also it was necessary to determine whether productive science experiments could be accomplished. Results of the medical findings, human factors and design, and productivity are given for the three missions. Skylab returned to Earth in 1979 and was a lesson in planning how to dispose of space assets.
Global Navigation Satellite System
Authors: Menshikov V.A. , Solovyev G.M.
Published: October 2003

The Global Navigation Satellite System (Glonass) was designed to provide global real‐time determination of the position and velocity of an unlimited number of moving objects at any point on the Earth's surface, in the air, and in space. This system was developed in response to an order from the USSR (Russian Federation) Ministry of Defense. By instruction of the Russian Federation's President, the Glonass system was put into operation on 24 September, 1993. A 7 March, 1995 decree of the RF Government put the system at the disposal of the world community in standard mode intended for civil, commercial, and scientific use without a user fee.

A RF Presidential decree of 18 February, 1999 designated the Glonass as a dual‐purpose (military and civilian) space navigation system.

The system makes it possible to obtain highly accurate navigation location information with a maximum error less than or equal to 50–70 meters for position and 15 cm per second for velocity from any point on the globe or in near‐Earth space. Information is received in real time after a two to three minute pause, when the user's navigational system has just been turned on and continuously thereafter. At the same time, the system provides the capability to link the user's timescale with the State unified timescale with an error of no more than one microsecond. If the user's equipment can implement special methods for processing navigational information or differential operating modes are used, the accuracy with which the user's position is determined may be improved significantly. Tests have shown that the maximum error in such cases does not exceed a few meters.

This article gives details on the concepts involved in positioning the system and the design of the satellite. Launch takes place at the Baykonur Spaceport. The Ground Control Complex tracks the satellite. The use of differential methods for navigation provides reliability and these methods are discussed. Because positioning is achieved through uninterrogated measurements of pseudorange and pseudovelocity, the number of users of the Glonass space navigational system is unlimited and may be as large as possible. Uses in space, air, ground, and the sea are detailed.
Global Positioning System (
GPS
)
Authors: Parkinson Bradford , Spilker James , Elkaim Gabriel
Published: October 2003

The Global Positioning System, commonly referred to as GPS, is a worldwide, satellite‐based positioning and timing system that allows suitably equipped radio receivers to locate themselves in four dimensions, latitude, longitude, altitude, and time, anywhere there is a reasonably clear view of the sky. The system is also known as NAVSTAR, a convenient nickname that is not an acronym. The GPS system was developed, deployed, and is currently operated by the U.S. Air Force. GPS enables precision weapon delivery for all branches of the U.S. Department of Defense, as well as allied nations. Additionally, GPS supports civilian positioning and was always intended to support civil operations. The complete satellite constellation and ground support equipment that make up GPS was declared “operational” in December 1994, although civil use of the developmental signals started in the early 1980s.

The fundamental operation is as follows: the 24 GPS satellites are uploaded from the ground with their current and predicted positions (called ephemeris or orbital parameters). Small corrections of their space‐borne atomic clocks are also uploaded. This information is broadcast to the user as a data modulation on an L‐band signal (1575 MHz for most civilian users) that doubles as a precise, one‐way ranging signal. Ranging is achieved by synchronizing the start time of a pseudorandom sequence of bits transmitted from the GPS satellites at an accuracy of about one nanosecond (10
−9
 s). Three very important results are achieved by this implementation. First, this makes GPS ranging a one‐way signal that allows an infinite number of users to receive the signal and compute their position without saturating the GPS system. Additionally, this makes the GPS receiver passive, so that it does not radiate radio‐frequency (RF) energy. Last, by receiving four or more satellite signals, users can synchronize their local clocks to GPS time, obviating the need for a very high quality and very expensive atomic clock in the receivers.

The design objectives of the GPS system were to provide a continuously available, worldwide, all‐weather, three‐dimensional precision navigation system for both military and civilian users on land, at sea, or in the air (or even in space). Selected application of the GPS system are discussed. Many topics presented are on the cating edge of research.
Chandra X‐ray Observatory
Authors: Weisskopf Martin C.
Published: October 2003

The Chandra X‐ray Observatory (originally called the Advanced X‐ray Astrophysics Facility—AXAF) is the X‐ray component of NASA's “Great Observatory” Program. Chandra is a NASA facility that provides scientific data to the international astronomical community in response to scientific proposals for using it. The Observatory is the product of the efforts of many organizations in the United States and Europe. The Great Observatories also include the Hubble Space Telescope for space‐based observations of astronomical objects primarily in the visible portion of the electromagnetic spectrum, the now defunct Compton Gamma‐Ray Observatory that was designed to observe gamma‐ray emission from astronomical objects, and the soon‐to‐be‐launched Space Infrared Telescope Facility (SIRTF). The Chandra X‐ray Observatory (hereafter CXO) is sensitive to X rays in the energy range from below 0.1 to above 10.0 keV, corresponding to wavelengths from 12 to 0.12 nanometers. The relationships among the various parts of the electromagnetic spectrum, sorted by characteristic temperature and the corresponding wavelength are illustrated in this article.

X‐ray astronomy is an extremely important field because it has been found that all categories of astronomical objects (or a subset thereof), from comets to quasars, emit X‐rays. Thus learning how and why these objects produce X‐rays are fundamental to our understanding of the way astronomical systems work. This, together with the large amounts of energy required to produce X‐rays, makes their study interesting and exciting. A second reason that the field is so important is that the vast bulk of the matter in the Universe that we can directly observe through the electromagnetic radiation that it emits is in the very hot (temperatures of millions of degrees) X‐ray emitting gas that fills the space between galaxies in clusters of galaxies, the largest collections of matter in the Universe. The CXO is the prime method of gaining new information about the X‐ray emission seen in the Universe.

The CXO was named in honor of the late Indian‐American Nobel laureate, Subrahmanyan Chandrasekhar, nicknamed “Chandra” which means “moon” or “luminous” in Sanskrit. He was one of the foremost astrophysicists of the twentieth century and, in 1983, was awarded the Nobel prize for his studies of the physical processes important to the structure and evolution of stars.

The observatory and its instrumentation are discussed. Scientific results are detailed CXO's role in solving the mystery of gamma ray bursts is also discussed.
Civil Land Observation Satellites
Authors: Stoney William E.
Published: October 2003

The first, and still the most dramatic, example of seeing where we live from the vantage point of space was the image of a pale blue and white globe hanging all alone in an infinite expanse of darkness taken through the window of Apollo 8 on its way to the Moon in December 1968. Three and a half years later on 23 July 1972, NASA launched ERTS‐1, later renamed Landsat‐1. This was the first civil imaging satellite that had enough resolution, 80 meters, to image human‐scale activities, that is, everything bigger than a football field. Its more capable successors now provide anyone, anywhere, the ability to see images of motorcycle size objects any place on the globe at almost any time. As of November 2002, there are 19 satellites in orbit whose resolutions range from 30 meters down to 0.6 meter. (The number of systems in orbit is somewhat volatile; four are old and may fail by the time this article is published, and five more are likely to be launched during that same period.) They are being operated by the United States, France, India, Korea, Canada, China/Brazil, the European Space Agency, and three private corporations, two U.S. and one Israeli. The number of satellites and the number of their national and private sponsors show that civil land observation satellites have arrived at the point where they are now another permanent payoff of the space age. It will take much longer than the Weather, Communication and Global Positioning System (GPS) satellites for their full economic and social effects to be felt, but they are already forcing national and international discussions on the effects on nations, corporations, and individuals of the worldwide transparency that these satellites will inevitably bring.

This article discusses the special set of Earth orbiting satellites designed to acquire detailed images of the global land surface. It is the high‐resolution subset of the larger family of Earth sensing satellites that image the land and oceans on a kilometer scale and measure the characteristics of the atmosphere to record the weather and to explore the complex interrelationships among the atmosphere, the oceans, and the land surface that cause the weather and our climate. The satellite, sensor, and data technologies involved are described. The landsat history is detailed. Programs of the international period are included. The possibilities of using radar in civilean satellites is discussed.
Pathfinder Mission to Mars
Authors: Anderson R.C.
Published: October 2003

On July 4, 1997, Mars
Pathfinder
landed safely on the surface of Mars. Designed under the new “faster, cheaper, and better”
Discovery
program philosophy, the lander deployed and navigated a small rover named “
Sojourner
” onto the Ares Valles landing site and began collecting data from its onboard scientific instruments. Pathfinder was designed primarily as an entry, descent and landing demonstration. The three major components are cruise stage entry decent sub system, and lander.
Pathfinder
returned 2.3 billion bits of new data, including over 17,000 images, 16 chemical analyses of rocks and soil, and 8.5 million individual temperature, pressure and wind measurements.
Sojourner
traversed approximately 100 meters (330 feet) clockwise around the lander exploring about 200 square meters (2,153 square feet) of area.

Pathfinder' objectives were to study geologic process, soil mechanics, petrology, geochemistry, and orbital dynamics, among others. Findings are discussed. Details are given on the characteristics of the landing site.
Image Processing Techniques
Authors: Russ John C.
Published: October 2003

Image processing includes those methods that operate on arrays of pixels to produce a modified image in which some of the information is enhanced in visibility and necessarily some other information is reduced. This is done presumably because the user can determine from the intended use of the image which information is currently important. In other situation, different processing might be used to extract other information from the image.

There are several different ways to organize image processing methods to aid in understanding and to provide a logical structure for explanation. One is by purpose: to correct defects in images that arise from imperfect cameras, illumination, etc; to enhance the visibility of particular structures within images; to recognize and locate features; etc. In many cases, the same tools can be used for several of these different objectives.

Another method is to distinguish between operations that work on single pixels, within small neighborhoods, and globally on the entire image. This article discussed single‐pixel operations.
Characterization of Image Systems
Authors: Huck Friedrich O. , Fales Carl L.
Published: October 2003

Communication theory is used to establish a mathematical foundation for characterizing image systems that combine image gathering and display with digital processing to produce sharp, clear images consistently and economically. Characterization entails three elements:

A mathematical model that accounts for image gathering, signal coding, and image restoration as a whole, from the scene to the observer.

Figures of merit that account for the critical limiting factors that constrain the performance of image systems.

Computational simulations that correlate quantitative assessments with measurable and perceptual performance.

The pivotal figure of merit is the information rate in the image system. This rate is paired with the theoretical minimum data rate to assess the efficiency with which information about natural scenes can be conveyed, and it is paired with the maximum realizable fidelity to assess the quality with which images of these scenes can be restored. Quantitative assessments show that the design of the image‐gathering device that is optimized for the highest realizable information rate corresponds closely, under appropriate conditions, to the design of the human eye. Consistent with this convergence of communication theory and evolution, it is intuitively attractive to find that the performance of the informationally optimized image system is highly robust. The Performance not only reaches the best that is possible for scenes with aprioriprescribed statistical properties, and it also approaches the best that is possible for a wide range of other scenes, even for those that have periodic features or transients.
Charged Particle Optics
Authors: Orloff Jon
Published: October 2003

This article describes the the lenses used for high‐resolution charged‐particle optics and how their performance—in particular, their resolution—is analyzed. There are many applications for beams of charged particles (ions and electrons) that have very different resolution or beam size requirements. The optical systems described here are for high resolution, a resolving power near or at the atomic level in a microscope, or a probe focused to the 0.3–10 nm range.

Today, high resolution means beams of electrons focused to a size less than 10 nm (100 Å) or beams of ions focused to a size less than 100 nm (1000 Å) using a scanning probe instrument such as a scanning electron microscope.

High‐resolution electron beams are used primarily in electron microscopes and in electron beam lithography machines for making the lithographic masks employed for integrated circuit manufacturing. High‐resolution beams of ions are primarily used for microscopy (imaging), for micromachining and for ion‐beam‐induced chemistry. These applications are frequently related to integrated circuit manufacturing and in both cases the imaging resolution of the beams is of great importance.

The way a beam of charged particles is focused depends on how the beam is generated, so the article begin with a discussion of electron sources. This is followed by a description of the way lenses that consist of electrical or magnetic fields can be made that will focus charged particles. Why an electromagnetic field is a lens in the same sense that a curved piece of glass is a lens for light is discussed and concludes with a discussion of the capabilities and limitations of some lenses.
Color Photography
Authors: Kapecki Jon A. , Rodgers James
Published: October 2003

Color photography is a technology by which the visual appearance of a three‐dimensional subject may be reproduced on a two‐dimensional surface with a pleasing balance of brightness, hue, and color saturation. There are two essentials in the practice of color photography: the camera and the light‐sensitive sensor. The task of the camera is to present an undistorted image to the plane of the sensor with an intensity level and exposure time appropriate to the sensitivity of the sensor being used. The sensor can either be silver‐halide based photographic film or an electronic sensor such as a charge couple device (CCD). A digital record of the scene may also be obtained by scanning the processed film.

The technology of silver halide color photography is discussed in this article. The physical record of the image is expected to have high permanence. The image may be viewed directly as a reflection color print, by projection as a color slide, or by back‐illumination as a display transparency. In the case of a digital image, it may also be viewed on a video monitor. References cited are general sources of information on the science and technologies supporting color photography.
Digital Watermarking
Authors: Chandramouli R. , Memon Nasir , Rabbani Majid
Published: October 2003

The advent of the Internet has resulted in many new opportunities for creating and delivering content in digital form. Applications include electronic advertising, real‐time video and audio delivery, digital repositories and libraries, and Web publishing. An important issue that arises in these applications is protection of the rights of content owners. It has been recognized for quite some time that current copyright laws are inadequate for dealing with digital data. This has led to an interest in developing new copy deterrence and protective mechanisms. One approach that has been attracting increasing interest is based ondigital watermarkingtechniques. Digital watermarking is the process of embedding information into digital multimedia content such that the information (which is called the watermark) can later be extracted or detected for a variety of purposes, including copy prevention and control. Digital watermarking has become an active and important area of research, and development and commercialization of watermarking techniques is deemed essential to help address some of the challenges faced by the rapid proliferation of digital content.

In the rest of this article, it is assumed that the content being watermarked is a still image, though most digital watermarking techniques are, in principle, equally applicable to audio and video data. A digital watermark can bevisibleorinvisible. A visible watermark typically consists of a conspicuously visible message or a company logo indicating the ownership of the image. On the other hand, an invisibly watermarked image appears very similar to the original. The existence of an invisible watermark can be determined only by using an appropriate watermark extraction or detection algorithm. In this article, we restrict our attention to invisible watermarks.

An invisible watermarking technique generally consists of an encoding process and a decoding process.

Invisible watermarking schemes can also be classified as eitherrobustorfragile. Robust watermarks are often used to prove ownership claims and so are generally designed to withstand common image processing tasks such as compression, cropping, scaling, filtering, contrast enhancement, and printing/scanning, in addition to malicious attacks aimed at removing or forging the watermark.
Display Characterization
Authors: Brainard David H. , Pelli Denis G. , Robson Tom
Published: October 2003

This article describes the characterization and use of computer‐controlled displays. Most imaging devices are now computer controlled, and this makes it possible for the computer to take into account the properties of the imaging device to achieve the intended image. CRT (cathode ray tube) monitors is emphasizes the article begins with the standard model of CRT imaging. How this model may be used to render the desired visual image accurately from its numerical representation is shown. The domain of validity of the standard CRT model is discussed. The model makes several assumptions about monitor performance that are usually valid but can fail for certain images and CRTs. How to detect such failures and how to cope with them are explained.

Primarily users who will be doing accurate imaging on a CRT are addressed. CRTs are very well suited for accurate rendering. Treatment of LCDs (liquid crystal displays) is brief, in part because this technology is changing very rapidly and in part because the strong dependence of emitted light on viewing angle in current LCD displays is a great obstacle to accurate rendering. Plasma displays seem more promising in this regard.

All the steps of a basic characterization are presented. The treatment emphasizes accuracy both in color and in space. The display characteristics that need to be taken into account to present an arbitrary spatiotemporal image accurately, that is, luminance and chromaticity as a function of space and time are reviewed. A number of topics of interest to the vision scientist who requires precise control of a displayed stimulus are treated.

This article explains the standard CRT model (and necessary basic colorimetry) and describes simple visual tests (available online) that establish the model's validity for a monitor. How to use the standard model to characterize your display for accurate rendering is shown. Finally, the discussion briefly presents several more advanced topics, including characterization of non‐CRT displays.
Dye Transfer Printing Technology
Authors: Matsushiro Nobuhito
Published: October 2003

This chapter describes the structure and operation of dye‐sublimation thermal‐transfer printing technology. In addition to the principle of structure and operation, other principles concerned, the capabilities and limitations of the technology such as resolution, speed, intensity levels, color accuracy, size, etc, are described. The subject of this article is the dye‐sublimation printer, however, the details of other thermal‐transfer printers are included to assist the understanding about the capabilities and limitations of the dye‐sublimation printer in comparison.

Dye‐sublimation technologies using thermal heads become some of the most commercially important printers in the first half of the 1990s. However, the system has now been improved in terms of performance. The problem of image storage properties, which was the crucial issue for dye‐heat transfer, has been solved substantially by stabilization of the dye itself by chemical reactions. In the area of recording materials, research continues in the search for better materials. In the area of heat sources, a high power laser has made it possible to produce ultrahigh‐precision images.
Electron Paramagnetic Resonance (EPR) Imaging
Authors: Eaton Sandra S. , Eaton Gareth R.
Published: October 2003

Electron paramagnetic resonance (EPR) imaging maps the spatial distribution of unpaired electron spins. Information about a sample can be obtained from images with one, two, or three spatial dimensions. Images also can be obtained with an additional spectral dimension that reveals the dependence of the EPR spectrum on the position in the sample. One can then seek to understand why certain types of spins are found at particular locations in a sample, why the concentrations vary with position, or why the concentrations vary with time. For the benefit of readers who are not familiar with EPR, a brief introduction to the principles of EPR is given in. The emphasis is on the aspects of EPR that impact the way that imaging experiments are performed. Types of species with unpaired electrons, also called paramagnetic species, that have been studied by EPR imaging are then discussed. Procedures for performing EPR imaging and provide examples of applications are given. More extensive introductions to EPR imaging can be found in the references cited.
Field Emission Display Panels
Authors: Hanson Robert J. , Hetzer David R. , Richter Duane F. , Straka Scott W.
Published: October 2003

Field emission display (FED) panels are a growing sector of the flat panel display market. FEDs have been developed using variations of semiconductor processing with a high degree of process control and cleanliness allowing for cost‐effective manufacture.

Many experts believe they have a strong future as a competitive display technology. In the present work, nearly all aspects of this emerging technology are discussed including: a brief historical review of the FED, fabrication and theory of the cathode and anode panels, phosphor technology, basic fundamentals of spacers, considerations for driving electronics, and final assembly. An expert in the subject of field emission displays will find this paper a refreshing review of several of the more important topics focused on FEDs. Conversely, a person with noa prioriknowledge of the FED should find this paper to be a sound introduction in the field of this relatively new display technology, and also provide a good reference to existing literature for further study.
Gravitation Imaging
Authors: Keller G. Randy
Published: October 2003

Gravitational imaging as defined here refers to geophysical mapping and interpretation of features in the earth's lithosphere (the relatively rigid outer shell that extends to depths of ∼100 km beneath the surface). In fact, the emphasis is on the upper crust of the Earth that extends to depths of about 20 km, because it is this region where gravity data can best help delineate geologic features related to natural hazards (faults, volcanoes, landslides), natural resources (water, oil, gas, minerals, geothermal energy), and tectonic events such as the formation of mountain belts. Such studies provide elegantly straightforward demonstrations of the applicability of classical physics and digital processing to the solution of a variety of geologic problems. These problems vary in scale from very local investigations of features such as faults and ore bodies to regional investigations of the structure of mountain belts and tectonic plates.

In order to produce images, we must first apply corrections to our gravity measurements that remove known variations in gravity with respect to elevation and latitude. Our goal is to derivegravity anomaliesthat represent departures from what we know about the gravity field and to construct images of these values. However below the density within the Earth varies (and varies complexly in the lithosphere), and there is a slow rotation present. However, all of these complications are second order.

Several different types of anomalies have been defined based on the known variations in the earth's gravity field that are considered before calculating the anomaly value. Calculations are given. Terms and concepts are given in order to understand the basics. Correction methods used for gravity measurements are discussed. Gravitational imaging usually involves digital processing based on Fourier analysis. Other topics include imaging capabilities, limitations and construction, and enhancement of gravitational images.

Gravity data are widely available and relatively straight forward to gather, process, and interpret. A particularly nice aspect of the gravity technique is that the instrumentation and interpretative approaches employed are mostly independent of the scale of the investigation. Thus, gravitational imaging can be employed in a wide variety of applications.