Verification Technologies: Cooperative

Aerial Surveillance in International

Agreements

July 1991

OTA-ISC-480

NTIS order #PB91-220020
Recommended Citation:

U.S. Congress, Office of Technology Assessment, Verification Technologies: Cooperative

Aerial Surveillance in International Agreements, OTA-ISC-480 (Washington, DC: U.S.

Government Printing Office, July 1991).

For sale by the Superintendent of Documents

U.S. Government Printing Office, Washington, DC 20402-9325

(order form can be found in the back of this report)
Foreword

In the changing geopolitical environment of 1989, President George Bush revived and amplified

President Dwight D. Eisenhower’s 1955 “Open Skies” proposal calling for mutual aerial surveillance

of NATO and Warsaw Pact territories. Meanwhile, Conventional Armed Forces in Europe Treaty

negotiators were considering aerial inspections as one measure for monitoring arms reductions.

Although neither of these applications of cooperative aerial surveillance have yet been agreed to,

negotiations continue on both. Recently, nations without access to the kinds of national technical

means of verification available to the United States and the Soviet Union have shown interest in

reciprocal overflights as a means of building confidence among international neighbors.

This report examines the potential and limitations of cooperative aerial surveillance as a means

of supporting the goals of a variety of international agreements. It surveys the types of aircraft and

sensors that might be used. It reviews the status of and issues raised by the Open Skies Treaty

negotiations as an extended example of an aerial surveillance regime. The report concludes with a

quantitative analysis of one possible use of cooperative overflights: the search for potential arms

control violations.

In 1989 the Senate Committee on Foreign Relations and House Committee on Foreign Affairs

asked OTA to undertake an assessment centering on the technologies and techniques of monitoring

the prospective START Treaty. In its request, the Committee on Foreign Affairs also called on OTA

to address the “. . . newer technologies that can be brought to bear on such cooperative verification

measures as reamed on-site inspections, manned perimeter and portal monitoring, and unmanned

on-site monitoring. The Committee added that “it would be useful to place these technologies in the

broader context of verification technologies and methods.” Since aerial surveillance is a potentially

significant means of arms control monitoring, this report is one response to the latter request. (Another,

Verification Technologies: Managing Research and Development for Cooperative Arms Control

Monitoring Measures, was published in May 1991.)

The larger assessment has also produced two other, classified, reports: Verification Technologies:

Measures for Monitoring Compliance With the START Treaty was delivered in the summer of 1990

and its unclassified summary was published in December 1990; Monitoring Compliance With Limits

on Sea-Launched Cruise Missiles was delivered in the summer of 1991, with an unclassified summary

scheduled for publication later in the year.

In preparing this report, OTA sought the assistance of several individuals and organizations (see

“Acknowledgments”). We very much appreciate their contributions. As with all OTA reports, the

content remains the sole responsibility of OTA and does not necessarily represent the views of our

advisors or reviewers.

- Directo r

. . . Ill
START Verification Technologies Advisory Panel

James R. Blackwell

Director, International Security

Meridian Corp.

Rodney Nichols, Chairman

Scholar-in-Residence

The Carnegie Corporation of New York

Ashton Carter

Director

Center for Science and International Affairs

Harvard University

Sidney Drell

Professor and Deputy Director

Stanford Linear Accelerator Center

Stanford University

Richard Garwin

IBM Fellow

Thomas J. Watson Research Center

James Goodby

Distinguished Service Professor

Carnegie-Mellon University

Lt. Gen. Andrew Goodpaster, USA (retired)

Chairman

The Atlantic Council

Sidney Graybeal

Chief Scientist

SAIC

Roger Hagengruber

Vice President for Exploratory Systems

Sandia National Laboratories

William R. Harris

The Rand Corp.

Admiral Bobby Inman, USN (retired)

SAIC

Michael Krepon

President

Henry L. Stimson Center

Stephen Lukasik

Vice President and Chief Scientist

TRW/Space Defense Sector

Raymond McCrory

former Chief, Arms Control Intelligence Staff

Consultant

Ernest Mettenet

former CEO, Hercules Aerospace

Consultant

Stephen Meyer

Professor of Politcal Science

MIT

Lt. Gen. William E. Odom, USA (retired)

Director of National Security Studies

Hudson Institute

George Rueckert

Senior Analyst

Meridian Corp.

Albert D. Wheelon

former Chairman and CEO, Hughes Aircraft Co.

Consultant

Charles Zraket

Trustee

The MITRE Corp.

NOTE: OTA appreciates and is grateful for the valuable assistance and thoughtful critiques provided by the advisory panel members.

The panel does not, however, necessarily approve, disapprove, or endorse this report. OTA assumes full responsibility for the

report and the accuracy of its contents.

iv
OTA Project Staff—Start Verification Technologies

Lionel S. Johns, Assistant Director, OTA

Energy, Materials, and International Security Division

Alan Shaw, International Security and Commerce Program Manager

Thomas Karas, Project Director

Arthur Charo

Brian McCue

Christopher Waychoff

Administrative Staff

Jacqueline R. Boykin

Louise Staley

v
Acknowledgments

OTA gratefully acknowledges the assistance of the following people and organizations for their help in

supplying information or reviewing drafts of this report (the contents of the report, of course, remain the

responsibility of OTA):

Thomas Crouch, Director, Department of Aeronautics, National Air and Space Museum, Smithsonian

Institution

Kenneth A. Dreyer, Lawrence Livermore National Laboratory

William Dunlop, Lawrence Livermore National Laboratory

John Fielding, M.I.T. Lincoln Laboratories

Henry Jacobs, Systems Research and Applications Corp.

Peter Jones, Contractor, Verification Research Unit, External Affairs and International Trade Canada, Ottawa,

Canada

James Moore, Defence Scientist, Department of National Defence, Canada

Office of International Negotiations and Arms Control, U.S. Air Force

William L. Pickles, Lawrence Livermore National Laboratory

Ellen Raber, Lawrence Livermore National Laboratory

Albert J. Ramponi, Lawrence Livermore National Laboratory

Priscilla Strain, Program Manager, Center for Earth and Planetary Studies, National Air and Space Museum,

Smithsonian Institution

R. Scott Strait, Lawrence Livermore National Laboratory

Strategic Air Command, U.S. Air Force

Hedy Zigman, System Planning Corp.

vi
Acronyms Used in Text

ACV

AIFV

APC

ATTU

CCD

CD

CSBM

CSCE

EMCON

GLCM

HACV

ICAO

ICBM

IIRS

INF

IRBM

—Armored Combat Vehicle, cf. AIFV,

APC, and HACV

—Armored Infantry Fighting Vehicle,

cf. ACV, APC, and HACV

—Armored Personnel Carrier, cf. AIFV,

ACV, and HACV

—Atlantic Ocean to the Ural Mountains

(Region)

—Camouflage, Concealment, and

Deception

—Conference on Disarmament

—Conventional Armed Forces in Europe

—Confidence- and Security-Building

Measures

—Conference on Security and

Cooperation in Europe

—Emissions Control

—Ground-Launched Cruise Missile

—Heavy Armored Combat Vehicle, cf.

AIFV, APC, and ACV

—International Civil Aviation

Organization

—Intercontinental Ballistic Missile

—Image Interpretability Rating Scale

—Intermediate-Range Nuclear Forces

—Intermediate-Range Ballistic Missile

JSTARS —Joint Surveillance and Tracking

Reconnaissance System

MAD —Magnetic Anomaly Detector

MEL —Mobile-Erector-Launcher, cf. TEL

MRBM —Medium-Range Ballistic Missile

NATO —North Atlantic Treaty Organization

—National Technical Means

0SI —On-Site Inspection

POE —Point of Entry (Exit)

RDA —Restricted Deployment Area

RPV —Remotely Piloted Vehicle, cf. UAV

RV —Reentry Vehicle

RVOSI —Reentry Vehicle On-Site Inspection

SALT —Strategic Arms Limitations Talks

SAR —Synthetic Aperture Radar

SIGINT —Signals Intelligence

SLAR —Side-Looking Airborne Radar

SNF —Short-Range Nuclear Forces

START —Strategic Arms Reductions Talks

TEL —Transporter-ErectorLauncher, cf. MEL

TERCOM —Terrain Contour Matching

TLE —Treaty-Limited Equipment, cf. TLI

TLI —Treaty-Limited Item, cf. TLE

UAV —Unmanned Aerial Vehicle, cf. RPV

WTO —Warsaw Treaty Organization

vii
Contents

Chapter 1: Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Chapter 2: Why Aerial Surveillance? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Chapter 3: Airborne Platforms and Sensors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Chapter 4: Open Skies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Chapter 5: Other Applications of Aerial Surveillance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Chapter 6: Broad Area Searches for Arms Control Treaty Violations . . . . . . . . . . . . . . . . . . . . . . . 73

Appendix A: Monitoring Nonzero Limits... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Appendix B: Photointerpretation and Image Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

Appendix C: Aerial Search as a Basis for Verification Decisionmaking . . . . . . . . . . . . . . . . . . . 104

Appendix D: NATO’s Proposed Basic Elements for Open Skies . . . . . . . . . . . . . . . . . . . . . . . . . . 113

. . . w
Chapter 1

Overview
Introduction .. ● . . . . . . . . . . ●

Summary of the Report . . . .

Organization of the Report .

Figure

1-1. Utilities of Cooperative

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Chapter 1

OVERVIEW

Introduction

On May 12, 1989, President George Bush took a

page from the history of the 1950s and called for

establishment of an Open Skies regime. His proposal

echoed and amplified the failed 1955 Open Skies

proposal of President Dwight D. Eisenhower, calling

for mutual overflights of sovereign territories to

provide common assurance as to the benign (or at

least inoffensive) intentions and capabilities of the

signatory nations. In its current incarnation, the

Open Skies Treaty is being negotiated by the

countries of the North Atlantic Treaty Organization

(NATO) and the members of the now formally

dissolved Warsaw Treaty Organization (WTO).

Under conditions to be specified in the treaty,

freed-wing airplanes equipped with special sensing

devices would fly over the territory of each treaty

party in turn to provide a clearer picture of the status

of the nation overflown.

The revival of Open Skies has also drawn attention to other uses for cooperative aerial surveillance

in international agreements. (Open Skies is just one

possible manifestation of cooperative aerial surveillance.) The idea of using cooperative overflights as

a tool of international policy has not been completely dormant since the 1950s: it has been applied

successfully in isolated instances (e.g., the Sinai and

Antarctica ) and is currently being negotiated into a

side agreement of the Conventional Armed Forces in

Europe (CFE) Treaty.3 But the acceptance of Open

Skies negotiations, particularly by the Soviets,

has led to a renewed willingness of governments

to consider mutual overflights as a means of

gathering information to promote a variety of

goals, from confidence building and weapons

counting to pollution monitoring and invasion

warning.

The collection of information about other countries has historically been of great importance. In the

case of the United States in the post-World War II

era, government officials were particularly concerned about the growing Soviet threat and tried to

obtain as much information about the Soviet Union

as they could. President Eisenhower in 1955 sought

to fill some of this informational void through his

proposed Open Skies. However, Soviet secretiveness and continued rejections of cooperative measures led the United States to spend billions of dollars

developing unilateral capabilities to collect information about the Soviet Union, especially regarding

military preparations. These capabilities ranged

from an early-and not particularly successful-use

of camera-carrying weather balloons snapping pictures at random,4 through airplanes (e.g., the U-2 of

Francis Gary Powers), to those current collection

practices (e.g., photoreconnaissance satellites),5known

in an arms control context as national technical

means (NTM) of verification. The superpowers

may find in cooperative overflights unique qualities that could—under proper circumstances--

supplement their NTM. Less technically advanced

treaty partners that have not had the luxury of -

knowing as much about the world around them

as the superpowers may look to cooperative

aerial surveillance as a partial remedy.

During the late 1980s the opportunity, and to

some extent the need, for cooperative aerial surveillance grew. Primarily, this was a result of “new

thinking’ and ‘glasnost’ in the Soviet Union-the

necessary prerequisites for what President Bush has

heralded as the dawning of a “new world order. ”

l~e p~ciple of a s~te ~ssess~ soverei~ fipace over which i~ and it alone, has control was established by the 1919 PE@ Convention. me

Chicago Convention of 1944 superseded the Paris Convention and provides the basis for modem international civil aviation. See Allen V. Banner,

Andrew J. Young, and Keith W. Hall, Aerial Reconnaissance for Verification of Arms Limitation Agreements: An Introduction (New York, NY: United

Nations, 1990), pp. 15,30.

%k?rflights of Antarctica do not violate sovereign airspace. Ibid., p. 22.

3~e ~ ~ea~ i~elf ~n~ l~t~ Provisiom for brief helicopter Ovefights. ‘r& side aqment, dubbed ‘ ‘CPE IA,” will, if agreed to, permit

much more extensive and intrusive aerial observations.

4s= Mefion E. Davis and Willim R. MS, RAND’s Role in the Evolution of Balloon and satellite Obsewation Systems and Related U.S. &XICe

Technology (Santa Monici& CA: The RAND Corp., September 1988).

5“Photoreconnaissance satellites have become an important stabilizing factor in world affairs in the monitoring of arms control agreements. They

make an immense contribution to thesecurity of all mtions.” —President Jimmy Carter, in a speech at the Kennedy Space Center, Oct. 1, 1978.

–3–
4. Verification Technologies: Cooperative Aerial Surveillance

- “ —

Photo credit: U.S. Air Force

The once-supersecret SR-71A Blackbird reconnaissance

jet used high altitude and record-breaking speed to avoid

interception as it gathered information for the U.S. defense

and intelligence communities. The SR-71 A was taken

out of service in 1990.

During the late 1980s, the Soviet Government,

under the direction of President Mikhail Gorbachev

and then Foreign Minister Eduard Shevardnadze,

developed a new foreign policy that emphasized

cooperation over confrontation and realism over

dogma. Not only did this policy loosen the Soviet

grip on Eastern Europe and lay the groundwork for

settlement of regional disputes, it also led to the

negotiation of more extensive mutual confidence

and security agreements. Cooperative measures,

e.g., on-site inspections (OSIs) and cooperative

aerial surveillance, which had previously been

rejected by the Soviet leadership as overly intrusive,

were declared acceptable. However, the optimism

that crested in 1990 has ebbed in 1991. While

Eastern European countries remain free, concerns

have been raised in the international community

about slowed withdrawals of Soviet troops, evidence

of bad faith regarding the recently signed CFE

Treaty, 6 and grumbling among Soviet reactionaries

about “who lost Eastern Europe. ” Inside the Soviet

Union, these same elements seem to be promoting a

reassertion of Stalinist norms: iron discipline, restricted speech, militarism, and an antagonistic

foreign policy.

In this environment where cooperation and competition coexist, negotiated agreements may:

● reduce tensions and build mutual confidence;

. limit, restrict, and reduce armaments;

. stabilize regional trouble spots;

. settle outstanding disputes; or

● provide for the monitoring of new environmental standards.

Without cooperation, no agreements would be

possible, and if there were no concerns, no agreements would be necessary.

Cooperative aerial surveillance, if applied appropriately, could be a useful instrument for

implementing some agreements and might add

unique capabilities to the tool box that already

includes NTM and cooperative measures, such as

OSIs.

Americans, in concert with others, may someday be able to fly aircraft through the airspace of

the Soviet Union and other countries on a

reciprocal basis, taking pictures and collecting

other data that will contribute to a more secure

future. This report explores the many potential

uses of cooperative aerial surveillance in international agreements and provides a basis for evaluating its applicability, effectiveness, and costs.

Summary of the Report

The Open Skies Treaty, which is being negotiated

by members of NATO and the now disbanded

Warsaw Pact, is intended to be primarily confidencebuilding measure to reduce international tensions

and foster trust and goodwill. Although there has

been some talk of Open Skies flights assisting in the

monitoring of other agreements, the provisions

being negotiated are largely designed for their

symbolic effect.7 In contrast, the possible inclusion of extensive and intrusive aerial surveillance

measures in a CFE follow-on agreement (CFE

IA) would augment other means of verification in

determining compliance with the CFE Treaty

limits.

This report examines the application of cooperative aerial surveillance to these and other possible

international agreements. Although the report often

focuses on agreements that include the United States

and the Soviet Union, the discussion is applicable to

6See, e.g., “Figures Row Suspends C’FE, ” Jane’s Defence Weekly, Mar. 2, 1991, p. 290. The outstanding CFE issues now appear resolved.

T~e @en Skies negotia~g partners releasd a joint communique on Feb. 13, 1990 stating that Open Ski= overflights “wotid Contibute to tie

process of arms reduction agreements and existing obsemation capabilities.” However, the parties have not as yet speeifled any agreements that Open

Skies will support. (“ ‘Open Skies’ Communique,” Ojicial Text, U.S. Arms Control and Disarmament Agency, Feb. 13, 1990.)
Chapter 1—Overview .5

production plant) or they may be elusive (e.g., a

mobile missile). They may be available for viewing

at known times (e.g., weapon eliminations or the

display of SS-25 launchers and sliding-roof garages

provided for under the Intermediate-Range Nuclear

Forces (INF) Treaty); or they may be spotted on a

catch-as-catch-can basis (e.g., underground nuclear

tests, which airborne “sniffers” could monitor for

radiation leaks banned under the Limited Test Ban

Treaty). The object being observed may, in fact, be

an entire facility, perhaps closed as the result of an

accord. If instituted, aerial monitoring flights are

most likely to be included in arms control agreements, but they might also be used to monitor civil

agreements (perhaps governing pollution levels).

All these flights are intended to observe compliance

with the provisions of an agreement, and through

this observation deter, detect, and warn of significant violations. Aerial monitoring may also be used

to assist other means of monitoring, such as NTM

and OSI. Aerial monitoring could take three

any combination of participants and to any region of

the globe.8 Conceivably, overflights might even be

conducted by international organizations in much

the same way OSIs are executed by the International

Atomic Energy Agency. “Cooperative aerial surveillance” describes a collection of concepts for

using sensors on airborne platforms as an important

element of bilateral and multinational agreements. A

party to an agreement providing for aerial surveillance would allow overflights of its territory in

exchange for rights to similar flights over the

territories of the other parties.9

Cooperative aerial surveillance, while generally

thought of as involving only airplanes and cameras,

could take many forms. Possible choices for aerial

platforms include airplanes, helicopters, unmanned

aerial vehicles, or lighter-than-air craft such as

blimps. Sensor choices include photographic, electrooptical, and radar imaging devices, as well as radio

receivers, air samplers, radiation or magnetic anomaly detectors, and acoustic devices. Different sensors’ strengths and weaknesses make them suited to

different inspection tasks, and the output of these

sensors can be synergistically combined to let them

see into one another’s blind spots.

Cooperative aerial surveillance could be the

subject of a stand-alone agreement in which the

flights are both the means and the objective (as in

Open Skies); it could be one provision among

several supporting the ultimate goals of an agreement (as in CFE); or it could be the basis for an

agreement that supports the goals of another agreement that does not itself provide for equivalent

overflights (as in CFE IA).

Cooperative aerial surveillance has three main

uses: mutual confidence building, aerial monitoring of specific targets or activities, and collateral

information gathering (see figure l-l). Confidence

about another country’s intentions and capabilities

can be built when two or more states work cooperatively and open themselves to outside scrutiny. The

Open Skies Treaty is an example of an agreement

whose primary purpose would be to build confidence among the signatories.

“Aerial monitoring,” as distinct from confidence

building, is the process of observing from the air

specific objects or specific activities (defined in

terms of changes in or movement of discrete

objects). These objects and activities may be found

at known (perhaps declared) locations (e.g., a

sFor e~ple, in my 1991 Hungary and Romania signed a bilateral aerial surveillance agxeement calling for four overflights ayeu of ~ch ~~try.

The Arms Control Reporter: A Chronicle of Treaties, Negotiatio~, Proposals, Weapons, and Policy (Brookline, MA: Institute for Defense and

Disarmament Studies, 1991), p. 409.B.25.

‘?Military and intelligence flights over or parallel to the borders of a noncooperative nation are not included in this discussion.
6. Verification Technologies: Cooperative Aerial Surveillance

Figure l-l—Utilities of Cooperative Aerial Surveillance

Confidence building

● Enhance stability

● Increase transparency

● Reduce tensions

● Promote further

cooperation

(Object of observation

undefined by agreement)

Aerial monitoring

● Compliance observation

-Aerial search

-Aerial inspection

-Aerial warning

● Raise cost and effort of

cheating

-Dater violations

(Object of observation

defined by agreement)

Utilities made explicit

by an agreement

SOURCE: Office of Technology Assessment, 1991.

Collateral information

collection

● Background information

● Collateral intelligence

● Aerial warning

● Cuing

(Object of observation

outside letter and spirit of

agreement)

forms: aerial search (looking for restricted ob- establish baseline counts and documentation of

jects or activities over a broad area); aerial

inspection (observing objects or activities at

designated inspection sites, as well as developing

an overall assessment of the site); and aerial

warning (alerting observers to threatening developments).

●

●

●

●

●

Utilities outside the

letter of an agreement

Aerial searches are intended to survey wide

areas in order to provide information that will

assist policy makers in making a determination of

compliance with an agreement. These searches

have two aspects: one is to locate and document

legal objects and activities; the other is to detect

objects or activities that violate an agreement.

Even if aerial searches are unable to provide

concrete evidence of violations, they might collect

useful information that could be used to plan

ground inspections or NTM observations.

Aerial inspection flights might resemble aerial

searches over small designated sites or they might

be used to:

treaty-limited items (TLIs);

conduct preparatory work for OSIs by developing site maps and pinpointing the most

promising search strategy;10

document the elimination of large TLIs and

monitor their status; ll

monitor the status of closed-out facilities and

bases; or

monitor the perimeter around a facility before

an OSI team can arrive.

Besides monitoring the number or existence of

certain objects and activities, aerial monitoring

might provide warning of potentially hostile acts.

This warning might result from discovering too

many objects, too much activity, or the presence of

objects and activity at restricted sites. Conversely,

the absence of legitimate objects or activities at

designated areas might constitute warning that they

are somewhere more threatening. Functionally similar to aerial searches or aerial inspections, aerial

warning flights could observe compliance with

military exclusion zones, border restrictions, or

lo~y sfi~on ~d Michel ~Pu 4‘Streng~e@ tie ~emic~Weapons Convention Through_ Monitoring, ” ~mio~ paper No. 4*

The Henry L. Stimson Center, Washingto~ DC, April 1991, pp. 15, 18-25.

1 IFo~e-pie, ~der~e SAL” ~ Tr~&, ~tir~~ofiers were Cutup ~dp~ced out in me open so tit msatellites could VtX@ dEkdhhShl.
Chapter 1—Overview ● 7

Photo credit: U.S. Department of Defense, On-Site Inspection Agency

In a spectacular display, a Soviet SS-12 missile is

eliminated by explosion in accordance with the INF Treaty.

military exercise limitations (and in fact aerial

surveillance already has been used this way, for

example, in the Sinai).

Overflights could also be used to gather information beyond the letter and spirit of an agreement.

Indeed, the gathering of some such information

would be hard to avoid. The use of this collateral

information could support the stated goals of the

agreement, or it could serve other intelligence

purposes, e.g., strategic assessment, targeting, and

general warning. Because of fears of spying, negotiators may seek to limit the gathering of collateral

information to an absolute minimum by placing

restrictions on overflights and the equipment carried

aboard. Controlling the costs associated with the

loss of collateral information to a military, political, or even economic adversary may be more

important to a country than the financial costs of

an overflight regime.

The advisability of agreeing to aerial surveillance would depend on the goals of the agreement

in question, the capability of overflights to accomplish the missions set for them, a comparative

analysis of different combinations of informationgathering options (e.g., NTM and OSI), and the

costs and benefits of the overflights. Potential

aerial surveillance regimes can range from the

purely symbolic to complete openness with correspondingly high intrusiveness.

An understanding of cooperative aerial surveillance issues can be useful to Congress because:

●

●

●

●

Two agreements that may include cooperative

aerial surveillance (Open Skies and CFE IA)

are under negotiation, though talks are currently stalled. The Senate may be asked for its

advice and consent on one or both of these, and

the Congress as a whole will be asked to fund

any implementation.

Cooperative aerial surveillance is a relatively

new form of information gathering that maybe

useful as a supplement to NTM or other

cooperative measures (e.g., OSI). As such, it

could be incorporated into a wide variety of

current or future international accords governing anything from arms control monitoring and

border patrols to radiation and pollution measurements.

A study of aerial search, in particular, illuminates some of the complexities inherent in all

types of searches. This knowledge, therefore,

provides a basis for evaluating search by NTM.

Witnesses testifying before Congress on the

topic of arms control treaty verification are

often pressed to quantify what they mean by

such statements as ‘If the Russians cheated, we

would be 90 percent sure of catching them,

given enough time.” Though most such estimates are impressionistic, and best taken as

figures of speech, some have a possible empirical basis. In the context of aerial search, this

report illustrates how such estimates could be

generated and interpreted.

This report addresses both the diplomatic and the

technical aspects of cooperative aerial surveillance

as a tool of international cooperation, and it builds a

foundation for evaluating the costs, benefits, and

effectiveness of aerial surveillance regimes. In

particular, it examines the possible provisions currently being negotiated for overflights in the Open

Skies and CFE IA treaties,12 which may have much

in common procedurally and technically when the

actual provisions are agreed upon.

Unlike arrangements that might focus on building

confidence alone, an aerial monitoring regime lends

itself to rigorous analysis. The selection of aerial

platforms and sensor suites and the monitoring

lzNei~er trea~ was completed at tie time of this writing, and drafts of each remain internal exeeutive branch working documents, uvtikble to

legislative branch staff (and thus OTA) until signed by the President.
8. Verification Technologies: Cooperative Aerial Surveillance

procedures can all be optimized for the targets in

question.

Important points in the negotiation of an agreement to permit aerial monitoring would include

limitations on the number, frequency, and territorial

scope of overflights. Negotiators might also agree to

restrictions on the capabilities of sensors and data

storage. They would need to create an inspection

protocol that recognized and limited the potential for

camouflage, concealment, and deception before a

flight can arrive.

The chances that aerial monitoring will function as hoped are lessened by the difficulties

presented by the task of discriminating illegal

targets (e.g., covert missile launchers) from legitimate ones (e.g., flatbed trucks), the potential

mobility of the targets, and the desire to detect

cheating before it becomes significant. Under

some plausible restrictions, aerial monitoring

could be so perfunctory as to be of symbolic value

only—perhaps providing a false sense of confidence. At the other extreme, flights that provide

much useful information might be too intrusive to

tolerate.

As noted above, aerial monitoring of treaty

compliance could perform search, inspection, or

warning functions. Chapter 6 and its associated

appendices A, B, and C apply quantitative analysis

to one of those functions: aerial search.13 Focusing

on this one mission permits OTA to illustrate:

how quantitative methods can be applied to the

larger problem of estimating confidence levels

in our ability to find treaty violations if they

exist;

how comparisons could be made among various monitoring options to produce more costeffective monitoring regimes; and

the importance of applying multiple, complementary instruments to monitoring tasks.

In the case of a wide-area search, any single

flight--even a relatively intrusive one-would be

unlikely to catch a treaty violation, for several

reasons. First, the overflown party might not be

cheating (perhaps as a result of the prospect of

overflights). Second, if the overflown party is

cheating, the illicit objects or activities would

probably be restricted to a region that is relatively

Photo crefit: U.S. Department of Defense

The existence of small, off-road-capable, mobile missile

launchers, like this Soviet SS-20, has made the task of

monitoring covert deployments more difficult. SS-20s have

been eliminated as part of the INF Treaty.

small when compared to the nation as a whole:

because of the limitations of the airborne platform,

any one flight could probably cover only a small

percentage of the territory subject to overflights.

Without knowing where to look, the probability of

finding the violation would be relatively small.

Third, given sufficient prior notice and information

about how a flight is to be conducted, the cheater

could take steps to minimize the chances of being

observed through camouflage, concealment, or deception, so that violations would be missed even if

they were inside the region inspected by a flight.

To be reliable, a program of aerial search

would need a series of flights to compensate for

the relative unlikelihood that any one flight

would catch a violation if it existed. Prior information about the characteristics of the target

could narrow the region to be searched and thus

lessen the reliance on chance alone. Several kinds

of prior information can be helpful: the results of

previous aerial searches; the outputs of other information sources, e.g., NTM, OSI, and other types of

aerial monitoring; the natural constraints provided

by topography and weather, as well as the additional

constraints imposed by infrastructure; and a sense of

the overflown side’s operational practices and doctrine. The full use of such prior information is one of

the skills of the photointerpreter, an artisan whose

craft remains largely unautomated.

13Note that aerial warning is closely related to aerial search and that many of the same principles apply.
Chapter 1—Overview .9

The most difficult part of using information

gathered by aerial search (or, indeed, any other

means) in treaty verification is deciding what to

make of a continuing stream of reports that no

cheating has been found. Bayesian statistics, a

recently revived14 body of early statistical thought,

allows the incorporation of such negative evidence

into a continuously updated view of the situation.

Bayesian calculations make possible the form of

expert testimony that decisionmakers want most:

“Based on the fact that we haven’t seen any

cheating, on the probability that we would have seen

it if it were going on, and on our original estimate of

how likely it was that they would cheat, we assess

that there is an x percent chance that they are

violating the treaty. ’

Although the prospective Open Skies Treaty is

primarily intended to build mutual confidence among

its signatories, it is also presented by some of the

participants (and indeed, the aforementioned joint

communique) as helpful for monitoring provisions

of other, particularly arms control, agreements. As

an illustration, OTA applied the publicly released

Open Skies overflight provisions to the task of

monitoring Soviet mobile missiles of the types

covered by the Strategic Arms Reductions Talks

(START). OTA’s analysis, while preliminary, suggests that the number of flights would be far too few

to make an exhaustive search of the Soviet Union.

However, their measurable chance of uncovering a

sizable violation—should it exist—in a matter of

months would loom large in the minds of Soviet

planners. The chances that flights would find a

violation—should it exist-would be raised if the

use of prior information obviated the need for

exhaustive search of the entire Soviet Union. Flights

could cue NTM as well as be cued by them.

The mobile missiles limited by START are not the

only possible items of interest to arms control treaty

verifiers. Some other topics, e.g., the location and

status of declared sites, the absence of undeclared

freed facilities, and the location or movement of

large-scale military formations, could be readily

investigated by a program of aerial monitoring. Nor

is the utility of overflights limited to search-for

example, flights could aid in the monitoring of

START or START-like provisions by loitering over

the site of a challenge inspection while an OSI

After data has been gathered by an aerial surveillance

flight, the arduous task of sifting, sorting, and analyzing the

data commences. In the case of imagery, highly skilled

photointerpreters must carefully examine each frame for

valuable information.

ground team was on the way, or provide clues as to

the best locations to conduct such inspections.

Organization of the Report

Chapter 2 of this report presents an overview of

the utilities of cooperative aerial surveillance-both

good and bad—and discusses the interaction of

cooperative aerial surveillance with other means of

information gathering, most notably NTM and OSI.

Chapter 3 surveys the types of airborne platforms

and sensors that might be applied to a prospective

overflight regime and raises some of the issues

associated with their use. In chapter 4, Open Skies is

discussed as both the source of renewed interest in

using overflights as an instrument of international

relations and as a prime example of the use of

cooperative aerial surveillance as a means of build14M.G. Bulmer, principles of statistics (New York NY: Dover, 1979), pp. 169-176, especially p. 176. See ako Steven M. Wlm, The HiSfo~ of

Statistics: The Measurement of Uncertain~ Before 1990 (Cambridge, MA: Belknap Press, 1986).
10. Verification Technologies: Cooperative Aerial Surveillance

ing international confidence. Chapter 5 looks at chapter 6 builds an analytical framework for evaluatother possible applications of cooperative flights in ing overflight monitoring regimes using quantitative

agreements designed, inter alia, to build confidence, methods and Bayesian statistics. The first three

monitor arms and environmental restrictions, and appendices to this report continue the quantitative

safeguard borders. Through a discussion of the discussion. The final appendix records NATO’s

capabilities and limitations of broad area search, initial Open Skies proposal.
Chapter 2

WHY AERIAL SURVEILLANCE?
summary . . ..*,...*.

Introduction . . . . . . . . .

Contents

What Is Cooperative Aerial Surveillance? . .............,.........,.,,..,,, * 13

The Utility of Aerial Surveillance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Confidence Building . . . . . . . . . . . . . . .....,..................,...,... * 15

Aerial Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Collateral Information Collection ... ... ... ... ... ... ... ... ... , 19

Aerial Surveillance and Other Means of Observation . ................*,,,,,, + 23

Aerial Surveillance and NTM . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . 23

Aerial Surveillance and OSI ... ... ... ... ... .*. ... ... ..*+ .

4

. *.*. **. *.. .*** .. .. 25

Overlapping Agreements and Assets ... ... ... ,.. ... ... ... ... ... .,+. **+***,, 26

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

Boxes

BOX Page

2-A. Balancing Monitoring and Incentives To Cheat ... ... ... ... ... +.. ... ,. 20

2-B. Aerial Surveillance for Countries Without Advanced NTM . . . . . . . . . . . . . . . . . . . . . . 26

2-C. Reading Tags From Aircraft ... ... ... ... ... .*. ... ..*. +

.. *.*. .*. *.. #*. .*o. ****e* 26

Figures

Figure Page

2-1. Utilities of Cooperative Aerial Surveillance . ...,..**...,.*.,.,**.++,.****,.*+*** 15

2-2. Interaction of Utilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Chapter 2

WHY AERIAL SURVEILLANCE?

Summary

Cooperative aerial surveillance could be the

subject of a stand-alone agreement in which the

flights are both the means and the objective (as in

Open Skies); it could be one provision among

several supporting the ultimate goals of an agreement (as in the Conventional Armed Forces in

Europe Treaty (CFE)); or it could be the subject of

an agreement that supports the goals of another

agreement that does not itself provide for equivalent

overflights (as in CFE IA).

Aerial surveillance has three main uses: mutual

confidence building; aerial monitoring of specific

targets, sites, or activities; and collateral information

gathering. Confidence building and aerial monitoring would be explicit functions written into an

overflight regime, whereas the collection of collateral information is an implicit byproduct contrary to

the spirit of an agreement. Aerial monitoring can be

used to search for, inspect for, deter, detect, and warn

of noncompliant behavior, as well as to provide

information that might assist other means of monitoring. Collateral information can supplement agreed

sources of information about treaty compliance or it

can be used for other intelligence purposes, e.g.,

strategic assessments, targeting, and general warning.

Aerial surveillance can work collectively and

synergistically with on-site inspections (OSIs), other

cooperative measures, and national technical means

(NTM) of verification. The decision to include aerial

surveillance in an accord would depend on the goals

of the accord, an assessment of the relative strengths

and weaknesses of the different monitoring options,

the costs and benefits of the regime, interactions

with other agreements, and negotiability.

Introduction

In 1955 President Dwight D. Eisenhower proposed “Open Skies,” a plan for an international

program of reconnaissance flights intended to reduce fears of surprise military attack. The Soviet

Government rejected this proposal as a U.S. effort to

spy on the Soviet Union. But after President George

Bush revived the proposal in May 1989, a transformed Soviet Union seemed more receptive. It

agreed to interalliance negotiations on an Open

Skies Treaty to build mutual confidence. The same

23 nationsl were already negotiating provisions for

cooperative aerial surveillance as part of the CFE

Treaty’s compliance monitoring regime.

The Open Skies negotiations eventually stalled

and the CFE Treaty was signed on November 19,

1990, without extensive aerial monitoring provisions (though further negotiations--CFE IA-may

yet add such provisions).3 The fact that these

cooperative aerial surveillance negotiations took

place reflects the promise of the idea; their inconclusiveness reflects the difficulties of designing an

overflight regime that would satisfy the goals and

concerns of different nations.

This chapter qualitatively examines the utility of

aerial surveillance in supporting the goals of an

agreement. 4 Depending on how they are implemented, overflights can build confidence in the

inoffensiveness or benignancy of the other parties,

monitor agreements, or gather collateral information. This chapter also explores the interaction of

aerial surveillance with NTM and OSI.

What Is Cooperative Aerial

Surveillance?

“Cooperative aerial surveillance” describes a

collection of concepts for using sensors on airborne

1~~ ~mber b~me 22 with the unification of @ ITIWly in October 1990.

?For the purposes of tis report, “~fi surve~~~,” “acrid obscrvatio~” and “~fi r~ti sance” are regarded as synonymous and

encompass all types of airborne observation described.

Swhen the CFE Tr~ty ent~s into form, it mbe vfiled by NTM and cooperative measures, such as 0S1S. ti~inspections~be include4

but they will be limited to brief host-operated helicopter flights over inspection sites. These overflights ~e much less extensive and intrusive than those

under consideration for CFE IA. The signing of CFE before the completion of all its aerial monitoring provisions implies that the CFE IA flights may

serve a more supplementary, than critical, role in verMcation.

4Aeri~ mofito~,~ p~c~m, lendsi~el.f t. qmti~tive analysis. The foundations for such an analysis are presented in chs. 3 ~d 6.

–13–
14. Verification Technologies: Cooperative Aerial Surveillance

platforms as an important element in bilateral and

multinational agreements. A party to an agreement

providing for aerial surveillance would allow overflights of its territory in exchange for rights to

similar flights over the territories of the other

parties. 5

While generally thought of as involving only

airplanes and cameras, cooperative aerial surveillance could take many forms. Possible choices for

aerial platforms include airplanes, helicopters, unmanned aerial vehicles (UAVs), or lighter-than-air

craft such as blimps. Sensor choices include photographic, electro-optical, and radar imaging devices,

as well as radio receivers, air samplers, radiation or

magnetic anomaly detectors, and acoustic devices.

The selection of platform and sensor will depend on

the nature of the agreement being negotiated.

Cooperative aerial surveillance could be included

in an agreement in three general ways: it could be

both the means and the objective (as in Open Skies);

it could be one provision among several supporting

the ultimate goals of an agreement; or it could be the

basis for an agreement that explicitly supports the

goals of another agreement that does not itself

provide for overflights.

Although this report focuses primarily on negotiations of which the United States and the Soviet

Union are a part, the principles discussed would be

equally applicable to any set of nations.

The Utility of Aerial Surveillance

Cooperative aerial surveillance could have three

main uses in an international accord: mutual confidence building, aerial monitoring of specific targets

or activities, and collateral information collection

(see figure 2-l). Confidence building and aerial

monitoring are legitimate functions, which follow

the letter and spirit of an accord. The collection of

collateral information is a generally unavoidable

byproduct of an overflight regime which tries to

restrict either the quantity or quality of the data

collected.

Confidence about the inoffensiveness or benignancy of another country’s intentions and capabilities can be built when two or more states work

cooperatively and open themselves to outside scrutiny. The Open Skies Treaty is an example of an

overflight regime whose primary purpose would be

to build mutual confidence among the signatories.

The phrase “confidence building” is fairly amorphous, but captures a range of positive concepts,

e.g., a reduction of tensions, greater transparency,

and the development of common understanding

through increased contact and openness.

“Aerial monitoring,” as distinct from confidence

building, is the process of observing from the air

specific objects, sites, or activities (described by the

movement of discrete objects). The objects and

activities may be declared with their locations

known (e.g., a production plant), or they may be

mobile and difficult to see. Aerial monitoring flights

are likely to be included in arms control agreements

to search for, inspect for, raise the cost of, deter,

detect, or warn of compliance violations as well as

to provide information that might assist other means

of monitoring, but flights can also be used to monitor

civil agreements (e.g., pollution levels).

Overflights could also be used to gather information beyond the letter and spirit of an agreement.

Indeed, the gathering of some such information

would be hard to avoid. The use of this collateral

information could support the stated goals of the

agreement, or it could serve other intelligence

purposes, e.g., strategic assessments, targeting, and

general warning. Because of fears of spying, negotiators may seek to limit the gathering of collateral

information to an absolute minimum by placing

restrictions on overflights and the equipment carried

aboard.

There are only two instances in which the utility

of the overflights and the purposes of an agreement

might coincide completely, but these are extreme

cases that will not likely form the basis for a

negotiable agreement. First and most simply, parties

to the agreement could recognize and legitimate the

broad capabilities of aerial surveillance. The parties

could then gather as much information as the

negotiated sensors would allow. By definition, there

would be no collateral information to gather, since

all information would be fair game. At the other

extreme, exceptionally tight controls could be

placed on the inspection team, aircraft, sensors, and

data to ensure that only information related to the

agreement would be gathered and processed.

5~i~ and ~te~gence fJ,ights over or pm~lel to the borders of a noncooperative nation =not included in this dis~ssion.
Chapter 2—Why AerialSurveillance? ● 15

Figure 2-l—Utilities of Cooperative Aerial Surveillance

Confidence building

● Enhance stability

● Increase transparency

● Reduce tensions

● Promote further

cooperation

(Object of observation

undefined by agreement)

Aerial monitoring

“ Compliance observation

-Aerial search

-Aerial inspection

-Aerial warning

● Raise cost and effort of

cheating

-Deter violations

(Object of observation

defined by agreement)

Utilities made explicit

by an agreement

SOURCE: Office of Technology Assessment, 1991.

Negotiators are unlikely to agree to these two

extreme cases. They are more likely to pursue

restrictions on both the methods of information

collection and the type of information collected.

Parties will negotiate a middle ground, trading some

benefits of confidence building or monitoring for

some losses of collateral information. Striking this

balance is perhaps the most difficult challenge

facing overflight regime designers.

Confidence Building

The role of aerial surveillance in confidence

building is epitomized in the current negotiations

over an Open Skies Treaty. The stated goal of Open

Skies is primarily confidence building. The framers

of this treaty do not envision it as an arms control

agreement that uses aerial surveillance to monitor

limits on military hardware or activities. Instead,

they have argued simply for greater international

openness on the grounds that transparency leads to

enhanced stability and predictability, reduced tenCollateral information

collection

● Background information

● Collateral intelligence

● Aerial warning

● Cuing

(Object of observation

outside letter and spirit of

agreement)

Utilities outside the

letter of an agreement

sions, and international cooperation, and lays the

foundation for future, more specific arms control

measures.

6

The potential for aerial surveillance to gather

information about the inspected party is great. To the

extent that this information corroborates positive

declarations and policies or deters undesirable

behavior, the agreement can be said to enhance

stability, reduce tensions, and thus build general

confidence. To the degree that this information

would be able to reveal in a timely fashion duplicity

or bad faith, should such occur, confidence is built

in the agreement itself.7 Ironically, if such duplicity

is discovered, it would, at least temporarily, exacerbate instability and tensions. (See figure 2-2.)

The confidence-building aspect of aerial surveillance is also reflected symbolically in nations

pursuing common goals, in multinational inspection

teams (possibly dominated by military personnel)

%e Open Skies negotiating partners released a joint communique on Feb. 13, 1990 stating that Open Skies overflights “would contribute to the

process of arms reduction agretxnents and existing observation capabilities.” However, the parties have not as yet specitled any agreements that Open

Skies will support. This differs tlom an agreement like CFE that includes limited helicopter surveys of inspection sites or the CFE follow-on treaty

(dubbed “CFE LA”) currently being negotiated that is explicitly designed to provide monitoring of CFE restrictions. Open Skies is discussed in ch. 4;

CFE and CFE IA are discussed in ch. 5. (“ ‘Open Sties’ Communique,” OficiaZ Text, U.S. Arms Control and Disarmament Agency, Feb. 13, 1990.)

T~e det@.ion of cheating do= not n~ss~ym~ that a treaty is flawed. It maybe that this level of activity would not have kendetatibletitiout

the monitoring provisiona of the treaty. The cheating does, however, require some appropriate response including possibly the abrogation of the treaty.
16 Verification Technologies: Cooperative Aerial Surveillance

Figure 2-2—interaction of Utilities

Confidence building

Ill

[

Collateral information

)

Ili

collection

SOURCE: Office of Technology Assessment, 1991.

working side-by-side, and in laying groundwork for

more ambitious cooperative efforts.

Confidence building is likely to be a part-either

as a primary goal or as a side benefit--of all

potential agreements that include provisions for

cooperative aerial surveillance. For example, mutual

aerial surveillance of nuclear reactors to ensure their

safe operation might have the specific utility of

measuring reactor radiation levels, but they might

also foster a cooperative atmosphere. The only

instances where confidence might be undermined b y

overflights of countries following both the spirit and

the letter of an agreement (i.e., compliant countries)

would occur when a signatory has underestimated

the potential of overflights to be used against it for

gathering collateral information (see below).

Aerial Monitoring

Aerial monitoring is the process of observing

from the air objects, sites, or activities (described by

the movement of discrete objects) that have been

specifically designated in an agreement. Because the

subject of observation is explicitly defined (e.g., a

tank, a chemical plant, a combined-arms exercise),

negotiations over airborne platforms and sensors can

be based to a larger degree on objective criteria. For

example, an agreement that seeks to count individual

tanks must provide for sensors that at a minimum

can distinguish a tank from an automobile. In

general, aerial monitoring regimes can be subjected

to quantitative analyses (e.g., the number of flights

needed to search a given area, the minimum

requirements for a sensor suite) more readily than

overflights intended only to build confidence. Theoretically, this should make negotiations somewhat

clearer.

Parties to an agreement with provisions that

require verification could employ aerial monitoring

for purposes of search, inspection, or warning.

Aerial monitoring could also, by its very presence,

raise the expense of, and possibly deter, cheating.
Chapter 2--Why Aerial Surveillance? ● 17

Photo credit: U.S. Department of Defense, On-Site Inspection Agency

Working side-by-side, inspectors and their escorts sometimes develop a better understanding of their former adversaries and

perhaps even mutual respect. Here, the Soviet inspection team chief and his American escort counterpart sign the official

report that marks the completion on an Intermediate-Range Nuclear Forces Treaty inspection.

Compliance Observability

An agreement that includes numerical limits,

bans, or restrictions on actual weapons, equipment,

facilities, or activities may permit aerial monitoring

to observe compliance. Compliance observability is

most often discussed in the context of arms control

agreements. However, there are many potential

applications for aerial monitoring where it might be

desirable to observe activities or objects that have

little or nothing to do with traditional arms control

(e.g., peacekeeping or pollution monitoring).

Aerial monitoring, as used in this report, encompasses the narrower terms: “aerial search,” “aerial

inspection, ’ and “aerial warning. ’ Aerial search

refers to overflights that survey wide areas to detect

and determine the legitimacy of specfied objects or

activities. Aerial inspection differs from aerial

searches only in that it focuses on objects or

activities at specific sites. Aerial warning also

involves the observation of specific activities, objects, or sites, but with the intent to warn of

threatening acts. These distinctions are artificial and

partially overlap, but they are a useful tool in

clarifying the discussion.

Aerial Search8—Aerial searches are intended to

survey wide areas in order to provide information

that will assist policymakers in making a determination of compliance with an agreement. These searches

have two aspects: one is to locate and document

legal objects and activities; the other is to detect

objects or activities that violate an agreement. For

example, an agreement might allow a certain number of objects, which aerial search could help count.

If the objects were entire facilities (e.g., Intercontinental Ballistic Missile (ICBM) silos or chemical

plants) or large-scale activities (e.g., division-sized

exercises), this might be a relatively straightforward

8 See ch. 6, which builds an analytical framework for examining the effectiveness of serial search.
18. Verification Technologies: Cooperative Aerial Surveillance

mission. Smaller and relocatable treaty-limited items

(TLIs), e.g., cruise missiles, would add more difficulties.9 If monitoring is possible at all from the air,

it might be facilitated by focusing on chokepoints

that the TLI must pass through (e.g., a final assembly

plant, abridge, or a railroad junction), or by remotely

reading active tags on the TLI.10

The second aspect of compliance observability is

to ensure that the observed party is not significantly

violating the provisions of an accord through the

possession of prohibited items or the conduct of

restricted activities. As above, the size and mobility

of the TLIs in question is often important. Most

troublesome are small and mobile TLIs that can be

concealed or moved before an overflight. Under a

plan suggested by North Atlantic Treaty Organization (NATO) for Open Skies, the amount of time an

illegal TLI would have available to hide would be 46

hours plus the time to fly to the TLI if concealment

began at the time of flight notification, or 24 hours

plus the time to fly to the TLI if this concealment

began with the filing of the flight plan. (See

discussion inch. 4.) Clearly, this would an ineffective interval for detecting easily hidden, illegal TLIs.

Thus, negotiators must take such timelines into

account when deciding to include an aerial surveillance option and adjusting it to fit the TLI under

observation. The interval must be short enough to

detect cheating or at least to flush the TLI into the

open for detection by other means.ll

For some classes of objects or activities, signatures other than size are most important for violation

detection. For example, a plant releasing restricted

pollutants might be detectable not so much by its

dimensions, but rather by its effluents. Air samplers

on aircraft might be able to detect these emissions or

their residue if the time it takes for the aircraft to

arrive is less than the time for the emissions to

dissipate after the violator shuts down operations.

Even if aerial searches are unable to provide

concrete evidence of violations, they might collect

useful information that could be used to plan ground

inspections. (For more on the interaction of OSI and

aerial surveillance, see below.)

Photo credit: U.S. Central lntelligence Agency

In the 1962 Cuban missile crisis, military

reconnaissance aircraft were used to search for and

document Soviet medium-range nuclear missile

emplacements. This photograph of a missile preparation

area was taken at an altitude of about 250 feet,

and at the speed of sound.

Aerial Inspection-Potential aerial inspections

differ from aerial searches in that they seek to

monitor compliance at known (and often treatydesignated) locations. Some aerial inspections might

closely resemble a search, only over a smaller

region. For example, photographs taken by the

inspection team from a helicopter might be used to

look for illicit TLIs within the grounds of a restricted

deployment area. However, other types of aerial

inspection might be very different. Among other

things, they might be used to:

●

●

establish baseline TLI counts and documentation;

conduct preparatory work for OSIs by developing site maps and pinpointing the most promising search strategy;12

9See ch. 6 for a quantitative discussion of the challenge of searching for such ~sfiOm tie W.

1oSee box 2-C.

lls~ety and logistical reasons will limit the reduction of this interv~ as may -tyCOncerns.

lz~y s~~on~Mictiel fiwm“s~~e~tie CIIemiCaI Weapons Convention Through Aerial Monitoring,” tiwio~ Wper No. 4,

The Henry L. Stimson Center, Washington.L DC, April 1991, pp. 14, 17-23.
.

Chapter 2—WhyAerial Surveillance? . 19

document the elimination of large TLIs and

monitor their status;13

monitor the status of closed-out facilities and

bases; or

monitor the perimeter around a facility before

an OSI team can arrive.

Aerial Warning—Besides monitoring the number or existence of certain objects and activities,

aerial monitoring might be written into an agreement

to provide warning of hostile acts. This warning

might be the product of discovering too many

objects, too much activity, or the presence of objects

and activity at restricted sites; or conversely, the

absence of legitimate objects or activities from

designated areas with the implication that they might

be somewhere more threatening. Functionally similar to aerial searches or aerial inspections, aerial

warning flights could observe compliance with

military exclusion zones, border restrictions, or

military exercise limitations. Unlike confidencebuilding flights, warning flights would be explicitly

tailored to sense a specific set of objects or activities

(defined by objects). (See ch. 5 for some current and

potential examples of aerial warning.)

One of the chief concerns of any party to a

militarily significant agreement, and the predominant reason for its monitoring regime, is the threat of

a dramatic breakout from the terms of an agreement

by another party. Breakout can be defined as a

violation of an accord so rapid as to confer a

militarily significant advantage before the other

side(s) has time to react. No agreement can prevent

a party from attempting a breakout; however, a good

monitoring regime and effective intelligence could

make successful breakout impossible by being able

to detect the intended action with sufficient time to

respond, thus providing strategic warning.14 (Responses could be diplomatic, economic, or military;

and reciprocal or asymmetric.15)

Make Cheating More Difficult and Expensive

A side benefit of being able to observe compliance from an aircraft is that any attempt by a country

to cheat on an agreement, even if the violation is not

in the end detected, is necessarily more difficult and

expensive than if overflights were not permitted.

This is because the violator must expend some effort

to avoid detection. If the agreement were poorly

formulated or if the sensors carried aboard the

aircraft were inadequate, this effort might be minimal (e.g., raising a camouflage net).l6 However, if

the agreement were designed with potential evasion

paths in mind, the difficulty and expense of cheating

might be raised to some deterrent level (e.g., by

forcing the violator to avoid a TLI’s legal manufacturing, testing, and support infrastructure, and to

build an entire covert one). The idea is to make the

anticipated gain of cheating not worth the effort (see

box 2-A). Note that an agreement that does not restrict or allow the inspection of sensors has the

greatest deterrent potential since the overflown

country can only guess at the capabilities onboard

and would probably be inclined to make a conservative estimate.17

Collateral Information Collection

Another utility of overflights is the gathering of

information not specifically mandated by an accord

(what the Soviets have sometimes labeled spying) .18

This collection is very hard for both the host country

and the observers to limit. For example, a flight

looking for a missile silo may take hundreds of

square miles’ worth of photographs for every hundred square feet of silo. Similarly, an air sampling

spectrometer may reveal more compounds than just

the ones subject to the accord. At a minimum, the

inspectors aboard a plane must be allowed to

confirm visually that the plane is following its

13F~~~9@3 ~d~rthe s&T~Tr~~, ~~bo~rs Werecutup ~d p~c~ out irl me Opn so tit ~satemtes could verify their ehilUltiOIL

14The ~tio~ fitelfigmw ~m~~ wo~d ~ve ~sponsibility for detecfig mili~y s~~t developments with or withOut a -.

ISR~iproc~ r=wmw some~es~ve tie negative @ity of ~o~the vio~tor to ~n~l the ~~ of competition. For eXSmple, ifa p-with

adominant air force violates a conventional arms accord by building extra attack aircraft, it might make more sem.se for a less sophisticated cosignatory

to buildup antiaircraft batteries, rather than build a like number of relatively inferior planes.

16~com, if comp~a were not obs~ab]e from the ~, Overflights wo~d ~ve no dete~nt v~ue, ~d m@ h fact act tO 13Mke the OVeffl@lg

nation unjustifiably conlident.

17~acom@ &d notm~e ~ accmte ~~te and chow to ch~~ its vio~tionwould likely be det~t~. (see Smithson and Kmpo~ Op. Cit., fOOb30te

12, p. 4.)

18~e ~lce of TW~oloBAsswmat dms not endo~ the coll@ionof co~atm~ ~o~tion, but presents it~ an @)OWtfaCtOrh3 determining

the risks and benefits of aerial surveillance.
20. Verification Technologies: Cooperative Aerial Surveillance

Box 2-A—Balancing Monitoring and Incentives To Cheat

The conceptual graph below depicts two general cases of how the balance of incentives might be related to the

monitoring provisions of an agreement. The curves generated by the examination of a real treaty are bound to be

much more complex, with many nuances and ambiguities.

o

I

Point of balanced incentives and

disincentives.

Monitoring effort — ~

*Effective or absolute monitoring may not be possible for all agreements.

SOURCE: Office of Technology Assessment, 1991.

The characteristics of the objector activity to be monitored and how they fit into the monitored country’s

security arrangements, as well as the propensity of the country toward cheating, provide the starting point on this

graph. This point is the net incentive to cheat on the agreement in the absence of all monitoring. In this graph, the

more interesting example of a positive net incentive without monitoring is described, but for some violations there

may be no incentive to cheat at all.l

Curve A depicts the case where no amount of monitoring will lower the net incentive to cheat to zero. This

might occur when violations are too easily hidden to monitor effectively, when the positive incentives to cheat are

extraordinarily high, or when the cost of getting caught is comparatively low. Even if effective monitoring (defined

as monitoring that detects any significant violation in time to respond) or absolute monitoring (defined as

monitoring that detects all cheating) are possible--and not all potential agreements can be effectively monitored,

the positive incentives to cheat continue to outweigh the disincentives.2 In this case, the best that can be hoped for

is an agreement that provides, at a minimum, an effective monitoring effort.

IH& moni~~ cmtgt imptea no value to the freaty, then this point would equal the net incentive to engage in the restricted activity (e.g..

build another bomber) without the agreement. However, if the country values the agreement on its own merits, then the country will have a lower

inmmtive to engage in the restricted activity than it did without the agreement. In some cases, the legal and moral imperative of the treaty itself

may beenoughto lower the incentive to cheat below zero. On the otherham$ the existence of an agreement might actually raise the net incentive

to cheat above the preagreement level if mutual restrictions opened new opportunities for gaining strategic advantages. For example, building

another bomber might make little sense if the other side were doing the aam~ however, an advantage might be gained by building that same

bomber if the other side were abiding by an agreement not to do so.

2’I’&s ~ph~ ill~m~how @rnOni@@ pmy might unwisely squander limited monitoring resources by payi.UgfOrmOnitO*g bond

what is required for deterrence, or effective or absolute monitoring.
Chapter 2—Why Aerial Surveillance? .21

Curve B illustrates the case where some amount of monitoring lowers the incentive to cheat past the level of

indifference (i.e., the zero line where incentives and disincentives are balanced) until the costs and difficulties of

cheating offset the expected benefits. It is in this region below the indifference line where deterrence operates. An

agreement might be considered to have sufficient monitoring if the net incentive to cheat could be forced into this

negative region, regardless of whether or not the monitoring regime was deemed “effective” or “absolute.”

Of course, the real world is more complicated than this. The incentive structure of the monitored party and how

it varies with increasing monitoring is hard for the monitoring party to gauge. Because of this element of uncertainty,

a real graph would be less well defined and the monitoring party would want the disincentives to cheating to fall

well below the line of indifference, rather than just across it. Moreover, the monitoring party must be prepared for

sudden shifts in the incentive structure--shifts that would void the deterrent value of monitoring.

proper path and not being flown off course by its host

country pilots, should they be piloting.19

The definition of what constitutes collateral

information in an aerial monitoring regime is

relatively simple since the objects of observation

(e.g., tanks, bombers, military exercises) are stated

in the agreement text. Any information gathered that

does not specifically conform to the letter and spirit

of the text is collateral. In the case of confidencebuilding regimes, however, this distinction is less

clear since the object of observation is undefined.

Yet, there will likely remain some degree of

consensus—reflected in the selection of airborne

platform, sensors, and operational procedures-as to

what is expected of the confidence-building overflights and what behavior violates the spirit of the

agreement.

For the country conducting a cooperative overflight, collateral information can be a side benefit

(obtained passively or actively) of an agreement,

providing background information on the agreement, collateral intelligence, warning, or cuing. For

the side being overflown, collateral information may

be going to a country that may not have the

overflown country’s best interests at heart. Of

course, cooperative aerial surveillance is likely to be

reciprocal, so each country will both enjoy the

benefits and suffer the loss of collateral information.

Negotiated constraints could limit the compromise of this type of information. These include:

●

●

●

●

●

●

closing sensitive airspace to overflights;

permitting flights only at night or at high

altitudes;

restricting sensor and data storage capabilities;

disallowing storage of data (all monitoring

would have to be done by an inspector in real

time);

passing collected information (raw data)

through host country preprocessing;20 and

employing only UAVS.

21

Moreover, not all of this information is equally

valuable (to the inspecting party or the host country).

Each party must weigh its potential informational

losses against the gains of the accord and the gains

from conducting its own overflights.22

Background Information

Background information is that acquired beyond

the specific mandate of the agreement, but still

useful for achieving its goals. For example, a treaty

may call exclusively for the aerial counting of a

hypothetical TLI. During the overflight, sensors

image the sole production facility for the TLI. Using

photogrammetric techniques, the volume of the

facility is measured and combined with other clues

(e.g., on-hand supplies and storage areas) to estimate

its production potential. If this potential correlates

with the legal number of TLIs, confidence in the

treaty is enhanced; if the figures do not correspond,

and there appears to be excess capacity, then the

inspecting party would be alerted to the possible

presence of covert TLIs.

19TW~c~@, MS could be confii~by navigation equipment alone (as might be necessary at night). However, if the level of animosity is high (~

thus the stakes as well), the observers may want to see for themselves that the aircraft is on course.

m~wmuss~gti~t ~volve the ~n~expwgation or computer fdtration of all material not deemed necess~ for the PWoSeS of tie agreement.

zlUA”5 ~ &Cu5wd in more de~l fi & 3.

%ecause the Soviet Union and the United States already enjoy advantages provided by ~ their informational gains will be relatively small

compared to those of other, less advanced countries. (The French SPOT-Image multispectral remote-sensing satellite produces relatively low resolution

imagery for international sale.)
22. Verification Technologies: Cooperative Aerial Surveillance

Collateral Intelligence

Information collected that is not related to an

agreement, but instead covers the gamut of social,

economic, political, and military targets is collateral

intelligence. 23 This information ranges from the

trivial to the vital. Collateral intelligence can provide a clear view of a previously obscure fact or

confirm other, unverified facts. One example of

collateral intelligence is the collection of imagery of

agricultural areas to get a better understanding of

annual crop yields and potential shortages. Another

example would be photographs of a piece of

sensitive military hardware.

Also in the class of collateral intelligence would

be all information gained from training sensors on

parties not subject to an overflight agreement when

flying near their border or during transit over their

territory to or from a host country. Transit flights

would probably be restricted to commercial air

corridors.24

Through the collection of intelligence, a nation

refines its strategic assessment of another country

and acquires a better understanding of the threat it

may pose.

25 It is in the national security interest of

each country to know the most it can about the

others. The paradox is, however, that it is not always

in each country’s national security interest to share

like information about themselves with others.

Certainly, the United States has all sorts of sensitive

facilities it might not like the Soviets to fly over. On

the other hand, U.S. analysts would like to get a peek

at comparable Soviet sites.

The conflict between a desire to maximize the

intrusiveness of overflights over other countries and

the need to minimize this same intrusiveness over

one’s own country is central to aerial surveillance

negotiations. Increased transparency may not always build confidence and good relations. There are

two levels of transparency: the macro and the micro.

At the macro level, information on force structures,

military readiness, and operational practices can

indeed add confidence that one power does not pose

an immediate threat and perhaps has adopted a more

defensive posture (e.g., moving troops away from

the border). However, at a lower, micro level, little

additional confidence is won by granting more

information (e.g., a weapon’s design), and perhaps

something important is lost to potential adversaries

(e.g., knowledge of a weapon’s vulnerabilities).

In negotiating an overflight regime, the issue of

what the agreement will cost in terms of information

lost must be weighed against the benefits.

Aerial Warning

Unlike the other categories of information collection, aerial warning might actually be a specified and

negotiated utility of an overflight regime (see

above). However, even if aerial warning is not an

intended utility, aerial reconnaissance over militarily significant areas might provide warning at the

tactical or strategic level.26

Aerial surveillance could add to a monitoring

regime’s ability to reveal a breakout attempt by

providing treaty-mandated information and collateral information, which could be synthesized and

combined with other sources of information.27

Similarly, militarily significant developments that

may or may not be restricted by another treaty might

also be revealed by overflights negotiated for some

unrelated function. For example, aircraft monitoring

air pollution levels over large cities might detect the

~N~te tit~~tis defined ~ ‘tm~ter~ int~lligen~e$$ and ~~t k ‘C~c@ound info~tion” is wexpticidy ~dimplicitly On the WOrdi.llg Of

an agreement.

~~s~~fi d~s not address the ifleg~ ~oll~tio~ of in~lligence except to mention tit p&@t @CCtiOIIS my be nect$s~ tO UnCOVm i~egd

sensors secreted among the legitimate sensors. Illegal efforts could include covert sensors and intentional diversions from an agreed flight profile (e.g.,

dipping below minimum altitude to enhance sensor resolution beyond legal limits or changing course to document some event off the flight path). The

collection of collateral information diffexs from the illegal collection of intelligence in that collateral information is collected as a byproduct of the

overflights and does not violate any law.

25~e discussion hem of ~omtiongath~g,p~c~lyof collatti~ intel~g~ce, p~~e~ tit d~eloped earlier on confidence building. The

difference is that background information% collateral intelligence, warning, and cuing, as defined in this report, are collected outside the provisions and

spirit of an accor~ while the information gathered for confidence building is countenanced by an accord. The same information might be labeled as

contldence building in one regime and collateral information in another.

26~e U.S. ~faw r)ep~ent defines ~ctic~ ww@m “aw-fier initiation of a ~eatening or hostile act based on WI eVtdl@On Of

information from all available sources” and strategic warning as“a warning prior to the initiation of a threatening act. ” (U.S. Joint Chiefs of S@ff,

Department of Defense Dictionary of Military and Associated Terms, Joint Pub. 1-02, Dec. 1, 1989, pp. 350, 363.)

27~ ~MS ~temction of fio~tion wo~d lad t. a more efficient we of av~able monitofig IIXOUXIX. See cll. 6 for a discussion of how pIiOr

information can be used to enhance the utility of overflights.
Chapter 2—Why Aerial Surveillance? ● 23

movement of large military formations toward a

border.

Overflights might also indirectly indicate the

possibility of threatening activities. This would be

the case if a party suddenly began to refuse

overflights of certain areas or over its territory as a

whole. Refusals would alert the observing party to

possible mischief, compel it to focus other assets

more intently, and, if no satisfactory resolution to the

problem is found, respond as if militarily significant

activities were occurring.

Furthermore, the inspecting party might use aerial

surveillance to disrupt or delay an impending

breakout by requesting overflights of critical areas

(e.g., forward staging areas for conventional forces)

and forcing the host country to conceal this hardware

or activity (potentially throwing off its entire breakout schedule), or to expose it prematurely, thus

giving the inspecting party time to react.28

Cuing29

As with collateral intelligence gathering, the

potential role for aerial surveillance in cuing or

targeting is controversial. It is arguable that using

overflights to direct other systems may go against

the spirit of an accord; but some types of cuing can

reinforce the main goals of an agreement. This is the

case when overflights uncover ambiguous activities

or objects that are beyond the airborne sensors’

ability to resolve. If the inspecting country did not

have any other way of determiningg the legitimacy of

its discovery, the result might be unfounded recriminations or an unanswered threat, thus raising tensions or danger. However, if the location of the

discovery could be passed on to human inspectors or

NTM, the ambiguity might be easily resolved.

But cuing can also be used in a way that is obviously antithetical to the spirit of most agreements:

the same information that can localize an ambiguity

for further observation may also be used to target the

items being observed (or others not related to an

accord) for military attack or covert operations.

Target information can be specific, e.g., coordinates

of a fixed site; or it can be general, e.g., the

operational behavior of mobile systems or groups of

forces. Aerial surveillance could also be used to

provide accurate tactical maps for military or other

purposes. These are further examples of how transparency may not be a wholly beneficial objective.

Aerial Surveillance and Other

Means of Observation

The utility of aerial surveillance to gather information in support of an agreement is not unique.

Many of its features are shared with NTM and OSI.

The selection of which monitoring systems to use,

and in what combinations, will be determined by the

negotiating parties based on the ability of each

measure to detect the desired signatures, the synergistic effects of different sensors, the degree of

cooperation possible between parties, the capabilities and capacity of NTM, the political advantages of

open cooperation, the intrusiveness of the measure,

and financial costs.30

Aerial Surveillance and NTM

There is considerable overlap in the potential

roles of aerial surveillance and NTM. Both kinds of

systems can take imagery from overhead and over

wide areas. However, while aerial surveillance as

described here is cooperative, NTM is generally

unilateral or alliance-based. Cooperative measures

can be (and have been) negotiated to enhance NTM

capabilities, but the sensors and platforms themselves can operate independently of any agreement.

Among the potential advantages that aerial surveillance holds over at least some NTM assets are

greater flexibility, possible real-time physical access

to the sensors, direct cooperation between parties,31

and relative political and technological insensitivity.

An aerial surveillance regime could be negotiated

to be more flexible than some NTM, varying flight

~For~ne ~pfiwtionof~id~, .s~ J~~~ R.B-,“@.Site ~ections: me ~i@ysi~~cance of an-Control ~o~~,” SIJ~”VcZ/, VO1.

26, h’iily/#hW 1984, pp. 98-106.

%3ee ch. 6 for a discussion of the value of prior information.

-e relative f~nckd costs of aerial surveilla~, 0S1, and N’l%f depend heavily on the specilic details of a prospective agreement as well as on

the overlap of this agreement with other agreements and national security requirements. This report briefly examines the relative costs of NTNfand aerial

surveillance for synoptic search inch. 6, box 6H.

al~e 1~~cmwation~~=ntie Ufitti S@tes and tie Soviet Ufion on ~~&ncofim~ to facili@@ the obsaationof TLXs tbrOUgh

movement freezes, nonconcealmen~ delibemte exposure, and noninterference.
24. Verification Technologies: Cooperative Aerial Surveillance

profiles by timing, ground track, and altitude.32 As

a recent report to the U.S. Defense Department

stated,

The existence and utility of reconnaissance satellites is accepted by both sides. Satellite orbits are

highly predictable. It is taken as a given by each side

that the other will refrain from some activities, which

would otherwise be observable, during a satellite

pass--once or a few times per day, say for a total of

20 minutes. The long advance predictability of

reconnaissance coverage makes it possible to hide,

by careful advance scheduling, even very large and

elaborate activities. Each side might worry, in the

extreme case, that preparations for war or treaty

breakout could be thus hidden.33

With a sufficiently narrow preflight notification

period making it impossible to conceal a violation of

an agreement before a plane might arrive, aerial

surveillance might be able to plug gaps in NTM

coverage. Airborne platforms might have the flexibility to adjust their flight profiles to optimize sun

and sensor look angles, and to change altitude to

maximize a sensor’s resolution or field of view.34

Aircraft might also be permitted to fly under cloud

cover or loiter over areas of interest.

In addition, overflights could have the advantage,

if negotiated, of real-time interaction between the

sensors and the inspectors. An inspector manning a

sensing device on a plane could maintain, free-tune,

retarget, or change the focal length of the instrument

if something interesting caught his or her attention.35

The inspector could also mark and annotate important sightings to facilitate postflight analysis.36

And as mentioned above, because observers are in

constant contact with host country escorts, a cooperative atmosphere can be nurtured that is wholly

missing from NTM.37 The confidence that arises

from this may lay the foundation for more significant

accords. And denial of requested flights could signal

a less cooperative relationship, heightening vigilance by other means.

Lastly and perhaps most importantly, information

collected by an overt airborne sensor—particularly

if parties inspect or share sensors--could more

easily be released publicly to confirm compliance,

build general confidence, or support charges of

noncompliance. Direct release of NTM data is

contrary to government policy and is done so only in

the most extreme cases. Even in these cases, the

evidence of violation displayed is likely to be

degraded to avoid giving away information about

which system uncovered the violation and how

advanced the NTM sensors really are.

The primary advantage of NTM assets is that they

are largely independent of political events and

negotiations. If an important agreement is abrogated

or if surveillance flights are refused, aerial surveillance could leave a country blind to critical developments. NTM would remain unaffected, because it

does not usually depend on the cooperation of the

country under observation.38 NTM employment is

also not constrained by sensor-limiting compromises, formal notifications, or flight plans. A second

advantage of NTM assets is that they can monitor

more than one agreement at a time.

Of course, the choice for the United States and

the Soviet Union probably will not be between

aerial observation and NTM. The questions are

more likely to be: what can aerial observation

add to current NTM and how can they interact

effectively? According to the NATO Open Skies

proposal, aerial surveillance is supposed to “complement” NTM.39

Besides filling gaps in NTM coverage and capabilities, overflights might be used to cue NTM to

particularly interesting sites and to clarify ambiguous NTM information.40 Overflights or their notification might also be designed to trigger activity that

3@n the ~tha ~@ ~egotiator~ @@ ~we t. limi~tions and restrictions on Ovefights tit wo~d we them rehtively less flexible.

SSS. Drell et al., Verification Technology: Unclassified Version, JASON Report, 1$9-lB1 1, me~Corp., McLearL VA Mar. 7,1990, p. 131.

~,,oWnsties ~r~t: A Review of Sensor Suite Considerations, “ The MITRE! Corp., Bedford, M& unpublished manuscript.

35 mid.

360n the other ~d,esco~ wo~d ~looq over the inspector’s sho~der and co~d thus get an id= of w~t the ~spector thought @Otit. Thk

information could be useful in ref~ concealment techniques.

37@ the Otha ~nd, ~lo.se con~ct ~ tie ~ten~ for_ into ~ctionshotid relations take a ~ for the worse.

38A mentioneda~ve,tie United Stites ~d the Soviet Union ~ve negotiated some cooperative m~ustitWskt~

%ee app. D.

‘See ch. 6.
Chapter 2—Why Aerial Surveillance? .25

Box 2-B—Aerial Surveillance for Countries Without Advanced NTM

Until fairly recently, countries with little or no NTM have had to rely on the generosity of the superpowers for

a detailed view of the world, including information about the compliance of their neighbors with international

agreements. The superpowers’ monopoly on advanced NTM limited the quality, quantity, and timeliness of NTM

information available to third parties. Yet increasingly, countries have other options: participation in consortia to

develop independent NTM or the purchase of commercial imagery from other countries. France, Italy, and Spain

are investing in the Helios military reconnaissance satellite system to be operational in early 1994. The United

States, France, and the Soviet Union sell relatively low-grade satellite imagery. In the future, international

organizations might pool national resources to deploy reconnaissance satellites to monitor agreements or increase

global transparency.

Cooperative aerial surveillance might also be used to fulfill the informational need of some countries. With

the negotiation of mutual overflights, these countries would at last obtain an independent source of compliance

observation and confidence building. If the cost of an aerial surveillance regime remained beyond their reach, they

might spread the cost among like-minded countries by maintaining a fleet of common aircraft or by promoting aerial

surveillance by international organizations. If they are willing to negotiate the use of an advanced airborne sensor

suite, they might even eventually narrow the current informational gap between themselves and the superpowers.

This capability will still be limited to overflights of participating states, so participants would still lack the NTM

owners’ ability to monitor the territory of potential adversaries without their consent.

Granting foreign countries the right to overfly U.S. territory has important implications for the U.S.

Government. Such overflights will, to a certain extent, level the informational balance between these countries and

the United States, ending an American advantage over all countries except the Soviet Union. How important this

leveling is must be determined by U.S. policymakers. It may be the necessary price to get other countries to sign

onto important treaties that had traditionally been left to the superpowers to verify. It may also be the price of a

more open world. (See table 4-2 in chapter 4 for a listing of the asymmetric advantages and disadvantages of

countries negotiating Open Skies.)

would be detectable by NTM. For example, NTM aerial surveillance and OSI, not shared with NTM,

might be able to spot a large mobile TLI-during its

transit from an area to be overflown to shelter

elsewhere. In some areas, aerial surveillance might

even be used to free up NTM assets for other targets.

(See box 2-B.)

Aerial Surveillance and OSI 41

Unlike NTM or aerial surveillance, an OSI is an

inherently close-up, but local, affair. OSIs, like

aerial surveillance, are also cooperative measures,

requiring the consent of the inspected state. On-site

inspectors can go places and do things that would be

impossible for other monitoring systems. For example, only an OSI can take radiation measurements of

a warhead from close enough to negate concerns

over shielding; only an OSI can examine the interior

of a closed-out production facility. Yet on-site

inspectors are limited in the territory they can cover

during a given inspection. A similarity between

is that they both take place inside the earth’s

atmosphere and thus can both take part in air

sampling. All forms of monitoring, with the right

technology, could take pictures and read identifying

tags on TLIs.

It is in the areas where aerial surveillance and OSI

are dissimilar that they may work best interactively.

At a minimum, OSI can cover the declared inspection sites, while aerial surveillance flights (and

NTM) survey the potentially vast territory not

subject to inspection. If ambiguous or suspicious

activities or objects are detected during these flights,

an inspection team might be sent to visit the site,

perhaps while the aircraft loiters overhead.42 A

broad aerial search could trigger a more time-consuming, but more precise, inspection. Conversely,

overflights might be used to examine several inspectable sites at a time, both to prioritize subsedlFor a diswssion of on-site inspection types, benefits, and costs, see U.S. Congress, OffIce of Technology Assessment-i verification Technologies:

MeasuresforMonitonng Compliance With the STARTTreaty+lmmary, OTA-ISC-479 (Wasb.ingtoG DC: U. S.Government Printing OffIce, December

1990).

42~s is ~mvid~ tittie site is on ~ ~egotiat~ ~st of fi~~ble sites or me &@y WOWS for m-t-site or invitational il)S~tiOIIS.

292-900 - 91 - 2
26. Verification Technologies: Cooperative Aerial Surveillance

Box 2-C—Reading Tags From Aircraft

Tags on treaty-limited items (TLIs) have been suggested as a method for identifying and counting legal TLIs

and for making it more difficult for a potential treaty violator to intersperse illegal TLIs among legal TLIs.l Tags

that might be read from an aircraft are of three basic types: 1) self-powered tags that send a signal to a receiver on

the aircraft; 2) tags that are powered by an interrogation signal from the aircraft and respond; and 3) tags that are

powered by the host country at the time of overflight.

Reading tags remotely has been a controversial issue, because of a fear that the tag could be used to militarily

target the tagged TLI in a crisis. Although it might be possible to design a tag incapable of being used for this

purpose, the somewhat irrational fear of compromising legal TLIs remains, making negotiations difficult

The first and second types of tag bring out targeting concerns the most often. It is argued that during a crisis

these tags could be read (either by a direct signa12 or an illumination-induced signal) and their corresponding TLI

targeted. One relatively simple solution would be to provide each local commander with a hammer to destroy the

tags early in a crisis. However, while this solution may lower the potential for direct targeting, it does not address

the possibility that operational analysis of the tagged TLIs’ positions would, over time, provide general targeting

information and movement predictability.3

The potential for targeting TLI through the operational analysis of tag reading data also applies to tags that are

incapable of transmitting without an attached power source under the control of the host country. However, these

tags leave less room for misuse of the tags. They could not be covertly interrogated for position information. With

this third type of remote tag, when an overflight begins, the host country activates all of its tags so that they can

be read from the plane. TLIs not transmitting or responding with invalid information would be considered

violations, After the exercise the power supplies would be switched off.

l~s W& Cm bpW@CUMy impomt if look-alike objects are both covered by a treaty and also outside its @riadiction. For example,

the Conventional Armed Forces in Europe Treaty doea not cover Soviet naval equipment that is physically indistinguishable ftom its atrny

cOUntO~lUt which is mStl’itXOd.

2some m~e that the signal power of an active tag could be set low enough so that ody pl~es m vew low ~titude (~d *o~Y

cooperatively) could read them. However, the example of the extremely low-powervd Voyager II spacecraft transrm‘iwions being picked up at

interplanetary distances casts doubt in some minds about the electiveness of such power restrictions. Another suggestion is tbat infrared tags

be used which couid be shielded against pulsed hdiared detection. Likewise, some shielding might be made for the other types of tags as well.

Three suggestions are really variations of the third category of tags: those that can essentially be turned off except during overflights.

3fisis me for any monitoring mechanism tbat e xamines deployed TLIs.

quent inspector visits and to avoid using up a ground Aerial surveillance does have some advantages

inspection quota on obviously compliant locations.

Further in the future, over-flights and inspections

might be combined in a kind of ‘‘SWAT team’

approach. A long-range helicopter loaded with

inspectors and escorts would fly over the host

country searching for suspect TLIs. Upon seeing a

TLI, the helicopter would have the option to land and

conduct a ground inspection (e.g., a tag reading).

The helicopter would then continue its flight,

stopping for further inspections, perhaps according

to a set quota. Another unconventional idea would

be to have aerostats anchored at perimeter portal

monitoring sites as a kind of floating perimeter

control.43 Sensors on the balloon would detect the

movement of TLIs into or out of the monitored site.

over OSI. Overflights could be used to examine sites

considered too militarily sensitive to allow inspections. And because of their ability to cover large

amounts of territory quickly, over-flights could be

used to read tags remotely on large numbers of

far-flung TLIs (see box 2-C).

Overlapping Agreements and Assets

Current international agreements and security

concerns already require U.S. surveillance of most

of the world’s land masses. This surveillance is

mainly in the form of NTM, but includes cooperative

arrangements such as OSIs. Future agreements will

probably mean more intensive and extensive coverage. Examining each prospective agreement separate from others that cover much the same ter43~w+@ppedaems~~ me cwen~y us~ ~ong tie U. S.-Mexic~ border to monitor the illegal entry Of ticlllft into U.S. *pace. Concerns over

operations in severe weather would need to be addressed.
Chapter 2—WhyAerial Surveillance? ● 27

ritory may result in an inefficient and costly

allocation of surveillance assets as well as a

duplication of support and organizational resources. This is particularly true for Europe, where

a series of overlapping agreements are in force with

several others under negotiation. For example, an

aerial surveillance agreement covering a small

region may be relatively cost-effective when compared to anew photo reconnaissance satellite, but the

same satellite might be able to adequately monitor

several other treaties as well at a lower net cost.44

The executive branch and the Congress need to

consider how different verification regimes might

interact.

Conclusion

Whether an agreement is intended primarily to

foster good will, watch over a tense border, prepare

for an OSI, or search for illegal weapons, aerial

surveillance may be able to play a role. It can be the

central mechanism of an accord or one provision

among many, performing only those functions it can

do most effectively and cheaply. Through the collection of collateral information, it can also lend

additional support to treaty monitoring, hone our

assessments of our adversaries, and warn of threatening activities. The decision to include provisions

for aerial surveillance in an accord should result

from an assessment of the suitability of overflights

for the task at hand, the unique qualities of the

different monitoring options, the potential for synergism with NTM and OSI, and possible interactions

with other verification regimes. Finally, the ideal

verification package will have to be weighed against

financial and intelligence costs, as well as negotiability.

,

44SW box 6-H in ch. 6 for some rough cost estimates.
Chapter 3

AIRBORNE PLATFORMS

AND SENSORS
summary . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

Airborne Platforms . . . . . . . . . . . . . . . . . .

Types of Platforms . . . . . . . . . . . . . . . .

Platform Issues .

Sensors . . . . . . . . . . .

Types of Sensors

Sensor Issues . . .

. . . . . . . . . . . . . . . . . .

Contents

Page

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

Operational Concerns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Time: Notification and Duration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Flight Quotas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

Territorial Restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46

Details .

Conclusion

Box

3-A.Types

Figure

3-1.Partial

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .,.....* 46

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46

Sensors . . . . . . . . . . . . . .

Electromagnetic

. . .

. . .

Box

Page

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Figure

Page

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Tab/es

Table Page

3-l. Ground Resolution and Targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

3-2. Comparison of Airborne Imaging Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Chapter 3

AIRBORNE PLATFORMS AND SENSORS

Summary

This chapter surveys some of the types of airborne

platforms and sensors that might be appropriate for

agreed overflights and examines major issues for

each. It also discusses how negotiations on operational issues can affect the success of an aerial

surveillance regime.

The type of airplane or helicopter used in overflights must meet requirements for range, sensor

payload, passenger room, safety, reliability, and

negotiability. More exotic aerial surveillance regimes might use unmanned aerial vehicles (UAVs)

or lighter-than-air craft.

A wide variety of imaging sensors, spanning the

electromagnetic spectrum, could be employed during a cooperative overflight. Air samplers or sniffers

and radiation detectors could be used to detect

restricted chemical and radiological emissions. Signals intelligence (SIGINT) collection, passive acoustic devices, and magnetic anomaly detectors (MAD)

might also be used to ferret out information. Sensors

can be combined to provide 24-hour, all-weather

effectiveness and to complicate attempts at concealing treaty-limited items (TLIs).

Operational considerations are also important.

The number of flights relative to the area and

composition of the overflown territory, the frequency and duration of overflights, and the amount

of advance notice given must be appropriately

matched to surveillance goals.

Introduction

Cooperative aerial surveillance involves flying

one or more sensing devices (a sensor suite) over the

territories of the signatories of an agreement. The

platform flown could be an airplane or helicopter,

but a case might be made for other craft, e.g., UAVs

and lighter-than-air craft. The sensors carried might

simply be the eyes of a human observer or more

sophisticated cameras, signal gatherers, or air samplers.

The aerial platforms and sensors should be suited

to their missions as defined by the overflight

agreement. At the same time, the choice of platforms

and sensors will likely be limited, primarily for

reasons of cost and intrusiveness, to the minimum

configuration needed to accomplish the goals of the

accord. In the case of some potential agreements,

e.g., Open Skies, the goals might be so broadly

defined that no minimum configuration is readily

apparent. However, in a regime meant to sample the

pollutants near designated powerplants, loading a

plane with SIGINT equipment would be clearly

unnecessary. Similarly, operational criteria should

be appropriate for the flights. If the agreement being

negotiated calls for short-notice monitoring of some

easily relocated TLIs, a prearrival notification period of 48 hours may render the overflights irrelevant. Likewise, an accord that allows the monitoring

of troop movements might be undermined by

territorial restrictions on overflights.

Airborne Platforms

Types of Platforms

Airplanes

Airplanes are especially useful for missions that

require fast air speed, long durations, large sensor

payloads, or film changing and sensor maintenance

in flight. A wide variety of civil and military

Photo credit: U.S. Navy contractor, released by Department of Defense

The P-3C Orion, a maritime patrol version of the Lockheed

Electra, began service in the U.S. Navy in 1969 and has

since found its way to many other countries. Its 10-

person crew employ a variety of sensors to detect

submarines. Note the magnetic anomaly detector

protruding from the tail.

–31-
32. Verification Technologies: Cooperative Aerial Surveillance

 

Photo credit: U.S. Air Forces

Helicopters might prove useful in agreements that seek to

combine aerial surveillance and on-site inspections.

airplanes have already been modified for surveillance activities—horn sophisticated spy planes, like

the TR-1 (descendant of the U-2), to transports, like

the C-130. Even a two-seat, civil aircraft could be

modified to play some role. Most agreements would

probably require at least one representative of the

overflown country to be on the plane as an escort, if

not as the pilot and sensor operator.l

Helicopters

Provisions of the 1990 Vienna Document2 permit

observers in host-country helicopters in Europe to

monitor large-scale conventional military activities.

Generally of more limited speed and range than

airplanes, helicopters might be particularly useful

for missions exploiting their relative strengths:

low-level flying, slow flying and temporary hovering, and close-quarter landing. Helicopters, like

airplanes, could allow sensors to be adjusted or

reloaded with film during flight.

Low-altitude flights would enable sensors to

probe beneath all but the lowest cloud cover or fog.

This might mitigate the need, in the daytime at least,

for sensors more sophisticated than human vision or

Photo credit: U.S. Department of Defense

The AV-8B Harrier jump jet (top) and the developmental

V-22 Osprey tilt-rotor aircraft (bottom) are examples

of platforms that share features of both airplanes and

helicopters.

conventional photography. It might also improve the

utility of sensors that need to get close to their targets

to work efficiently (e.g., MADs). (But note that

lowering altitude reduces the amount of territory

visible to the sensors on board.)3

Similarly, slow flying4 or hovering over a potential target or a declared site might permit more

1Although most scenarios include both inspecting and host country representatives on a plane, either party might be granted sole overflight authority.

2

This product of the Conference on Security and Cooperation in Europe provides for aerid and ground observation of military exercises above a

certain size.

3

The line-of-sight to the horizon varies as the square root of the sensor height. For a helicopter flying at an altitude of 1 mile, the line-of-sight to the

horizon is approximately 90 miles, For the same helicopter at an attitude of 1/4 mile, the distance to the horizon is approximately 45 miles.

4

Slow air speeds (about 30 knots) minimize photographic image blurring and platform vibration. Higher speeds and hovering increase vibration. As

cited in Allen V. Banner, Andrew J. Young, and Keith W. Hall, Aerial Reconnaissance for Verification of Arms Limitation Agreements: An Introduction

(New York, NY: United Nations, 1990), p. 139. Maintaining minimal vibration may not be as important as hovering for some types of sensors.
Chapter 3—Airborne Platforms and Sensors .33

sensitive instrument readings. It would also give the

inspectors time to examine a suspicious object from

a variety of altitudes, look angles, and sun angles.

Unlike most airplanes, a helicopter, however, can

land without an airstrip. This enables a helicopter to

combine the role of aerial monitor and on-site

inspector. A sensor-bearing helicopter could detect

an anomaly from the air and then land with

inspectors who could document any violation.5 All

other modes of reconnaissance require that the

sensor collect unambiguous evidence of violation

directly (necessitating a more refined sensor) or that

it cue other means of collecting evidence, such as

ground-based, suspect-site inspection.6

Unmanned Aerial Vehicles

UAVs include “remotely piloted vehicles (RPVs),

which require remote control by human pilots;

autonomous aircraft (drones), which do not; and

aerial vehicles which permit, but do not require,

remote control by human pilots. ’ UAVs may

resemble either an airplane or a helicopter: some fly

in a straight path, while others can hover. Most

UAVs are small and have relatively short range;

however, Boeing’s recently demonstrated Condor

can stay aloft above 65,000 feet for several days.8

Because these aircraft are unmanned, there is no one

on board to maintain sensors, reload film, or look out

in a direction where the sensor is not pointing. At

most, a human controller on the ground might be

able to redirect and focus the sensors on board in real

time. These characteristics make UAVs an attractive

alternative to other platforms, because the potential

for collateral information gathering can be reduced

to an absolute minimum. Only that which is recorded

by the sensors on the UAV or seen on a remote

monitor is revealed to the inspectors on the ground.

This information can be readily restricted by mePhoto credit: U.S. Department of Defense

UAVs, equipped with television or forward-looking infrared

sensors, collected reconnaissance and targeting

information during Operation Desert Storm.

chanical adjustment of the sensors. Covert sensors

would also be difficult to hide on the relatively small

vehicles.9 Lastly, UAVs could monitor events that

might be hazardous to human observers (e.g.,

chemical leaks and nuclear test venting) .10

Ssuch landings wo~d likely be mbj~t to some numerical or time quota to lessen their intrusiveness and C@ as well m tO Mety comtr~ts.

6Helicoptm~ ~o~d ~so ~employ~ t. ~d~ ~ick.r=wme tem tit wo~d fig a supt facility with rapidly deployable perimeter ~IISOrS tO

ensure that no mobile TLI escaped the facility while it was being prepared for an internal suspeet-site inspection. Note that this is not specifically an

aerial surveillance task. The preparations required at a sensitive site can be quite extensive and time consuming. If the preparations were not allowed

the site might not be included in the accord for reasons of national security. A discussion of the trade-offs in on-site inspection systems can be found

in U.S. Congress, Office of Technology Assessment, Verification Technologies: Measures for Mom-toting Compliance With the S7XRT

Trea~ummary, OTA-ISC-479 (Washington, DC: U.S. Government Printing Oftlce, December 1990).

~.S. Congress, OffIce of Technology Assessmen4 New Technology for NATO: Implementing Follow-On Forces Attack, OTA-ISC-309

(Washington, DC: U.S. Oovermnent Printing Office, June 1987), p. 230.

gBr~k W. Hendersoq ‘‘Boeing Condor Raises UAv perfo~ ce Levels,” Aw”ation Week and Space Technology, Apr. 23, 1990, pp. 36-38.

%lany aircraft other than current UAVS, could be converted for remote operation.

10~y sfi~son and ~c~el ~ewm “stra@e~g me chemi~ weapons convention Throu@ Acrid Monitoring, ” OUXlsiOIld ~Wr W, The

Henry L. Stimson Center, Washingto~ DC, April 1991, p. 26.
34. Verification Technologies: Cooperative Aerial Surveillance

Dirigibles, balloons,ll airships, aerostats, and

blimps may be uniquely attractive for some purposes. Floating aerial platforms have the advantages

of sensor stability (extremely low vibration), relative

background silence for acoustic sensors, unrestricted access to sensors (on crewed craft), large

payload capacity, endurance, and extended hovering. 12 The last attribute could enable tethered

aerostats to provide an airborne sensor perimeter

around a site (e.g., rocket motor plant) either for the

term of an agreement or until preparations for an OSI

were completed.

During the 1989 celebration of the French bicentennial, Paris police, stationed aboard a blimp, kept

almost continuous vigil over the crowds and the

comings and goings of world leaders. They professed the ability to identify an individual 1 mile

distant. 13

The chief disadvantages of these platforms are

their slow air speed and vulnerability to severe

storms. In particular, they would not be a good

choice for searching for easily moved and hidden

objects or for covering large areas of territory in a

relatively short time.

Platform Issues

Aerial platform issues include: whose aircraft is

used, who flies it, how many inspectors and host

country escorts are on board, where can it land

(refuel), what flight rules apply (perhaps those set by

the International Civil Aviation Organization (ICAO)),

and what will be the language of air traffic control.

Negotiators will also have to decide whether

aircraft will be allowed to loiter over a particular

spot, make repeated passes over the same territory,

or change its flight plan during the flight (at a

minimum, to avoid storm fronts). Moreover, minimum (and possibly maximum) altitudes may need to

be codified.

Irregularities will also need to be considered:

what if an aircraft crashes, what if the pilot

intentionally strays off the mandated course,14 

or

what if the plane fails a preflight inspection or safety

check?

Overflown nations may be concerned that contraband sensors could be secreted aboard (or even in the

skin of) the aircraft. If an accord disallowed a type

of sensor or put limits on the capabilities of the

agreed sensors, a preflight inspection of the platform

and its sensor suite by the host country might be

necessary. In all cases, except for some UAVs, this

could be a fairly difficult and time-consuming

endeavor. The provision of platform and sensor

manuals and specifications may speed this process

up. If the preflight inspection is too long, it may

impinge on the ability of the aircraft to accomplish

its mission (e.g., searching for easily relocated,

mobile missiles). Keeping the aircraft under guard in

the host country or some other agreed location after

it had been cleared by inspectors might be one

solution to this dilemma, because it would obviate

the need to inspect the craft before every flight.15

ll~e Frach were the fiwst t. we Mwm for mili~ reconnaissance in 1794. William E. Burrows, Deep Black: Space Espionage a~Natio~l

Security (New York NY: Random House, 1986), p. 28.

12some fighter.than-air craft cm alSO land without a prepared airfield, but unlike helicopters, they usudy wire the Presence of gro~d crews and

a comparatively large clearing.

ls”~e Blimp IS Bac&” NOVA, Public Broadcasting System teleeast in Washington DC, oCt. 30, 1990.

14A pilot ~ght be tempt~ t. divefi his or her come to get a ~~er look at a su@cious obj~t or activity, or to gather collated hltelligeIICe 011 SOnle

sensitive site in an exclusion zone.

150n the Otha hand, the exwnw of hav~g aircraft dedicated solely to an Oveflight ~gime might be too dear for tiler COUntrieS, W~e relying 011

aircraft provided by the larger countries might be politically unacceptable. (Private communication from Peter Jones, Contractor, Verification Research

Unit, External Affairs and International Trade Camda, Ottaw% Canada, Mar. 25, 1991.)
Chapter 3—Airborne Platforms and Sensors .35

Box 3-A—Types of Sensors

Imaging Sensors

Human vision

Unaided

Binoculars

Optical transducers (night-vision goggles)

Aerial photography

Optical

Infrared

Stereoscopic

Multispectral

Electro-optical devices

Electronic still camera

Television (including low-level-light TV)

Radar

Synthetic aperture radar (SAR)

Conventional radar

Lidar (laser radar)

Nonimaging Sensors

Signals intelligence (SIGINT)

Air sampling and sniffing

Radiation detection

Acoustics

Magnetic anomaly detector (MAD)

SOURCE: Office of Technology assessment 1991.

Sensors

Types of Sensors

Imaging Sensors

Human Vision—Although in many ways outmoded by modern technology, human vision remains a viable means of aerial surveillance. A

confidence-building regime of purely symbolic overflights might have little reason for permitting more

advanced sensors.

Human eyesight might have application in more

rigorous monitoring systems as well. If the objects

or activities being observed are suitably large and

difficult to conceal, then unaided observations might

be sufficient for the purposes of an agreement.

Peacekeeping missions along desert borders, aerial

inspections of missile silos, and observation of

military exercises are examples of agreements where

eyesight alone might provide satisfactory confidence. Moreover, human vision might cue other,

mechanical sensors. For example, a crew member,

having spotted a suspicious objector activity, could

order the airplane to diverge slightly from its flight

path (agreement provisions permitting) in order to

photograph the anomalous object from a more

advantageous distance or angle.16 Likewise, the

crew member could alter the sensors’ scanning mode

from a low resolution, wide-area search setting to a

higher resolution mode focused on the object.

Under the proper circumstances, selected human

beings can perform remarkable feats of visual

detection. During World War II, General (then

Lieutenant) Charles Yeager could spot German

fighters at a range of 50 miles;17 astronauts in orbit

have sighted terrestrial objects as small as trucks in

freak occurrences labeled the “hawkeye effect.”

Binoculars can extend human vision even further.

The detection capabilities of the human eye vary

strongly with the angular size of the target (a

function of the diameter of, and the distance from,

the target), the size of the region in which it might be

found, the contrast between the target and its

background, the amount of time for which the

detection opportunity lasts, and the level of alertness

and training of the observer. The shape of the target

is less important for detection alone.18

Some devices can extend human vision beyond

the “visible spectrum” (see figure 3-l). Optical

transducers, e.g., night-vision goggles, can enable

users to see in the infrared portion of the spectrum.

Exploiting the far infrared portion of the spectrum in

which objects glow by virtue of their own warmth,

infrared goggles allow the wearer to see in the

dark.19 Furthermore, because they depict objects

according to their temperature, infrared vision systems also reveal phenomena not normally visible to

the human eye, e.g., distinctions between convenIGB-2 advocates cite such decisionmakm“ g by bomber crews in search of mobile missile launchers (which are also ST~TTLIs) and other

“look-shoot” and “relocatable” targets, though they may have in mind the human use of on-board radar or TV sensor equipment. See General John

T Chain Jr., ‘‘A Warrior’s Perspective on the B-2, ” ArmedForcesJournal International, September 1990, p. 78; and U.S. Senate, Committee on Armed

Services, “Threat Assessment Military Strategy; and Operational Requirements,” Mar. 7, 1990, p. 873.

ITChuck Yeager and LEO Janos, Yeager: An Autobiography (Toronto, CMMda: Ban-, JUIY 19*5), p. 56.

18For more ~omtioq~clu~g bibliographic~ referenws, on this topic, see app. E in Bernard Qsgood KooPma.u, Search and Screening: General

Principles With Historical Applications (New York NY: Pergamon Press, 1980).

l~i~ some mod~lcatiom perhaps they could also be worn during the daytime.
36. Verification Technologies: Cooperative Aerial Surveillance

Figure 3-l-Partial Electromagnetic Spectrum

Visible light

Gamma rays Microwaves

X-rays Radar

Infrared TV

Ultraviolet — — Radio waves

11111111111111111 I I

10 13 10 11 10 9 10- 7 10 5 10 3 10’ 10 103 10 5

Wavelength In meters

SOURCE: Office of Technology Assessment, 1991.

tional camouflage netting and foliage of the same

color and pattern; and images of relatively hot

objects obscured by foliage, conventional camouflage, smoke, or fog. (Concealment measures that

would be more effective are discussed below.) This

latter ability to penetrate a leafy canopy would raise

confidence that one was not missing TLIs simply

because they had been driven into the woods before

the aircraft flew over.

In addition, infrared vision systems can in some

cases provide a short-term history of an object. For

example, residual heat in the engine of a tank or

missile transporter, or warm patches of taxiway

heated by jet engines, would indicate recent activity

that might have been prohibited by movement

restrictions (a “freeze”) in effect during an overflight or OSI. The heat signatures of overflown

facilities might also assist on-site inspectors in

deciding where to focus their search effort or reveal

covert operations at supposedly closed-out facilities.20

For aerial monitoring purposes, it is worth noting

that human vision is the one sensor system whose

results cannot be recorded for postflight data processing or sharing. Inspectors making visual sightings might take notes or be debriefed after the flight,

but they would lack concrete evidence of any

wrongdoing. 21 Moreover, the human failing ‘f

boredom sets in quickly during a search for sparsely

distributed targets, greatly degrading the searchers’

effectiveness. 22

Aerial Photography—Military aerial photography predates the airplane. In fact, placing photographers in intelligence balloons during the U.S. Civil

War was considered, though never carried through.23

It was not until the Spanish-American War that

aerial photography first made its military debut in

the form of a camera carried aloft by American

kites. 24 Since that time, aerial photography has

found a wide range of useful applications from

strategic reconnaissance by supersecret spy planes

to the documentation of local agricultural crops.

A variety of considerations bears on the quality of

an aerial photograph. Of these, “resolution” is the

most commonly cited parameter, though the ability

of a camera to see in more than one part of the

spectrum, or to create stereoscopic (three-dimensional) images, can also be important. Stereoscopic

imagery aids in the interpretation of photographic

reconnaissance data, discussed in appendix B.

Cameras carried aboard aircraft offer a great deal

of freedom, affording views at a variety of altitudes,

look angles, and sun angles.

%ared information about a site’s operations might also be compared to the facility’s material flow records (obtained through data exchanges) in

order to uncover inconsistencies. Smithson and KrepoQ op. cit., footnote 10, pp. 15, 23-24.

zlU-iWous vis~ sigh~s ~o~d pm~bly provide ~lcient gro~s for the ov~ying ~tion to me lmi~t~cOUntSmlemUra, eVen if

violations could not be “proved” to the other parties of an accord.

% the case of World War II airborne radar search for surfaced U-boats, analysis of sighting data showed that operator fatigue caused a marked

decrease in sighting efficiency after only a half an hour. C.H. Waddington, OR. in WorZd War 2 @mdon, England: Paul Elek (Scientific Books) Ltd.,

1973), pp. 138-139.

~~om~ouch, The Eag/e AZofi (wMl@to~ DC: Sm.ithSOti hMit’UtiOn pr~s, 1983), PP. *MI.

24~e fit~e~annonmfiat photographs were men from a Moon in is@. s= BUITOWS, op. cit., foo~ote 11, pp. 29-31.
Chapter 3-Airborne Platforms and Sensors .37

Spectrum-The advantages of seeing in the infrared, as opposed to the visible, part of the spectrum

have already been mentioned above in the section on

human vision. The most obvious disadvantage--

fundamentally lower resolution25 owing to the use of

longer wavelengths of light--can be compensated

for by a relatively lower sensing altitude, agreement

permitting. One aircraft vendor’s concept of aerial

search operations includes infrared sensors, but

specifies that they would be used during low-altitude

segments (5,000 feet, lower than some regimes

might permit) of the flight. At such an altitude, the

“swath width" 26 of a notional infrared sensor is

given as 5 kilometers, or 3 miles.27

Resolution—Resolution is often taken to be

“ground resolution,” the distance by which two

objects on the ground must be separated in order to

be distinguishable in a picture; this quantity depends

on the altitude of the camera as well as its optical

characteristics. 28 (This distance is often about twice

the minimum size necessary for an object to appear

at all.) More fundamentally, a camera’s film has a

resolution, ultimately determined by the grain of its

emulsion. The ideal camera would project, in a

distortion-free way, the image of the ground onto the

image plane, where it would be captured. Actual

cameras depart from the ideal and degrade resolution

to a level somewhat below that which would be

expected on the basis of the film alone.29 As in the

case of the human retina, the resolving power of the

film depends on the contrast ratio between the target

and the surrounding background.

Estimates of the ground resolution needed for

various purposes differ from source to source.

One commonly cited source30 draws distinctions

between the ground resolutions needed for detection, recognition, identification, and analysis. “Detection” refers to noting that the object is present at

all; “recognition” to determiningg that it is a missile,

vehicle, missile site, or aircraft; ‘‘identiilcation” to

determining what type of missile, vehicle, missile

site, or aircraft it is; and ‘‘analysis” to the performing of detailed technical analysis based upon the

image at hand. Table 3-1 shows values for selected

agreement-relevant items.

Another source31 provides a nearly identical list of

items and five levels of interpretation-detection,

general identification, precise identification, description, and technical intelligence. Not surprisingly, the addition of a less exacting category widens

the range of identifiably useful ground resolutions.

A submarine, for example, can be ‘detected,” in the

sense used by the latter source, given only a

resolution of 100 feet (v. 25 feet).

A third source adduces digitized examples to

show a tank at the picture element sizes (picture

element, or pixel, sizes correspond closely to resolutions) at which it can be identified as an artifact, as

a tank, and as a Soviet T-62. These resolutions

appear to be approximately 16, 6, and 3 inches,

respectively .32 Note the lack of close agreement with

those values cited for a vehicle in table 3-1, typical

of the way parameter estimates vary in this field.

A fourth source33 introduces the Imagery Interpretability Rating Scale (IIRS) which is not based on

resolution. Using subjective criteria, the IIRS sets up

eight separate slots (labeled rating categories 1

through 8) into which targets are placed according to

the aforementioned detection, recognition, identification, and analysis paradigm.

MA ~n~pt treated at length bdow.

~ThWreti~sw~pwid~ in our terminology; * ch. 6.

27Jo~~, ~ ~fibome Remote sem~ for @nSkies: The platfo~” inopens~”es: Technical, &g@UkdO?Id, Operational,kgd, andpolitical

Aspects, Michael Slack and H@her Chestnutt(tis.)~oronto, @tario, Canada: Center for Internatioti and Strategic Studies, York University, 1990),

p. 29.

~~e basic ~xp~~~ion of tie resolution of a ~mera is its -mre~olutio% the a@e subtend~ at the ~~a by wo obj~fi on the threshold Of

appearing as one. ‘Ground resolution” or “ground sample distance” is the projection of this angle on the ground. The term “ground sample distance”

clarifies the point that resolution is an angle inherent in the camera-film combination whereas image interpretation depends upon the size of the ground

sample subtending that angle.

~A~osph~c e&-~, such as mois~e, pollutiow and turbulence, can also degrade theoreti~y ideal llXOhltiOn.

m~{%m ~omd (’)bjwt Sims for ~gev ~tewre~tioq+’ Ascc ~ STD 101/8, quoted in the Reconnaissance Ha@ ~00~ (St. ~uis~ ‘0:

McDonnell Douglas, 1983), p.125.

31Jefiey T+ Richelso% The U.S. Intelligence co~~ni~, Zd. ~.(C-dge, MA: Ball@w, 1989), p. 161.

32 David Hafemeister, Joseph Ro~ and Kosta Tsipis, ‘‘The Veri.tIcation of Compliance With Arms-Con&ol Agreements,” Scientific American,

vol. 252, No. 3, March 1985, p. 41. The number of shades of gray avai~ble in this digital presentation appears to have & either four or eight.

33’ ‘Open Skies Aircraft: A Review of Sensor Suite Considerations,” The MITRB Corp., Bedford, M& unpublished manuscript.
38. Verification Technologies: Cooperative Aerial Surveillance

Table 3-l-Ground Resolution and Targets

Detect Recognize Identify Analyze

Object (feet) (feet) (inches) (inches)

Missile . . . . . . . . . . . . . . . . . . . . . . 3 2 6 1.5

Vehicle . . . . . . . . . . . . . . . . . . . . . 5 2 6 1.5

Nuclear weapon . . . . . . . . . . . . . . 8 5 12 0.5

SSM site . . . . . . . . . . . . . . . . . . . 10 5 6 1.5

Aircraft . . . . . . . . . . . . . . . . . . . . . 15 5 6 1.5

Submarine . . . . . . . . . . . . . . . . . . 25 15 6 1.0

Troop units . . . . . . . . . . . . . . . . . . 20 7 24 6.0

SOURCE: “Minimum Ground Object Sizes for Imagery Interpretation,” ASCC AIR STD 101/8, quoted in the

Reconnaissance Handy Book (St. Louis, MO: McDonnell Douglas, 1983), p.125.

For example, in rating category 5, the lettering on

the wings of a large aircraft can be detected;

command and control headquarters can be recognized; a tank can be identified as light or medium/

heavy; and technical analysis can be made of airfield

facilities. Interestingly, some surfaced submarines—

though detectable in rating category l—have sufficiently similar overall dimensions34 that they can be

identified by type only in rating category 6. For

example, the Soviet Romeo-class attack submarine

can be distinguished from its Whiskey-class predecessor by the presence of a snorkel cowling.

Photographic film can have a resolution of about

1/5000 of an inch35, so that a 10- by 10-inch picture

similar to that produced by the Fairchild KC-lB

framing camera36 could capture a 50,000 by 50,000

field of resolvable units, the equivalent of 25,000

feet (or about 4 nautical miles) square at 6-inch

resolution. This very approximate calculation suggests a sweep width of 4 nautical miles if the camera

simply points straight down from, in the case of the

Fairchild camera, an altitude of about 20,000 feet.

An Itek camera, derived from the Large Format

Camera built for the Space Transportation System

(the space shuttle) can resolve 1 meter or better from

12,000 meters.37 From 20,000 feet, this camera

could therefore resolve 20 inches or better, with a

very wide field of view. The technology embodied

in this camera, however, may make it unexportable

and thus unusable in some cooperative aerial surveillance regimes.

The amount of search effort available per sortie is

determined, in the case of many aircraft, by the

amount of film in the camera. The Fairchild camera

cited above carries about 400 feet of film, and could

thus take almost 5004- by 4-nautical mile photographs. These photographs could easily be taken in

sufficiently rapid succession to cover a swath 4

nautical miles wide and almost 2,000 nautical miles

long; the film can advance through the camera at a

rate of 3 inches per second, corresponding to 1.2

nautical miles of ground per second and thus almost

10 times faster than would be needed for perfect

coverage of the swath. Some amount of overlap

between adjacent pictures would be desirable from

the standpoint of a photointerpreter. The aerial

surveillance mission may differ enough from conventional military reconnaissance in that larger

airplanes could be used, permitting the inflight

replacement of film.

Electronic Still Camera—Though normally associated with TV-style ‘‘moving picture’ cameras,

electro-optical technology can also be used in a still

camera. Some such cameras use a ‘‘push broom’

technique, in which a linear array of detectors

images thin slices of the scene and the motion of the

sensor platform laminates these slices into a twodimensional image. A 1979-vintage aerial device of

this type could record a 3-mile-wide swath at a

distance of up to 12 miles with enough resolution to

allow counting of individual people and discrimina-

~me Watertie length of a modern Submarin e is somewhat variable because the hull is pickbshaped and the length of the exposed portion therefore

depends upon the trim.

ssReconmi~$anceHa~y Book, op. ~~, foo~ote 30, p. 610 v~ues vw widely from f~ to f~ and de~nd gr~dy upon the contit iI1.helWlt in the

scene itself.

%~id.,p. 8. ~s~-m~s modest &~~h f~-le@ p~ms it my in the “m@~.t~h” ~che: export res~ctio~ @fe, a IV2-kh fOCd lem

cmddreadilybeused instead, affording “the capability to perform extior&nq feats” aeeording to one exprt. (prepared stitement of Michael KrepoQ

President of the Henry L. Stimson Center, Washington DC, delivered before the Senate Foreign Relations Committee, Mar. 29, 1990.)

sT’’peaW~ Watchdogs,” IEEE Spectrum, November 1989, p. 31.
Chapter 3--Airborne Platforms and Sensors .39

tion of different models of automobile.38 More

modern devices use staring arrays, making them

completely analogous to TV cameras.39 They can

attain ground sample distances comparable to those

of film cameras, and record 8 to 12 bits per picture

element, enough to express from 256 to 4 million

shades of gray.40

The large dynamic range of these systems—larger

than that of the human eye41—allows postprocessors to bring out latent details hidden amid

shadows or glare. (Digital postprocessing of some

film images can have the same effect, as will be seen

in app. B.) Such postprocessing might be done on

board the surveillance aircraft, allowing sites of

interest to be revisited later in the flight after

processing of imagery taken on the frost pass.42

Television—TV systems for aerial surveillance

share some attributes of human vision and others of

photographic and electro-optic systems. Like human

vision, airborne TV can be analyzed in real time as

the plane is flying, allowing for deviations from the

flight path to examine interesting targets more

closely or from a more advantageous angle.43 Like

photography and electro-optics, its results can also

be recorded and it can operate outside the spectrum

normally thought of as “visible.” (The advantages

offered by operating in the infrared portion of the

spectrum are discussed above in the section on

human vision.)

Whereas the screen of a digital TV system is

divided into pixels (picture elements) whose preimages on the ground readily define the system’s

resolution in terms of ground sample distance, the

resolution of the conventional, analog, scanning TV

system found in most homes is somewhat more

complicated to determine. Such a TV system builds

its image out of parallel lines scanned onto the

screen. The spacing of the lines (512 of them in a

conventional home set) determines, much like the

number of pixels, the screen’s resolution in the

vertical dimension. The horizontal dimension’s

resolution is governed by the ability of the system to

make intensity changes along a single scanning line,

rather than from line to adjacent line as in the vertical

dimension. A conventional 512-line TV image is

refreshed 30 times per second; from its 4-megahertz

input signal it can make 8 million meaningful

samples per second, so each line would consist of

508 samples if none were lost to such “overhead

expenses’ as blank time between each image

refreshment. a A realistic assessment of such losses

could cut the number of samples per line to 400.45

As in film photography, the parameter of interest

in TV systems is the ground resolution (and the

effective ground sample distance), determined by

the line spacing of the TV camera and screen. If

6-inch spacing on the ground were the standard

required for aerial surveillance, the conventional

512-line home TV screen would depict a patch of

ground 256 feet in length and approximately square.

Even a substantially improved TV display would

thus be a far cry from a film system in terms of the

ability to cover ground (25,000 square feet in the

film example above) at a given resolution.46 Even a

digital TV with a 1024- by 1024-pixel array, which

could approximate the performance obtained by the

combination of the human eye and state-of-the-art

conventional optics, could do so only over a narrow

field of view comparable to that of a submarine

periscope. 47

38Bmj~ F. Schemmer, “ ‘Electronic Cameras’ With Instantaneous Ground Read-Out Now Make Real-Time Precision ‘1hctica.1 ‘hrgeting

Operationally Feasible,” Armed Forces Journal InternatioMl, November 1982.

39’’ Communications, Electronics, Scientific Advances Explode,” Signal, September 1990.

%e MITRE Corp., op. cit., footnote 33.

AIThe humm we ~meives ~out a tition shades of gray in its photopic (cone-mediated) mode and another million h its XOtOpic ~d mixed

(rod-mediated and rod-and-cones-together) modes. (See Koop~ op. cit., footnote 18, p. 322.) A periscope device described by Clark and Stevens

likewise has a dynamic range of 60 decibels: its brightest bright is a million times brighter than ita dimmest dim. (See David Clarke and Eric G. Stevens,

“High-Resolution Camera Provides Key to Electronic Periscope,” Sea Technology, September 1990, p. 65.)

4ZASS- tit me flight protocol permits real-time changes of flight plan or rept%Wd overflights of the -e~~

AsR~-~e @ysis orr~~fig of semom @ tie &awback tit on.bo~ host country es~rts IIMy & able to witness Wbt p@X the in&tXt Of

the inspecting sensor technician, thus enabling the host country to perfect any attempts at camouflage, concealment or deception (discussed below).

44FJi@t million samples per second divided by 30 images per second and by 512 lines per image yields 508 mIJ1es Per tie.

4YIMS description dram fim Albert Rose and Paul K. Weimer, ‘‘Physical Limits to the PdOrTIMII ce of Imaging Systems,” Phy.n”cs Toaby,

September 1989, p. 30.

46~w-l@-level ~ wo~d & able t. fiprove con~t due to tie or ~ght. This co~d compensate to some extent for lower ground reSOhltiOIL

47C~k and Stwem, op. cit., foornote 41, p. 63.
40 ● Verification Technologies: Cooperative Aerial Surveillance

A special-purpose TV system, such as one to be

used in aerial surveillance, might outperform the

home set described above by a factor of five.

Synthetic Aperture Radar—Radar actively

bounces radio waves off targets to determine their

location and size. Airborne SARs use the motion of

the airplane during the time that the radio pulses are

in transit to and from the target to create the effect of

having an antenna far larger than the one actually

carried. The duration of the transit and the Doppler

frequency shift of the returned signal are used to

build up an image of the passing terrain. Because the

process involves collation of returns and intensive

computation, a SAR cannot produce an image in real

time like a TV camera. High-end SARs can approach

real time, but lesser SARs are often subject to a

considerable delay. The resulting image has a

somewhat photograph-like appearance and level of

detail.

The along-track (azimuth) ground resolution in

SAR is ultimately limited by the wavelength of the

radar, but in practice the ability to resolve ground

targets closely spaced in azimuth is a function of the

physical aperture size (i.e., physical antenna size and

thus physical antenna beamwidth) and the ability to

remove motion-induced phase errors from the data

while synthesizing the long virtual aperture. Phase

errors are rinsed out through the use of antenna

motion compensation and data processing. The

crosstrack (range) resolution is limited by the

bandwidth of the radar’s transmitter/receiver. The

ability to resolve ground targets closely spaced in

range depends upon an ability to distinguish very

precisely the closely spaced times of arrival of the

echoes returning from these targets. This timedomain resolution is inversely related to bandwidth,

so fine time resolution implies large bandwidths.

With a large bandwidth and good data processing, a

SAR image may approach the appearance of an

aerial photograph. The filly focused SAR can see

farther to each side and provide wider coverage than

could the photographic system, and without loss of

resolution at longer ranges.

Characterizations of SAR resolution vary and

often depend upon unstated assumptions as to the

quality of the SAR and the height at which the

aircraft is flying. The U.S. Air Force cites the ability

of the F-15 SAR to see ‘‘a car in a driveway."48

Another source cites a 12-inch ground sample

distance for a SAR, but asserts that the difficulty of

interpreting SAR images degrades their utility to

that of photographs with twice that ground sample

distance.49 A third, writing in a context similar to the

film and TV examples above, says that a SAR would

have a ground resolution of 20 feet (v. 6 inches) .50

Yet another source addresses “sensor swath,”51

citing a width of 25 kilometers (15 miles) for a

notional SAR operating from an altitude of 25,000

feet. 52

SARs contain advanced digital electronics, so

they could be especially problematic from the

standpoint of technology transfer. One extreme

example is the Joint Surveillance Target Attack

Radar System (JSTARS) that was created to support

military operations by detecting force deployments

and movements behind enemy lines, but could in

principle be used for aerial monitoring as well. The

Boeing 707-mounted system uses 154 computers,

amounting to “the equivalent capability of three

Cray supercomputers,” to support its mission.53 In

addition to causing technology transfer concerns,

such high technology could raise fears in the

overflown country that the receiver might be illegally gathering signals intelligence (should such

collection be banned by the aerial surveillance

agreement). A SAR for cooperative aerial surveillance need not be nearly as complex as the JSTARS

SAR: removal of moving-target-indicator, battlemanagement, and near-real-time capabilities could

result in a system able to perform necessary aerial

search tasks but palatable from the technologytransfer standpoint and incapable of performing

illicit tasks.

Conventional Radar-Conventional, as well as

synthetic aperture, radars could find an aerial

surveillance application. Reportedly, Boeing’s Ad4sQuot~ in Interavia Aerospace Review, vol. 45, August 1$W, P. 649.

4%e MITRE Corp., op. cit., footnote 33.

m,cu s SoVie@ Ne~r t. AM Monitoring Deal, ” Dejense News, NOV. 27, 1989, PP. 1 et s~”

. $$

slcomeswn~g to “thamtic~ sweep width” as discussed ixI ch. 6 of thiS report.

52King, op. cit., footnote 27, p. 9.

ss’’s~ei~nce Aircraft Tests Slated in European Scenario,” Signal, September 1990.
Chapter 3--Airborne Platforms and Sensors .41

vanced Technology Radar Project has demonstrated

a 4.2-mile range for its millimeter wave radar

designed expressly for use against relocatable targets, such as the SS-24 and SS-25 mobile missiles.

This short range (projected to increase to over 6

miles) allows for a superb ground resolution (for

radar) of about 18 inches. Because of the short

timeline for attacking a ground target from a

low-flying jet, Boeing’s system uses automated

pattern recognition to identify targets, placing icons,

not images, on the user’s display. This identification

is aided by the automated use of information derived

from other on-board sensors.54 Such a system could

be used in aerial monitoring to cue other sensors to

focus on suspicious objects.

Radar, in both SAR and conventional variants, is

also useful in defeating conventional camouflage

and concealment measures. The relatively long

wavelengths of radar allow it to pass unimpeded

through clouds,55 smoke, dust, thin foliage, conventional camouflage, and other visual obstructions.

Moreover, radar can be used at night, giving the

observer a round-the-clock, all-weather capability.

Lidar—Lidar, a laser cognate of radar, is analogous to conventional radar in many respects except

that the laser light is of a much shorter wavelength.

The shorter wavelength has the benefit of allowing

a theoretically higher resolution, but the drawback of

being blocked by weather, foliage, and other impediments.

Comparison of Airborne Imaging Systems

Table 3-2 compares the imaging systems considered thus far. Each has its own unique set of traits.

In terms of those tabulated, there may seem to be

little reason to adopt SAR. However, as discussed

later in the sensor issues section, point-by-point

comparisons of sensors omit important synergisms

obtainable by using more than one sensor at a time.

Nonimaging Sensors

While imaging methods have received the widest

attention in discussion of aerial monitoring and

aerial reconnaissance in general-and will continue

to be our primary focus in the remainder of this

study-certain nonimaging means of information

collection merit some mention. Two of these, air

sampling and the use of acoustic methods, require

that the sensor be within the Earth’s atmosphere.

Signals Intelligence--SIGINT collects information through the interception of radio waves. In

addition to communications and radar signals, airborne receivers might collect electromagnetic emanations from electrical equipment of all kinds.56

Such receivers would so closely resemble SIGINT

collection devices that a ban on SIGINT collection

could effectively prohibit their use as well. Because

of the large potential for collateral information

collection during a SIGINT flight, the inclusion of

SIGINT devices in an accord appears at this time to

be unlikely. In fact, the only sensor technology that

the United States ruled out for Open Skies was

SIGINT.

Air Sampling and Sniffing-A variety of air

sampling technologies might be applied to a cooperative overflight regime. Through air sampling or

sniffing, aircraft could detect trace amounts of

telltale chemical signatures of the production-and

perhaps storage-of chemical weapons and missile

fuels,57 the venting of radioactive particles and gases

from underground nuclear weapon testing, the

release of outlawed pollutants, and other treatyrelevant or defense-related activities. The masking

of some of these telltale aerosols or gases by

legitimate effluents could complicate the matter of

monitoring. Likewise, localizing the source of

illegal emissions, particularly near a border, may

cause difficulties. (See ch. 5 for a discussion of

applications of air sampling and sniffing.)

Radiation Detection-Radioactive emissions from

illegal tests or facilities in the form of telltale

flBr~kW. Hendersoq $ CBoeing Develop~g Millimeter Wave Radar To Spot Soviet UrdOn’S Mobile Missile,” Aviation Week and Space Technology,

Oct. 8, 1990, pp. 55 et seq.

55fia ~~wows fi@ts at lowm ~ti~des, cloud cover co~d ofienbe flow under, th~ e~b~ any semor to sw below the clouds. However, thh

is not always the case and flying low results in a narrower swath width.

56For exwple, ~ncmnefisted titthe ~$race~ck~~ d~eptive ~s~g of the p~~k~permissfle(~enknown m Mx) could be compromised by the

detection of electromagnetic emanations resulting from transient loads on its powm supply. U.S. Congress, (lfi7ce of Technology Assessment, MX

Missile Basing, OTA-ISC-140 (Washington, DC: U.S. Government Printing ofilce, September 1981), p. 37.

sT~id+, p+ 36. Concmnefisted tittie “race~ck’ deceptive b~ing of the peacekeeper missile (then kIIOWn ~ hfX) cotdd be compromised by the

chemical detection of airborne emanations from its i%el.
42. Verification Technologies: Cooperative Aerial Surveillance

Table 3-2-Comparison of Airborne Imaging Systems

System Real time 3-dimensional Record Color Night Resolution

Vision . . . . . . . . . . . . . . . . . . . . . . Yes some No Yes infrared Medium

Photo . . . . . . . . . . . . . . . . . . . . . . NO Yes Yes Maybe Infrared High

Electro-optical still. . . . . . . . . . . . Maybe Yes Yes Maybe infrared High

l-v . . . . . . . . . . . . . . . . . . . . . . . . Yes No Yes Maybe infrared Low

Synthetic aperture radar . . . . . . . Almost Yesa Yes No Yes High

Radar . . . . . . . . . . . . . . . . . . . . . . Yes Yes Yes No Yes Low

Lidar . . . . . . . . . . . . . . . . . . . . . . . Yes Yes Yes No Yes High

a phase information allows recovery of a 3-dimensional image.

SOURCE: Office of Technology Assessment, 1991.

neutrons or gamma-rays might also be measured

from aircraft carrying detectors. Lighter-than-air

craft and helicopters might be particularly useful

platforms for these sensors because of their ability to

hover for more precise readings. Using these systems for uncovering small radioactive sources, e.g.,

nuclear weapons, however, may be seriously undermined by shielding and background radiation.

Acoustics-Though usually thought of in a submarine context, passive acoustic detectors can be

used in the atmosphere instead of in the ocean.

Development work has been pursued in this area.58

Acoustic detection could be useful in special aerial

monitoring tasks where a signature noise could be

positively correlated with a monitored item. For

example, concern existed that the location of the

mobile Peacekeeper might be revealed by the sound

of its cooling fans.59 Of course, in this scenario,

observers must be confident that the signature sound

cannot be muted or altered to avoid detection.

Magnetic Anomaly Detector—Another sensor

technology usually associated with submarines,

MADs are designed to detect the presence of large

ferrous objects by the size of their magnetic field

relative to the background. Because detection of this

field follows the inverse cube rule, the detector must

get very close to find an object. It has been stated that

a submarine can be discovered by an airborne

(airplane or helicopter) MAD at about 1,000 yards.60

Other possible TLIs that might be considered for

MAD detection (e.g., mobile missile transporters

and trains) are much smaller than submarines and

would require higher sensitivities or closer proximity. The latter makes it more likely that helicopters

would be the platform of choice.

Sensor Issues

If an aerial sensor suite is to be more than

symbolic, it must be able to detector characterize its

target reliably. To do this, its users need to consider

the possibility that an overflown country may try to

undermine the effectiveness of the sensor system

through camouflage, concealment, or deception.

Participating states should also assess the intelligence (and perhaps proprietary) costs of having

similar sensors fly over their own sensitive facilities.

Finally, the United States, in particular, has to decide

whether a specific accord requires and is worth the

technology-transfer cost of sharing advanced sensors.

61

Target Characteristics

Effective aerial monitoring necessitates that the

objects of attention be observable, either directly or

indirectly, by the mutually agreed-on sensor package. For imaging systems this means that the

observed item or activity must be resolvable enough

to be detected, recognized, identified, or analyzed

according to the goals of the accord. For example, a

treaty that called for directly counting battle tanks

would not be adequately served by a camera with a

resolution too poor to distinguish a tank from a truck.

Secondary characteristics, e.g., the formation of the

tank-like objects, might, however, provide indirect

evidence to support the treaty goals.

58’l”he ~Corp., op. cit., foomote 33.

59u.s. COWSS, ~~ce of TechnoIo~ Assessment, op. cit., foomm 56 p. 36.

WKOsta Tsipis, Arsenal (New York NY: Simon& Schuster, 1983), p. 233.

61some exW~ ~ve s~t~ titfi~accords fi@t be word~ wi~ enough fl~ibil.i~ to ~low for ~terations or upgrades of the Sensor Suite =

conditions change, technologies advance, or the parties become more comfortable with the regime. However, leaving the specifications of the sensor

array deliberately vague or adopting standards that are currently inadequate with hopes of later adjustment may restit in temions (and possibly danger

if the omitted sensors are needed for effective monitoring) if subsequent negotiations block any positive changes.
Chapter 3--Airborne Platforms and Sensors ● 43

Nonimaging systems must also be selected with

their target in mind. Insensitive chemical sniffers

might pass over a tightly sealed, covert missile

production plant. And SIGINT might yield no clues

to the presence of covert facilities that practice strict

emission control.

Moreover, looking at the target alone is not

enough. The observed object must be put into

context. (Remember that resolution is only one

factor aiding detection: contrast is important too.)

Acoustic and MAD sensors might be overwhelmed

by background signatures if their targets were

located in an urban area. The object’s operating

environment and habits need to be examined. Is it

important to be able to monitor the object at night or

in bad weather? Clearly, the smaller, more mobile,

and less emissive an object is, the more difficult it

will be for sensors to locate. If all these target

characteristics have not been studied in advance of

the sensor decision, and the sensor-target relationship not adjusted to the goals of the agreement, the

monitoring system could be irrelevant (and indeed

misleading).

False Alarm Rate

To the degree that sensors are to build confidence

both internationally and domestically, the reliability

of sensors becomes a critical issue. If a sensor

detects targets that are not there, tensions could be

raised for no good reason: one side would think it

had detected a violation, the other would react to

being falsely accused. In addition, if sensors are used

to cue on-site inspectors, false alarms could quickly

eat into that country’s inspection quota (if there is

one).

Camouflage, Concealment, and Deception62

Another critical issue for the sensor package

decisions is the possibility of an observed party

attempting to defeat the airborne sensors by camouflage, concealment and deception:

Persuasiveness in camouflage consists of suiting

the camouflage to the situation and of giving the

enemy an impression of reality and probability. For

example, when concealing objectives, it is necessary

to make them blend in with the terrain or with typical

local objects that do not attract attention. False

Photo credit: U.S. Department of Defense

Camouflage net shields M1A1 Abrarns Tank from

overhead observation during Operation Desert Storm.

Such operational camouflage measures would not

necessarily be banned by arms control agreements.

objects should be created in those places where they

fit into the setting; they must be similar enough to

actual objectives not only in appearance but also in

activity.63

If a party’s primary motivation for countering

surveillance is to proliferate restricted TLIs, it might

resort to camouflaging and concealing those TLIs

above an agreed ceiling. Camouflage could consist

of covering the TLI with leaves and branches cut

from a tree, variegated four-color paint, or a camouflage net. Concealment could entail removing the

TLI from view by moving it under the cover of

another object (e.g., a shelter or the tree canopy) or

masking it with fog-like smoke. As mentioned

s~orsome historical examples of CCD, S= app. B.

&Camu~age: A Soviet Vim, Soviet ~i~l’hough$ no. 22, translated and published under the auspices of the U.S.fi Force ~-~~:

U.S. Government Printing Oftlce, 1989), p. 180.
44. Verification Technologies: Cooperative Aerial Surveillance

above, some sensors can see through conventional

camouflage and concealment measures. However,

the manufacturers of camouflage and smoke have

been busy creating new and improved products that

are designed not only to obscure objects at visible

wavelengths, but also at infrared, radio, and ultraviolet. 64

Another objective of the cheating party might be

deception. By applying deception in the form of

decoys-of a TLI itself65 or of the objects that one

would expect to find near a TLI (i.e., an indirect

indicator of the TLI)--this party could: 1) divert

monitoring assets from true covert activities occurring elsewhere, 2) present a picture of compliance

while preparing to break out of the agreement (e.g.,

the movement of troops out of a designated deployment area and toward the border), 3) dilute OSI

quotas by sending inspectors on wild goose chases,

and 4) undermine confidence in the reliability of the

sensor suite (perhaps as a precedent should a real

violation be discovered).

A final complicating factor is that some potential

TLIs rely on CCD to survive in a conflict. These

TLIs may be exempted from prohibitions on using

normal CCD techniques, as is the case for TLIs in the

Conventional Armed Forces in Europe (CFE) Treaty.66

Multiple Indicators

The best solution to the problem of CCD is to

make the job of the violator as difficult as possible,

if not impossible. Different imaging systems have

different strengths and weaknesses. Configures of

an aerial monitoring aircraft might want to combine

complementary imaging systems for a maximum

overall probability of achieving the goals of an

accord; i.e., detecting the target regardless of countersurveillance measures.

Credible Evidence of a Violation

and Data Storage

What happens if a violation of an agreement is

discovered? Some would say that this alone would

be just cause for abrogating an agreement. However,

the history of compliance policy suggests that such

black-and-white distinctions are extremely rare.

More than one sighting from perhaps more than one

source might be required for firm evidence of an

intent to cheat.

If the overflight had made no permanent record of

the discovery (e.g., visual observation) or the

recorded data was ambiguous, the violator could

claim that the accusation was a false and political

provocation. Inspectors seeking to revisit the site

(possibly in a quick-response helicopter) might not

at-rive in time or might be rebuffed. If a record of the

observation were made and the data were clear

enough to interpret, the party could credibly argue

that the violation spotted was simply an aberration,

an accounting error that will be rectified immediately. Therefore, data storage can be important for

supporting assertions of noncompliance.

However, stored data can also be a major source

of collateral information that the parties might not

want revealed. The task is to balance the informational requirements of an agreement against the cost

of greater intrusiveness.

Depending to some extent on the sensor, data can

be stored in either analog or digital form. In their

digital manifestation, the raw data can be more

easily processed by computer to bring out important

details that might remain hidden in its analog

counterpart. This, of course, helps increase the

effectiveness of flights; however, it also increases

the amount of collateral information lost by the

overflown state. For this reason, restrictions might

be placed on data storage: it could be limited to

analog devices or prohibited entirely. Or, conceivably, the raw data could be passed through a computer

~Newly NCO1OM, ~tr~ight camouflage new ordered for Operation Desert Shield (subsequently, Operation Desert Storm) in the persi~ G~ me

designed to scatter radar in the 6-to 140-gigahertz mnge. (“Deployment of Saudi T!a~” Jane’ sDefence WeeMy, Oct. 27, 1990, p. 805.) One company’s

camouflage netting-laced with metallic dipole~reflects, scatters, and polarizes radar signals so that the returns approxirnate the background. It can

also be given a foliage appearance or match the background in the near infrared. (“Camouflage Systems,” company brochure, Teledyne Brown

Engineering, Huntsville, AL.) See also Banner et al., op. cit., foomote 4, pp. 88-89.

~A TLI decoy might consist of another object that closely approximates the original at the sensitivity of the StXISOrS invoked (e.g., a mik e~ for

a mobile missile transporter or a set of radar corner reflectors). However, a decoy could also be an elaborate imitation that resembles the TLI in every

way (visual, infrared, radio>xcept that it can be dismantled and stowed before an inspection team arrives. See Teledyne, ibid.; and Camouj7uge: A

Soviet View, op. cit., foomote 63, pp. 203-206.

fiArticle ~, paragraph 3.
Chapter 3--Airborne Platforms and Sensors .45

program that filters out detail beyond that required

by the accord. Lastly, the data gathered could be

shared amongst all parties, even to the point of joint

analysis.67

Sensors Targeting the United States

Aerial overflight agreements cut both ways. If

they are effective in ferreting out useful collateral

information about another country, they may reveal

more information about your own country than you

would like. If an agreement permitted sophisticated

sensors with capabilities beyond those of NTM,

aerial surveillance might undermine U.S. national

security by adding considerably to the Soviet

Union’s (as well as other signatories’) knowledge of

the American defense and intelligence establishment. 68

Even if agreed sensors were limited in their

capabilities to prevent the collection of this extra

information, the overflown country might still be

concerned about the presence of covert sensors

placed on the aircraft. This concern might be

alleviated by preflight inspections of the aircraft.

If the agreed sensor suites were restricted to a

capability equal to or below that of NTM, the United

States, in particular, and the Soviet Union might

have relatively little to gain by overflights beyond

confidence building.69 Instead, their monopoly on

information would be broken by granting equivalent

overflight rights to countries with limited independent NTM assets .70

Technology Transfer

Parties to an aerial surveillance regime might

permit access to each others’ aircraft and sensors.

The primary reason for such access is the fear of the

collection of collateral information. Aircraft inspections would verify the legitimacy of allowed sensors

or check for covert instruments. In some cases, for

reasons of equity as well as security, identical sensor

suites might be shared among all the parties. Since

many sensing technologies are on the cutting edge of

U.S. technology, and since these sensors may have

military and intelligence applications that are important for national security,71 it maybe in the interest

of the United States not to compromise them by

putting them on an aircraft that will be inspected. In

these cases, it may be best to rely solely on

commercially available devices; in others, however,

it may be worthwhile to give up some technical

information in exchange for the benefits of an

accord. 72 Of Course, settling for less capable technology may affect the ability of the sensor to serve the

monitoring goals of an accord, and thus its utility.

Only in regimes where there are no restrictions on

overflight activity and no inspections of aircraft will

the United States be likely to use its technology to

the fullest.

Operational Concerns

Time: Notification and Duration

If the task is to monitor a region for certain objects

or activities, time can be an important operational

factor. This is particularly true for TLIs that are

easily relocated or hidden. If a TLI can be removed

from aerial view before a flight can reach it, then the

overflight has questionable utility. (The time it takes

to reach a TLI is the sum of the notification/preflight

inspection period and the minimum flight time to the

target.) If monitoring success does not necessitate

reaching a TLI in a short time, then the length of the

notification/preflight inspection period is irrelevant.

The duration of the actual flight is also a central

issue in that it determines (when combined with air

speed) the amount of territory a flight can cover.

Except in the case of symbolic flights or flights to

specific destinations, the ratio of the territory

scanned to the total territory73 can have an important

impact on how confidently one interprets the data

gathered.

670pponents of data sharing argue that revealing this information would aid a potential cheater nation in perfecting its CCD measures.

@conceivably, ovefighk could rev~ proprietary and economic tio~tion m wel~ ~d~geconomic -ty.

69A discWs~ emlier, even sasom ~enor t. ~fi@t provide me superpowers Mm US&UI -h capabilities, p-y because of the

flexibilities of the platforms.

~see tile 4-2 inch. 4 for a discussion of some of the regional and national asymmetries of ~chacmrds.

71A we~ as the mtional economy.

vz~sS-of~o~tionimplies some loosening of export control legiSkttiO12.

73~s ~~t~tie en~e temtov of ~ pmor tit pm of it where me ~getti Westion wotid likely appear.
46 ● Verification Technologies: Cooperative Aerial Surveillance

Flight Quotas

Similarly, the number and frequency of flight is

important to the level of confidence one can invest

in a monitoring regime. As will be addressed

mathematically in chapter 6, the number of flights,

combined with their duration, puts statistical bounds

on certain types of monitoring, especially aerial

search. Put simply, the more often and longer a

country is overflown, the more confident is the

observer in making statistically based judgments of

compliance. Increasing the frequency of the flights

(i.e., shortening the time between flights) builds

confidence faster.

Methods offered to fairly apportion the number of

flights for countries of varying size have been based

on relative size of the countries’ entire territory, their

searchable territory, their military, and their population.

Territorial Restrictions

In the broadest of all aerial surveillance schemes,

aircraft would be free to roam where they please. In

the interest of flight safety, however, some restrictions might be deemed necessary. Active military

exercise or test sites might have to be bypassed

unless there were a mandated stand-down period.

Severe weather systems might also have to avoided,

although these could be predicted by the inspecting

country in advance. Moreover, adequate air traffic

control might not be available in some areas.74

Restrictions could also be adopted to ensure the

safety of overflown facilities and people. The

Soviets have made this argument in the Open Skies

negotiations over such sites as nuclear power plants

and major cities (see ch. 4).

The Soviets also believe it is necessary to restrict

flights over sensitive facilities, where aerial surveillance might be used to gather information contrary

to Soviet national security. By setting up exclusion

zones, the Soviet Union would try to shield secret

military and intelligence installations from prying

Western eyes. To varying degrees, many other states

agree with these concerns over the collection of

collateral information, but they have tried to deal

with them through means other than territorial

restrictions. For example, the United States agreed

that including SIGINT sensors in Open Skies would

be too intrusive.

In some accords, free-ranging flight might not

even be considered necessary. For example, overflights might be made only over designated regions

(e.g., mobile missile deployment areas) or over

declared facilities (e.g., chemical plants) .75 In the

narrowest of schemes, tethered aerostats could be

anchored at a specific site in order to observe local

activities or site perimeters.

Details

If the central issues of a cooperative overflight

regime were settled, there would still remain a host

of details to work out. There are personnel questions

such as who can be selected as an inspector or escort,

whether a nominee can be rejected by the other

parties, the inspectors’ diplomatic status, and whether

the inspector can be subjected to a physical search.

There are questions of which party is responsible for

what costs, including aircraft servicing and aircrew

accommodations. A joint consultative mechanism

also needs to be established to handle concerns over

compliance and gray areas of the agreements.

Conclusion

Negotiators of aerial surveillance provisions must

determine which types of platforms and sensors

would be both effective in achieving the goals of the

accord and still mutually acceptable. If the overflights were intended to be purely symbolic, then

perhaps only visual observations by the aircrew

would be required. In contrast, if overflights were a

major component of a monitoring regime, a wide

variety of complementary sensors, spanning th e

electromagnetic spectrum, might be essential. Negotiators making the final selection of the sensor and

platform package would have to balance the

strengths and weaknesses of the various airborne

equipment with the costs and benefits of the

agreement as a whole.

74T&myorwynot& consider~ important. TheUnit~ states itself has large areas that are not covered by air tmfllc control, but stifl Permitfi@tS.

75Restricfig surveillan~ to designat~ sit~ undermines the ability of the flights to detect suspicious activities beyond these sites. ~~ssense, tie

flights begin to resemble some types of 0S1: rhey can determine compliance at the designated site, and make cheating more diffkultand expensive by

_ it elsewhere, but they cannot detect cheating off site.
Chapter 4

OPEN SKIES
Contents

Page

summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 9

Open Skies 1955 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Open Skies 1989 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

‘The Goals of Open Skies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

The Initial NAT-O Position . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

Points of Disagreement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Conclusion ... ..1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

Box

4-A.

Box

Page

Canadian-Hungarian Trial Overflight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Figure

4-1. NATO

Table

4-1. Open Skies Chronology

4-2. Asymmetric

. . . .

and

. . . . . . .

. . . . . . .

Figure

. . . . . . . .

Tables

. . . . . . . .

Page

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Page

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Disadvantages in Open Skies . . . . . . . . . . . . . . . . . . . . . . 55
Chapter 4

OPEN SKIES

Summary

One example of how aerial surveillance might be

used in a multilateral agreement can be found in the

Open Skies Treaty intermittently being negotiated

by the members of the North Atlantic Treaty

Organization (NATO) and the now dissolved Warsaw Treaty Organization (WTO).l

The goals of the Open Skies Treaty are broad: to

further international openness; to reduce tensions; to

enhance military transparency and predictability; to

further the progress of arms control; and to promote

a more open Soviet society. In sum, the overall goal

could be described as international confidence

building. This is to be accomplished by opening the

national airspace of the participants to relatively

unrestricted overflights by aircraft carrying sensors

and inspectors from other countries.

Designing a treaty to build confidence is a much

more nebulous and subjective task than devising

schemes for monitoring compliance with specific

agreements. As of this writing, negotiations are

stalled due to deep divisions between the United

States and the Soviet Union over the degree of

intrusiveness required to build an appropriate level

of confidence. In general, the United States argues

for maximal intrusiveness, while the Soviets hold

out for tight restrictions on all aspects of the

overflights. Other NATO and former WTO states

tend to occupy the middle ground, but when pressed,

lean toward the U.S. position.

Introduction

On May 12,1989, during a speech at Texas A&M

University, President George Bush resurrected President Dwight D. Eisenhower’s 1955 proposal for a

multilateral Open Skies Treaty. The Open Skies

agreement he proposed would send NATO aircraft

carrying sensors over Warsaw Pact countries and

vice versa. The purpose was to use the characteristics of aerial surveillance to promote openness and

to further reduce tensions in Europe. While the

original proposal in 1955 was suffocated by an

unfavorable political climate, the closing days of the

Cold War offered more propitious conditions. (See

table 4-l.)

Despite an initial period of public skepticism, the

superpowers agreed to begin negotiations on the

Open Skies initiative. Gradually, experts in the arms

control field began to reconsider the utility of aerial

surveillance as a component in international treaties.

Just as the Intermediate-Range Nuclear Forces (INF)

Treaty paved the way for broader discussions of the

utility of on-site inspections, Open Skies seemed to

move aerial surveillance into the realm of the

practical.

Open Skies offers a detailed example of the issues

involved in negotiating multilateral overflights.

While most of these issues will surface in any

negotiation on aerial surveillance, Open Skies does

have one unique quality: its goals have been defined

so broadly that no objective standard exists for

establishing what the characteristics of the flights

should be. Unlike a monitoring measure intended to

search for a specific weapon system, inspect a site,

or warn of a particular activity, Open Skies flights

would aim to build confidence among the signatory

countries. 2 As is discussed below, the vagueness of

the goals of Open Skies has given Soviet negotiators

some basis for their attempt to limit the intrusiveness

of the treaty.

Open Skies—1955

In the summer of 1955, an Iron Curtain separated

East and West Europe. Hard information about the

intentions and military capabilities of the Eastern

bloc was difficult to obtain. Early American attempts at clandestine aerial surveillance had been

met by ever-increasing Soviet air defense capabilities. Overflights of Soviet territory by the superl~emilitary snc~es of the Warsaw Pact were abandoned Apr. 1, 1991. The ftipOlitiCal remnan ts of the WTO were disbanded on July 1, 1911.

(See “Warsaw Pact Formally Ends,” The Washington Post, July 2, 1991, p. Al 1.

zA~ mentioned ~ ~ha 2, the ~~es t. tie @en sties negotiations agr~d in principle that an @n sties T~aty should SUppOfi other arms COntrOl

agreements. However, as the negotiations now stand, no such support has been written into the treaty. The Conventional Armed Forces in Europe

(CFE) Treaty and the Strategic Arms Reductions Talks (START) are but two of the treaties and potential treaties that might benefit from overlapping

monitoring coverage with Open Skies. However, such coverage would tend to be haphazard and incidental, since it is not being formally addressed in

the negotiations.

-49–
50. Verification Technologies: Cooperative Aerial Surveillance

Table 4-l-Open Skies Chronology

Date Event

July 21, 1955

April 29,1958

May 26, 1972

May 12, 1989

September 23,1989

September 25, 1989

December 14-15, 1989

January 4-7, 1990

February 12-28, 1990

February 13, 1990

April 24 to May 10,1990

May 12, 1990

October 3, 1990

April 1,1991

July 1, 1991

President Eisenhower’s “Open Skies”

speech; series of proposals follows.

Soviets veto final Eisenhower proposal

for an Open Skies regime.

Strategic Arms Limitation Talks (SALT

1)legitimize national technical means

(NTM) of verification.

President Bush’s Open Skies speech.

Soviet Foreign Minister Shevardnadze

and U.S. Secretary of State Baker

agree in principle to Open Skies

concept and call for international

conference on Open Skies.

Canada offers to host the Open Skies

conference.

NATO ministers finalize a common Open

Skies position.

Canadian-Hungarian mock overflight.

Open Skies first round, Ottawa,

Canada.

Open Skies Communique.

Open Skies second round, Budapest,

Hungary.

One-year anniversary of Resident Bush’s

Open Skies speech; possible date

for signing Open Skies Treaty

passes without an agreement.

Unification of Germany.

Warsaw Treaty Organization’s military

organization is officially disbanded.

Warsaw Treaty Organization informally

dissolved.

SOURCES: The Arms Control Reporter 1990; The Disarmament Bulletin,

Canada, External Affairs and International Trade, no. 12,

winter 1989/90; “Warsaw Pact Formally Ends,” The Washington Post, July 2, 1991, p. Al 1; and the Office of Technology

Assessment, 1991.

secret, high-altitude U-2 aircraft and GENETRIX

reconnaissance balloons3 were still a year away; and

only in March of 1955 had the U.S. Air Force issued

a formal system requirement for a reconnaissance

satellite. 4 This situation fostered Western concerns

about the potential for a surprise attack by the Soviet

Armed Forces, newly equipped with nuclear weapons.

In an effort to lift the curtain, President Eisenhower proposed, at the Geneva Conference of Heads

of Governments (United States, United Kingdom,

Soviet Union, and France) on July 21, 1955, the

establishment of a system of mutual overflights by

unarmed reconnaissance aircraft. In this well-known

“Open Skies” speech, Eisenhower evoked the

specter of nuclear war in his call for a system of

mutual aerial surveillance:

I should address myself for a moment principally

to the delegates of the Soviet Union, because our two

great countries admittedly possess new and terrible

weapons in quantities which do give rise in other

parts of the world, or reciprocally, to the fears and

dangers of surprise attack.5

But Eisenhower saw Open Skies as more than

simply a warning mechanism. He also believed that

Open Skies would lead to a lessening of tension and

general danger, and eventually to ‘a comprehensive

and effective system of inspection and disarmament." 6 

The specifics of Eisenhower’s proposal included

an exchange of “a complete blueprint of. . . [each

side’s]. . . military establishment,’ identical facilities for aerial photography, and allowance for the

removal of photographs for study. The French and

British Governments quickly agreed to join in this

system.

At the time of its announcement, Open Skies was

a revolutionary concept that offered to enhance

radically the quantity and quality of information

available to each superpower about the other.

However, the Soviet Government still equated its

security with absolute secrecy, and therefore eventually rejected the U.S. proposal as an effort to spy on

the Soviet Union.

Over the next 2 years, the United States, through

the United Nations and bilaterally, sought to find

some way to make Open Skies work. These efforts

focused on limiting the regime geographically to the

Arctic countries, including the United States, the

Soviet Union, Canada, and the Nordic states. The

qsee ~x 6-1 inch. 6.

AMefion E. Davies and Wilti R. m,~D’~ Role in the Evolution of Balloon and Satellite Obsemation system and Related U.S. SpaCe

Technology (Santa Monic% CA: The RAND Corp., 1988), p. 61.

%lwight D. Eisenhower, “Statement on Disarmament Presented at the Geneva Conference,” July 21, 1955 as cited in Dwight D. Eisenhower, Public

Papers of the Presidents of the United States 1955, No. 166, p. 715.

‘Ibid., pp. 715-716.

~id., pp. 715.
Chapter 4—Open Skies .51

Photo credit: U.S. Air Force

Lockheed U-2R aircraft in flight.

Soviet representative at the United Nations Security

Council vetoed the final American attempt to find

some basis for an Open Skies agreement on April 29,

1958.8

Open Skies—1989

The original Open Skies proposal lay dormant for

nearly three and a half decades. Then, President

Bush judged that the international political climate

had changed sufficiently for another attempt at

negotiating a mutual overflight agreement. This

time, the Soviet Union appeared to decide that its

security would not be severely undermined by an

Open Skies regime and might in fact be strengthened. Part of the reason for this changed attitude was

undoubtedly the fact that the superpowers had

essentially already had their skies opened with the

orbiting of sophisticated reconnaissance satellites

beginning in the 1960s.9

Moreover, in 1989 the world community was

receptive to a resumption of Open Skies talks. In

particular, the acceleration of reforms in the Soviet

Union and Eastern Europe and the completion of an

agreement on intermediate-range nuclear missiles in

Europe, which included a verification regime of

unprecedented intrusiveness, invoked both the optimism and cooperative spirit necessary for a panEuropean agreement. Simultaneously, fears of instability and of the threat from residual military capabilities made monitoring important to a growing

list of nations. Without the changed political climate,

Open Skies would remain nonnegotiable; without

the fears, Open Skies would not be necessary.

On May 12, 1989, in an address to graduating

students at Texas A&M University, President Bush

revived President Eisenhower’s proposal for an

Open Skies agreement:

Thirty-four years ago, President Eisenhower met

in Geneva with Soviet leaders who, after the death of

Stalin, promised a new approach toward the West.

He proposed a plan called Open Skies, which would

allow unarmed aircraft from the United States and

the Soviet Union to fly over the territory of the other

8The Arm conpol Reporter: A chro~ic[~ of Treaties, Negoti~tio~, proposals, weopo~, a~po[icy @r~klinq w: kstituk fOr Defense ad

D“uxwrnament Studies, 1990), p. 409.B.1.

~ese overflights were legitimized with the ratification of the Sfrategic Arms Limitations Talks agreements in 1972 which recognized the use of

national technical means (P/TM) of verification. The Soviet Union accepted the principle that national sovereignty does not extend into outer space in

a 1963 United Nations resolution. (See Michael B. Beschloss, Mayday: Eisenhower, Khrushchev, and the U-2 A#air (New Yo~ NY: Harper& Row,

1986), p. 393).
52. Verification Technologies: Cooperative Aerial Surveillance

Box 4-A--Canadian-Hungarian Trial Overflightl

Outside the United States, perhaps the strongest advocate for an Open Skies regime has been the Canadian

Government. This interest goes back to the inception of the idea in 1955 when Canada became the first Western

nation to endorse formally President Eisenhower’s proposal.z In September 1957, Prime Minister John Diefenbaker

made this statement:

. . . the Canadian Government has agreed, if the Soviet Union will reciprocate, to the inclusion of either the whole

or a part of Canada in an equitable system of aerial inspection and will do its utmost to ensure that the system works

effectively. 3

This interest has carried over to the present. Prime Minister Brian Mulroney made his support of Open Skies

clear to President Bush even before the public address.4 And as mentioned above, the Canadian Government quickly

offered to host the first round of the talks.

In an effort to get the conference off on the right foot, the Canadian Government proposed, and the Hungarian

Government accepted, a mock aerial surveillance flight over each of their countries. The purpose of the flights was

to demonstrate that the procedures involved in Open Skies would be safe, nondisruptive, and practical. The two

countries opted not to allow sensors on the test plane and instead concentrated on facilitating the preflight inspection

for contraband and on gauging the success of air traffic control of an airplane with an unconventional fright plan

(outside commercial air corridors).

Crossing Czechoslovakia, a Canadian Forces C-130 airplane arrived in Budapest, Hungary on January 4, 1990

for the first of the two flights. The time intervals for each aspect of the flight from arrival to departure were expanded

somewhat to allow a detailed analysis and discussion of the proposed procedures. Hungarian authorities, watched

by the Canadian aircrew, inspected the plane for armaments for about 4 1/2 hours (normally, this inspection would

also look for illegal sensors and, perhaps, verify the specifications of the legal sensor suite). At the same time, the

Canadian crew submitted its intended flight plan to the Hungarians, who had 24 hours to clear the route and ensure

its safety.

On the morning of January 6, 1990, the C-130, along with its Canadian crew and Hungarian observers,5 flew

a figure-8 route over Hungarian territory for about 3 hours. The plane changed altitude several times during the flight

from approximately 5,000 to 16,000 feet.6 The flight plan took the plane over a variety of commercial and residential

areas as well as Hungarian and Soviet military installations.

Declared a general success by the participants, the trial flight was said to demonstrate that Hungarian air traffic

control could handle the unusual flight path without undue effort or expense. One concern raised was that

host-country escorts during the preflight inspection might inadvertently damage the plane and undermine flight

safety. The participants felt that providing manuals for the plane and appropriate tools for opening flight instruments

could be a partial solution to this safety problem. On January 7, 1990, the Canadian plane left Budapest.

Neither Hungary nor any other WTO member has taken advantage of Canada’s offer of a reciprocal overflight

of Canadian territory.

lmtis of tie a~~ surveil~~ exercise can be found in the following sources: CMIIM@ Exte@ AffZWS“ and International Trade,

“Reporton the Canada-HungaryT rial ‘Open Skies’ Overflight, Jan. 4-6, 1990, Open Skies: l%parz’ngfor the 1990s,Backgrounder No. 3, Feb.

1, 199Q “Canada Conducts Trial Open Skies Overflight of Hungary,” The Diwr?name nt l?uUetin, Cana@ Extmud Affairs and International

Trade, No, 12, winter 1989/90, pp. 7-8; “Open Skies Treaty Will Give 23 NatioN s~eill~~e R@%” A~’ation Week @ndSPace Tech~olo#J

Feb. 19,1990, p. 21; The Arms ControZReporter 1990, p. 409.B.6-8; and “CanadianFlight Over Hungary Marks Trial Run of U.S. Open Skies

Initiative,” Defense News, Jan, 15, 1990, p. 25.

2~c~l Slfickmd H~&er~~tt (@se), @en skies: Te~h~’~a{, orga~zatio~l, oper&On~, tigal, andPoliticalAspects (’fbrOJ3@,

Canada: Center for International and Strategic Studies, York University, February 1990), p. 105.

41bid., p. 4.

5~ esm~s ~= &M t. move Wout &e p~ne as they saw fit. However, since there were no SeUom modtie Pl~e* ~~e was ‘t~e

for them to obsave besides that the plane did not stray from its planrted course.

%twm concluded that for reasons Of Mfet’y tie minimum altitude for any overflight should be 2,000 feet above the highest obstacle within

10 nautical miles of the flight path.
Chapter 4—Open Skies .53

country. This would open up military activities to

regular scrutiny and, as President Eisenhower put it,

“convince the world that we are lessening danger

and relaxing tension. ”

President Eisenhower’s suggestion tested the

Soviet readiness to open their society. And the

Kremlin failed that test.

Now, let us again explore that proposal, but on a

broader, more intrusive and radical basis, one which

I hope would include allies on both sides. We

suggest that those countries that wish to examine this

proposal meet soon to work out the necessary

operational details, separately from other arms

control negotiations.

Such surveillance flights, complementing satellites, would provide regular scrutiny for both sides.

Such unprecedented territorial access would show

the world the true meaning of the concept of openness. The very Soviet willingness to embrace such a

concept would reveal their commitment to change.10

As a side effect, the proposal generated renewed

interest in using aerial surveillance for a wide variety

of other monitoring and confidence-building tasks.

(Some of these are discussed in the next chapter.)

On September 22-23,1989, Soviet Foreign Minister Eduard Shevardnadze and U.S. Secretary of State

James A. Baker III met in Jackson Hole, Wyoming,

where they released a joint statement agreeing in

principle to the Open Skies concept and calling for

an international conference. Two days later, the

Canadian Government offered to host the conference in its capital.ll

Then, in mid-December in Brussels, the 16 NATO

foreign ministers gathered at NATO headquarters

and hammered out the final details of a joint NATO

position that covered virtually all aspects of a

potential accord. They sought to keep the agreement

flexible, simple, and, above all else, minimally

constrained. 12

In January 1990, the Canadian and Hungarian

Governments set the stage for the Ottawa Conference by conducting a mock Open Skies overflight of

Hungarian territory (see box 4-A). When the first

round of talks began, a wide gap appeared between

NATO’s opening position and that of the Warsaw

Pact. The resulting draft treaty did little to narrow the

significant differences.

13 The principal outcome of

the Ottawa meeting was a joint communique on the

second day. This statement laid the foundations both

for future agreement and disagreement.

The second round (Apr. 24 to May 12, 1990) of

Open Skies talks in Budapest, Hungary produced no

further progress and quashed hopes for a signing

ceremony on the l-year anniversary of President

Bush’s Open Skies speech. Publicly, at least, the

Open Skies negotiations have been stalled since the

Hungarian Conference. As of this writing, no date

has been set for a third round.

The Goals of Open Skies

According to the joint communique released at

the Ottawa Conference, the 23 nations (22 nations

after the unification of Germany) participating

foresaw many benefits arising out of an Open Skies

agreement:

. . . although an “Open Skies” regime is neither an

arms control nor a verification measure per se its successful implementation would encourage reciprocal

openness on the part of participating states. It would

strengthen confidence among them, reduce the risk

of conflict, and enhance the predictability of military

activities of the participating states. Finally it would

contribute to the process of arms reduction and

limitation along with verification measures under

arms limitation and reduction agreements and existing observation capabilities. The Ministers noted

further that the establishment of an “Open Skies”

regime may promote greater openness in the future

in other spheres.14

lofiesident George Bush “Remarks at the Tem A&M University Commencement Ceremony in College StatiOQ Texas,” my 12, 1989 as cit~

in Weekly ContpiZafion of Presidential Documents, vol. 25, No. 20, May 22, 1989, p. 702. (Paragraph breaks not in original text.)

lk)t~waconferencep~ cipmtsw=e theNATOcountries (Belgi~Cana@Denmark, ~~,W~tGerman y, Greece, Icelar@Italy,Luxembourg,

the Netherlands, Norway, Portugal, Spa@ lk.rkey, the United Kingdom, and the United States) and the Warsaw Pact states (Bulgari% Czechoslovak@

East Germany {until reunillcation) ,Hungary, Polan~ Roma@ and the Union of Soviet Socialist Republics). Observers fromAus~ Cyprus, Finl@

Irelant Monaco, Swede% Switzerland, and Yugoslavia also attended.

IZSW appe D, U.S. Arms Control and Disarmament Agency, “NATO’s Proposed Basic Elements for Open Skies,” ~cial Text, Dec. 14-15, 1989.

lsJo@than B. lhcker, “Back to the Future: The Open Skies Talks, ” Arms Control Today, Octob= 1990, P. 22.

IAU.S. Arms Control and Disarrnam ent Agency, “ ‘Open Skies’ Communique,” Oj%iul Text, Feb. 13, 1990.
54. Verification Technologies: Cooperative Aerial Surveillance

From this passage and other statements by Open

Skies participants, a general list of goals set for the

treaty can be distilled:15

. enhance military transparency and predictability,

. reduce international tensions,

. further the progress of arms control, and

● pl-emote a more open Soviet society.

As a whole, these broad goals can be described as

confidence-building measures. The aerial surveillance provisions of the treaty are not intended to

count treaty-limited items (TLIs), measure specific

quantities, or monitor restricted behaviors; instead,

they are primarily meant to provide assurance that

the current political warming is continuing apace by

making widely available information that demonstrates good intentions and nonthreatening capabilities. This vagueness has led to a debate (primarily

between the Soviet Union and the other participants,

but also among the other participants) as to the level

of intrusiveness needed to accomplish the declared

goals.

The Initial NATO Position

As mentioned above, the 16 NATO foreign

ministers gathered December 14-15, 1989 at NATO

Headquarters in Brussels to finalize a joint proposal

for Open Skies. This proposal formed the basis for

negotiations with the seven WTO member states. To

limit the complexity of the talks and facilitate

unanimous consent, the NATO ministers decided to

restrict the Open Skies discussions to these two

alliances.

Here, in brief, are the key operational details of the

original NATO proposal. They are referenced by

letter to ease comparisons between NATO and nonNATO positions in the following section. The

bracketed citations correspond to the official text in

appendix D.

A.

B.

c.

D.

E.

F.

G.

H.

Initially Open Skies negotiations will be

between the NATO and WTO alliances {III},

but later they might include any other European nation {1.3}.

Open Skies flights will encompass the entire

territory of the participants16 and, in principle,

will be limited only for reasons of safety or

international law {1.4 and VIII.7}.17

An unarmed, freed-wing military or civilian

aircraft will be provided by the inspecting

party. The plane will carry host-country observers during its overflight {V and VIII.6}.

Overflights may be conducted individually or

jointly within alliances {1.4 and IV.1}. 18

Equipment and aircraft may be shared among

allies {VII}.

The planes will be allowed to carry a wide

variety of sensors. Only signals intelligence

(SIGINT) devices will be banned {VI}.

All participants share a commitment to conduct and receive overflights on the basis of

national quotas {1.4}. These quotas will set

both the number and duration of overflights.

The standard for the quota apportionment will

be national geographical size {IV.1}. There

should also be rough parity of quotas between

NATO and the WTO and between the Soviet

Union and the combined territories of the

United States and Canada {IV.3}.19 Larger

countries should be subject to several overflights per month {IV.1 }, and all nations must

receive one flight per quarter {IV.4}. Smaller

allied states may group themselves and act

according to their combined geographical size

{IV.5.}.

Overflights will begin and end at a Point of

Entry (POE) and a Point of Exit, respectively

{VIII.1}. These points can be the same

{VIII.7}.

The host country will arrange service as for a

commercial airliner {VIII.2}.

ISAS a proximate and unstated goal, Open Skies would add to the information-gathering capabilities of the participants, particularly the

nonsuperpowers. These expanded capabilities, depending on their fti negotiated parameters, could beneilt the verification of other current and future

treaties, provide a broad range of collateral intelligence, and add to strategic, and perhaps tactical, warning.

16For me ufit~ s~t= MS ~cludes me 50 s~tes, G-, ~~0 Rico, and the U.S. Vi@ Ish.nds.

1TA5 sPll~ out by tie Ufitd Natiom-spomo~ ~termtio~ Civil Av~tion ~~mtionQCAO) ~d bilate~ md multikiterdaccJXds.

18~e Ne&er~&_o~~onFebc 12,1990, tit it would conduct joint fi@ts wi&Be@m ~d Luxembourg i.norderto reduce COSR. paid hwi.$,

New York Times, Feb. 13, 1990 as cited in The Arms Control Reporter 1990, op. cit., footnote 8, p. 409.B.9.

lgAt tie B~&pest co~ermw,&Ufited S@tes propos~ to ~oc~e quo~ on a bflate~ his wong ~ p~es, superseding the O@ld NATO

proposal to allocate them by alliance. This was done in recognition of the gradual dissolution of the WTO. The new proposal raised the possibility tbat

East European countries might be able, with Soviet permissio~ to oveffly the Soviet Union. (’lhcker, op. cit., footnote 13, pp. 22-23 and pemonal

communication Apr. 5, 1991.)
Chapter 4—Open Skies .55

Table 4-2—Asymmetric Advantages and Disadvantages in Open Skies

Region/state Advantages Disadvantages

Superpowers . . . . . . . . . . . . . . . . Superpowers have more resources and better NTM already provides much of the information that

intelligence apparatuses; Open Skies data Open Skies would provide, thus superpowers

can cue NTM. gain relatively less and lose relatively more than

other nations.

Nonsuperpowers . . . . . . . . . . . . . Treaty puts superpowers and nonsuperpowers Fewer resources than superpowers.

on equal political footing; gives these

countries an independent means of

surveillance. a

NATO . . . . . . . . . . . . . . . . . . . . . . Access to more closed societies. No technology gain; technology loss to WTO.

Soviet Union . . . . . . . . . . . . . . . . . Might gain access to Western sensor and Least open society has the most information to be

processing technology. revealed.

Non-Soviet WTO . . . . . . . . . . . . . Might gain access to Western sensor and Least-capable sensor and processing equipment.

processing technology.

a France Currently operates the commercial grade SPOT-image photoreconnaissance satellite and is developing the Helios military reconnaissance satellite

system with Spain and Italy.

SOURCE: Office of Technology Assessment, 1991.

I. The inspecting party must transmit an inspection notification 16 hours before arriving at the

POE {VIII.3}. After arrival, the flight crew has

an additional 6 hours to file a flight plan for the

overflight { VIII.4 } .20 This done, the host

country has 24 hours in which to inspect the

plane for illegal devices and arrange for the

flight {VIII.5 }. (See figure 4-l.)

J. Loitering by aircraft over one spot is not

permitted {VIII.6}.

K. Alliances will decide amongst themselves

how to share overflight information {IX}.

The NATO position, as embodied in a U. S.-

Canadian draft treaty, served as the basis for the joint

working draft at the Ottawa Conference.

Points of Disagreement 21

According to press reports, the Open Skies

negotiations often did not follow the usual pattern of

alliance versus alliance differences. Instead, individual nations-including for the first time the newly

independent Eastern European countries--made proposals on their own initiative. The result has been a

series of disagreements with and departures from the

NATO baseline identified above.

In general, the United States has sought to

maximize the openness of Open Skies arrangements

as defined in the NATO Basic Elements. Although

there have been signs of compromise, the United

States continues to advocate relatively unrestricted

overflight procedures and equipment. The other

NATO allies, as well as the non-Soviet WTO

member states, have been more flexible in the

negotiations, but, “when push has come to shove, ”

have tended to adopt the U.S. point of view. The

Soviets, on the other hand, have so far blocked most

efforts to reach a grand compromise (see table 4-2).

In all areas, the Soviets consistently argue for the

least intrusive regime, leading many observers to

question whether the Soviet Union has really abandoned its historical demand for secrecy. That the

goals of the treaty are so ambiguous and hard to

translate into concrete terms (e.g., how many flights

are needed to “reduce tensions? ’’)22 has left the

Soviet negotiating team room to maneuver and stall.

The Soviets disagreed with points throughout the

NATO proposal. It is ironic, though, that in most

cases the Soviets cited as the basis for their dissent

two agreed phrases from the joint statement of the

Ottawa Conference:

~epenods listed in this bullet fornotiiication and flight plan fding am maximumvalues. The host country, in cooperstionwiththe inspecting party,

would retain the option to shorten these periods.

21~s s=tion (ad ind~d the en~ rwofi) is bas~ on ~classfl~ so~es and therefore ~vers o~y those d..imgreements that haVe been eXplESSCd

publicly.

%Me analyst suggesta that an unstated standard of adequacy for an Open Skies agreement is in fact emerging from the negotiating process: it is “to

enable participants to ident@ rapidly massing military formations by the generic types of vehicles within them. ’ Furthermore, participants should be

able to accomplish this mission day or nighg and in all weather conditions. This warning function for Open Skies gives negotiators a more deftite target

in their discussions. However, the Soviets have not formally recognized this standard for the agreement. See Peter Jones, “CFE? Aerial Inspections and

Open Skies: A Comparison” in Heather Chestnutt and Michael Slack (eds.), Verifiing Conventional Force Reductions in Europe: CFEZ and Beyond

(Toronto, Ontario: Center for Intermtional and Strategic Studies, York University, 1991), p. 90.
56. Verification Technologies: Cooperative Aerial Surveillance

Figure 4-l—NATO Proposed Timeline

+16 hrs +

(or less)

<6 hrs >

(or less)

o

=

L

<— 24 hrs — >

(preflight inspection)

A. Notify Host Country

a

C. File Flight Plan and Inspect Aircraft

E. End Flight at POE

SOURCE: Office of Technology Assessment, 1991.

B. Arrive at POE

D. Overflight
Chapter 4—Open Skies .57

● “implemented on a reciprocal and equitable

basis”; and

● ‘‘maximum possible openness and minimum

restrictions.

The United States views the first point as a

statement of equal opportunity and equal application

of the rules. The Soviet Government argues that

equality means a leveling of capabilities and minimizing burdens. On the second point, the United

States maintains that openness should apply predominantly to territorial and sensor access, while the

Soviets stress the sharing of equipment and collected

information. These differing emphases are evident at

each point of disagreement.

Participation in the conferences themselves has

been one such point of contention. In item A of the

above listing of NATO’s position, the alliance

insisted that the first phase of negotiations be open

only to WTO and NATO members. The rationale

was that fewer participants would make it easier to

obtain a unanimous and relatively uncomplicated

treaty. The Soviets, on the other hand, have questioned this rationale, with Soviet Deputy Foreign

Minister Viktor Karpov declaring atone point,’ ‘Our

opinion differs: All neutral and nonaligned CSCE

[Conference on Security and Cooperation in Europe]

countries should be included in this process if they

so wish.”23 Thus, the Soviets argue for greater

openness.

A second, and major, topic of dispute has been

restrictions on the territory subject to overflights. As

indicated in item B above, the NATO position calls

for maximal coverage of national territory with

restriction based solely on safety and international

law. The Soviets, on the other hand, have sought to

both restrict and expand the covered territories. First,

they have argued for several types of exclusion

zones:

There are such zones in virtually all countries.

And here neither military or civilian aircraft can

fly-for example, over major cities or chemical or

other ecologically dangerous enterprises, or nuclear

power stations or water installations except in

emergency situations. Why then should we make an

exception to this rule for foreigners, thus subjecting

the lives of our fellow citizens to extreme danger?

Moreover, we still have regions that are closed in the

interests of preserving state secrets.24

Not surprisingly, some of these restricted zones

(particularly the ones preserving state secrets) are

precisely the ones that NATO would like to see to

advance the stated purposes of the treaty.

Then, the Soviets have argued on the grounds of

equality and greater openness for the inclusion of

member nations’ military bases in other countries.25

NATO has flatly rejected this proposal, because

these countries would not be party to the treaty and

their airspace is sovereign.

Soviet exceptions to items C, D, and H all revolve

around the issue of whose planes will be used for

overflights. The Soviet Government has sought to

avoid being overflown by foreign aircraft. One

reason for this was laid out by Soviet Deputy

Foreign Minister Karpov:

The present level of the development of electronics makes it possible to fit an aircraft with a tiny

sensor which could collect a vast quantity of

information having nothing to do with “Open

Skies” and would be very difficult to detect by

inspectors when checking someone else’s aircraft.26

Moreover, the Soviets have argued that the cost of

flying airplanes from the Soviet Union to North

America would be prohibitive and unequal.27 For

these reasons, the Soviets have proposed alternatives

to the NATO plan:

We proposed the setting up of a single pool-we

found no support. But our main idea” is that there

should be freedom of choice. If some state wishes its

territory to be overflown by aircraft of its own design

with standard equipment, a mixed crew, and a group

of observers, this wish ought to be respected. If it

wants an aircraft belonging to some third country—

23s. G* ~$Dw. ~eUSSR Advomte ~~nSties> With E~~lusion ~nes? me Soviet position- Been Distorted. USSR D~uty Foreign ?vfh.liSter

Viktor Karpov Replies,” Izvestiya, Mar. 5, 1990, p. 3, as translated in Foreign Broadcast Information Service, Soviet Union Daily Report,

FBIS-SOV-!XL043, Mar. 5, 1990, p. 2.

~T~, ~~~e spy p~ce ~Wi~ the ~w~: ~~temiew Witi ~jor ~a~ V. K~ev, First Dquty Chief of tie General SW,” Mm. 27, 1990,

p. 3, as translated in Foreign Broadcast Information Service, Soviet Union Daily Report, FBIS-SOV-90-063, Apr. 2, 1990, p. 3.

2SSee, e.g., Tr@ ibid., p. 3; and Gulq op. cit., footnote 239 P. 3“

26v. She&ov, ~~~temiew for ~av~~$ praV&, ~. 4, lggo, ~ tram~t~in Foreign Broadc@ ~o~tionS-ice, Soviet Union Daily Report,

FBIS-SOV-9(MM3, Mar. 5, 1990, p. 1.

z7T~, op. cit., fOOtnOte 24, p. 3.

292-900 - 91 - 3
58 Verification Technologies: Cooperative Aerial Surveillance

Photo credit: U.S. Air Force

Source: Jane’s A// the Wor/d’s Aircraft: 1990-91, Mark Lambert (cd.) (Coulsdon, Surrey, United Kingdom: Jane’s Information Group, 1990), p. 281.

The Soviet Tu-95D Bear maritime reconnaissance aircraft, a variant of the Bear strategic bomber, is outfitted with radar domes

(radomes) under its nose and midsection and electronic intelligence collectors on each side of its rear fuselage.
Chapter 4—Open Skies .59

by all means. And finally, aircraft belonging to the

monitoring side could overfly another state’s territory only subject to its consent.28

Sensors (item E) have been a particular source of

concern for the Soviets.29 Up until the Budapest

Conference, the Soviet Union wanted only standardized optical and electro-optical cameras; NATO

advocated a wide variety of sensors with only a few

listed restrictions (the primary one being a ban on

SIGINT devices). NATO argues that the language of

the Open Skies Communique on this issue is very

clear: “The agreement will have provisions concerning the right to conduct observation flights using

unarmed aircraft and equipment capable in all

circumstances of fulfilling the goals of the regime.’ ’30 The key phrase here is “equipment capable in all circumstances,” which can reasonably be

interpreted to encompass sensors that can function

effectively day or night, rain or shine. Optical

cameras that can see neither in the dark nor through

clouds would clearly not suffice.31

At the Budapest round, the Soviets accepted the

use of synthetic aperture radar (SAR) to achieve an

all-weather capability. However, the SAR they

proposed had a resolution of only 10 meters,

compared to the 3-meter resolution thought necessary by most NATO states.32 The Soviet compromise of 30 centimeters on optical resolution also

exceeded the Western-proposed maximum of 15

centimeters. 33 The Soviets maintain that these resolutions are sufficient for the purposes of the treaty,

and that any more information would begin to harm

national security.

Some countries, particularly in Eastern Europe,

are concerned about the inequality of sensor technology between the more advanced (typically Western)

nations and the rest. On this basis they have called

for standardized and simple hardware. This seems to

be a natural request. On the other hand, these

countries may be doing themselves a disservice. The

NATO countries (through the United States) and the

Soviets already have extensive intelligence capabilities outside of Open Skies. If advanced sensors were

permitted in Open Skies, the less-capable nations

would have the opportunity to develop and eventually deploy advanced and independent sensor systems. The United States has compromised on this

issue, and is looking to ease trade restrictions in

order to supply these countries with commercially

available sensors.34 Since sensors will most likely be

subject to preflight inspection, the United States

itself is inclined to adopt commercial technology for

Open Skies to avoid compromising classified technologies.

On a related issue, the Soviets believe that sharing

collected sensor data (item K) is the best way to

fulfill the goals of the treaty:

The “Open Skies” system must be imbued with

the principle of universal and full equality. Equality

in gaining access to information which cannot be

used to the detriment of any of the parties.35

Information obtained during overflights would be

shared at a new international agency:

The data would be processed in a single center

sited in any country. Parties to the agreement would

pay for this also according to an agreed scale. The

information arriving in this center should be available to all regardless, of course, of the financial

contribution made by the different countries. This

proposal of ours was rejected out of hand.36

The Soviets believe the NATO approach would be

“detrimental”:

. . . the main content of the position expounded by

U.S. representatives in Ottawa boils down to the fact

that the United States, taking advantage of its

technological potential, intends to overfly other

2S(j~ op. ci~, footnote 23? p. 2“

%or a more complete discussion of sensors and sensor issues see ch. 3.

‘“ ‘Open Skies’ Communique,” op. cit., footnote 14.

Mky ~m~thathadp~ctiarly overcast weather with low-level clouds would have anasymmetrical advantage if only optical cameras were used.

BzAr~ Control Reporter 1990, op. Cit., fOOtllOte 8, p. W.B.16

ss~c~r, op. cit., footnote 13, P. 23-24.

~Jones, op. cit., footnote 22, p. 91.

ss~umdshevm~, Soviet ForeiW~st=, s~hato~waco~mence, fiom~s~ternatio~Service,Feb. 12,1990, as translated inForeign

Broadcast Information Service, Soviet Union Daily Report, FBIS-SOV-9@030, Feb. 13, 1990, p. 3.

~She~ov, op. cit., footnote 26, p. 1.
60. Verification Technologies: Cooperative Aerial Surveillance

countries’ territory, collect information, and tuck it

safely away. So where is the “openness?”37

The NATO proposal would allow sharing information within alliances. The primary reason for not

sharing information with nonallies is that it might

help the observed country improve its camouflage,

concealment, and deception techniques, because the

inspected party could see precisely what the inspector could see. A second reason is that it could give

some idea of just what objects the inspecting party

was looking for. There has been some movement

toward common ground by all the participants,

except for the Soviets, who have yet to officially

respond to the latest proposals. Raw data might be

shared before it is processed.38

Finally, there have been disagreements on some

of the specific numbers in the treaty. The Soviets

have generally argued for fewer overflights (item F)

than NATO. The Soviet Union has proposed 25 to 30

flights per year for each alliance,39 of which 16

would be over the Soviet Union;40 the United States

has offered to receive about 52 flights per year with

as many as 130 to 140 overflights per alliance .41

(Complicating matters is the breakup of the Warsaw

Pact and a possible shift to a matrix of bilateral quotas.) The Soviets also advocated at one

point expanding the prearrival notification period

(item I) up to 48 hours42 and holding the time the

sensors are activated to 3 hours.43 It can be argued

that these limitations would lessen the value of the

overflights, and thus perhaps that of the treaty as

well.

Conclusion

Soviet proposals and those of the other negotiating parties seem to reflect differing ideas about what

is required to build confidence under Open Skies.

The Western allies argue that Open Skies will be

most effective in building confidence if restrictions

on overflights and sensors are kept to a minimum.

They believe that at a minimum the regime probably

needs to provide some degree of warning of largescale hostilities. The non-Soviet former WTO members are enjoying new freedom in the exercise of

international diplomacy, but tend to agree with

NATO on the details of an agreement.

The Soviets do not appear ready for the degree of

openness sought by the West. In sum, negotiations

remain stalled at this time.

371bid., p. 1.

ssJones, op. cit., footnote 22, p. 98.

sgshe~ov, op. cit., footnote 26, p. 1.

~Ar~ Control Reporter 1990, op. cit., footnote 8, p. m.B.l 1.

dlshe~ov, op. cit., footnote 26, p. 1.

42Td, op. cit., footnote 24, p. 3.

dsshe~ov, op. cit., footnote 26, p. 1.
Chapter 5

OTHER APPLICATIONS

OF AERIAL SURVEILLANCE
Contents

Page

summary . . . . . . . . . . . . . . . . . . . . ... ... ... ... ... ... ... ... ... ... ..*. .$. **. 63

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. .. .+ .. .. ... o.. ... ” 63

Conference insecurity and Cooperation in Europe and Open Skies . . . . . . . . . . . . . . . . . . 63

Conventional Armed Forces in Europe . . . . . . . . . .. .. .. .. .. .. ... ... ...... . . . . . . . . . . . 64

Chemical Weapons Convention . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . 67

Other Potential Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ●68

Conclusion .. +. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. ..-. .”..”” 69

Box

Box Page

5-A. Airborne Monitoring of Chemical Weapons--Three Cases . . . . . . . . . . . . . . . . . . . . . . 66

Figure

Figure Page

5-1. Territory Subject to Overflights in Various Talks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Chapter 5

OTHER APPLICATIONS OF AERIAL SURVEILLANCE

Summary

President George Bush’s call in 1989 for a

multilateral Open Skies Treaty resulted not only in

Open Skies negotiations, but in a reexamination of

the use of cooperative aerial surveillance for a wide

variety of international applications. These applications include measures for confidence building (as in

Open Skies) and monitoring (search, inspection, and

warning).

Limited aerial surveillance in conjunction with

on-site inspections (OSIs) is currently being used to

observe large-scale military exercises in Europe

under the Vienna Document of 1990. An extensive

aerial surveillance regime is also being negotiated as

aside agreement to the Conventional Armed Forces

in Europe (CFE) Treaty that was signed on November 19, 1990. CFE overflights would be used as a

complement to OSI and national technical means

(NTM) of verification in monitoring treaty-limited

items (TLIs).

Other possible applications for aerial observation

can be found in a wide variety of potential international agreements. Agreements that limit objects or

activities, that require measurements of chemical

effluents in the air, or that provide for warning of

threatening actions might utilize periodic overflights. Cooperative aerial surveillance, like NTM

and OSI, is simply another form of observation.

Whether to include aerial surveillance in a negotiated package depends on the characteristics of the

items or activities being observed, the costs and

benefits of the package, as well as its negotiability.

Introduction

Some Open Skies participants advocate expanding Open Skies to include not only the former

members of the now dissolved Warsaw Treaty

Organization (WTO) and the members of the North

Atlantic Treaty Organization (NATO), but all European nations and perhaps others as well. At the same

time, the CFE negotiators have committed their

nations to further talks incorporating extensive

aerial monitoring of compliance into the recently

signed CFE Treaty. This chapter discusses a

variety of conceivable future negotiations that

might include aerial surveillance, e.g., an extension of Open Skies, CFE, and a Chemical Weapons Convention. While exploring some of the

possible applications of aerial surveillance, OTA

neither advocates nor rejects them.

Conference on Security and Cooperation

in Europe and Open Skies

As mentioned in chapter 4, the Soviets (as well as

some other participants) would like to invite those

European nations not already included to join in the

Open Skies negotiations. However, the NATO

position is that an expansion of the talks at this time

would only complicate the proceedings. Still, NATO

stated in its initial proposal that it would be willing

“to consider at an appropriate time the wish of any

other European country to participate in the Open

Skies regime.”l As a first step, this could mean

expanding participation to include not just the

NATO and WTO states,2 but the neutral and

nonaligned (NNA) states as well.3 These 34 nations

already hold talks under the umbrella of the Conference on Security and Cooperation in Europe (CSCE).

The extension of Open Skies to all CSCE

members would not be unprecedented. In 1986, the

CSCE-sponsored Conference on Confidence- and

Security-Building Measures and Disarmament (CDE)

Isee app. D, article I, section 3, pwrqpph 5.

2~e NATO ~ow~e~ we Bel@~ ~m~De-,Fmnce,West ~~ny, ~e~e, Ice~& Itiy, Luembourg, the Netherlands, Norway,

Portugal, Spa@ Thrkey, the United Kingdom, and the United States. The Warsaw Pact states were Bulgaria, Czechoslovak@ East Oermany (until

unifkation), Hungary, Poland, Romani& and the Union of Soviet Socialist Republics.

31’r’hem me fou neu~~ ~om~es (Am~& F~md, Swdem ~d Switirland) ad eight no~gned colmtries (CypmS, the Holy SeC, I.A~d,

Liechtenstein Malta, Monaco, San Marine, and Yugoslavia). The U.S. Government does not recognize the incorporation of the Baltic republics into

the Soviet Union. Albania is the only other European nation not represented.

-63-
64.Verification Technologies: Cooperative Aerial Surveillance

U.S. Army officers listen to a Warsaw Pact observer of the

1987 NATO Reforger exercise in then-M&t Germany.

produced the so-called Stockholm Document4 which

permitted, among other things, aerial inspections of

large-scale military activities with no right of refusal

(except in the case of force majeure), but only in

host-owned and host-operated aircraft (including

helicopters). No sensors were to be installed on the

aircraft and inspectors were to carry only binoculars

and hand-held cameras.6 Strict quotas were set on

inspections (both air and ground). Each state would

be subject to at most three inspections per year. No

single state could inspect another state more than

once per year. The Stockholm Document was

superseded by the Vienna Document of 1990, which

reaffirmed its predecessor and added further confidence- and security-building measures. As of June

15, 1990,40 inspections had been conducted.7

Either the Vienna Negotiations on Confidenceand Security-Building Measures (CSBM) or a revived CDE maybe the most appropriate established

forum for Open Skies under the CSCE framework.

(The CDE was split into the CSBM and the CFE

talks-both opening on March 9, 1989.)8 The CSCE,

however, except in the case of CFE, has traditionally

limited its territorial jurisdiction to the European

continent, thus excluding North America. Alternately, the Open Skies talks could simply take more

petitioners under their umbrella. Eventually, the

concept of Open Skies could be broadened by

inviting individual states into the system on a

case-by-case basis, by taking all comers, or by

moving the talks to the United Nations.

Conventional Armed Forces in Europe

The CFE nations are negotiating, somewhat in

parallel with Open Skies, an aerial inspection

protocol that was intended to be part of the

monitoring arrangements for the Conventional Armed

Forces in Europe Treaty. The 7 (now 6) WTO states

and the 16 NATO nations—the same group as in

Open Skies-opened CFE negotiations in March 9,

1989 with the goal of equalizing and reducing

conventional force levels in the Atlantic Ocean to

the Ural Mountains (ATTU) region. They signed a

treaty during the CSCE Paris Summit of November

19-21, 1990. This treaty included provisions for

brief host-operated helicopter flights over inspection

sites, 9 but set aside more extensive and intrusive

aerial monitoring provisions to be negotiated with

4The Stockholm Document entered into fome on Jan. 1, 1987. Its official title is the Document of the Stockholm Conftience on co~lden~- ad

Seeurity-Building Measures and Disarmarnent in Europe Convened in Accordance With the Relevant Provisions of the Concluding Document of the

Madrid Meeting of the Conference on Seeurity and Cooperation in Europe. For full text, see app. 10A in Stockholm International Peace Research

Institute, !$ipri Yearbook 1989: WorZdAnnuments andllisarnuvnent (New York NY: Oxford University Press, 1987).

S~id., p~~ph 76 of the StddiolmDocument.

6~id-, p~mph 87 of the StOCkhOh.tl Document.

l’s= U.S. kms Control and Dis armament Agency, “Strengthening Stability Through Openness: The Vienna Negotiations on Cotildence- and

Seeurity-BuiMing Measures,” July 1990, pp. 16-19.

8~emis ~me ovalw ~~=n CSBM and ~,titin gen~~ CSBM d~s wi~ p~-Europ~nco~lden~- and s~urity-buil~ measures

(including inspections and observations) and CFE focuses on NATO-WTO conventional force reductions.

?rhese overflights are described in the CPE Protocol on hspectio~ section VI, paragraphs 16-21. Although the parties involved in an overflight can

agree to other terms, the standard provisions permit the inspecting country to spec@ in advance whether an inspection is to be conducted by foot,

cross-counqvehicle, helicopter, or a combination of all three. If the area to be inspected is less than 20 square kilometers and an overflight is requested,

the host country must provide a helicopter large enough to carry two ins~tors and one escort and fly them over the site for not mom than 1 hour total.

The pilot must allow the inspectors “a constant and unobstructed view of the ground” during which time the inspectors can use any of their equipment

(portable passive night vision devices, binoculars, video and still cameras, dictaphones, etc.). The host country may delay, limit or refuse flights over

sensitive points, but must permit the rest of the site to be ovefflown.
Chapter 5—Other Applications of Aerial Surveillance .65

other loose ends in discussions dubbed "CFEIA."10

Apparently, the parties believed that the CFE

verification regime consisting of NTM, limited

helicopter flights, and other cooperative measures

including OSIs was sufficient for ratification. This

implies that the aerial monitoring provisions of

CFdE IA will be supplementary, and not essential.

Although CFE and Open Skies overflights are

being negotiated by the same set of states (NATO

and former WTO) and may end up with very

similar operational procedures and technologies,

crucial differences exist between the two aerial

surveillance regimes.

The most significant difference is that, unlike

Open Skies, CFE surveillance flights will help

monitor compliance with specific treaty provisions,

in addition to building confidence in general.

Monitoring tasks might involve counting legal

TLIs, ll searching for and documenting illegal TLIs,

observing exercises and troop movements, inspecting closed-out facilities and eliminated TLIs, and

pre-OSI surveys. According to a Canadian diplomat,

the Soviets have tried to limit the scope of the

protocol solely to observing compliance; i.e., confinning that legal TLIs are located at permitted sites.

The other CFE participants argue that the overflights

must be able to search for violations of the treaty

beyond declared sites, and in this way, also act as a

deterrent to such violations. 12 CFE flights, like Open

Skies flights, could, of course, also build confidence,

but as the result of confined treaty compliance.

The primary CFE TLIs are battle tanks, armored

combat vehicles (ACVS),13 artillery, combat aircraft,

and attack helicopters. To monitor such small TLIs

will most likely require more advanced sensor

Photo credit: Department of Defense

One CFE TLl is the battie tank. Defined by weight and

weapon capability, battie tanks wiii be iimited to

20,000 per aiiiance within the treaty’s

area of application.

capabilities (most notably, higher imaging resolution) than a minimal Open Skies regime.14 A s

discussed in chapter 3, it takes one grade of

resolution to detect an object (e.g., “There’s something there.’ ‘), another to recognize the object (e.g.,

‘ ‘It’s a tank.’ ‘), and quite another to identify it from

technical details (e.g., “That tank is a Polish

T-72. ’’1515

A second major difference between Open Skies

and CFE overflights is their respective territorial

coverage: while CFE encompasses only the ATTU

region of Europe, Open Skies includes all the

territory of the participants. Most importantly, it also

includes Soviet territory east of the Ural mountains.

(Soviet military equipment reportedly has been

transferred beyond these mountains to avoid being

destroyed under the recently signed CFE Treaty.16)

lo~cle HV, paragraph 6 and article XVIII.(cFE IA has alSO been referred to as CFE 1A in the West and Vienna-lA by the Soviet offlcti news

ageney TASS. See for example, ‘‘I@pov Meets NATO Ofilcial for CFE Talks, ” Moscow TASS in English Dec. 3, 1990, in Foreign Broadcast

Information Service, Soviet Union Daily Report, FBIS-SOV-90-233, Dec. 4, 1990, p. 1.)

ll~so ref=ed t. ~ ~t~a~-limited ~~pment~ or TLE, this smond term negl~ts the possibility that facfliti~ and structures might *O be limitd.

lzThe Anns Con frol Reporter: A Chronicle of Treaties, Negotiations, Proposals, Weapons, and Policy (Brookline, MA: @titute for D~e= and

Disarmament Studies, 1990), p. 409.B.18.

Iq’rhe t-ACV includes armored personnel carriers (APCs), armored infantry fighting vehicles (-s), and h~w armament combat vehicles

(HACvs).

14A5 ~U s~t~ fi ch. 4, peter Jon= believes tit an all-w~ther, ro~d-the<l~kwarning of massing forces ~~ome tie underlying stan(kd Of

adequacy in the Open Skies talks. [See Peter Jones, “CFE Aerial Inspections and Open Skies: A Comparison” in Heather Chestnutt and Michael Slack

(eds.), Venfiing Conventional Force Reductions in Europe: C’FE Z and Beyond (Toronto, Ontario: Center for International and Strategic Studies, York

University, 1991), p. 90.] The Soviets have not formally accepted this mission for Open Skies and argue more for symbolic flights. In either case, the

requirement of CFE sensors to distinguish among types of TLIs and to count numbers accurately suggests a more extensive and sophisticated regime

than that of Open Skies.

lssee table 3-2 for targets and necessary ground resolution.

IG’’Fi~es ROW Suspends -,” Jane’ sDejence Weekly, Mar. 2, 1991, p. 290.
66. Verification Technologies: Cooperative Aerial Surveillance

BOX S-A—Airborne Monitoring of Chemical Weapons—Three Cases

The size of the chemical stockpiles to be monitored and their supporting infrastructure are important

considerations when evaluating the potential success of aerial monitoring in supporting the goals of an agreement.

A group could both make and store sufficient amounts of chemical agent for its terrorist acts (measured in

gallons) in just about any building. Overhead imaging sensors would reveal no clues to this activity and door-to-door

searches would be impractical and prohibitively expensive (as well as illegal in many countries). Extremely

sophisticated air sniffers and samplers might narrow the area of search but probably not appreciably so. Thus, the

role for aerial surveillance appears dubious.

However, in the ease of chemica1 stockpiles sufficient for waging war between nations (rneasured in hundreds

or thousands of tons), the potential role for aerial monitoring grows. Such a capability entails not only substantial

chemical weapon production and storage facilities, but also the development of reliable delivery systems and, to

some extent, operational training, Clearly, the number of potentially observable secondary characteristics grows

with the size of the chemical stockpile and its support infrastructure.

If the negotiators of a potential chemical arms accord are concerned only with revealing militarily significant

quantities of chemical weapons in time for other signatories to take appropriate counteractions, then aerial

surveillance might be useful. Overflights in this case would no longer be looking for laboratories hidden in

basements,but for large-scale chemical plants and storage areas, test ranges, and chemical offensive exercises, Thus,

unlike the terrorist case, an aerial monitoring system, in conjunction with national technical means (NTM) of

verification and on-site inspection (OSI), might be useful.

The enormous chemical stockpiles of the Soviet Union and the United States (measured in tens of thousands

of tons) were designed to be used in a massive Central European conflict between two well-protected alliances.l

They were meant at least as much to slow down and impair military activities on a continental scale as to inflict

casualties. Although any nation possessing chemical weapons might use them in war, such huge quantities are held

only by the world’s two military superpowers. The United States and the Soviet Union have other means of mass

destruction, as well as awesomely powerful conventional capabilities, that can compensate for large [interstate-size)

covert chemical stockpiles secreted by the other. They also both have extensive intelligence assets that can warn

them of threatening activities. Therefore, the requirements placed on an aerial monitoring regime might not need

to be as stringent as for the other cases.

lb Pqow of the united &ates stockpile is to deter Soviet fust use.

Furthermore, overflights would commit the North using its own aircraft for its inspections; the former

American participants-the United States and Canada—to receiving overflights, something CFE would

not do. That the United States and Canada would

share some of the overflight burdens could make

Open Skies a politically desirable adjunct to CFE

aerial monitoring. 17 (Figure 5-1 illustrates the overlapping territorial coverage of overflights of three

negotiating fora in Europe.)

The few publicly revealed disagreements over the

CFE aerial monitoring protocol resonate with those

of Open Skies. For example, NATO again advocates

WTO nations insist that the host country’s aircraft be

used.

18 But because the procedures needed to

achieve the goals of CFE overflights can be defined

more concretely than those of Open Skies, perhaps

these disagreements can be more easily resolved.

Aerial monitoring provisions beyond those now

being discussed in CFE IA could also be negotiated

in the CFE follow-on talks proposed by NATO on

August 30, 1990. The so-called CFE II talks would

provide an opportunity to fine-tune the original CFE

17Joe Clark c~di~ Secre@y of State for External Affairs, “Foreword: @en Skies, “ in Michael Slack and Heather Chestnutt (eds.), Open Skies:

Technical, Organizational, Legal, and Political Aspects (Toronto, Canada: Centre for Intermtional and Stzategic Studies, York University, February

1990), pp. vi-vii.

18 Timothy J. Pounds, “ContextforTechnologies That Monitor CFE Compliance,“ Verification TechnologiesReview, vol. 2, No. 4, July/August 1990,

p. 7.
Chapter 5—Other Applications of Aerial Surveillance .67

Figure 5-l—Territory Subject to Overflights in Various Talks

EUROPE

---------- -

ma) . -

3

fn

c

0

8

T

NORTH AMERICA

1

I

NATO

I

United States

Canada I

I

1

CFE IA

NATO t ~ (former )

>

Belgium, Denmark, Bulgaria,

France, Germany, Czechoslovakia

Greece, Iceland, Italy, Hungary

Luxembourg, Poland

Netherlands, Norway, Romania

Portugal, Spain, Soviet Union

Turkey, United (west of Urals)

4

9 1 CFE 1A I

I ASIA

I ~ (former)

I

Soviet Union

(east of Urals)

I

I

)

I T

E

-nonaligned - -

Cyprus, Holy See,

‘=--

Austria

P

Ire/and, Liechtenstein, Finland

Malta, Monaco, Sweden

San Marino, Yugoslavia Switzerland I

I CSCE and CSBM I

The United States Government does not recognize the incorporation of the Baltic republics into the Soviet

Union. Albania is the only other European nation not represented. I

SOURCE: Office of Technology Assessment, 1991.

IA overflight procedures, as well as add new capabilities to advance the goals of the CFE process.19

Chemical Weapons Convention

The talks on reducing and barming chemical

weapons currently under way both at the multilateral

Conference on Disarmament (CD) and bilaterally

between the United States and the Soviet Union

offer other opportunities for the introduction of

aerial monitoring (although provisions for overflights are not now being negotiated). There has also

been some international discussion of creating

chemical-weapon-free zones in Central Europe, the

Balkans, and Southeast Asia.

Since 1980, the 40 member states of the chemical

Weapons Ad Hoc Committee at the CD, under the

auspices of the United Nations, have been working

to draft a ban on chemical weapons. 20 Thes e

discussions have led to several inspection demonstrations using chemical sampling and sniffing

technologies, but none of these demonstrations has

involved an airborne platform. 21 Similarly, the

U.S.-USSR negotiations on chemical weapons, which

began on June 28, 1984, are incorporating intrusive

monitoring techniques.22

A notional agreement restricting chemical weapons could, among other things, authorize cooperative overflights to:

1~=.we of rapidly~~~events ~EasternE~~,the ~~nce b~is for tie~~fi probably not survive until a second ~~ent

can be signed. If this is the case, CFE might become a discussion behveen NATO and the individual nations of the WTO, or it could be moved to another

forum altogether.

mAr~ Contiol RepOrfer 1990, op. cit., footnote 12, p. 704.A.1.

21~eu,s, ~hemi~indus~ is ~dy5ubjwtto=fi@wtion~ Enfimen~ ~o&tionAgenqr_t. (Amy Smithscmand MichaelKrepon,

“Strengthening the(%nnical Weapons Convention Through Aerial Monitoring,” Occasional Paper #4, The Henry L. Stimson Center, Washington, DC,

Apd 1991, p. 8.)

22Ar~ control Repo~er 1991), op. cit., fOOIIIOte 12, p. 7~.A.4.
68. Verification Technologies: Cooperative Aerial Surveillance

directly monitor compliance with the agreement (as in CFE);

observe and warn of prohibited activities, e.g.,

illegal build-ups of weapons, redeployment of

weapons, or training exercises (as in CDE);

collect information (such as optical and infrared photographs) on sites that could help

prioritize and focus OSIs;23

document destroyed production plants;24 or

build confidence and trust (as in Open Skies).

following example of one possible use of aerial

surveillance in support of a chemical weapons

agreement will focus on the first of these roles.

These overflights might be conducted by individual

states or collectively as a group with common

aircraft and sensors.

If the goal of a chemical weapon overflight

agreement is monitoring compliance, the characteristics of the TLI are a key issue. Unlike the battle

tanks and combat aircraft of CFE, however, chemical agents (liquids and gases) and chemical munitions (relatively small shells and bombs containing

chemical agents) do not readily lend themselves to

direct observation from the usual airborne imaging

sensors.

If the monitoring regime allowed chemical samplers or sniffers, it might be possible to collect a

minute sample of a chemical agent, although the

release of agents into the atmosphere would be

tightly controlled for obvious reasons. Even if a

violation were detected, supporting indirect evidence from other sensors or a follow-up inspection

on the ground might be desirable, if for no other

reason than to verify that the airborne chemical agent

did not float in from some other country or was not

planted by the inspecting team.

The difficulty of uncovering direct evidence of a

violation means that the presence of covert production, storage, and, conceivably, deployment areas

may have to be inferred from the discovery of

secondary characteristics of chemical agents and

munitions. These characteristics or indicators might

include unusual safety or security measures; industrial structures similar to chemical or pesticide

plants; chemical storage tanks; proximity to shell

casing or missile manufacturing plants or storage

sites; or the presence of precursor chemicals or

byproducts in the air.

Precursors are chemicals that are combined to

create a toxic agent; byproducts are chemicals that

remain after the agent is complete. Some of these

chemicals are used in a variety of products that have

nothing to do with chemical warfare. Because some

may be relatively harmless, controls on their escape

into the atmosphere might be less secure. The

presence of one or a few comparatively rare precursors or byproducts could be added to the list of

secondary characteristics of weapon production.25

In cases where only indirect evidence of a

violation is exposed, some other mechanism must be

established for determining noncompliance. This

mechanism might take the form of a human suspectsite or invitational inspection.26 Thus, a potential

role for overhead imaging sensors and sniffers in a

chemical weapon accord would be to detect possible

covert production or storage of chemical weapons by

examining secondary characteristics, and then to

pass the information along to an inspection team that

would investigate the site more closely.

Other Potential Applications

Several other potential arms control agreements

might conceivably benefit from aerial surveillance:

a Short-Range Nuclear Forces (SNF) accord, a

Strategic Arms Reduction Talks follow-on agreement (START II), or regional conventional arms

reduction talks similar to CFE. Inspection teams in

airplanes could try to count, identify (by remotely

reading tags or sensors), and document legal TLIs,

as well as search for covert ones. (By looking for

illegal TLIs, the overflights could help deter their

very construction.) Discovery of unusual activities

or objects could be used to target suspect-site

inspections or cue NTM. Tethered aerostats could

temporarily monitor the perimeter of an OSI site for

illegal movements while preparations were made for

an inspection or until a ground perimeter could be

~Smi~on and K.repoq op. cit., footnote 21, pp. 15 and 18-25.

‘Ibid., p. 2A-25.

~Conceivably, some r~ pr~msors or byproducts could be banned along wi~ ~eir warfare Product.

~For a discussion of On.site fip=tion ~es, benefits, and cos~, we: u-s. Congress, OffIce of T@~ology ~sessment, Verification Technologies:

Measures for Monitoring Compliance With the ST~T Treaty-Summa

December 1990).

V, 0’E4-ISC-479 (M%shingtom DC: U.S. Government Printing Oftlce,
Chapter 5—OtherApplicationso f Aerial Surveillance .69

established. Similarly, restrictions on military force

movements, deployments, and exercises could be

observed from the air.

Regional warning and confidence-building agreements might also involve aerial surveillance in order

to add stability to and reduce tensions in some of the

world’s hot spots (e.g., the Korean Peninsula, South

Asia, and the Middle East). Furthermore, aerial

surveillance could be used by United Nations

peace-keeping forces to extend their ability to

observe and document (and thus deter) violations of

the terms of United Nations involvement (e.g., a

cease-fire agreement) .27 Aerial surveillance has

already been used in similar circumstances in

Yemen and the Sinai.28 In the case of the Sinai, since

1974 American and other reconnaissance aircraft

(airplanes and helicopters) have helped to ensure

compliance with demilitarized and force-limited

buffer zones between Israeli and Egyptian forces.

They have also periodically undertaken surveillance

of sites prior to ground inspections.29 Mutual aerial

mapping ventures might also provide the basis for

settling disputed borders.

Beyond the military arena, airborne chemical and

radiation detectors could be employed cooperatively

to measure pollution or radiation levels as part of a

regional or international prohibition or cleanup

effort. 30

Finally, one of the more unusual ideas for aerial

surveillance is the plan of one company to lease to

television networks art airplane equipped with sidelooking airborne radar (SLAR), infrared, and lowlight TV sensors, and film-editing facilities.31 This

commercial airplane could cover fast-breaking news

events globally in a way previously only enjoyed by

the superpowers. Thus, aerial surveillance might not

only take the virtual monopoly on overhead monitoring away from the superpowers and give it to other

states,32 but it might take away from governments in

general.

Conclusion

A wide variety of agreements that require monitoring or confidence building could take advantage

of sensors on aircraft. Yet, just because cooperative

overflights might have some utility does not mean

that they are necessarily the best choice for the job.

As was discussed in chapter 2, aerial observation is

not cost-free, nor does it always have unique

qualities that can not be provided by some other

means, especially NTM or OSI. The choice of one

type of monitoring measure or combination of

measures depends on many factors, including the

capability of each measure, the robustness of NTM,

the degree of cooperation between the negotiating

parties, the political advantages of open cooperation,

the intrusiveness of the measure, and financial costs.

Aerial surveillance is not a panacea; it may be a

useful tool.

zTSeeMichel Krepon and Jeffrey P. Tracey, “ ‘Open Skies’ and UN Peace-Keeping,” Survival, vol. XXXII, No. 3, May/June 1990, pp. 251-63.

~~lenv. B~er, “Overh~dIm@ng for verification and Peacekeeping: Three Studies,” Canad% External Afftis ad~te~tio~Tr~e~ Arms

Control Veritlcation Occasional Papers No. 6, March 1991, p.29.

%rian S. Mandrell, The Sinai Experience: Lessons in Multimethod Arms Control Verification and Risk Management, Arms Control Verification

Studies No. 3 (Ottaw% Ontario, Camda: Camdian Department of External Affairs, 1987), pp. 5,8, 13, 17,22,25,45.

%VU-2A aircraft, varian ts of the U-2, were dispatched in the late 1950s and early 1960s to sample at high altitude the sp~ad of nuclear debris

following tests. David Donald, Spyplane (Osceola, WI: Motorbooks Intermtional, 1987), p. 29.

3~Aviafi”on Week and Space Technology, “Upscale Eye-in-the-Sky,” Aug. 20, 1990, p. 13.

32For com~es @t do not ~ve extemive ~ ~pabifities, a~~ swei~nce fflls an info~tioti void tit previously co~d ody be ffled by One

of the superpowers. This leads to the philosophical question of whether it is in the superpowers’ own mtional security interest to negotiate away their

near monopoly on overhead reconnaissance in exchange for the principle of enbanced regional or international security.
Chapter 6

BROAD AREA SEARCHES FORM

ARMS CONTROL TREATY

VIOLATIONS
Contents

Page

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Quantification.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

The Limitations of Aerial Search. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

“Search as an Operation in Practical Life” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Multiple Searchers and/or Targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Treatment of Target Concealment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Simple Aerial Monitoring Calculations: Aerial Search for SS-24 ICBMS

Simple Aerial Monitoring Calculations: Aerial Search for SS-20 IRBMS

‘and SS-25 ICBMS . . . . . . . .

Discussion . . . . . . . . . . . . . . . . . . . . .

Sources and Exploitation of Prior

Terrain . . . . . . . . . . . . . . . . . . . . . .

Infrastructure . . . . . . . . . . . . . . . .

Previous Searches . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . .

. . . . . . . . . . . . . .

. . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

. . . . . . . . . . . . . . .

Other Sources of Prior Information. . . . . . . . . . .

The Problem of Misleading Prior Information.

Box

6-A. Search Effort, Width, and Rate.....

6-B. Lateral Range Curves . . . . . . . . . . . . .

6-C. Coordination of Search Efforts . . . . .

6-D. Coverage Factor . . . . . . . . . . . . . . . . . .

6-E. Use of Imaging Systems unconcern

Boxes

. . . . . . . .

. . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +...

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

73

73

74

74

75

77

78

79

80

82

84

84

84

87

87

88

Page

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

. . . . . . ..6..., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

. . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . 79

6-F. Treatment of Deliberate Target Concealment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

6-G. Calculation of Sighting Probabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

6-H. Satellites v. Aircraft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

6-I. The GENETRIX Project . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

6-J. Mobile Targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87
.

Chapter 6

BROAD AREA SEARCHES FOR

ARMS CONTROL TREATY VIOLATIONS

Summary

Congress can reasonably expect quantitative assessments of the uncertainties inherent in arms

control treaty verification. While such assessments

are often provided, witnesses need to be clear about

the assumptions and methods (if any--some quantitative statements are hunches or figure of speech, not

a bad thing as long as the recipients understand the

spirit in which the statements are made) by which

they reach their assessments.

The arms control efficacy of aerial monitoring—

whether as an anomaly detector, a violation deterrer,

or a confidence builder-rests on the search capabilities of the aircraft and their associated equipment.

Searches such as those entailed by aerial monitoring

can be analyzed mathematically: simplistic analysis

suggests that relatively heavy aerial monitoring

alone would probably find some types of arms control treaty violation, if present, in a year. Refinement of the analysis shows that considerable prior

information--clues about where to look and for

what—will be needed if aerial monitoring is to

make a significant contribution to arms control

verification.

Introduction

The use of cooperative aerial surveillance in arms

control agreements may be its most important task.

Not only might overflights tend to build confidence

in an accord, but aerial monitoring flights may fulfill

a search, warning, inspection, cost-raising, or deterrent function by observing compliance with specific

provisions of an agreement. Information from monitoring can also be used to support other verification

methods, particularly on-site inspections (OSIs).l

For example, aerial surveillance in an arms control

context might:

●

●

e

●

●

●

observe military exclusion zones or disputed

borders to deter, detect, and warn of the illegal

presence of restricted forces;

inspect conditions at declared bases or facilities

to observe compliance, to monitor movement

or other restrictions, or to assess the need for

and prepare for an OSI;2

confirm the destruction of declared facilities,

equipment, or weapons;

search for indications of noncompliance that

require other methods of verification for final

confirmation;

by virtue of an increased chance of detection,

force a cheater to expend more effort and

money to violate the treaty or deter him or her

completely;3 

or

search for treaty violations distributed over

some large area being surveyed.

This chapter applies a quantitative search

analysis method to the last role, searching large

areas for violations. Focusing on this one mission

will serve several useful purposes. First, it will allow

us to illustrate how quantitative methods can be

applied to the larger problem of estimating confidence levels in our ability to find arms control treaty

violations if they exist. Second, the analysis shows

how comparisons could be made among various

monitoring options to produce more cost-effective

monitoring regimes. Third, examining the potential

and limits of aerial search underscores the importance of applying multiple, complementary instruments to monitoring tasks.4

1~e v~om u~ities of aefi surveillance are discussed in detail in ch. 2.

~or example, sensor information and photographs might be used to create a map of the site and indicate the most important locations to inspect.

Amy Smitbson and Michael Krepon, “Strengthening the Chemical Weapons Convention Through Aerial Monitoring,” Occasional Paper No. 4, The

Henry L. Stimson Center, Washington DC, April 1991, pp. 14,21-22.

qrbido, p. 3. Amy Smithson and Michael Krepon stite, ‘‘Aircraft overflights could marginally increase deterrence if approved flight plans and sensors

increase the likelihood of detection or the possibility of follow-up investigations. ”

‘$Note tit aerial warning is closely related to aerial search and that many of the same kSSOnSapply.

–73–
74. Verification Technologies: Cooperative Aerial Surveillance

Quantification

Congressional demand exists for quantification of

answers to questions regarding compliance,5 though

the urge to quantify verifiability is not universal.6

The expression, in the Intermediate-Range Nuclear

Forces (INF) Treaty hearings, of such matters in

round numbers suggests that Members and witnesses understand that great precision is neither

possible nor needed. However, testimony and colloquy in the INF case also indicate an absence of

consideration of important factors which should

enter into an assessment-quantitative or otherwise-of the verifiability of a treaty: the length of

time allowed for detection of the violation, the

difference between verifying compliance with the

treaty as a whole and verifying compliance with any

one subset of its provisions (e.g., in the INF case,

those pertaining to SS-20s), the significance of the

violation, and the difference between the probability

of detecting the presence of a covert force and the

probability of detecting any single missile therein.

Congress needs to decide how much to invest in

verification measures, and quantitative analysis

can indicate how much additional confidence

might be obtained as a benefit of increased

spending. This report discusses the quantifiable

aspects of aerial search at some length, not only for

their own sake, but as a good example of certain

statistical issues arising in treaty verification. Inasmuch as most verification assets, especially those

subsumed under the heading national technical

means” (NTM) of verification, monitor more than

one treaty at once, a complete analysis of treaty

verification would simultaneously embrace all treaties and all verification assets. The simple examples

explored in this report are thus intended as models

for discussion and analysis, not as the last word on

the utility of aerial search.

Even if one does not resort to quantification when

interpreting data from aerial search flights, an

important lesson of the approach we will examine--

that lack of evidence must be interpreted in light of

the likelihood that evidence would have been

obtained were it to exist-retains its validity.

The Limitations of Aerial Search

As discussed in chapter 3, the aerial monitoring

provisions of particular treaties will set limits on the

number of flights, their duration, the equipment that

may be carried, and the freedom to fly anywhere at

any time. These constraints limit the effectiveness of

aerial monitoring. Even without them, however,

aerial monitoring would remain subject to certain

limitations inherent in most treaty-monitoring or

intelligence-gathering means.

The most general trait of these limitations is the

everyday finding that we notice things far more

readily if we are looking for them. Treaty-monitoring efforts to date show distinct signs of this

limitation: for example, the monumental radar near

Krasnoyarsk (a treaty-limited item (TM) of the

Anti-Ballistic Missile (ABM) Treaty) went unnoticed for many months despite its detectability by

NTM, because the managers of NTM had no reason

to examine its particular locale for SALT I TLIs.7 In

another example, efforts to find and destroy Iraqi

Scud launchers during the Persian Gulf War were

impeded by the use of launchers other than the

expected Soviet-made transporter-erector-launchers

(TELs). These examples and others suggest that

aerial monitoring may be most efficiently applied if

specialized: such specializations might include the

monitoring of declared deployments or the inspection of particular locations. When used more generally, aerial search (like any other means of collection) benefits greatly from the use of prior information as to where to look and for what to look (a point

addressed more fully below)

5wi~e~~a and se~t~~~ in the hm~~~ the ~te~edia@R~ge Nucl~For~s Treaty VfiOUS1y Stite.d that the “ink@?IlCf3 CODIIIIU@ . . . pUt

the potential for verifying compliance somewhere in the lo-or 20-percent regiom” that “the chances of the United States detecting covert SS-20’s is

[sic] about 1 in 10,” tbat “we can detect 1 in 10” SS-20s, that therefore if “we suddenly detect 5 [SS-20s], . . . the Soviets could have a viable force

of up to 50inhiding,” that “given the entire verification package, including mtional technical means,. . .we have high contldencein the ability to verify

the provisions of the treaty,” and that “high cotildence” means “well above 50 pement.” (See U.S. Congress, hearings before the Senate Foreign

Relations Committee, The ZNF Treacy, looth Cong., 2d sess., Part 3, p. 35; Part 5, pp. 8&96 passim.)

6~o~a ~~ess at the Sme has contested the c- tit the inte~igence COmIINU@ ~d produced the tie 10- to 20-percent figure On the

grounds that theintelligence comnmnity does not assess verifiability at all, and does not express estimates in terms of percentages. ‘rhewitness also stated

that the U.S. Arms Control and Disarmament Agency would not use percentage terms either. (Manfred Eimer, Assistant Director of the Bureau of

Verifkation and Intelligence, U.S. Arms Control and Disarmament Agency, Ibid., Part 5, p. %.)

T~co~ w~lop~d~thonyc~evill~ The Ar~ Contro/De/u~ion(Sm Fr~sisco, CA: ICS ~ti~te for Contemporary Studies] pr~S, 1987),

p. 65.
Chapter 6--Broad Area Searches for Arms Control Treaty Violations ● 75

Box 6-A-Search Effort, Width, and Rate

The following example introduces the concepts of search effort, search width, and search rate.

Consider a l-hour search for mobile missile launchers, conducted from an aircraft flying at 200 rniles/hour.

The effort devoted to the search is the hour of flying; the output will be the number of launchers spotted

For simplicity’s sake, we will make the assumption (soon to be dropped) that the vision of the observers and

equipment in the aircraft operates in a completely deterministic fashion: they see any launchers within 2.5 miles

of the airplane’s ground track If we knew a priori that launchers inhabit the territory with a density of one launcher

per hundred square miles, we would expect that an hour of searching would discover 10 launchers. The aircraft will

examine a swath 200 miles long by 5 miles wide for a total of 1,000 square miles, and

200 miles X 5 miles X .01 launchers/square mile= 10 launchers.

If we were uncertain as to the capabilities of the observers but knew a posterior that they had seen ten

launchers, we could view this result as confirmation of their stated capability to examine the territory 2.5 miles to

either side of the airplane:

10 launchers seen@ 0.01 launchers/square mile= 1,000 square miles seen

and

1,000 square miles/200 miles flown= 5 mile “sweep width.”

Relaxing the assumption of determinestic sighting, let us suppose that we recognize that luck will play a role

in the sighting of missile launchers-some launchers near the ground track of the airplane will be overlooked, while

others located a distance away will be spotted by chance. Still aware that launchers have been spread out at an

average density of one per ten square miles, we discover that 10 launchers have been sighted and interpret the result

to mean that the crew and equipment can see an average of 2.5 miles away from the airplane. We will therefore say

that the aircraft has an effective sweep width1 of 5 miles, computed by the two equations above. This width,

multiplied by the speed of the aircraft, leads to the sweep rate: 1,000 square miles/hour.

The effective sweep width is related to, but different from, the theoretical sweep width--the width of the swath

in which the sensor could detect a target. The effective sweep width cannot possibly be greater than the theoretical

sweep width, and is likely to be considerably less, The disappointingly low ratio of the effective sweep width to

the theoretical sweep width was one of the first findings of the investigation of aerial search for (German submarines

in the Second World War. Even after discounting the theoretical sweep width in proportion to the fraction of the

time that U-boats spent submerged, a factor-of-two discrepancy remained, explicable only in terms of human

factors. z

lc~~ Ope~tiOMI _ Width in the -theory literature

ZNP Morse and George ~Methods of Operations Research (WasMngtq DC: Departme@ of the Navy, 1946), p. 43.

Most important, monitoring is more effective application of that theory to hypothetical aerial

when multiple means of monitoring can be used searches for Soviet SS-24 and SS-25 intercontinento cue one another. (The second part of this tal ballistic missiles, missiles that would be limited

chapter addresses this point.) Aerial monitoring under the proposed Strategic Arms Reductions

would thus rely on other monitoring methods, Talks (START) Treaty.8

e.g., OSI and NTM, but this reliance ought not to

be construed as a defect, because the other “Search as an Operation in methods would rely on aerial monitoring in turn. Practical Life” 9

This chapter begins with an introduction to search Reflection on our everyday experiences of search

theory; it then offers concrete examples of the reveals some important characteristics of searches:

gAefi s~eillmce is not contemp~ted for inclusion in the START Treaty, and Open Skies surveillance is not officially wed with -con~ol

treaty monitoring as such. Nevertheless, the question of how Open Skies-like surveillance would perform in searches for these START TLIs is an

instructive one to answer.

?Bemard Osgood Koopma~ a pioneer in the mathematical development of a theory of search used this phrase as a section heading in his book.

(Bernard Osgood KoopmawSearch and Screening (New York NY: Pergamo~ 1980), p. 12.)
76. Verification Technologies: Cooperative Aerial Surveillance

Box 6-B—Lateral Range Curves

The “sweep width” assessment of search effec- Lateral Range Curve and Equivalent

tiveness merits some scrutiny. It seems plausible in a “Cookie-Cutter”

bottom-line sense: the searcher has spotted as many

launchers as it would have if it could see perfectly out Probability of sighting

to the 2.5-mile limit and not an inch beyond. Moreover, , 1.0

the crew has missed a launcher within 2.5 miles for ‘

each that it spotted beyond 2.5 miles. Thus the 0.8

interpretation of 2.5 miles as an averagel spotting 

distances reasonable and useful, even though it treats 0.6 -

all sightings as occurring when the launcher is directly 

abeam of the airplane, which is certainly not the case: 0.4

many targets, perhaps all, will be detected some time -

before or after they pass abeam of the aircraft.2 0.2 -

Keeping track of the targets according to their distance 

when they pass abeam of the aircraft is, however, a o “’’’’’’’~’’’’’’”

1I 11I 1111 1I 1! ! t 111! 1 11I 1! [ 11, I I ! 1 ! 1I ! 1

useful accounting convention, according to which we -7.5 -5 -2.5 0 2.5 5

can form a lateral range curve, plotting the probability Range to target as of closest approach

that a launcher is spotted as a function of its distance

from the ground track of the airplane.

The lateral range curve contains far more information about the characteristics of the searcher than

does the sweep width. In particular, it keeps explicit the

point that, given an imperfect searcher, no amount of

searching can guarantee that a target will be found. The

“effective sweep width” characterization of the imperfect search of a broad width as a perfect search of

a narrower width can give a misleading impression of

how the efforts of many such searchers (or the repeated

The arch-shaped lateral range curve depicts the probability

that the target will be detected as a function of the searcher%

distance of closest approach. There is some chance that

nearby targets will be missed and, conversely, that a distant

target might be seen. The rectangular curve represents a

%ooide-cutter” deterministic lateral range curve, guaranteed

to see the target if it passes within 2.5 miles and to miss it

otherwise. The two curves are equivalent In the sense that,

assuming a random distribution of targets, each searcher will

detect the same number.

SOURCE: Office of Technology Assessment, 1991.

efforts of one such searcher) combine: the temptation to take the sweep width concept literally and imagine a lawn

spreader-like application of perfect search to the region of interest must be avoided. Mathematically correct ways

of assessing searchers’ combined or repeated efforts exist and will be presented below. The sweep width, however,

retains its utility as a one-number fig&e of merit suitable for use in practical calculations.

the role of luck, our ability to make statements about

the difficulty of the search, the utility of coordination

of the search effort in the (usual) case that it is

performed by more than one searcher, and the

question of efforts on the part of the target to stay

hidden. (See also box 6-A.)

Luck plays two major roles. In the case of a search

for a moving target, e.g., an escaped pet, the searcher

and the target move about in the same area and only

encounter one another by chance. Even in the case of

a stationary target, e.g., a mislaid set of keys, the

searcher might approach the keys very closely

without finding them, perhaps later exclaiming,

“But I looked right there!” when somebody else

locates the keys. The first example shows the role of

luck in bringing a searcher-target encounter about;

the second shows the role of luck in determining

whether an encounter results in a sighting. (See also

box 6-B.)

The role of chance notwithstanding, assessments

of a search’s difficulty or likelihood of success can

be made in advance. A set of keys misplaced

somewhere in the house is one thing; a contact lens

lost during a fast break on the basketball court is

quite another. The likely outcome of the search is

determined by the effectiveness of the searcher (how

good he or she is at searching), and by innate

characteristics of the target of the search, the size of
Chapter 6-Broad Area Searches for Arms Control Treaty Violations .77

Box 6-C-Coordination of Search Efforts

Suppose that we wish to use airplanes of the type considered in boxes 6-A and 6-B to sweep a 5,000 square mile

region clean of treaty-banned missile launchers.l The effort required would thus seem to be the searchable area

divided by the sweep rate:

5,000 square miles ÷ 1,000 square miles per hour= 5 hours,

This calculation (despite its dismaying implications

for a Soviet Union of roughly 6,500,000 square

nautical miles) is, in fact, overoptimistic. The reason

becomes apparent when we try to decide on the correct

search pattern to fly: despite the 5-mile sweep width,

simply spacing adjacent sweeps 5 miles apart won’t do

because the 2.5-mile sighting range is an average, not

a guarantee. Five-mile spacing is good (apart from any

exploitation of terrain and or other prior information),

but not good enough: in fact, the nondeterministic

nature of the search ensures that no search pattern or

allocation of search effort can be certain to see all

targets. Given the notional lateral range curves shown

here, for example, the target has an 88-percent chance

of being missed by the sweep that passes 2.7 miles

away, a 92-percent chance of being missed by the

sweep that passes 5 miles away, and a %-percent

chance of being missed by the sweep that passes 7

miles away, for a combined 78-percent (0.88X 0.92X

0.96) probability of being missed completely and thus

a 22-percent chance of being sighted

l~tjs, for m.i#.le launchers obligingly left out in the Opem

Lster we wiU take up the question of searcbingfor targets tbat might

be concealed.

Sighting by Successive Sweeps at Ranges of

3,5, and 7 Miles From Target

Probability of sighting by each sweep

“1

1.0 -

0.8 -

0.6 -

0.4 -

0.2 -

0 ~ ‘ ‘ ‘ ‘ ~ ‘ ‘ ‘ ‘ ‘ ‘ ‘ ‘ ‘ i ‘ ‘ ‘ ‘ ‘ ‘ ‘ ‘ ‘ -

-2.5 0 2.5 5 7.5

Range from target

Like crop-dusters, searchers can coordinate their flights so

as to compensate for a somewhat uneven application of

search effort. These overlapping lateral range curves show

how even distant passes contribute to the overall probability

that the target will be detected.

SOURCE: Office of Teetinology Assessment, 1991.

the region in which the target is located, the search coordination can also ensure that the child does not

effort available, the presence of any prior knowledge

as to the target’s whereabouts, and how well the

search effort is coordinated.

Multiple Searchers and/or Targets

Coordination of the search effort can help a great

deal if the amount of search effort available is

comparable to that needed for a complete search of

the region of interest. A dragnet search, perhaps for

a child lost in the woods, is conducted with searchers

walking shoulder-to-shoulder---clearly a superior

approach to the uncoordinated alternative of simply

turning the same number of searchers loose in the

woods for the same amount of time. Coordination

ensures that no location goes unstarched while

another is oversearched. (In the lost-child example,

wander from an area that has not been searched into

one that already has. See also box 6-C.) If only

meager search resources are available, no amount of

coordination can confer a high probability of success; a plethora of searchers, on the other hand, can

do a good job without particularly coordinating their

efforts. (See also boxes 6-D and 6-E.)

Thus far we have assumed that the searcher seeks

a unique target. Many searches, however, would be

satisfactorily concluded if they were to find any

single target out of a large population. For example,

a hungry cat searching for mice is not particular as

to which mouse it catches. Similarly, many would

consider the search for treaty violations to end if

even one violation were found, inasmuch as that is
78. Verification Technologies: Cooperative Aerial Surveillance

Box 6-D--Coverage Factor

Detailed lateral range curve information such as that used in the example is rarely available: an analyst is likely

to be asked what to make of a given search situation given only the search effort, an estimate of the sweep rate and

perhaps a rough idea of the shape of the lateral range curve. In this situation, the analyst can state some bounds on

the probability that a given target will be sighted. Each

starts with the coverage factor, the product of the Probability of Sighting as a Function of

search effort and the sweep rate, This quantity can be Coverage Factor

thought of as the numberof square miles searched: the Probability of sighting question is how these square miles are applied to the

square mileage of the territory to be searched. In the 1.o “

case at hand, the coverage factor is equal to unity.

The upper bound is that given by the optimistic O.8 -

calculation cited above: 100-percent probability of

sighting the target given 5 flying hours of effort, a 0.6 -

5-mile sweep width, a 200-mile/hour speed, and 1,000

square miles of searchable area. This upper bound 0.4 -

treats the 5-mile sweep width as a guarantee instead of

as an average, and assumes that the airplane can fly so 0.2 -

as to search every point in the searchable region: 1,000

square miles’ worth of searching have been laid neatly, o

like 5-mile-wide wallpaper, on 1,000 square miles of O 0.5 1 1.5 2

territory. Coverage factor

The lower bound, recognizing that the 2.5-mile Perfect coordination of completely deterministic sighting

sighting range is a mathematical construct, assumes

that the 1000 square miles’ Worth of search effort are

would lead to a sighting probability (as a function of the

coverage factor) shown by the upper curve. Compietely

laid down like confetti instead of like wallpaper. haphazard application of search effort leads to a, sighting

Absent any assumption that the pilots are intentionally probability shown by the lower curve. Real-world cases. often

iie near the curve in between: note that 100-percent coverage suboptimizing the search, this assumption of a com- does not In such cases, guarantee a sightlng.

pletely haphazard search results in the lowest possible SOURCE: 8emard Osgood !@opman, Search and Scre#?@ (Nw

value for the probability that a target will be detected York, NY: Pergamon, 1980), p. 78.

because it gives the searchers no credit for organizing

their efforts. Some parts of the region are oversearched at the expense of others. In the case at hand, with 1,000 square

miles’ worth of coverage factor distributed confetti-style on 1,000 square miles of searchable region, a target has

a 63-percent chance of being sighted. Doubling the coverage factor would raise the probability of detecting a target

to 86 percent.

IR~~@, *m fact that as llliiny targets are sighted beyond bt-e~ =@ ~~~~it”

all that is required to brand the other side as a treaty be driven into buildings, caves, or tunnels and thus

violator.

10 - hidden from aerial searches.11 In fact, these treaties

allow concealment according to normal operational

Treatment of Target Concealment procedures. For example, mobile missile launchers

can be camouflaged, even though fixed silos cannot

Many—if not most—INF, START, and Conven- be, because camouflage is customary for military

tional Armed Forces in Europe (CFE) TLIs, e.g., vehicles. Is aerial search then useless for assessing

airplanes, mobile missile launchers, and tanks, could compliance with these treaties?

10_f& ~tfite .smction ~g~t ~ ~om~ aught ch~afig ~o~d & abrogation of the @wty itse~. The United Stites prepared a c,odIl&XICy Pkl fOr

the resumption of atmospheric testing in the event of a Soviet breach of the Limited Test Ban Treaty. (Michael Krepou Arms Contro/-Ve@cafion and

Compliance, headline series No. 270 (New York, NY: Foreign Policy Association 1984), p. 16.) Henry Kissinger saw the consequences of a revealed

violation as spilling over from treaty to treaty: “Any country that contemplates a rupture of the treaty or a circumvention of its letter and spirit must

now face the fact that it will be placing in jeopardy not only a limited arms control agreement, but a broad political relationship. ” (Quoted in WallOp

and Codevilla, op. cit., footnote 7, p. 89. ) Historically, recourse to treaty abrogation in the event of violation has rarely, if ever, been carried out when

an instance of violation has been discovered.

llFor a ~eatment of camouflage, concedmen~ and deceptiow S= ch. 3.
Chapter 6-Broad Area Searches for Arms Control Treaty Violations . 79

Box 6-E--Use of Imaging Systems in Concert

Clearly the chance of detecting a target is improved if additional imaging systems are brought to bear. The

question is best addressed through the paradigm of lateral range curves and sweep widths. Indeed it is in this sort

of calculation that the sweep width comes into its own as a simple and useful one-number summary of the searcher’s

efficacy.

Suppose that a visible-light photography system records a 4-mile swath with, after interpretation is complete,

an 80-percent chance of detecting a treaty-limited item (TLI) within that swath; suppose further that a synthetic

aperture radar records an 8-mile swath but because of a lower resolution, has only a 40-percent chance of seeing

TLIs within that swath. (Note that each of these systems has a 3.2-mile sweep width.) We wish to know the

combined effect of the two systems, i.e. the effective sweep width of an airplane carrying both.

A target within the camera’s field of view has a 20-percent chance of being missed by the camera and a

60-percent chance of being missed by the radar. Thus, assuming that detection by one system is statistically

independent of detection by the other,l it has a 12-percent (because 0.2 X 0.6= 0.12) chance of being missed by

both, for a complementary 88-percent chance of being detected by one or the other or both. The two 2-mile strips

to either side of the camera’s field of view are seen only by radar, with its 40-percent chance of detecting a target

therein. Therefore the combined sweep width of the two detectors is

2 x 0.4+4x 0.88i“2 x 0.4 = 5.12 miles.

This is a considerable improvement over the 3,2-mile sweep width offered by either system alone, but

somewhat less than the 6,4-mile sweep width which one might naively have thought would result from their

combination.

l~s Mwtion *SSOIISO if the main source of detection uncertain‘ ty for targets within the two systems’ fields of view is the

interpretation step. These interpretations will be conducted separately, and probably by dfferent people. If actuai target charactmistics, e.g.

orientation contribute to the probability of not being see% then the assumption of independence would breakdown. There is reason to think that

orientation has little to do with probability of detection (see Koopmq op. cit., footnote 9) and we may note for the present exampla that many

other target characteristics, e.g. relative brighmess compared to the backgrount$ will be different for the two systems and thus unlikely soumes

of correlation between the two detection probabilities. Lack of correlation would itself be a desirable quality for candidate pairs of detection

mechanisms; inverse correlationwould be evenbetter, because with inverse corrclationeach sensor would becspixiallygood at aeeingthe tatgets

with respect to which the other sensor was eSpOC~y bad.

Of course, aerial searches might still see the

buildings, tire tracks leading to caves, and so on, so

that suspicions could be aroused even if no actual

violations were perceived during the flight. In this

way, the overflights could aid other inspection

procedures allowed for in the particular treaties,

including the use of NTM.

Nevertheless, one might suppose that a system of

deliberate TLI concealment, even one that worked

well, would not work perfectly. The scramble

(perhaps nationwide, depending upon the treaty

protocol implementing the aerial search proposal) of

the TLIs for cover when an overflight was announced would on occasion be marred by some units

not getting the word, units breaking down on their

way to the concealment facility, and so on. Thus

deliberate concealment measures could degrade the

performance of the overflights, but not necessarily

vitiate them completely. (See also box 6-F.)

Simple Aerial Monitoring Calculations:

Aerial Search for SS-24 ICBMS

The Soviet SS-24, a rail-mobile intercontinental

ballistic missile (ICBM) physically comparable to

the U.S. Peacekeeper, is powered by solid fuel and

delivers 10 reentry vehicles.12 Unlike the proposed

rail-mobile version of the Peacekeeper, SS-24s

frequently deploy to the rail net in peacetime. The

Soviet Union has over 145,000 kilometers of track

to which SS-24 can deploy. 13 This figure overstates

the difficulty of finding the SS-24 because it

includes considerable amounts of dual trackage

(though not as great a proportion as would be found

on other rail nets, e.g., that of the United States). A

more accurate figure for the total amount of roadbed

WJ.S. Dep~ment of Defeme, Soviet MiZita~ Power 1990 (Washington DC: U.S. Government w%OffIce, 19W), P. 52.

lsWor/d Factbook 1990 (w~hhgto~ DC: U.S. Government Printing office, 1990), P. 217.
80. Verification Technologies: Cooperative Aerial Surveillance

Box 6-F—Treatment of Deliberate Target

Concealment

Deliberate target concealment, like any other

degradation of search effectiveness, can be characterized mathematically as a reduction (perhaps a

very large reduction) of the aircraft’s sweep width.

For example, if each TLI had a 99-percent chance

of reaching cover when bidden to do so, an aircraft

with a 3.2-mile sweep width would find its width

reduced to 0.032 miles. That is to say, an aircraft

with a 4-mile wide photographic field of view,

backed up by a staff which finds 80 percent of the

TLIs present in the photographs would-if confronted by an opponent who successfully concealed

his TLIs 99 percent of the time-see on the average

as many TLIs as an aircraft which exerted perfect

scrutiny, with no possibility of concealment, on a

strip 0.032 nautical miles (or about 200 feet) wide.

The above statement should not, of course, be

construed as a (ludicrous) statement that concealment measures somehow restrict the camera’s field

of view to a narrow strip; to reiterate, concealment

lowers the number of targets seen to that which

would be seen if scrutiny were perfect and the field

of view were so narrowed. In fact, of course, the

scrutiny is imperfect (with much of the imperfection introduced by the targets’ concealment), and

the field of view is much wider. The narrow strip,

however, proves to be a useful mathematical

construct, as will be seen below.

in the USSR would be 100,000 kilometers, or 68,000

nautical miles. Moreover, logistical and communications considerations may constrain the SS-24

force from using the entire rail system.

An aerial search by a single vehicle could perhaps

overfly 3,000 nautical miles of roadbed, suggesting

a 4-percent (i.e., 3,000 divided by 68,000) chance of

seeing any particular SS-24 train. If mobile ICBMs

were completely banned by some arms control

agreement, this simple calculation suggests that

each flight’s chance of detecting a violation would

be roughly 4 percent per deployed train .14

Most refinements to the above simplistic calculation---other than those modifying the assumption

that the search is performed by an unassisted

aircraft-tend to lower the estimated probability of

Photo credit: U.S. Department of Defense

Artist’s conception of rail-mobile SS-24 missiles on

maneuvers in a dual-tracked section of the Soviet

railroad system.

finding a violation. (See also box 6-G.) For example,

not all extant trains would be deployed at all times,

and the aerial search task is complicated by the

presence of ordinary trains--perhaps one every 50

miles.15 The missile-carrying trains would have to

somehow be discriminated from the ordinary trains,

and caution about accusing the Soviets of a violation

would introduce a benefit-of-the-doubt effect by

which some SS-24 trains could escape identification. These considerations could lower the flight’s

chance of finding a violation from 4 percent per train

to 2 percent overall.

With 10 warheads per missile and more than one

missile per train, and in an environment of reduced

strategic arsenals, only a handful of trains would be

needed to constitute what could plausibly be deemed

a militarily significant force. If considerations such

as those raised in the preceding paragraph were to

lower the overall chance of finding a violation to 2

percent per flight, 50 flights (nominally a year’s

worth) would have only a 63-percent chance of

finding a violation even if they were all dedicated to

the search for illegal rail-mobile missiles.

Simple Aerial Monitoring Calculations:

Aerial Search for SS-20 IRBMS and

SS-25 ICBMS

The SS-20 is a three-warhead, intermediate-range

ballistic missile (IRBM), deployed on land-mobile

launchers by the Soviet Union. It is an item banned

14~e ~~nce of fm~g at lw~t one out of ~ ~fii5 1. ().96”. For ml values of n, 1- t3.96n is about@ to 0.04 X n.

lsBased on WorldFacrbook 1990, op. cit., foomote 13, fi~es for total ~c~ge ad tow ton-miles haded, and some estimates Of fr~ SWed, n-r

of ears, and tons per car.
Chapter 6-Broad Area Searches for Arms Control Treaty Violations .81

Box 6-G-Calculation of Sighting Probabilities

This box explains how overall sighting probabilities can be calculated given the search effort, the size of the

region to be searched, and an assumption about how the search effort is organized. These probabilities result from

consideration of the problem in terms of the Poisson probability distribution, whose density parameter p is the

coverage factor, sweep rate times effort per area searched, The probability of a target being sighted n times is then

p

n

e

-p/n!. Substituting n = O gives the probability e-p of the target not being sighted at all, for a complementary

probability l-e-p of it being sighted.

The upper bound for the probability of sighting, then, results from considering the search as perfectly

coordinated and is the coverage factor or unity, whichever is the lesser:

P(sighting) = min (coverage factor, 1).

The lower bound results from considering the search as splattering coverage over the searchable area confetti-style:

P(sighting) = 1- e-coverage factor

The truth will lie somewhere between these two extremes. Differing assumptions as to exactly how well the

searchers can coordinate their efforts lead to differing values for the probability that a target will be sighted as a

function of the coverage factor. One commonly used function is

P(sighting) = cnorm(coverage factor),

where ‘cnorm’ represents the cumulative normal distribution. This (rather startling) appearance of the cumulative

normal distribution can be derived from a widely applicable expression for probability of sighting as a function of

true-not lateral-range, and has the advantage of being easily looked up in commonly available tabular form or

as a “canned” function on a computer or calculator.

Note that the three functions agree for very small coverage factors and for very large ones: the exact degree

of coordination only matters for medium values of the coverage factor because very sparse coverages run little risk

of redundant overlapping and very dense ones can afford the wasted effort.

In a case in which the coverage factor is based on an effective sweep width drastically reduced by sensor

imperfections or target concealment (see box 6-J?), the instances of sighting will be so randomized that the

confetti-style equation for probability of sighting should be used.

by the INF Treaty, and the Soviets are obliged under percent (i.e., 3,000 divided by 1.1 million) chance of

the INF Treaty to destroy their existing SS-20s and

not build any more. The SS-25 is a single-warhead,

land-mobile ICBM physically comparable to the

proposed U.S. Midgetman. Unlike the proposed

‘‘garrison-mobile’ Midgetman, SS-20s and SS-25s

deploy to the countryside in peacetime.

The Soviet Union has 1.6 million kilometers (1.1

million nautical miles) of roads.16 The SS-25 TEL is

billed as off-road-capable, so it would not (except

perhaps during mud season) be restricted to the

800,000 miles of hard-surfaced road. However, the

SS-25 TEL is not considered to be as off-road

capable as the proposed U.S. Midgetman TEL. We

might therefore assume that operational SS-25s

would operate on unimproved roads and even off the

road, but would not stray far from the road. A

simplistic calculation would then suggest that a

3,000-nautical-mile flight would have a 0.37-

seeing a particular SS-25.

Refinements to this calculation include consideration of the fact that more than one section of road

would be visible at a time, raising the probability of

detecting the launcher. Other refinements, like those

suggested above in the case of the SS-24, reduce the

estimated probability of seeing a launcher: not all

launchers are out of their garrisons at any one time

and the reluctance to cry ‘‘wolf’ at the sight of any

large truck with a cylindrical cargo would tend to

mask some actual sightings. In particular, aerial

search for illegal SS-20s would be greatly complicated by the presence of legal SS-25s, whose

launchers are outwardly similar. Chances of finding

any particular illegal SS-20 or SS-25 on a road

would be worse than those of finding a particular

rail-mobile SS-24. Compared to the SS-24, the small

number of warheads per missile on the land-mobile

systems would require that 10 times as many be

16 World Factbook 1990, op. cit., footnote 13, p. 217.
82. Verification Technologies: Cooperative Aerial Surveillance

Photo credit: U.S. Department of Defense

In an artist’s conception, road-mobile SS-25 ICBMs take to

the field in a remote area of the Soviet Union. The mobility

of such systems increases their survivability, but also

complicates verification of any numerical limits

placed on them.

deployed to reach a given level of military significance. However, the lower chance per missile of

finding a violation counteracts this effect.

SS-20s and SS-25s can also leave the roads and

roam the countryside. The arable land and meadowlands of the Soviet Union total 1.8 million square

nautical miles,17 and another 2.7 million square

nautical miles of the Soviet Union is covered by

forest. Arable lands and meadows generally support

tractors, and thus can be considered capable of

supporting the off-road capability of the SS-25

launcher. In addition, these launchers could penetrate the forested and mountainous regions of the

Soviet Union18, as well as operating on nonarable

tundra, even if they could not negotiate each and

every square meter of such territory. Thus one might

credit the SS-25 with creating an ‘uncertainty area’

of at least 5 million square nautical miles.19 (The

entire landmass of the Soviet Union is about 6 1/2

million square nautical miles.) The calculations

performed in the previous chapter thus apply roughly

to this case: an overflight might see, on the average,

a mile-wide swath throughout its 3,000-mile flight,

leading to a 0.06-percent chance per missile that a

single flight would find a violation.

As will be discussed later, knowledge of Soviet

infrastructure could help. For example, there might

not be enough bases to serve TELs spread out over

the whole 5 million square nautical miles, in which

case the inspections could concentrate on regions

near bases.

Discussion

Many important considerations do not appear in

the simple calculations described above. A more

complicated calculation could take these into account, but for now we will simply point them out.

Some make the calculation look pessimistic while

others make it look optimistic. (See also box 6-H.)

For example, the inspecting side would not

necessarily know which mode of violation the

violating side had chosen, and would thus not know

whether to concentrate a year’s worth of flying on

road, rail, or countryside search. Effort would be

diluted by the need to address all of these regions.

Other searches would be required too: for example,

the 4,530 usable and 2,360 nonusable airfields of the

Soviet Union20 would provide cover and some

amount of infrastructure for deployment of mobile

ICBMs, and examination of these airfields would

use up flying time which might otherwise be

allocated to searching roads, rails, or countryside.

Finally, a breakout deployment would occur gradually over a period of time (perhaps a year). At the

beginning of that period the force is very small, and

thus almost impossible to detect; only at the end of

the period is the force of the "militarily significant"

171bid., p. 216.

18~ey ~ d~ict~ opaa~g ~ rough w~d COuntry in U.S. Department of Defense, Soviet Militav Power 1988 (was@to%~: U.S.

Government Printing 0f13ce, 1988), p. 47.

lgAt&r@s to d~je an ‘‘@vtdent uncertainty ZtKXi’ of a road network or otherwise deal with the problem of searching a combination of

two-dimensional and one-dimensional regions (e.g., fields and roads) have in general been disappointing because the equivalency depends upon whether

or not multiple roads can be captured in the same view, and thus upon what sensor is in use.

mWorld Factbook 1990, op. cit., footnote 13, p. 217,
Chapter 6--Broad Area Searches for Arms Control Treaty Violations .83

Box 6-H—Satellites v. Aircraft

Because satallites pass over so much territory so frequently, as compared to aircraft, one might wonder whether

they would be cheaper platforms for overhead surveillance. An analysis shows that this is not necessarily the case.

One may compare the $10/square mile figure for airborne photography (see in box C-F’) with the costs derived

for a notional MediaSat newsgathering satellite based roughly on the French SPOT commercial satallite.1

MediaSat pictures would cost, all told, from $35,000 to $73,000 each depending upon how various design

choices between the austere and the desirable were made and assuming a demand of approximately 1,000 pictures

per year. Towards the desirable (and thus more costly) end of the design regime, pictures would each cover an area

of 15 by 15 miles and thus cost in the neighborhood of $300/square mile. Thus these pictures cost about 30 times

more than their aircraft-obtained counterparts. Their 5-meter resolution is not even close to the resolutions identified

as necessary for aerial monitoring of treaties, so one would infer that satellite photography suitable for

treaty-monitoring would be even more costly than the MediaSat estimates would indicate.

If the treaty-monitoring effort could benefit by collection of more pictures,2 economies of scale would make

satellites more cost-competitive. While 1,00015- by 15-mile pictures cover an area comparable to the 50 flights’

worth of 5- by 1,000-mile strips we have considered in several examples so far, most of their cost is the investment

cost of building and launching the satellite. Extra satellite pictures would be almost free. The investment cost of

aerial surveillance, on the other hand, is but a small part of the total, so amortization of that cost over a larger number

of pictures would not greatly lower the cost per picture.

Of course, satellite-derived pictures could be worth their extra cost because of other possible advantages of

satellites, e.g. more frequent revisit times, than would be allowed to aircraft in a treaty context. One must be careful,

however, in drawing facile comparisons between such different systems: where the partisan of satellites points to

frequent revisit times, for example,his or her airplane-favoring oppositenumberpoints to the greater unpredicability

of airplanes’ flight plans.

qjw U*S, cqe~, mee of Technology &sessm~4 commercial Newsgathering From Space+ Technical Memora.d~

O’IX-Tf-IC$40 (Wash@tan DC!: U.S. Government Mnting Office, May 1987), espdally pp. 25,39-41.

2AS ~@ WM M the mif many treaties were to be monitored by the same stttellb

size according to which detection probabilities are would hold important lessons for those who plan to

normally computed, but by then it is too late: the

militarily significant force is already in place and

there is no time to make an appropriate response.21

Concealment, camouflage, and deception (CCD)

could all lessen the probability that a TLI would be

sighted even if an aerial monitoring aircraft flew by.

On the positive side, other arms control monitoring

and intelligence sources (as well as cogent use of

previous results of aerial monitoring) could provide

valuable clues facilitating the air search for treatyl.imited objects. Aerial monitoring assets could then

concentrate on the most likely regions, increasing

their effectiveness. The interplay of CCD and

intelligence on the other is quite complex: a study of

the search for mobile Scud-B launchers in Iraq

search for illicit SS-20s and SS-25s.

So far we have considered only searches for items

totally banned by treaties. START or other treaties

might limit, but not ban, such weapons as the SS-24

and SS-25. Aerial search would then need to count

TLIs rather than simply look for them. This important topic is treated in appendix A.

The United States and the Soviet Union had atone

time reportedly agreed on restricted deployment

areas of 125,000 square kilometers (36,400 square

nautical miles) for road-mobile ICBMs in a START

contex t

. 2 2Assuming no wasted effort, a 3,000-nauticalmile flight with a l-mile sweep width as described

above would have a 8-percent chance of seeing any

particular TLI Inspection of the deployment areas is

an important minimum requirement, and not an easy

21 R- Scott Sht of Laweren~e Liv~ore Natio~~~ratow ~~inted out he impo~ce of ~S r~p-upeff~t on the detection Of breakouts.

He has further noted the convenient mathematical fact tha~ assuming a constant deployment rate, the average detectability of the force is half of the

maximum detectability attained when the force is fully deployed.

22~b~ ~~o@“Ve~g START, From Satellites to Suspect Sites, ’ Arms Control Toalzy, vol. 20, October 1990, p. 18.
84. Verification Technologies: Cooperative Aerial Surveillance

one to fill if the aerial monitoring process is

supposed to verify a nonzero limit. Nevertheless, it

would be a mistake to assess one’s inspection

capability on the basis of inspections of designated

deployment areas. To do so is to run the risk of

accepting a verification regime that will work only

if the other side does not cheat.

Simplistic calculations portray a comparatively

heavy aerial search schedule as offering only slightly

more than even odds of finding a nominally sized

treaty violation in a year. Most refinements of these

calculations, e.g., consideration of CCD, the difficulties presented by the task of discriminating illici t

TLIs from legitimate ones, and the desire to detect

a treaty-violating deployment before it is complete,

lessen the chances that aerial search will function as

hoped. One important consideration, however, has

the opposite effect: the use of prior information

about the TLIs’ likely whereabouts—perhaps gained

by NTM, or by previous aerial monitoring flights—

can focus the attention of the aerial search assets

upon those regions most likely to contain items of

interest.

Sources and Exploitation of Prior

Information

As the preceding sections of this chapter suggest,

an aerial search program that had no prior information as to where to look would be an unguided tour

or photographic ramble of the target country. It

would not be much more focused than the random

searches of the GENETRIX project, in which

automatic cameras drifted across the Soviet Union

beneath weather balloons. (See also box 6-I.) Even

complete photographic coverage, were such to be

available given treaty constraints, would not provide

a practical solution. As we have seen in chapter 3,

photographic equipment used in aerial monitoring

might resolve a ground sample distance of 6 inches,

imaging those 6 inches as a 5,000th of an inch: in

that case, the 6.5 million-square-nautical-mile Soviet Union would lead to a quarter of a million

square feet of photographs. If these were assembled

into a single photograph of the Soviet Union, it

would cover more than five football fields and

require a microscope for detailed analysis. Some

means of directing the search is needed.23 Potentially useful kinds of such prior information include:

terrain characteristics, target-associated infrastructure, results of previous searches, knowledge of the

inspected side’s operational habits, and other intelligence data.

Terrain

In most areas, terrain sharply limits the possibilities for the locations of many kinds of TLIs.

Land-mobile SS-20 or SS-25 missile launchers, for

example, might not be able to enter swampy land.

More generally, land-mobile missile launchers are

likely to be found in regions where accessible terrain

is not only available but plentiful, because the

concept of operation of such launchers calls for them

to be able to disperse and create enough uncertainty

as to their whereabouts to stymie an attack by

ballistic missiles. This consideration would lessen

the area of the region in which launchers might be

found. However, as mentioned earlier, such launchers might use roads to enter and move about in a

region of difficult terrain.

Infrastructure

Infrastructure can provide many valuable clues to

the location of reconnaissance targets. A photointerpreter’s account of how she found the German V-1

cruise missile during the Second World War shows

her use of infrastructure clues. (See app. A.) More

recently, a British analyst of Soviet earth-resources

satellite Soyuz Karta stereoscopic pictures discerned

a 750-meter-long building, new roads, embankments, and signs of possible excavation at a site in

Iraq; these clues (taken together with information

collected by Kurdish separatists in the region) led

the analyst-a mineralogist by training—to conclude that the Iraqis were developing the site as a

‘‘uranium mine’ or a nuclear weapon production

plant.24

In general, the tracks made by troops and vehicles

“are the most important and obvious signature of

any military activity."25 Not only do some military

vehicles create tracks unlike any civilian vehicle, but

the presence of such military-related infrastructure

can be given away by tracks: the presence of barbed

Zti the ~me of ~ much~Wcr ~om~, ~ome 25 ~~ties of f~wme shot by U-25 and low-flying aircraft in the COm.W of the (hbh@Sile

Crisis. (Robert Kennedy, Thirteen Days (New Yorlq NY: W.W. Nortoq 1971), p. 46.)

24~~Satellite Reve~s ‘Uranium Mine’,” Jane’s Defence Weekly, Nov. 31990, p. 879.

~ItigeV AWIY$C, Soldi~’s Mmti STP 34-96D1.SM @hshingtorL DC: Headquarters, Department of tie ~Y, November 1987)* P. 2-456.
Chapter 6-Broad Area Searches for Arms Control Treaty Violations .85

BOX 6-I—The GENETRIX Project

The GENETRIX project presents, in purest possible form, an airborne search undertaken without any recourse

to existing knowledge of important targets’ locations.

During the mid-1950s, the U.S. Strategic Air Command launched a program of balloon-borne reconnaissance

of the Soviet Union and the People’s Republic of China. High-altitude balloons bearing automatic cameras would

float East from Europe across the Soviet Union and the P.R.C. to Arctic recovery areas in the Pacific. In January

and February of 1956,516 balloons were launched, of which fewer than 10 percent were recovered. These furnished

almost 14,000 100-square mile exposures of Soviet or Chinese territory, accounting for about 8 percent of those

countries’ area. The utility of the pictures was characterized as suitable only for “pioneer” work, and the Soviet

reaction-which included a press conference featuring many fallen balloons-was vehement.1

“Pioneer reconnaissance” was elsewhere defined at that time as a resolution of 20 to 400 feet; pictures taken

at such resolutions would not be useful to military photointerpreters.2 The balloons may have performed at the better

end of this range. They carried pairs of cameras whose fields of view slightly overlapped-with a

then-readily-attainable film resolution of 10 lines per millimeter and optics to match, the resulting 9- X 9-inch

images 4 would, if showing a region 10 statute miles on a side, attain a ground resolution of

(5,280 X 10)+(9X 25.4X 10)=23 feet.

From a mapping standpoint, however, the pictures were quite usable, and the program was characterized as

a suceessful and even cost-effective mapping mission.5

The militarily disappointing results of the GENETRIX program are instructive because they stem in large

measure from the scattershot nature of the search. Not only were the users unable to target the balloons (some even

missed the Soviet Union altogether), but their first order of business upon receipt of the product was to determine

where the balloons had been. The principal lesson of the project is the price it paid for its inability to capitalize upon

existing information as to the whereabouts of interesting targets.

l~s a~o~t~ nOmSS C!rouc@ The EagZe A/o# (Wbshingtoq DC: Smithsonian Institution ~SS, 1983), PP. @44547.

2Rg@OnEe Dav@ and w-R. Ms, RAND’sRole in the Evolution of Balloon and Satellite Observation $Mtem andRelated U.S.

Space Technology ($anta Monkq CA: The RAND Corp., 1988), pp. 26-27. French SPOT and U.S. L.andsat pictures fail in the “pioneer

reconnaissance” category according to this standard.

31bid., p. 11,

41bid., p. 60.

5~id., p+ 61: At@t ~der $50/_ mile, GENETRIXqolStXted mapping data on the soviet Ution more ch~ply *~Y o~r

then in use for mapping the United States

wire (a difficult photographic target), for example, buildings of the same appearance as those housing

can be deduced by observing the otherwise inexplicable convergence of tracks.26

Soviet SS-20 and SS-25 mobile missiles deploy to

prepared sites consisting of turnouts and berms.27 To

assure survivability, the Soviets have doubtless

prepared far more of these sites than there are

missiles, but the sites, and the regions surrounding

them, are still likely places to look for mobile missile

launchers.

Between deployments, SS-25s (and SS-20s, to be

eliminated under the provisions of the INF Treaty)

occupy unique sliding-roof buildings. Clandestinely

deployed missiles would probably not be based in

the overtly deployed force, but the sliding- roof

feature (which enables the missile to be launched

without moving the TEL outdoors) might be retained.

Despite their off-road capability, SS-20 an d

SS-25 missiles are more mobile on roads than off,

and therefore an aerial monitoring search for these

missiles or their shelters could be guided by the road

network. Bridges would channelize missile launcher

traffic (along with all other traffic), making them and

their vicinities especially likely places to find TELs.

Rail-mobile SS-24 missiles are constrained by an

even more obvious item of infrastructure: railroad

‘Ibid., p. 2457.

zTAs show in Soviet Milita?y power, various iSSUeS.
86. Verification Technologies: Cooperative Aerial Surveillance

tracks. Railroad tracks seem to be important for

Soviet silo-based ICBMs as well: the existing fields

string out along the Trans-Siberian Railway. As is

well-known, most of the Soviet Union’s rail network

is broad-gauge (5 feet): the SS-24 operates on this

broad-gauge track.28 Some western regions of the

Soviet rail network have the same standard-gauge (4

foot, 8.5 inches) track as the neighboring European

countries. The standard-gauge sectors would merit

some surveillance, lest the Soviets exploit U.S.

overreliance on this particular infrastructure cue and

clandestinely produce illegitimate SS-24s deployed

in standard-gauge railcars.

In general, railroads are such an important part of

the Soviet infrastructure that an aerial search for

almost any kind of facility could sensibly be begun

on the assumption that the facility would have handy

access to a railroad.

Illicit TLIs, especially small numbers of them,

might well be found mixed in with legitimate TLIs

or even non-TLIs. For example, SS-23s (TLIs

banned by INF) were found amidst the treatyunconstrained missiles of an East German Scud-B

unit.29 As mentioned in chapter 6, an aerial monitoring aircraft searching railroad tracks for SS-24 trains

would also see many ordinary trains, probably

seeing one in motion every 50 miles or so and many

others stopped at sidings or in railyards. These trains

would have to be judged missile-free. Discrimination of missile-carrying trains from ordinary ones

might not be easy: the United States plans to

disguise its Peacekeeper-carrying trains as ordinary

ones,

30 so the Soviets could do the same without

incurring charges of the use of ‘deliberate concealment measures” to defeat NTM.

Certain treaty provisions could have the effect of

mandating infrastructure. “Designated deployment

areas, regions expressly designed to simplify

detection without so constraining weapon deployment as to constitute a threat to survivability, have

been proposed for mobile ICBMs under START.

Conversely, designated test areas are designed to

Photo credit: U.S. Department of Defense

Plans for possible rail-mobile deployment of the U.S.

Peacekeeper ICBM call for the use of normally

marked trains.

assure the verifier that weapons found within their

limits are not deployed, but are merely test items.

The SALT I ABM Treaty codifies infrastructure in

this way. Finally, the intended purpose of a deployment may be established by its location: the ABM

Treaty requirement that putative early warning

radars face outwards from positions on the perimeter

of their countries establishes that they are not

proscribed battle management radars.3

1 Not only do

such mandated details of infrastructure facilitate the

counting of deployed weapons; they also simplify

the decisionmakin“ g process in case a TLI is sighted

outside an allowed region: “detection of a single

item in proscribed places or times would constitute

a violation. ’32

Finally, and most simply, TLIs are likely to be

found near other TLIs, and other military hardware.

Even targets such as mobile missile launchers,

which try to spread themselves out for survivability’s sake, spread out only on a tactical level and not

on an national one. If total bans on weapon systems,

like total bans on operating certain weapon systems

outside of designated deployment areas, are especially verifiable because “if we see even one then

we’ll know they’re cheating,” then having seen

%Soviet Milita~ power 1990, op. cit., footnote 12, pp. 51-52.

~Washington Times, May 4, 1990, P. 6.

mApplyingcommci~emblem, au~mtic-lm~ amounts of dirl and rus~ and even blending in a few mal freight CarS. Remainin g functionally

related observable differences include the number of axles on the missibcarrying cars and the undercarriage of the fuel car. (“U.S. Plays

Cloak-and-Boxcar,” Chicago Tribune, June 14, 1989, p. 1.)

sl~e famed Krasnoyarsk radar violates this condition.

gzIvan oe~c~ “ne Verification of Conventional -SL~ts, “ in New Technologies for Secun”ty and Arms Control, Eric H. Arnett, ed.

(Washington, DC: American Association for the Advancement of Science, 1989), p. 192.
Chapter 6--BroadArea Searches for Arms Control Treaty Violations .87

more than one would help clinch the case. Thus

searchers who find a target might do well to modify

their search plan and look for more targets in the

same region.

Previous Searches

In a search for a stationary target, e.g., a clandestine factory, the results of all searches can be

considered simultaneously, amounting to one big

search. In dealing with mobile targets, e.g., mobile

missile launchers, one must keep in mind the

possibility that a target has moved to the site of an

earlier picture, so that it can evade detection even

after the entire region has been photographed.

Studies addressing the search for mobile, or

‘‘relocatable,’ ’33 surveillance targets, e.g., mobile

missile launchers, often contain assumptions about

such targets’ movement habits based upon current

practice. Because these habits may be as much a

matter of policy as of necessity, they could perhaps

be changed—say, by making movement more frequent—if necessary to elude detection by a newly

deployed surveillance asset or a newly introduced

program of aerial monitoring. (See also box 6-J.)

Other Sources of Prior Information

Other sources of prior information include analysts’ assessment of what developments to expect,

previous sightings of the same item, and the fruits of

other intelligence collection means.

Unaided by previous sightings or collection by

other means, an intelligence collection effort can be

aided by an awareness of the operations of one’s own

side’s forces. For example, the British discovery of

a German V-2 intermediate-range ballistic missile at

Blizna (see app. B for an account of this) may have

been aided by the analyst’s having seen a V-2 before,

in a picture of Peenemunde. Similarly, the initial

Allied discovery (also described in app. B) of the

German V-1 ground-launched cruise missile was

owed partially to the photointerpreter’s having been

briefed on the possibility of pilotless aircraft and the

ramps needed to launch them: these cues were the

result of other means of intelligence collection.

Radio direction-finding can contribute strongly to

the a priori information available to searchers. Most

Box 6-J--Mobile Targets

In looking for a fixed facility such as a factory,

one can at least count on the fact that that the target

will not move between searches. Searches for

mobile targets, such as Soviet SS-25 ICBMs, are

complicated by the fact that the target might move

during the search. In an aerial monitoring search, in

which the target country is examined in installments, even cumbersome “relocatable” targets

might move between installments of the search. The

contrast between searching for mobile targets and

immobile ones bears some resemblance to the

contrast between sampling with replacement and

sampling without replacement in, for example, a

reentry vehicle on-site inspection (RVOSI) context.

In calculating the probability of finding a target

(assuming some known target density], the case of

mobile targets can be handled by the confetti-search

formalism described above. In what might be called

“the (mathematically) ideal worst case,” in which

the targets are constantly moving about and the fact

that a target has not been seen at a particular place

has absolutely no bearing on whether or not there

might be a target there the next instant, the expected

number of targets found is

total X(1 - e

-effort/area ).

(see box 6-G) instead of

total x (effort/area)

The probability of finding at least one target is

still

1- ~-totd X efforttarea

as in the case of randomly located stationary targets.

observers believe that an aerial monitoring agreement will not include collection of electronic

intelligence by the flights themselves, but the

planners of the flights could capitalize on electronic

intelligence obtained by other sources.

Other sources of intelligence could also be of

great use to planners of aerial monitoring searches.

The search effectiveness of U-boat skippers prowling the Atlantic during the Second World War, for

example, was doubled when they had access to radio

intercepts revealing the intended routes of Allied

convoys.

34

ss~e term connotes sometig less than full mobility; usually the inability to opemte on the move, and perhaps even the ne~ to spend setip time

between cessation of movement and onset of operations, and teardown time between cessation of operations and onset of movement.

‘Operations Evaluation Group Report No. 533, available from the Center for Naval Analyses, Alexandria, VA.
88. Verification Technologies: Cooperative Aerial Surveillance

The Problem of Misleading Prior

Information

Prior information, or simply predisposition, can

reduce the probability of detection as well as raise it.

R.V. Jones recounts that the “ski” or “catapult”

V-1 launchers at Peenemunde (on one of which

Flight Officer Constance Babington-Smith was later

to discover the V-1 itself):

were, for example, interpreted as “sludge pumps,”

a theory perhaps coloured by the interpreter’s

previous experience as an engineer with a river

Catchment Board after his Cambridge Ph.D. thesis

on classical hydraulic engineering[.]35

Jones does not mention that a long-term landreclamation project going on at Peenemunde was

another source of confounding false clues as to the

true nature of the launchers. (See also app. A.)

In the case of the V-2, search for launching sites

in France was originally planned on the basis of an

assumption that launchers would be sited close to

rail lines.36 Only later was a V-2 recognized in a

photograph of Peenemunde on what would today be

called a TEL, disassociated from any rail line,

leading to the realization that the search for rocket

launchers near rail lines-and indeed the search for

freed rocket launchers at all-was fundamentally

misconceived.

Prior Information and the Assumption

of Rationality

Most of what we have called ‘prior information’

regarding the placement of rocket launchers and so

on contains, to greater or lesser degree, reasoning as

well as facts. Much of this reasoning concerns what

the other side would or would not do, typically based

on an assumption that they are reasonable people.

For example, advocates of the INF Treaty-while

admitting that illicit SS-20s would be very difficult

to detect--discounted fears that the Soviets would

hide illicit SS-20s in SS-25 canisters on the grounds

that doing so would simultaneously deprive the

Soviets of the military benefits of having a missile

that could reach the United States and the political

benefits of having a missile demonstrably targeted at

Europe:

If they wanted to cheat on the INF Treaty, I would

give them a little more credit than taking an SS-20

and putting it in an SS-25 canister. . . . The problem

is, you would have to ask why they would do it. The

purpose of the SS-20, in my opinion, was to provide

a political threat to Europe. An SS-20 which is

covert, hidden, or an SS-20 which is in an SS-25

canister would not represent that political threat.37

Some may question any such argument based on

perceived lack of Soviet incentives or lack thereof.

It is true that such reasoning can sometimes lead the

analyst astray, but the error so induced is rarely

larger than the penalty paid by the other side for its

failure to act rationally.

For example, the British detection of the V-2 was

considerably retarded by the belief that a militarily

effective ballistic missile of sufficient range was

either impossible to build or ludicrously uneconomical. In particular, once the V-1 program was

understood, those who believed in the existence of

a V-2 program had to weather the argument that the

Germans would not go to the trouble of building a

ballistic missile simply to deliver the same size

warhead as was carried by their V-1 cruise missile.

As it turned out, the V-2 missile did in fact deliver

a warhead only slightly larger than that of the V-1,

and with much greater trouble and expense. Those in

Britain who doubted the existence of the V-2

program on the grounds that Germany would have

no incentive to build two weapons for one mission

neglected the considerations of improved penetration, interservice equity,38 and technological romanticism39 that compelled the German authorities to

allow the Wehrmacht and Luftwaffe each to develop

its own system.40

Though the British were surprised by the V-2

project, they were not dismayed: they were correct in

their belief that the weapon would be a grossly

35R.V. Jones, Most Secret War (hndou England: I-hmish-ton,1979), P. 433.

~Cons~ceBabir@on-Smi@ Air Spy (New York, NY: Harper and Brothers, 1957), P. 215.

svTes~ony of~jor ~ner~ wi~m F, B-, ‘The INF Tre@, he-s ~fore the co~ttee on Forei~ Relations, U.S. Semte, Pti 5, looth”

Cong., 2d. sess., p. 89.

~~ou@th.is motivation was anticipated by some in Britain. (Jones, op. cit., footnote 35, PP. 456-457.)

3~id., pp. 573.575; and h4ichael J. Neufeld> ‘‘Weimar Culture and Futuristic Technology: The Rocketry and Spaceflight Fad in Germany,

1923- 1933,” Technology and Culture, vol. 31, No. 4, October 1990, especially the concluding paragraph.

@See *O David II-@, The Mare’s Nest (hmdo~ England: WilliiWI Kimber & CO. Ltd., 1964).
Chapter 6--Broad Area Searches for Arms Control Treaty Violations ● 89

inefficient use of German resources and erred only

in believing that the Germans would abandon the

project accordingly. The German war effort needlessly bore the burden of ballistic missile production, with each V-2 representing a debit to the

Germans of many V-IS’ worth of resources and thus

a saving to the British of many V-is’ worth of

damage. Analogously, advocates of the idea that the

Soviets would not place SS-20s in SS-25 canisters

might well (and in some cases do) take the attitude

that “if the Soviets did that, they are sort of playing

into our hands. ”41

The assumption of rationality is simply an instance of the usual worst-case planning: the worst

case is that the other side behaves rationally and in

one’s own worst interest. This standard is sometimes

equated to the more dangerous ‘‘mirror-imaging”

assumption that the other side behaves rationally and

in what we see as its own best interest, which may

not be the same thing.42 For example, U.S. analysts’

consistent underprediction of the growth of the

Soviet ICBM force in the 1960s has been ascribed to

mirror-imaged imputations of the costs and benefits

to the Soviets of building ICBMS.

43 Interestingly, it

has been pointed out that mirror-imaging would

have correctly predicted the growth of the Soviet

ICBM force if the U.S. civilian analysts had imputed

to Soviet military planners the mindset of their

uniformed U.S. counterparts, not that of U.S. civilian analysts.44

One could undertake a program of aerial monitoring without any recourse whatsoever to assumptions

about the other side’s rationality. Searches in such a

program would be scoped only by the physical

constraints under which the other side operated:

aircraft would not search for ships in the middle of

deserts or for missile silos in quicksand. However,

the need to search for silos in the desert and ships in

the quicksand would deprive the searching side of

any means by which to cut down on the raw area it

needed to search. A better aerial monitoring program

would impute rationality to the other side, but also

hew to the assumption that the other side was—

rationally-pursuing the most damaging possible

course of action.

Searches in such a program would respect physical constraints and, to some degree, fiscal ones as

well; searches for isotope separation plants, for

example, would be concentrated in regions plentifully supplied with hydroelectric power plants. The

“if they want to, let them” principle would be

observed: occasional searches of inappropriate or

unlikely terrain would be performed, but the principal search effort would be allocated to the regions

most likely to contain the objects of the search. The

theoretical ideal would be to create a situation in

which the costs of committing a violation—

including the difficult-to-quantify cost of being

caught—were equalized over all locations in the

other side’s territory.45 Any other allocation Of

search effort would create favorable locations for

cheating and thus allow it at too low a cost.

41T~timony of Major General William F. Burns, op. cit., footnote 37, p. 90.

dz~e PMmse of dete~nce deserves mention because of its importance in U.S. planning. To be deterred may be in the adversary’s best ~ter~4

but for him or her to fail to be deterred is in one’s own worst interest. As in the case of Pearl Harbor, the would-be deterrers’ eventual victory does not

assuage the dismay they feel when the target of their deterrence fails to see the light and executes a worst-case attack.

dswa.lter Laquew, A World of Secrets: The Uses andLim”ts of Intelligence (New York NY: Basic BOOICS, 1985), PP. 190-194.

44BmceD. Berkowi&andfinE.~qs~~~tegiC]~teZ/ige~CefO~Am~”cu~Nutio~aZsecU~i~ (Princeto~NJ: princetonUniversity press, 1989),

pp. 91-93. Such insights can be exploited on the tactical level as well. During the Cuban Missile Crisis, when aerial photography revealed that “the

Russians and Cubans had inexplicably lin~ Up their aircraft wing tip to wing tip on Cuban airfields, making them perfect targets, [President John F.

Kennedy] requested General [Maxwell] Taylor to bave a U-2 fly a photographic mission over our fields in Florida. ‘It would be interesting if we have

done the same thing,’ he remarked. We had. He examin ed the pictures the next day and ordered the Air Force to disperse our planes.” (Robert Kennedy,

op. cit., footnote 23, pp. 37-38.)

4fMIdMy,the air search effort for U-boats in the Second World War was apportioned overnight and day so as to make @acing ~~Y -do~

at all times. See Brian McCue, U-Boats in the Bay of Biscay (Washington, DC: National Defense University Press and the U.S. Government Printing

office, 1990).

292-900 - 91 - 4
APPENDIXES
Appendix A

MONITORING NONZERO LIMITS

In chapter 6, our discussion addressed the monitoring

of limits on banned systems, e.g., the SS-20.1 In verifying

compliance with a ban, one can follow the line of

reasoning made familiar in discussions of the Intermediate Range Nuclear Forces (INF) Treaty, that ‘‘the

detection of a single SS-20, and not even the missile, just

the launcher or a single-bay garage that was supposed to

have been eliminated by the treaty, would be a violation

of the treaty. ”2 Other treaty limitations allow certain

systems, but restrict their numbers. Such nonzero limits

are much harder to monitor through aerial surveillance

than are the total bans addressed so far in this report. Not

only is the ‘‘If we see even one, then it’s a violation”

dictum inapplicable, but even the more sophisticated

notion of extrapolation from a sample is likely to fail.

Reporting of the results of public opinion polls has

accustomed Americans to the power of extrapolation

from polling of a manageably small sample to deductions

about large populations. Some pollsters state their sample

size and provide an estimate of the accuracy of the result:

a common protocol polls about 1,600 Americans and

returns what is describedasa‘‘3-percent margin of error’

and a‘ ‘95-percent confidence level. The Gallup organization, for example, describes these parameters as reflecting a 19-to-l chance that the response of the entire

American population, if taken, would not have differed

from the response of the 1,600 Americans by more than

three parts in one hundred.3 One may reasonably wonder

whether aerial monitoring could hold out the hope of

providing similarly accurate data on treaty-limited (but

not banned) items on the basis of the modest sample size

available from a single flight. In general, the answer is that

it cannot.

Such an extrapolation scheme would use an aerial

monitoring flight to examine part of the region in which

Treaty-Limited Items (TLIs) were deployed! TLIs in this

region would be counted during the flight and then a

“population estimate” for the whole region would be

made on the basis of proportionality: if 10 percent of the

deployment region had been inspected, the enumerated

TLIs would be construed as 10 percent of the total, leading

to an estimate for the total. The flaw of this scheme is that

it assumes an even distribution of TLIs,5 whereas there is

no reason to think that such an assumption would be true,

and several reasons to think that it would be false.

Communications and logistical arrangements, for example, might well be eased by the operation of mobile

missiles in groups. More subtly, the missiles’ effectiveness as a deterrent would be enhanced by bunching them

up and thus linking their fates: the plainer of a barrage or

reconnaissance-strike attack would then have to contend

with the possibility that all of the targets would survive.7

Thus bunching has to be considered likely, weakening the

aerial observer’s ability to estimate the total number of

deployed TLIs based upon the number observed in some

part of the deployment region. Finally, the other side

might take deliberate steps to make sure that the sample

population was-in one or more respects--simply not

representative of the whole. A clever treaty violator could

slant the results of inspections, allowing enough TLIs to

be seen that the inspecting side would conclude that a

plausibly large, but treaty-compliant, force had been

fielded when in fact the true force was far larger than

allowed by the treaty. In public-opinion polling, there is

no “other side” to take such steps.8

In a similar vein, some have suggested that treaty

veri.tiers borrow the statistical methods used by industrial

“quality assurance” specialists. These methods also offer

little hope in the case of monitoring treaty compliance,

because they address the question of how to feed back

information gained from product inspections into the

manufacturing process, so as to reduce the number of

defects produced. These methods are inapplicable in arms

control treaty monitoring, because one side does the

l~e SS.20 is banned under IN?.

Z1’’hepointw~mde in this instance by Major General WilliamF. Burns, TheZNF TreaO, hdgs before the Semte Committee on ForeignRelations,

U.S. Semte, looth Cong., 2d sess., Part 5, p. 88.

sG~up on-tie Saiu.~s description would see a ~~si~ s~tistici~ ~ ~c~in ~th~tic~rigor because it mmes CIOSe to ~SigTliIlg a

probability to something which is in fact either true or false: the proposition that the response of the population as a whole is within 3 percent of that

of the sample.

dsome trea&mWements wo~d facfi~te Such monitoring by creating prescribed deployment mgiOIIS fOr, my, tid-mobile fitercontinen~~~tic

missiles (ICBMS).

5A5 the po~sterg caution US, sampling error is only one source of error in the fidesdmilte.

GA logic~ mission for a mobfle ICBM, with its heavy investment in survivability.

7~s possibi~~~eml~ from theme ~ which he ~ppm to Ovtilwk the one subregion tit con~ed ~en~e fom~wo~d loom l~er ill

the attacker’s mind than the contrary case, in which all of the targets are found and destroyed.

8~ou@ some Pollsttis ~ve exp~~the dismepanq ~Wwn theirrw~ts ~dtho~ on Election Day by ~~eg~ relucwceon the p~of voters

to admit that they intend to vote for especially controversial candi&tes.

–93 –
94 ● Verification Technologies: cooperative Aerial surveillance

allowed number exist even though

can be seen at once.

monitoring and the other side does the

violation).9

not all

compliance (or

Tags

The use of tags (nontransferrable, nonduplicable identifying markers--analogous to automobile parking stickers--

issued by the inspecting side to the owning side) has been

proposed to facilitate monitoring. Tags might be made

readable from aerial monitoring aircraft.10 A tagging

scheme would avoid difficulties posed by potential

bunching of TLIs because it would not rely on statistical

sampling: enough tags are handed out to account for the

allowed number of TLIs, and any TLI found without a tag

is presumed to be a violation of the treaty.

Even in the absence of a detected violation, however,

statistical analysis of the tags found on the legitimate TLIs

could enhance the tags’ utility as a verification device.

One such procedure,ll conceptually similar to the capturerelease-capture protocol used to estimate bird populations, would consider two successive “takes” of tag

numbers as samples of the larger population. Those TLIs

seen in the first “take” are considered to be “banded.”

Assuming that the chance of a TLI being seen in the

second “take” is not increased or decreased by the

inclusion of the TLI in the first “take,” the proportion of

“banded” TLIs in the second “take” ought to be equal

to their proportion of the population as a whole. For

example, if the first ‘take’ identified 30 TLIs, 2 of which

appeared in a second “take” of 20 TLIs, one would

conclude that the 30 TLIs represented 10 percent of the

total population, yielding an estimate of 300 for the total.

If this total is less than the allowed total, then (assuming

that the other side has not voluntarily sacrificed some

TLIs) the estimated “total population” is not the true total

population but only the total subpopulation of which these

observations have been made. In this case, the aerial

monitoring needs to be expanded because its scope does

not even cover all the legitimate TLIs. A total greater than

the allowed total would indicate that, for some reason,

TLIs seen in the first take were less likely than others to

be seen in the second “take”; this finding would suggest

that TLIs are being rotated through the region subjected

to aerial monitoring, an ominous prospect.

With the possible exception of flights examining TLIs

restricted to designated deployment areas, a single aerial

monitoring flight is unlikely to see enough TLIs for the

“banding” approach to be used. A generalization of the

above method, however, could deal with the very small

takes-perhaps of only one TLI even on a “good

day’ ’-expected under some aerial monitoring regimes.

Under this generalization, each sighting of a TLI would be

logged and periodically-perhaps annually-the sightings would be totaled so as to create a listing of those TLIs

seen once, those seen twice, those seen three times, and so

on.

One would hardly expect sightings to be absolutely

evenly distributed among TLIs. Through chance alone,

some will be seen more than others. The Poisson

distribution tells us how much “clumsiness” to expect in

the repeat sightings. Fitting the observations to a Poisson

distribution would reveal any departure from the expectation that the tendency of a TLI to be sighted is unrelated

to its previous history of sightings. If the data failed to

conform to a Poisson distribution because of an unduly

small proportion of repeat sightings, one would have

reason to suspect “hot-bunking,’ ’12 or some other form of

rotating TLIs through the region subjected to aerial

monitoring. If, on the other hand, the data departed from

a Poisson distribution by virtue of an overly large

propensity of TLIs to be sighted repeatedly, then one

9AS a saying now favored by quality assurance specialists holds, “Quality cannot be ‘-tedin.’ “ The import of this saying is that inspection

canordy hope to fiiter out rejects, and cannot be used as a means of actually adding quality. Quality can only be added by manufacturers, not inspectors.

Similarly, tzeatycompliance cannot be ‘inspected in.’ Moreover, the producers and the inspectors are, in the case of treaty compliance, on different sides.

Such a contrast between acceptance testing and treaty monitoring was drawn by Patricia M. kvis in “VerMcationof Conventional Forces in Europe,”

IEEE Technology and Society Magazine, December 1990/January 1991, p. 11.

l~gs we briefly discussed h C)wvs ~clmsfled Verification Technologies: Measures for Monitoring Compliance with the ~~

Treaty4wnmary, OTA-ISC-479 (Washington, DC: U.S. Government Printing Oftice, December 1990).

llfiopo~ by Stephen Davis ~ ‘$Vefilcation ~d compfi~ce for ~con~o~” comparative strategy, VO1. 9, No. 4, 1990; pp. 44)3-413.

WII this method of chea~, an operating base supports excess TLIs by keeping some in tie field at all times.
would suspect that the inspection process was somehow

being manipulated so that the same TLIs, once seen, were

presented over and over.

If the numbers of TLIs seen five, four, three, two, and

one times each seem consistent with a Poisson distribution, one would be justified in extrapolating to a number

seen zero times, and thus to an estimate of the total

population size. The Poisson-based approach is particularly attractive because of this self-checking feature, by

which the applicability of the imputed Poisson distribution can be checked in the cases of repeated sightings

before it is used to estimate the number of TLIs never

sighted.

Appendix A—Monitoring Nonzero Limits .95

Additionally, the Poisson system does not rely on any

knowledge of how many tags have been given out.13 For

this reason, as well as the self-checking feature, it is

promising as a means of interpreting sightings of “buddy

tags.’ ‘ Buddy tags, analogous to automobile license

plates, uniquely identify the TLIs with which they are

associated, yet (in some schemes) forego the elaborate

precautions against duplication and transfer that complicate many conventional tagging schemes. Unlike these

more technologically ambitious tags, buddy tags could

easily be made large enough that they could be read from

an airplane.

lsFor this r~o~ it wo~d be well suited to use in con@nction with intn”nsic tags (innate identifying cticteristics Of individual Tf-h--@OgOUS

to fmgerprinttiatalogued by the inspecting side). These hold out the promise of great security from illicit transfer or duplication. However, most

proposed intrinsic tags, e.g. the marks left on the TLI by the tools used to make i~ require such close examina tion of the TLI as to preclude the aerial

reading of the tags.
Appendix B

PHOTOINTERPRETATION AND IMAGE PROCESSING

Summary

Collection of images is only the beginning of aerial

surveillance. They must be processed and interpreted to

make the information they contain available as a basis for

action or decision. Camouflage, concealment, and deception methods can be effective, but do not always defeat the

photointerpretation and image processing steps. Image

processing, the enhancement of pictures through filtering, pattern recognition, and contrast enhancement, seems

amenable to various forms of automation. Automation

can also assist in photointerpretation, but true automation

of photointerpretation may lie far in the future.

Introduction

Interpretation of aerial photography requires that

skilled analysts devote considerable time to each picture,

using optical equipment of various kinds and a comprehensive knowledge of sought-for targets and their tell-tale

traces, or “signatures.” Photointerpretation is the art of

eliciting information from photographs. Image processing, now largely done by computers, is the refinement of

Photo credit: Department of Defense

Despite some degree of automation, the photointerpreter’s

task remains largely one of skill, patience, and memory.

pictures so as to make them more amenable to photointerpretation. Photointerpretation and image processing each

benefit from the repeated collection of imagery overtime.

Detailed analysis and reporting might well consume a

person-hour per picture, or roughly a person-week of

work to exploit fully the data taken in a single aerial

monitoring sortie. Estimation of the time needed to

process aerial photography is in some sense impossible

because a photointerpreter’s work is never done.l There

is always some chance that extra time spent can result in

extra information gleaned, perhaps crucial information

not discerned initially: some photographs will have been

set aside as unpromising, and even promising ones may

not receive full exploitation. For example, British photography of the German missile test facility at Blizna

(Poland) captured a V-2 intermediate-range ballistic

missile; but the missile’s image passed unnoticed through

the entire image interpretation process, only to be

discovered months later by a government scientist untrained in image interpretation but willing to go over the

photographs “millimeter by millimeter for many minutes .

Examples of Photointerpretation

During the Second World War, British photointerpreters examined imagery of the German test site at

Peenemunde for signs of new rocket and jet weapons

under development there. Constance Babington-Smith’s

account of how she found the V-1 ground-launched cruise

missile merits quotation at length not only for the insights

it gives into the photointerpreter’s use of all the information at her disposal, but for the attitude with which she

approached her task.

I decided to follow the dead-straight road which led

northward along the eastern boundary of the airfield

toward the Baltic shore. I passed the limits of the airfield

and went on toward the extreme edge of the island. To the

right lay an untouched stretch of marshy foreland, but on

the left there was a great deal going on-the long-term

project of land reclamation for extending the airfield . . . .

Right at the edge of the road there was something I did not

understand--unlike anything I had seen before . . . .

Rumors of “launching rails” for secret weapons had

reached me earlier; and ever since I had been briefed about

pilotless aircraft I had been on the lookout for a catapult of

lnmretic~r~m, as well as experimental results, suggest that the cumulative probability of finding a target in a ViSU~ Semdhe.g of a photograp&

depends upon the time devoted according to the function

p = 1- e-k,

where the constant k embodies the diftlculty posed by the search because of the size of the target the size of the seamh are% the contrast between the

target and the backgroun~ and soon. The asymptotic approach of p to unity suggests that the interpreter’s work is never done. See also Koop~ Search

and Screening (Pergamom 1980) especially app. E.

~.V. Jones, Most Secret War (ImndomHanush“ liami.lto~ 1978), p. 550. Jones had earlier been the fmt to fmd aV-2 image anywhere, in a picture

of the test facility at Peenemiinde (Germany) which had also undergone previous interpretation to no avail. (Jones, pp. 433-434.)

– 9 6
Appendix B--Photointerpretation and lmage Processing .97

Photo credit: National Air and Space Museum, Smithsonian Institution

British reconnaissance photo of Peenemunde, site of

German World War II rocketry research. The arrow

indicates a V-2 missile lying on its side. Professor

R.V. Jones discovered the V-2 missile in a

photograph suoh as this.

some kind. I pondered over the photographs and reviewed

what I had found. There were four of these strange

structures. Three of them looked very much like the sort of

crane that have a box for the operator and along movable

arm. But the fourth seemed different, and it was the one

that drew my attention most. It was evidently a sort of ramp

banked up with earth-you could tell that from the

shadow-supporting a rail that inclined upward towards

the water’s edge. “I’d better check with the Industry

interpreters,” was my first thought. “They probably know

all about these things already. So I took the prints along to

the Industry Section, and was told that these “things had

been looked at long ago, and interpreted as something to

do with the dredging equipment. Back at my desk, I gazed

at the photographs again. . . . [On this basis, Flight Officer

Babington-Smith asked to see a newer set of Peenemunde

photographs.] Only the first print of the run showed it, so

there was no stereo pair. The quality of the photographs

was poor, but even with the naked eye I could see that on

the ramp was something that had not been there before. A

tiny cruciform shape, set exactly on the lower end of the

inclined rails-a midget aircraft actually in position for

launching. 3

The following extract from R.V. Jones’s Most Secret

War recounts Dr. Jones’s 1944 discovery of German V-2

intermediate-range ballistic missiles at a test facility in

Poland. These missiles, not yet used in action, had

previously been seen only at the Peenemunde test site in

Germany. The account illustrates several features of aerial

search for such weapons:

1.

2.

3.

4.

the importance of cuing by other intelligence

sources, in this case signals intelligence;

the way infrastructure points to weapon presence;

the way preconceptions based on the way one’s own

side operates, or would operate, color one’s interpretation of photographic evidence; and

the enhanced recognition ability conferred by previous sightings of the same target.

Jones wrote:

Something very odd had been taking place in Poland

because Blizna4 was from time to time dispatching what

were called Gerate (apparatuses) back to Peenemunde.

What could these be? I could understand things being sent

from Peenemunde to Blizna for trial, but what would be

worth sending back? I began to wonder whether these

might be items such as rocket jets that had been tested, but

there was no clue in the Ultra messages5 regarding their

nature. Certainly there were plenty of them, to judge by the

numbers by which they were identified. The first number

that I had was 17,053, about which I had learnt on 17 June,

and by early July the highest number I had heard of was

17,667. How could I prove that these were rocket

components? If only we had complete photographic cover

of the Blizna area we could have found the launching site

or the test rig, and perhaps found a rocket there; but even

though I had requested further cover more than a month

before, fresh photographs had not yet been obtained.

As I pondered, I tried to put myself in the position of the

Germans working in unfriendly territory, and began to

wonder whether--even with the rivalry between the

German Army and the Luftwaffe-I would have used two

sites, each of which would have to be defended, when there

should be enough room at a single site to launch both flying

bombs and rockets. I therefore took out again the 5th May

photographs of the flying bomb compound, even though I

knew these had been exhaustively searched at Medmenham. Going over them millimetre by millimetre for many

minutes, I suddenly realized that a familiar outline had

“clicked” into place with the memory of one that I had

seen before---on the photograph of Peenemunde on which

I had first found the rocket . . . .

But the account was not yet complete, because there was

no sign of any launching apparatus. Our experts had

assumed that the rocket would need to be fired from some

sort of a gun at a speed of 100 metres per second to make

it stable in its initial flight, and there was a large tower

erection at Peenemunde which had been assumed to be for

this purpose; but there was no such tower at Blizna. So on

a subsequent evening I scanned the photographs again,

looking for a concrete platform; ultimately in the center of

the compound, and showing only faintly because that part

scom~ce Babington-Snlith.Air spy (hk3w York NY: Harper and Brothers, 1957), PP. 22G229.

4~ow to Jones as a test site for the V-1.

s~ese were encrypted ~~radio signals intercepted by the British and decrypted. “Ultm” denoted the close hold the British kept on the results

of this effo~ “Enigma” was the name of the encryption machine used by the Germans.
98. Verification Technologies: Cooperative Aerial Surveillance

of the photograph was so light, was a square of about 35

feet wide. With this evidence and that from Molay,6 could

it be that the rocket needed no launching equipment more

elaborate than a flat pad, and simply stood vertical, nose

uppermost? If so this would explain the 40 foot “columns’

we had sometimes seen standing at Peenemunde. The

rocket would take off by itself, stabilized by gyroscopes

and the deflectable ‘jet rudders’ we had found among the

components mentioned in the Enigma messages.7

Babington-Smith, an expert, and Jones, by all accounts

a most remarkable individual, make their work sound

easy. In fact, considerable training is required. During the

Cuban Missile Crisis, policymakers had found themselves relying on the testimony of experts despite having

the photographic evidence directly at hand of Russian

missiles being deployed in Cuba.

Photographs were shown to us. Experts arrived with

their charts and their pointers and told us that if we looked

carefully, we could see there was a missile base being

constructed in a field near San Cristobal, Cuba. I, for one,

had to take their word for it. I examined the pictures

carefully, and what I saw appeared to be no more than the

clearing of a field for a fair or the basement of a house. I

was relieved to hear later that this was the same reaction

of virtually everyone at the meeting, including President

Kennedy. Even a few days later, when more work had

taken place on the site, he remarked that it looked like a

football field.8

Change Analysis

Perhaps the most potent tool in the photointerpreter’s

hands is change analysis, the study of a target through

interpretation of its evolving appearance. When she got

the picture containing the V-1, Babington-Smith’s attention was drawn to the new missile because of its

appearance on a ramp that had been empty in the earlier

picture. Babington-Smith later cited the German failure to

“use comparative covers” (i.e., to perform change

analysis), along with their lack of stereoscopic imagery,

as the reasons that the German photointerpretation effort

“never even got to first base” despite impressive basic

optics. 9

As will be discussed below, some mechanical aids are

available to help the photointerpreter perform change

analysis.

Photo credit: CIA and the National Air and Space Museum,

Smithsonian Institution

This U-2 reconnaissance photo provides concrete

evidence of missile assembly in Cuba. The infrastructure

items shown here are missile transporters and missile

ready-tents for fueling and maintenance.

A Test Case of Photointerpretation

The end of the Second World War provided American

analysts the opportunity to measure the success of the

photoreconnaissance effort to find antiaircraft guns and

coastal artillery in the Japanese homeland.10 This experience seems especially informative from the standpoint of

a Conventional Armed Forces in Europe Treaty monitoring regime.

The study found that errors of interpretation (e.g.,

misclassification of an antiaircraft gun as a coastal

artillery gun) occurred in 12 percent or fewer of the cases.

Errors of omission occurred at an even lower rate, 5 to 10

percent, in areas where photographic coverage was

complete, but went up greatly in areas not subject to

exhaustive search. Coast defense guns, lacking the

requirement to point upwards, were in some cases

concealed to the point of invisibility to “any vertical and

most oblique photography. ’ In the case of antiaircraft

guns, “strike photography, made while the guns were in

use and camouflage removed, revealed the location of

many guns which otherwise might not have been detected. ” Also, “One case of complete concealment of a

gun revetment by construction of a movable house built

Ssuchplatfoms had just been folmd n~ the ~at~u du Molay by advancing Allied troops. Jones recognized the roads on the grounds of tie chateau

as having the same configuration as a previously unexplained set of roads on the foreshore of Peenemiinde. These had been used, he deduced, to see

whether the V-2’s launching vehicle could maneuver in the chateau’s driveway.

TJones, op. cit., footnote 2, pp. 549-551.

8Robefl F. Ke~edy, Thirteen Days (New York NY: W.W. Norton& CO., 1971), PP. 1-2.

%abington-Smith, op. cit. footnote 3, p. 259.

l~s section is bm~on u-s. Shategic Bomb~g Swey (pacfic), photographic ~telfigence section, Evacuation of Photogr@tic ]nte//igence in

the .lupanese Homeland, Part Nine: Coast and Anti-Aircraft Arti//e~ (Washingto~ DC: U.S. Government Printing OffIce, 1946).
Appendix B--Photointerpretation and lmage Processing ● 99

Photo credit: The Lockheed Corporation

Before concerns about Japanese attack led to

concealment efforts, an aerial observer would have had

little trouble finding and identifying this airplane factory.

on rails had not been detected by photographic interpreters. ” Dummy installations proved very difficult to

discriminate from the real thing.

To interpret these results in terms of the lateral range

curve paradigm of box 6-B, we ought to keep the 4-mile

width and the steep shoulders, but lessen the height of the

plateau in recognition of the fact that some targets within

the picture will go unnoticed. It is difficult to estimate

how far the plateau should be lowered: if we felt that

targets in the picture (and thus in a region of complete

coverage as cited in the preceding paragraph) have a

20-percent chance of being misclassified or of remaining

undetected altogether during a normal amount of photointerpretation, we would lower the top of the curve to the 0.8

level, resulting in a sweep width of 3.2 miles.ll

Camouflage, Concealment, and Deception

Attempts to frustrate aerial search are almost as old as

aerial search itself-very old indeed if one counts ground

animals’ natural adaptations to avoid predatory birds.

Targets can be camouflaged (made to appear part of the

terrain), or concealed (merely hidden from view). Targets

can also be left out in the open but made, through

deception, to appear to be something that they are not.

Photo credit: The Lockhead Corporation

Painted buildings and sheets of painted fabric supported

by telephone poles make the plant blend in with the

surrounding suburbia. A careful photointerpreter might

nevertheless see such telltale clues as the road to

nowhere (arrow) and the airplane in somebody’s yard

(foreground).

The Second World War provides numerous instances

of imaginative and effective uses of concealment and

camouflage. The Lockheed Corporation, for example,

provided elaborate camouflage for its Burbank plant,

making the buildings appear to be rolling hills in suburbia.

Technically, some element of deception was also used, in

that artifacts such as houses and roads were included in

the camouflage. (See photographs.) Note the use of

rooftops painted on the runway and houses painted on the

corners of the large hangar in the foreground. Close

examination of the camouflaged plant shows certain

flaws, such as a road leading to nowhere (arrow) and

incongruous airplanes scattered in the left foreground of

the picture. Though one need not be a highly trained

analyst to identify the false buildings by their lack of

shadows, the disguise might have been sufficient to

confuse a bombardier.

Soviet military thinkers have placed great emphasis on

the techniques of camouflage, concealment, and deception known collectively as maskirovka in Soviet military

parlance. 12 The photo shows wartime efforts to disguise

the Kremlin by painting rooftops on the telltale expanses

of Red Square and the interior of the Kremlin. Again, the

false buildings’ lack of shadows gives them away in the

picture (compare, for example, the Lenin Mausoleum—

11Because if we see 80 percent of the targets in a 4-mile-wide swath, we are seeing as many as we would see if we saw 100 percent of the targets in

a 3.2- mile-wide swath. The 20 percent figure agrees from the combination of the 12 percent misclassification and 5 to 10 percent omission rates cited

in the previous paragraph but cannot be strictly derived from the Second World War experience; aerial search flights would hardly have the advantages

cited for strike photography flights, but would be able to penetrate some kinds of camouflage with infrared photography.

12See Camouflage: A Soviet View, Soviet Military Thought, No. 22, translated and published under the auspices of the U.S. Air Force (Washington,

DC: U.S. Government Printing Office, 1989). This is the U.S. Air Force translationof Victor Antonovich Matsrdenko’s Operativnaia maskirovka voisk

and Maskirovka deistvii podrazdelenii sukhotputnykh voisk by Anatolii Prokofevich Belokon and Sergei Grigorivich Chermashentsev.
100. Verification Technologies: Cooperative Aerial Surveillance

Photo credit: Photograph courtesy of the Department of Defense and the

National Air and Space Museum, Smithsonian Institution

This photograph from World War II shows camouflage in

the Moscow Kremlin and the adjacent Red Square. The

Russians sought to break up the eye-catching open spaces

by filling them with dummy buildings. To the trained eye,

however, the dummy buildings are given away by their lack

of shadows. Compare, for example, the Lenin Mausoleum

(at the tip of the shadow cast by the spire of St. Basil’s

Cathedral) to the “buildings” nearby.

located at the tip of the shadow cast by St. Basil’s--to the

nearby sham buildings), but they might have helped

confuse a bombardier looking for Moscow landmarks

amid the havoc of a wartime bombing mission.

Limitations of Deliberate Concealment Measures—

Many of the most memorable instances of military

deception involve creation of the appearance of military

hardware where none is present. Examples include

dummy aircraft and tanks to fool image analysts and even

false radio traffic to deceive electronic eavesdroppers.13

Only in the most special of circumstances, however,

would introduction of dummy TLIs make sense as a

treaty-evasion ploy. One possibility would be the deliberate attempt to make the other side use up a quota of

inspections wastefully. Such a ploy would run the risk of

violating treaty language regarding interference with

verification, or at the very least of showing “bad faith”

in compliance matters. Another possibility would be to set

up an apparent violation so as to be vindicated when, for

example, the seeming SS-20 transporter-erector-launchers (TELs) turn out to be tank trucks; then, after a while,

real SS-20 TELs could be deployed with confidence that

Figure B-l—Original Scene

Succeeding figures will show how this scene might appear at

various stages of image processing. For clarity, these figures

present the scene as if the sensor detected objects’ heights, not

their brightnesses.

SOURCE: Office of Technology Assessment, 1991.

no further violations would be charged.14 Still other

deception possibilities could be motivated by the desire to

test the other side’s monitoring capabilities.

The mere use of camouflage, much less the invocation

of a threatening-sounding term such as “maskirovka,”

does not guarantee success. During the Second World

War, German shipyards used carefully manufactured

pieces of camouflage to hide work on U-boats. British

photointerpreters monitored the progress of the submarines’ construction by careful observation of each new

camouflage module as it was deployed.15 Thus, detected

camouflage efforts may be worse than useless, calling

increased attention to suspect sites.

Image Processing

This section briefly illustrates a few methods of

improving images, using cartoon-like images-not actual

photographs—in which can be seen individual picture

elements (“pixels”: these are generated directly by

electro-optical devices and could be created from photographic images) and the transformations they undergo.

For clarity, these cartoons are made to look somewhat like

possible aerial monitoring targets. Inmost actual pictures,

the brightnesses of individual pixels do not correspond in

such a simple way to the heights of the objects pictured.

We will examine three sample methods of image

processing: contrast enhancement, filtering, and pattern

recognition. The first two methods address the problem of

retaining the target’s image while rejecting unwanted

impurities. The third assumes that a good image of the

target lies somewhere in the picture but needs to be found.

The original scene is pictured in figure B-1: two

submarines are pulling into dock. If digitized, the scene

might look-very simplistically-as shown in figure B-2.

131bid., pp. 96-98.

IAI’n tie s~e ve~ the British deployed masses of dummy artillery at El Mmeh: tie~, initially fooled, eventually caught o~ whereupon

the British replaced the dummies with the real thing. R.V. Jones, Rej7ecrions on Intelligence (London, England: William Heinemann Ltd., 1989), p. 123.

lsBab~gton.Sfi@ op. Cit., fodllote 3, p. 113.

16~steq from elec~c~ e~mfig,refers t. tit ~llich is r~eived but not w~ted, in ~n~adist~ction to “sign~,” tit which is received ~d

wanted.
Appendix B--Photointerpretation and lmage Processing . 101

Figure B-2—Digitized Scene Figure B-4-Enhanced Contrast Image

/ 1 I

/

Length

After digitalization, the submarines’ images have the boxy look

associated with computer graphics.

SOURCE: Office of Technology Assessment, 1991.

Figure B-3-Digitized Image With “Noise”

Em A

Length

The received image will contain not only the digitized scene

information, but also-inevitably-some electronic “noise” that

distorts the image.

SOURCE: Office of Technology Assessment, 1991.

“Noise," 16 however, inevitably intrudes and degrades the

image: the degraded image is shown in figure B-3. Any

image-processing method seeks to mitigate the effect of

noise by making the target stand out more from the

background. However, the method doesn’t “know” for

sure what is the target and what is the background. It must

therefore proceed on the basis of some a priori assumptions about what traits will characterize the target and then

Length

One way to recover some of the clarity of the original scene is to

enhance the contrast by showing only how much each cell stands

out from its neighbors. The human eye uses a similar process to

increase image clarity.

SOURCE: Office of Technology Assessment, 1991.

process the picture so as to increase the salience of those

traits. If the traits have been well-chosen, increasing their

salience will increase that of the target.

Contrast Enhancement-Contrast enhancement proceeds from the premise that the target’s brightness is

likely to differ from that of the background. On this basis,

the contrast-differences in brightness between light and

dark regions of the picture--is increased in the hope that

the targets’ outlines will become more apparent.

This method of image enhancement is performed

naturally in the human retina, in which cells respond to

light not only by emitting a neural output but by reducing

that of their neighbors.17 Such “lateral inhibition” results

in an increased perception of contrast because the

illuminated cells near a border between light and dark

regions of the image receive no inhibition from their

unilluminated neighbors on the other side of the border,

while the cells in darkness near the border have their

already-minimal output further reduced by their neighbors in the illuminated region.

Lateral inhibition can easily be implemented in software. Figure B-4 shows the image after contrast has been

increased by dimming each cell in proportion to the

brightness of its immediate neighbors and, to a lesser

extent, the brightness of its neighbors two cells away.

Notice how the images of the submarines and docks,

though still “spikey,” stand out more from the noiseinduced clutter.

16This tem from electrical engineering, refers to that which is received but not wanted, in contradistinction to “signal,” tit which is rweived and

wanted.

17R.L. ~egov, Eye a~Brain, Zd cd., (New York NY: World University LibrV (McGaw-HilI), 1973), P. 76”
102. Verification Technologies: Cooperative Aerial Surveillance

Figure B-5-Spatial Frequency Transform Figure B-6-Filtered Spatial Frequencies

Length

A more ambitious route to image clarity starts by considering the

image as a combination of waves (running lengthwise and

widthwise in the picture) and plotting the amplitudes of these

waves. The large spike in the left foreground, for example, is the

“wave” with a frequency of zero in each direction-its amplitude

is the average height of an object in the scene.

SOURCE: Office of Technology Assessment, 1991.

In a more realistic setting the targets would be more

than one pixel wide, and would thus more closely

correspond to the concept of contrast enhancement as

“edge enhancement. ”

Spatial Frequency Filtering—Another approach is to

assume that the noise. is random and thus that the noise

level in one pixel will bear no relationship to the noise

level in other pixels. Targets, however, can be assumed to

occupy more than one pixel, so that the presence of some

part of the target in a pixel makes adjacent pixels likely to

contain parts of the target as well. Furthermore, the

target’s brightness can be assumed to fluctuate less than

does the noise level. In the received image, therefore (see

figure B-3), the signal (the wanted part of what is

received) varies less than does the noise (the unwanted

part of what is received.)

Fourier transform methods and their close relatives18

allow the decomposition of signals into their component

frequencies. 19 Though most commonly used on signals

that are functions of a one-dimensional variable such as

time, these methods can be used on two-dimensional

images, producing an image in the “transform domain. ”

Figure B-5 shows the Hartley transform of figure B-3 and,

like the third picture, represents the received signal-plusnoise version of the scene showing the submarines pulling

into dock. Because, as argued above, noise is uncorrelated

from cell to cell in the original received image, the

A- Y 1A A I

Length

Whereas the submarines and the docks have some regularity to

them, the unwanted “noise” in the image varies irregularly from

cell to cell. In spatial frequency terms, it therefore has high

frequencies, lengthwise and widthwise. To eliminate it, the image

processor zeroes out the high frequency cells in the upper right of

the spatial frequency plot.

SOURCE: Office of Technology Assessment, 1991.

majority of the noise content is contained in the upper

righthand corner of the picture, whose cells represent the

amplitudes of rapidly fluctuating components. By artificially lowering these components’ amplitudes to zero, we

may hope to eliminate most of the noise. Inverse

transformation of figure B-6-the same as figure B-5, but

with the high-frequency cells zeroed out—shows (see

figure B-7) the submarines and docks clearly, albeit with

some distortion and residual noise.

Again, in a more realistic setting, the targets would be

larger compared to the pixels than they are in our example.

Therefore they would produce an even stronger lowfrequency content in the image and the spatial frequency

filtering approach would work even better than it does in

our simple example. Larger images could contain nontarget features, e.g., rolling hills, far larger than targets.

Elimination of the images’ low spatial frequency content

would filter out these features.

Pattern Recognition—A problem related to extracting

a target’s image from superimposed random “noise’ is

that of extracting a target’s image from its surroundings.

This problem arises when the imaged region is large

compared to the target, leading to the need to search

within the image.

The difficulty encountered when attempting to computerize pattern recognition is easy to understand when one

reflects on the difficulty of instructing (without recourse

Igsuch as the Bracewefl or “~ey” transform used here. This transform has two advantages in the present application: eXaCt reCiprOci9 of the @’o

domains and the exclusive use of real arithmetic.

1~ one -of tie ~fi@~ ~i@ as viewed on an oscilloscope, the Fo~er tramfo~ shows the s~e si@ as viewed on a ~oIlic a.MlyZ@X.
Appendix B--Photointerpretation and lmage Processing . 103

Figure B-7—Inverse Transform of

Filtered Transform

E

.QJ

z

Length

With its noise-dominated high- frequency components eliminated,

the transformed image is untransformed back from the frequency

domain to the original domain. The contours of the submarines

and docks are now much more clearly visible than in Figure B-3.

SOURCE: Office of Technology Assessment, 1991.

to pictorial representation) another person to recognize

unfamiliar patterns even within a limited domain. Consider, for example, the task of teaching somebody,

through words alone, to recognize and distinguish dogs

of the more than 100 different breeds covered in atypical

dog book. Automation of this process is notoriously hard;

the general problem of pattern recognition has posed great

difficulties over the years despite concerted efforts to

solve it. Successes have come only when the problem was

somehow restricted to a particular--often very small—

domain.

One area of success in pattern recognition has been the

guidance of cruise missiles. Terrain Contour Matching

(TERCOM) and Digital Scene Matching Area Correlator

(DSMAC) systems allow a missile to navigate by

comparing passing scenery to stored images. These

systems, however, deal with the recognition of whole

scenes expected along the route or in the target region, not

with the recognition of specified targets amid arbitrary

surroundings.

Two-dimensional Fourier transform methods and their

relatives can discern the presence of a target’s image amid

a clutter-filled scene by capitalizing on the fact that

although the target could be located anywhere within the

scene, its image in the transform domain will always

appear in the same place. A simple check of that region of

the transform domain will reveal whether or not the target

was present in the original image. Further subdivision and

retesting of the original image can help narrow down the

location of the target, if it is found to be present at all.

The use of a lens to accomplish the Fourier transform

simplifies the implementation of the above idea. The

transformed scenes are captured on a transparent medium,

as is the sample target image. One then shines light

through the superimposed transforms of a scene and the

sample target onto a screen; a bright blur will appear on

the screen if the target appears in the scene.20

This method suffers from significant limitations, notably that the image must be known exactly and that

although it can be detected regardless of its location

within the original scene, it cannot be detected unless it is

in the proper orientation. In practice, the latter restriction

requires that one test the transform domain for images of

the target in all orientations by rotating a test image 360

degrees. Even more problematical is that two images of

the same object will differ in far more respects than

orientation: scale, illumination, and configuration of

movable parts, e.g., turrets and guns, will all vary nom

image to image.

Change Analysis--The process of inspecting pairs of

pictures to see what has changed can be automated if those

features that remain unchanged from one picture to the

other are-or can be brought to be--superimposed.

Features that differ from one picture to the other can then

be made to stand out by a viewing device that rapidly

alternates from one picture to the other, causing discrepancies to flicker. In the case of halftone (black and white)

pictures, copies can be made in complementary colors

(e.g. one in green and white and the other in red and white)

and the copies superimposed. Unchanged features will

then appear in gray, while features that differ from one

picture to the other will appear tinted, owing to incomplete color cancellation. In the case of color originals, a

similar effect can be obtained by suppressing one of the

three primary colors in one picture and another color in

the other picture.21

Observations

The preceding discussion suggests that while automation can provide considerable assistance with image

processing (by, as we have seen, increasing contrast or

filtering out “noise“ in the picture) it has yet to make a

comparable contribution to photointerpretation as such:

the principal contributions to interpretation are really just

means of making interesting parts of the image (such as

changes) stand out. True automation of interpretation, or

even of search, lies in the future. One could say that

photointerpretation remains an art, albeit one whose

practitioners benefit from some advanced tools.

2os~ K. IizuQ Engineering Optics, 2d ed. @erh Ge~y: Springer-Verlag, 1983), pp. 288-290.

zlDi~~u~~ion ~dsome god exmplm of~t&~Weapw~ ~ Mien V. Banner, overhe~l~ging for Ve@Cu~On uti Peacekeeping (Ottit~,

Canada: Arms Control and Disarmament Division of External Affairs and International Trade Canada, 1991), pp. 15-19.
Appendix C

AERIAL SEARCH AS A BASIS FOR VERIFICATION

DECISIONMAKING

This appendix covers three major points:

1. Evidence gained from aerial search is best used to

chose between competing hypotheses, not merely to

bolster selected hypotheses. This is especially true

of negative evidence.

2. The process of arms control treaty monitoring leads

to a situation in which prior subjective judgments

and a continuous influx of evidence, much of it

negative, need to be blended into a single assessment. This need can be satisfied through the use of

Bayesian, as opposed to classical, statistics.

3. Bayesian methods allow calculation of the likely

benefit conferred by aerial monitoring, provided—

among other things-that the harm inflicted by a

violation can be expressed in the same terms, e.g,

dollars, as the rest of the calculation. Though

difficult, the assignment of a dollar cost to a

violation is sensible if we are rationally to allocate

money to forestall or detect such violations.

Discussions of unknown Soviet behavior often include

statements of the form “We have no evidence of their

doing that” on the one hand and “You have no way of

knowing everything they’re up to” on the other. Many

times, each of these statements will be true (see box C-l),

and the result a standoff. Yet it can be possible to get more

mileage out of negative evidence than is often obtained.

The trick is to use it to compare the relative likelihoods of

competing hypotheses.

When using aerial surveillance (or indeed any means)

to monitor an arms control treaty, the way to use the

information it provides is to compare the answers to two

questions: 1) “Given that the situation is as I think (or

fear) it might be, how likely would I be to see what I am

seeing?’ and 2) ‘‘If the situation were otherwise, how

likely would I be to see what I am seeing anyway?”1

Comparison of these likelihoods allows the evidence--

even if it is merely the negative evidence provided by a

flight that saw nothing-to mod@ one’s assessment of

the situation while avoiding the fallacy of “affirming the

consequent.

Box C-1—Introducing an Example

The following example will be used in the next several boxes to show various approaches to the problem of sizing an aerial

monitoring effort and interpreting its results.

Concern exists that 50 SS-20 transporter-erector-launchers (TELs) might still be somewhere in the Soviet Union.l In round

figures, the Soviet Union could have about 5 million square miles of ground accessible to off-road-capable TELs: considering

their ability to hide in woods, or to spend considerable portions of their time in shelters, the TELs might degrade the ability of

the aerial monitoring aircraft to the point that it has a l-mile effective sweep width. Given the 5-million-square-mile area a l-mile

sweep width of aerial monitoring aircraft for SS-20s, and a 1,000 mile flight path for each flight, as discussed inch. 6, each flight

has approximately a

1 x50x 1000/5,000,000 = 0.01

or 1 percent chance of detecting some SS-20 or other.2 Note that this figure is very much different from the flight’s

1 x 1 x l,ooo/5,000,000 = 0.0002

or .02 percent chance of detecting one SS-20 in particular.

l~5@~~~ilc level~b~~ ~~~ a ‘i~p~$’ &s~ld of mili~ si~lc~~ for the SS-20,s~ TheINF Trea~, heti~ before

the Committee on Foreign Relations, United States Senate, IOOth Congress, 2nd Sessiom Part 3, p. 45.

2~s ~pwo~tion is v~d o~y ~use the low demity of ~gets MOWS us to disregard the effects of mndom “ChlmpiIleSS”ill their

distribution. With ahun&ed times more targets we would not have a 100-percent chance per flight of fiiding at least one, because occasions

on which we saw one would be balanced out by occasions on which we did not see any.

- “When you hear hoofbeats, don’t think of zebras.” lphysicimme tau@t this adage for dia~osticians.

2~ this f~acy, ~so ~om as post hoc, ergo Propter hoc, the second question s~ted above is not considered. For example, the ar~ent “~ the

Russians were to launch a battleship, we would fust see them build a large hull; we see a large hull, therefore they will launch a battleship” neglects

the possibility that the large hull is being built for some other projec~ e.g., an aircraft carrier. Those who reason in this way can construe negative evidence

almost any way they want to: ‘‘If the Russians were building a nuclear airplane they would say nothing about ic they have made no mention of a nuclear

airplane, therefore they are working on one. ’

–lo4--
Appendix C—Aerial Search as a Basis for Verification Decisionmaking . 105

Box C-2—Probabilistic Approaches

The l-percent chance (see box C-1) of detecting some SS-20 or other remains unchanged from flight to flight; the

treaty-violating TLIs are mobile and can be redeployed between flights, perhaps to regions previously inspected, so that there

is no build-up of information about TLI-free regions. The sampling situation is thus one of sampling with replacement.l Each

inspection has a l-percent chance of finding some launcher or other and a complementary 99-percent chance of not doing so.

Taken together, each of a set of inspections must miss all of the targets if the whole set is to turn up no targets; their chance of

doing so is 99 percent per inspection, so

1 -(1 - .Ol~*rOfm* = chance of finding a violation.

Many violation scenarios of concern are at base breakout scenarios, so one should consider the question of detecting a force

during its installation, not afterwards as is normally done, If one assumes constant rates of inspection and violation-installation,

one can equate the problem of finding one of 50 launchers as they are installed over a year to that of finding one of 25 launchers

that are present the whole time.2 Deployments and inspections might go on at the rate of one per week, so in the 50 weeks required

to deploy the force the inspecting side will have a

1 -(1 - .O1/2)50 = 22 percent

chance of finding the violation before it is complete.

Simple probability as well as intuition suggests that if each flight has a l-percent chance of finding a violation, something

must be significant about 100 flights. The calculation that

1/0.01 = 100,

shows that, on the average, 100 flights will be needed before the first violation is seen.3

lms~adc@~m example of sampling with replacement is a situation in which one ks au urn containing utlkttownnumbers of

blue and red balls. ‘I%e problem is to determine the proportion in which the two colors are present by repeatedly drawing out a single ball,

examhdng it throwing it back k drawing another ball at random, and so on, In the present instance, considering red balls to be violations, the

question is how one’s cotildence that the urn contains no red balls increases with each blue ball examined.

2R. Scon strait of hwren~Livermore National Laboratory not only demonstrated this surprisingly simple fact but @O Poinw out is

importance in the analysis of the ubiquitous breakout scenario.

3~e pm~bility ~s~~tion underlying this statement is the “geometric distribution.”

Though often fruitful even when informally worded, decisionmakers want to know something else, namely the

the above approach can be codified mathematically using

Bayesian statistics. This appendix will show some

examples of how such calculations could be done; the

search models in ch. 6 readily provide the needed inputs.

Experimental use of Bayesian statistics at the Central

Intelligence Agency (including use in problems of

photointerpretation) led some to conclude that the method

held only limited promise.3

Asking the Right Question

Absent any detection of a violation, it is natural for

decisionmakers to want to know how the negative

evidence accrued up to any given present time affects the

probability that an undetected violation exists. The

natural tendency of analysts is to cast the answer in terms

of the probability that a particular level of violation would

have been detected if it existed (see box C- 2): high levels

of this probability are taken (given that no violation has

been found) as providing high confidence that the

particular level has not been exceeded. (See box C-3.) Yet

probability that a specified level of violation actually

exists, given the evidence collected.

The split can be seen as dividing the analysts and the

decisionmakers almost along the classical-v.-Bayesian

split in statistics itself. The analysts’ view of the problem

corresponds closely to that of the classical statistician

(who believes in a single-though unknowable--reality

and views experimental data as random samples thereof),

while the decisionmakers’ view more strongly resembles

that of a person working within the Bayesian paradigm

(who is willing to assign probabilities to various “realities” and views experimental data as fixed “givens”).

(See boxes C-4 and C-4a) 4

A flaw present (though not unavoidable even under the

classical paradigm) in many attempts to quantify matters

of verification arises from shifting assumptions about the

size of a violation. The classical analysis prevalent in the

verification literature scales the monitoring effort on the

basis that a violation will consist of a militarily significant

3sm wdta ~eu, A world Of Secrers (New York, NY: Basic Books, 1985): pp. 299-302. Laqueur cites Richards J. Heuer, Qwntitarive

Approaches to Political Intelligence: The CIA Experience (Boulder, CO: Westview Press, 1978).

dRWated fi~ces of this son of split ~d a renew~ emp~is on what might be called a decision-analytic view of s~tistics ~ve led to a s~

increase in the teaching of Bayesian statistics, once greatly out of favor in academia.
106. Verification Technologies: Cooperative Aerial Surveillance

Box C-3—The Classicist’s Approach

The classiccal statistician is used to dealing in high (90 percent, if not 95 percent or 99 percent) confidence levels, and to

looking at data and making statements about the state of the world. The statistician will want to assess an inspection scheme by

standing in the shoes of somebody examining some large amount of inspection data after the flights have been made; the

decisionmaking question is one of interpreting-the continuing flow of reports that no treaty-violating-missile launcher has been

sighted.

Mom specifically, the classicist seeks to make a statement about the world to which he or she can assign a high probability

that it is correct. In the present case, for example, a classicist might like to be able to make the statement that “there is no

significant violation” and assign to that statement a 90-percent chance of being correct. The classicist would therefore request

that 229 flights be made and when these flights reported that no violations had been seen, the classicist would make a finding

of compliance “at the 90-percent confidence level.”l

The basis for this statement is the binomial distribution, according to which there is a 10-percent chance that 229 flights

would all miss the violation even if it were present in its smallest militarily significant form, given a l-percent chance per flight

of finding it, i.e. that

0.9 = 1 -(1 - o.ol)229

so that 229 flights would have a 90-percent chance of detecting the militarily significant violation if it were present.z Two hunched

and twenty-nine flights which find no violation are required to make the classicist “reject the null hypothesis” that a significant

violation exists+

The classicist’s statement that he or she has 90-percent confidence in the proposition “no significant violation is present”

(given 229 flights which found no violation) might lead a decisionmaker to think that there is a 10-percent chance that a significant

violation exists. We may hope that the decisionmaker would ask the classicist to elaborate upon this point. The answer would

be that the classicist feels “confidence in the statement at the 90-percent level” because the statement has at /east a 90-percent

chance of being true: it was produced by a process3 which, if applied repeatedly, would yield correct statements at least 90 percent

of the time. When no violation is present the statement will always be made and will always be right: when a violation is present

the opposite statement (a finding of noncompliance, certain to be correct because it is backed by evidence from at least one flight)

will correctly be made 90 percent of the time4 and an erroneous finding of compliance will be made 10 percent of the time. Thus

the classicist feels that he or she “bats 1,000” in nonviolation situations and “bats 900” in violation situations, and is therefore

justified in claiming to bat at least 900 (i.e., make “statements at the 90-percent confidence level”) even without knowing the

true mix of violation and non-violation situations. The classicist might also point out that his or her method will never result in

an erroneous finding of non-compliance-findings of noncompliance are only made with hard evidence in hand.

Ninety-five Percent confidence could be obtained by flying 298 flights instead of 229. The correct choice of confidence level

depends upon the perceived balance between the cost of the flights and the cost of lack of confidence.

The classicist decries the Bayesian approach as “subjective,” because, among other reasons, the Bayesian assigns a

probability to the existence of a militarily threatening treaty-violating missile force. The classicist views such an assignment as

incoherent because the force either exists or it doesn’t.

IH a vio~tion is found, the cwsicist will be able to make a f- of noncompliance at the 100-percent confidence level.

2More generally, coti~dence = 1- (1 - detection tmobability-b

This easily-derived equation pervades the verification literature, being used, ~or example, by Dunbar Imekwoed in “Verifying MART: From

Satellites to Suspect Sites,” Arms Control To&y, October 1990, p. 16.

3~~~ ~bsicistis ~o}utely opP~ t. b~teqm~tion that the 90 Peramt refers to the probability tit~meWP~tionman‘ies

within the specifkd interval . . . . A classicist is willing to genemte statements with respect to the probability that the procedure leads to the

generation of comet statements . . . .“ (Robert Parsons, Statistical Analysis: A Decision-Making Approach (New YoriG NY: Harper and Row,

1978): p, 329, emphasis in original.)

4Note that @s figure ~rresWn& to the threshold level of violation. Larger violations would have had a single-flight detection probability

of more than 1 percent and thus would have an overall chance of more than 90 percent of being noticed by the 229 flights.

number of treaty-limited items (TLIs), e.g., 50 missile finding into an assessment of the probability that a force

transporter erector launchers (TELs), and is prepared to of 50 missiles is present. In contrast, the Bayesian’s

return a verdict of ‘‘not guilty” (at, say, the 95-percent method permits such a finding; if a missile or two are

confidence level) if that effort reveals no TELs. Yet the seen, the Bayesian will of course announce a violation but

classicist—like anybody else—is prepared to return a will also continue his or her estimation efforts, updating

“guilty’ verdict if even a single illicit TEL is found. The the probabilities that 0,5, or 50 illicit launchers have been

classical paradigm precludes the direct translation of this fielded. (See box C-5.)
Appendix C—Aerial Search as a Basis for Verification Decisionmaking . 107

Box C-4-The Bayesian’s Approach

In contrast to the classicist (see box C-3), the Bayesian analyst declines to make flat statements, even at specified levels

of confidence, preferring instead to describe the number of missiles present in terms of a probability distribution. He or she views

the classicist as “concealing information”l by boiling everything down to a statement regarding the presence or absence of 50

missiles and a figure for a reliability of the process that generated the statement.2

The Bayesian addresses the aerial monitoring problem by assigning probabilities to the existence of various numbers of

treaty-violating missiles and goes so far as to insist that even before the inspections there must be some a priori or “prior”

distribution for this number. He or she then interprets the flight data in light of how likely each fight’s outcome would be given

each number of missiles. Finally, the Bayesian combines the prior probabilities with the probabilities that each flight would turn

out as it did, arriving at a “posterior” set of probabilities of the existence of the different numbers of treaty-violating missiles.

To implement this approach, the Bayesian needs a single-flight probability of violation-discovery for each number of

missiles. Continuing with our example, we will recall the 0.02-percent chance of detection per missile. The Bayesian also needs

a prior distribution of different levels of violation. Suppose, for sake of illustration, that somebody supplies a prior distribution

to the effect that there is a 5-percent chance that the Russians have a threatening 50 extra missiles, a 70-percent chance that they

have a token 5 extra missiles, and a 25-percent chance that they are not cheating at all, This prior, perhaps reflecting a belief that

the Soviets are trying to comply but have not quite tracked down all their missiles yet, is expressed by the leftmost two columns

of the table, “Missiles” and “Prior.”

Missiles Prior Seen Joint Renormalized

o 25% 100% 25% 31%

5 70%0 80% 56% 69%

50 5% 10% 1% 1%

100% 100%

Now suppose that after 229 flights (not that 229 is a particularly special number of flights for the Bayesian) no violations

have been seen. The Bayesian generates the “Seen” column by computing the likelihood of this result under each of the three

assumptions about how many missiles are actually present. The probability that no missiles would be seen under an assumption

that no violations exist is, of course, 100 percent. If 5 violations are present, there is a O.1-percent chance per flight of seeing

at least one and an 80-percent chance of seeing at least one in 229 flights. As arose in the classical case, 229 flights have a

10-percent probability of leaving 50 missiles totally unnoticed. The fourth column shows the joint probabilities of 0,5, or 50

missiles being in existence and resulting in zero sightings after 229 flights. The entries in the fourth column are the products of

the respective entries in the second and third columns because of the chain rule of probability: the probability of events A and

B occurring jointly is the probability of A multiplied by the probability of B given that A has occurred. The fourth column thus

shows, for each number of missiles, the probability that they are present multiplied by the probability that the flights would have

the result that they did (no sightings) with that number of missiles present. These probabilities do not add up to 100 percent

because there was not a 100-percent chance that the flights would see no missiles. The fifth column shows the entries of the fourth

column renormalized, (that is, the entries are divided by their sum) so as to make their total 100 percent as is required of a

probability distribution.3

Thus the Bayesian’s report on the results of 229 flights shows that the probability of 50 existing undetected launchers has

been greatly eroded by the negative evidence of the 229 flights, while the probability that 5 launchers exist undetected has only

gone down slightly, because 229 flights are not enough to prove very much about such a small force. The clean bill of health

from the 229 flights has somewhat bolstered the case that the other side is not violating the treaty at all.

IBW Ble~@~ ~~~e ~pact of Israel’s Repris~s on Behavior of the Borderi% Arab Nations Directed at Erael,” Journal Of co~i~

Resolution, vol. XVI, No. 2, June 1972, p. 169.

2He or she ~=~ the ~l~~i~ist’s ~bje~tio~ to the probabili~iti~ des~ption of a fait accompli (~beh an IUlkJlOWU WE) W a ph.ilOSOphiCZd

quibble: people buy and sell unscratched lottery tickets on the view that the tickets have some probability ofwinning, when in fact each ticket

is foreordained to either win or lose.

3 ~sstep is n~dcd ~muse we have ~n Considefig o~y ce~ possible nmrs of viola~g missiles (0, 5, and 50), not M ~ssible

numbers (O, 1,2,3 ,.. .). The fact that the original probabilities (of 0,5, and 50 missiles being present) summed to 100 percent was somewhat

artificial in the first place: the originator of such an estimate would ensure for appearances’ sake that the sum was 100 percent but would not

mean thereby to exclude the possibility of 49 missiles being present. The mathematical operations do not carry this artificiality througl$ so it

has to be reintroduced via renormalization. Additionally, the fourth eolumm being a joint probability, cannot sum to more that the marginal

probability of either of its component events (columns 2 and 3). This will always be less than 100 percent if the evidence collected provides any

information at all. Some would object to the blending of the renormalization step (required only because the prior did not consider all possible

numbers of missiles) with the division of the joint probability (column 4) by the marginal probability of the evidence. As a practical matter,

however, the two steps are done at once by the same division. The marginal probability of the evidence is the denominator, called the

“prepmterior,” in Bayes’ Rule. The fifth column is thus the posterior probability of the violation in the first column given the observed

evidenct+no violations sighted.
108. Verification Technologies: Cooperative Aerial Surveillance

The Bayesian’s report has the virtue that it answers the question the decisionmaker wants answered: “What is the

probability that the other side is violating the treaty?” The Bayesian requires, however, a prior distribution in whose light he

or she can consider the findings of the aerial monitoring flights. While the classicist might lodge an objection that the Bayesian

is relying on subjectively obtained prim information, the Bayesian can retort that the classicist’s 50-missile theshhold and

90-percent confidence level were in themselves subjectively obtained prior standards-the Bayesian approach uses no such

standards.

Moreover, the Bayesian could continue, the classicist’s standards are inconsistent. The requirement for 229 flights stemmed

from a need to determine (with 90-percent confidence) that the Soviets had not fielded a force of 50 illicit missiles. A clean bill

of health after these flights will result in a finding (at the 90-percent confidence level) that the Soviets are not in violation; the

classicist has retained faith in the 229-flight figure while rejecting the 50-TEL figure on which it was based.4

q~old~l~er~es a~o~ gen~versionof this point (paraphrasing E.T. Jaynes): “ifthe null hypothesis is rejected in anon-Bayesti

analysis, then so too is the distribution of the test statistic tbat led to the decision rule for rejection.” (“ Bayesian Inference,” Time Series and

Statistics (New Yo&, NY: W.W. Nortou 1990), p. 56.)

Box C-4a-The Effect of a Different Prior

As a practical matter, the Bayesian may have difficulty mustering a prior distribution which is acceptable to all concerned.l

With a somewhat different prior, a somewhat different set of posterior probabilities will emerge from the same flight data, Let

us examine the effect of starting with a different prior distribution, perhaps created by a different analyst:

Missiles Prior Seen Joint Renormalized

o 20%0 100% 2 0 % 32%

5 50%0 8 0 % 4 0 % 6 3 %

50 30% 10% 3% 5%

100% 100%

Again, the flights have seen no violations, but this analyst’s calculations give far more weight to the possibility that a

significant violation exists because of his or her use of a different prior. The Bayesian will point out that as more information

comes in, the importance of the prior is diluted. Indeed, the right-hand column shows that the evidence of 229 flights that sight

no transporter-erector-launchers results in almost the same set of posterior probabilities with the second prior as it did with the

fret.

The alternative prior distribution shown above is in some sense a greater expression of ignorance than the original prior,

in that it accords more nearly equal probability to the three cases. One might be tempted to evade the responsibility of creating

a prior by simply assigning equal probability to all the possibilities.

The difficulty with this scheme2 lies in listing “all the possibilities. ” One could start with zero missiles and count up, but

surely there is some upper limit to the number that the Soviets could deploy, and surely some values near that limit are less likely

than some lower ones.

Worse, even if one could list all the possibilities, it is far from clear how one should assign probabilities to them in order

to reflect an absence of preconceived notions. For example, assume that incontrovertible evidence (perhaps related to production

capacity) shows that there can be no more than 99 illegitimate missiles deployed. An analyst could then perform calculations

like those shown above, according a prior probability of 1 percent to each of the 100 possible numbers of missiles (O, 1,2,3,

.. .99) and defending this prior on the grounds that its uniformity reflects the absence of any preconceived notion as to the number

of missiles. However, the assigned l-percent probability that zero missiles have been deployed reflects a 99-percent certainty

that the Soviets are cheating in some degree, hardly an absence of preconceived notions.

In any case, to seek parsimony of assumption through the use of an ignorant prior is to underestimate the amount of

information available size of a likely treaty-violating force is bounded from above by economic considerations and from

below by military effectiveness.

1A dfilc~~ mentioned by D.V. Lindley in “Statistical hftX@nC%’ Time Series and Statistics, op. cit., box C-4, p. 291).

2Termed ~~notonom$~ by K~p~n. (B~~d OSgo~ Koopw search a~SCree~ng, (Nw York NY: pergarnon, 1980), p. 286.)
Appendix C—Aerial Search as a Basis for Verification Decisionmaking . 109

Aerial Monitoring as a Basis

for Confidence

We should think of aerial monitoring in a broader sense

than that of simply catching Soviet violations of arms

control treaties. (Box C-6 sets the stage for the coming

examples.) Aerial monitoring might extend beyond treaty

monitoring to the more general function of providing

assurance that the other side was not mobilizing for war.

Even with regard to treaty monitoring the function of

providing confidence that the treaty is not being violated

would be at least as important as the function of giving

warning that it had been.

To perform this compliance-monitoring function, however, the aerial monitoring regime must bolster confidence in a negative-the proposition that the Soviet

Union is not violating a treaty or mobilizing for war. As

experienced lawyers and debaters are well aware, to

“prove a negative” can be difficult or impossible.

Treatment of Negative Evidence

As part of the Intermediate Range Nuclear Forces (INF)

Treaty verification process, the Soviets gave the United

States a data package regarding the SS-20 intermediate

range ballistic missile. Asked if the package was accurate,

Admiral William J. Crowe responded, “We do not have

the evidence or the conviction to say that it is inaccurate.”5 This “Scotch verdict” is informative only if one

has some idea of how likely the United States would be

to possess information disconfirming the package if the

package were in fact inaccurate.

Asked about many possible scenarios, intelligence

analysts will respond, “We have no evidence of such

activity.” These analysts can hardly be faulted for

declining to speculate in the absence of evidence, but

one must exercise care in interpreting their silence

because it raises the question, “Would you have

evidence if they were actually doing it?” This question

gets very close to the Bayesian’s question, “HOW likely

would I be to see what I am seeing if the activity were

going on?”

Much of the utility of the Bayesian formulation lies in

the fact that it can incorporate negative evidence as well

as positive evidence. A flight that produces no evidence

of treaty violation is viewed by the Bayesian as supporting

the case for treaty compliance insofar as a violation, were

one to exist, might have been noticed by the flight.6 This

measured use of negative evidence differs from the naive

conclusion that “absence of evidence is evidence of

absence” and from the traditional conclusion that a lack

of evidence proves nothing either way.

Discussion of treaty monitoring begs the question of

what action would be undertaken in response to the

discovery of a violation, so such an assessment must

hinge upon the action that the United States would take

upon finding an anomaly or violation as the result of a

flight, and upon the difference in impact upon the United

States of finding an anomaly or violation sooner rather

than later.

This report will not attempt to prescribe any such

actions, but we will consider one-the deployment of

countervailing intercontinental ballistic missiles (ICBMs)

—as an example of how the costs of reacting to a violation

affect the monitoring process itself.

Harm Inflicted by Treaty Violation

It is difficult to assess, let alone quantify, the harm

inflicted by a treaty violation. (Boxes C-7 and C-8 show

two possible approaches.) Much depends upon the treaty,

and the violation, but even so one might credibly follow

any of several lines of reasoning and attach costs varying

from close to zero to close to infinity to the harm inflicted

by a given treaty violation. Why then even try to estimate

the cost imposed by an arms control treaty violation? In

particular, the idea of assigning a dollar cost to the harm

caused by deployment of treaty-violating TLIs may seem

bizarre. However, we budget treaty-monitoring resources in dollars. Therefore, we need some estimate

of what these dollars buy us in terms of harm avoided,

just as if we were instead budgeting for the construction of a retaliatory force or a system of active

defenses. 7

The Expected Value of Information

For the purposes of illustration, we will proceed with

an analysis based on the example in box C-8, of $500

million per undiscovered (and hence encountered) missile

and $200 million per discovered (and countered) missile.

Different assumptions will produce different results.

Let us compare the cost of performing the aerial

monitoring inspections v. the cost of not doing so. The

reader is again reminded that this calculation is an

5N~o ~efen~e ~~ ~~e]N~ Tre~~, H~fi~~ B~f~~~ the c~mmitt~ on ~~d se~ices, Us, senate 1~ Cong., 2d Sess., part 1, p. 121. Asked

to clarify the point regarding “conviction,” the Admiral replied “I do not believe that the evidence supports it in what we have.”

6MOE ~ss~sti~ly, a fli~ttit prMuWs no evidence of a treaty violation can be viewed as evidence that the collwtion ~uiPment isn’t working>

insofar as one thinks that violations are present, The methodology presented in this chapter could be expanded to characterize formally this updating

of a prior probability that the equipment doesn’t work. A closely relatedi.fllculty is that one might be USing the equipment to look for the wrong thing,

as may have been the case in the anti-Scud campaign of the Gulf War, in which the search for Scud TELs overlooked the more prevalent “mobile erector

launchers’ expediently produced in Iraq.

7Classi~ statistics wo~d rq~tie even more problematic~ fiputation of v~ue to c~n@fen~e in missiles not being present. while One might

reasonably think that the presence of 50 illegitimate missiles is appro ximately twice as deleterious as the presence of 25 (or the 50-percent probability

of the presence of 100), there is little intuitive apperd to the idea that the absence of 100 missiles is twice as nice as the absence of 50.
110. Verification Technologies: Cooperative Aerial Surveillance

Box C-5—The Bayesian’s Report After a Sighting

The table shows what the Bayesian would report if one transporter-erector-launcher (TEL) were sighted in the course of

229 flights, given the same prior distribution for the number of illicit launchers deployed as was used in box C-4.

Missiles Prior Seen Joint Renormalized

o 25% o% 0.00 o%

5 70% 18% 0.13 92%

50 5% 23% 0.01 8%

100% 100%

The Bayesian again generates the “Seen” column by computing the likelihood of this result under each of the three

assumptions about how many missiles are actually present. The probability that one missile would be seen under an assumption

that no violations exist is, of course, O percent: sighting a TEL would be impossible if there weren’t any,l so no Chance remains

that the Soviets have fielded no illicit TELs. If 5 were fielded, 229 flights would have an 18-percent chance of seeing exactly

one; if 50 were fielded, 229 flights would have a 23-percent chance of seeing exactly one.2 Combined with the respective prior

probabilities for the deployment of these numbers of missiles, these probabilities result in a 92-percent chance that 5 TELs are

deployed and only an 8-percent chance that a significant violation featuring 50 illicit TELs is underway.

l~ou~ ~hin~ing that one ~si@~ ~ ~~o~d not ~, A more complete a~ysis Wotid tie into account the possibility of “f&R

alarms’ in which TELs are reported where none exist.

21t my W= p=~ofic~ tit a t~old &RWfi me deployment ~UXS such a mod~t incrase in the probability of seeing eXaCtly One

TEL. The reason is that although 1 TEL is a lot to find if 5 are deployed, it is a small number to fmd if 50 are deployed-the sighting of exactly

1 TEL is in fact mild evidence against the proposition that 50 are deployed, because one would expect the searches to reveal more than 1 TEL

in that case.

Box C-6—Introducing Another Example

The following example describes our treatment of cost considerations. We will maintain our focus on a violation that would

clearly be of some harm to the United States, namely a violation of a ballistic missile launcher limit. The following assumptions,

chosen purely for simplicity and plausibility, will govern our consideration of the problem: Aerial monitoring flights detect

illegitimate missile launchers as described in box C-5: each flight exerts an effective sweep width of one mile over a 1,000 mile

path in a 5-million-square-mile-region of the Soviet Union. The actual search portion of a flight consumes 2 hours of flying time,

with another hour spent in takeoff, landing, gaining altitude, and other nonsearch portions of the flight. The flights cost $50,000

apiece all told. This estimate is based on a 6-hour Washington-Los Angeles flight breaking even at about 200 passengers paying

about $300 apiece. Flying the aerial monitoring aircraft will cost roughly $10,000 per hour for 3 hem. The other $20,000 is the

cost of the reconnaissance functions themselves, including interpretation performed afterwards. To check this estimate, we may

note other indicators of the cost per flying hour of various types of aircraft. The manufacturer of a twin-engine turboprop aircraft

cites its $2,000/hour overall expense as a compelling factor in its favor.l Aerobureau, a private firm, proposes to lease a Lockheed

Electra (the civilian equivalent of a P-3 Orion), equipped with “side-looking airborne radar, infrared and low light television

sensors,’ to TV news networks for a $250,000 6-month lease and a $2,000/day operating fee covering the aircraft and flight

crew.

2 The owner/operator of a USAAF B-29 restored to flying condition reported a $3,000/hour cost of operation with a

volunteer crew.3 A B-1 wing flying four sorties per plane per month expends $242 million in operating costs per year, suggesting

a cost per sortie of almost $100,000.4

Costs of different aerial photography systems are often usefully compared in terms of dollars per square mile.5 Assuming

that the l-mile sweep width cited above stems from a 20 percent effective photographic search of a 5-mile swath (not an

unreasonable assumption: see box 6-A), this search costs $10 per square mile.

Some number of treaty-violating launchers may be deployed. The U.S. side’s set of prior probabilities for the number of

illegitimate missiles deployed is the same as it was in box C-5.

IJohn King, “Airborne Remote Sensing for Open Skies” Open Skies (Toronto: York University Center for Intermtional and Strategic

Studies, 1990), p. 33.

2Aviation Week and Space TccbrtoIogy, AuWst 20, 1990, p. 13.

3perso~ communication.

4Testimony of General John T. Chain Jr., . Threat Assessment; Military Strategy; and Operational Requirements, hearings before the

Committee on Armed Services, U.S. Senate, Mar. 7, 1990: page 898.

5Se, for example, Arnrom H. Kz@ “Let Aircraft Make Earth-resource Surveys,’Astronautics and Aeronautics, June 1%9, reprinted

under the same title as RAND Paper P-3753, available from The RAND Corp., Santa Monica, CA. Katz’s costs per square mile are considerably

lower than than the figure presented here not only because of the greater value of the dollar in 1969 but also because of the less-demanding

resolution requirements of the earth-resource survey mission.

———..
Appendix C—Aerial Search as a Basis for Verification Decisionmaking . 111

Box C-7—Harm Inflicted by Treaty Violation: Valuation According to Extra Potential Damage

One could also place a dollar cost on the harm done by a violation accordingto the destruction the violating weapons would

inflict were they used against the United States. If the extra loss of life and limb--always difficult to cast in dollar terms--were

costed at the rates paid in injury liability cases, the casualties from one nuclear missile could soar far into the billions. On the

other hand, densely populated areas are presumably already targeted by the missiles and other strategic nuclear delivery vehicles

allowed under arms control treaties: treaty-violating missiles will be applied to marginal targets left uncovered by the legitimate

force.

The damage done to inanimate objects is somewhat less difficult to cast in dollar tarns. One estimate of this amount comes

to 36 times the cost (procurement and lifetime operation, or about $200 million for the Peacekeeper) of the weapons themselves,z

so that a violating missile imposes a cost of about $7 billion on the United States. The factor of 36 could be assailed on the grounds

tha t although it assumes complete obliteration of the United States, its imputation of worth is restricted to “asset value,” and

as such includes neither loss of life and limb, or loss of items and sites of cultural value. Thus the factor of 36, obtained by

assuming that the entire heavy Soviet intercontinental ballistic missile (ICBM) force would destroy the entire United States, may

be assailed as too high on the grounds that it is an average value, not a marginal value.

IE not &rwtlY, tie~ throu@ the legitimate missiles they displace from the higher-priofity ~gets.

2Gregory Canavan and Edward Teller (in “Strategic Defense in the 1990,” Nature, Apr. 19, 1990) derive this estimate for the SS-18,

noting that “overestimates of the effects of nuclear explosions may have caused many readers to guess a higher figure.” They take the SS-18

to cost asmuchas its U.S. counterpa@ the Peaeekeeper, and they assume that theent.ire force of 308 SS-18s could destroy the e@ireUnited States.

The value thus destroyed is derived from U.S. gross national product and economists’ usual ratio (about 4:1) of total assets to production. An

upper limit on the total worth of American people, assets, and cultural items that could possibly be destroyed in a war would be the total insured

value underwritten by all insurers, property, casualty, and life. People, vehicles, and land aside, insurers cover about $12 trillion in assets:

inclusion of vehicles and allowance for the existence of various forms of uninsured property would raise this figure to $15 trillion or more.

Though we maybe startled by the seeming lowness of the 36:1 ratio of the missile’s cost to its destructiveness, we should recall that

conventional bombing notoriously destroys less than it costs.

. . illustrative one based on the assumptions listed above. launcher to counter and $500 million per launcher if it

Moreover, the real issue is the effect of aerial monitoring

upon monitoring as a whole; the correct comparison

would really be all other monitoring with versus without

aerial monitoring added. Without any aerial monitoring

flights, the cost is the harm done by the presence of any

illegitimate missiles, expressed in dollar terms as explained above. Using a prior distribution for the probabilities that various numbers (including zero) of illegitimate

launchers are present, we may find the expected value

(translated into millions of dollars) of the harm done by

the missiles: $3 billion.

remains hidden, recalling that the 200 flights themselves

cost a total of $10 million, and using our prior probability

distribution for the chances that each level of violation

(including none at all) is present, we may find the

expected value of the cost of each violation

Missiles Prior Find E(cost)

violation

o 25% o%

5 70% 18% $1,564

50 5% 87% $ 601

Missiles Prior cost E(cost)

o 25%

5 70% $ 2,50: $1,750:

50 5% $25,000 $1,250

$3,000

Aerial monitoring flights would have some chance of

detecting the violations committed in the 5-missile and

50-missile cases. Two hundred flights, each effectively

sweeping a l-mile swath 1,000 miles long, might each

have a 0.02 percent chance (as we have seen in ch. 6) of

finding one launcher: this probability can be multiplied by

5 of 50 to get the single-flight probability of finding a

violation, and the chance of not finding the violation then

raised to the 200th power to obtain the probability of not

finding a violation during the 200 flights. We may thus

compute the probability of finding the violations. Recalling that we assume that a violation costs $200 million per

$2,170

For example, the 5-launcher violation has an estimated 70 percent probability of being present in the first

place and a probability of

1 – (1 – 5 X 0.0002)200 = 0.18

of being detected by some one of the 200 flights or other

if it is present, so that the total expected cost of the

5-missile case (including the cost of performing the

inspections, even if they find nothing), is

0.7 X ((5 X (0.18 X 200+ 0.82X 500))+ 10) = 15648

or $1.564 billion: $200 million per missile if the violation

is detected and $500 million otherwise. The expected cost

of the situation as a whole is $2.18 billion if inspections

are undertaken-less than the cost without the inspections. Therefore the inspections are the preferable course

of action under these assumptions, though by a small

enough margin that other reasonable assumptions could
112. Verification Technologies: Cooperative Aerial Surveillance

Box C-8—Harm Inflicted by Treaty

Violdation: Procurement Cost of

Counteracting a Violation

Another position would evaluate the violation at the

cost of the violating weapons, or of their U.S. equivalents,

on the grounds that the U.S. response to a violation would

be to build similar weapons to maintain parity. However,

the U.S. preference for arms control over arms racing

suggests that the United States feels that having weapons

aimed at it has a cost greater than the cost of aiming our

own weapons back. Very roughly, then, this middle view

might attribute to an encountered treaty-violating missile

a one-time cost of $500 million to the United States.

A violation which was found and countered by the

deployment of a U.S. missile can be more readily

evaluated at the cost to counter, roughly $200 billion for

a U.S. intercontinental ballistic missile (ICBM). Use of

other legs of the triad to counter a violation would cost.

more: ICBMs offer the least cost per alert warhead.

lead to the opposite conclusion.80ne unstated assumption

with which serious issue might be taken is that finding one

or more illegitimate launchers somehow brings about

discovery of the whole violation. This is one effect which

brings down the cost of the 50-missile case. (Another is

the low prior probability assigned to that case.) The

assumption is not totally unreasonable, in that discovery

of a violation would shift the whole treaty-monitoring

effort into high gear and probably bring other intelligence

collection assets to bear. The expense of using those extra

assets should properly be charged against the cost of

countering a treaty-violating missile, perhaps increasing

the $200-million figure we have been using. Another

unstated assumption has been that the aerial monitoring flights afford the only opportunity for catching the

violations. In the real world, this assumption is

unwarranted and the analysis should be redone using

correct overall costs of monitoring and correct overall

probabilities of catching violations.

Savings Expected From Aerial Monitoring

Referring to the computations of the previous sections,

we may attempt to assess the worth of the 200 aerial

monitoring flights by finding how much money we can

expect them to save us. Given all of our assumptions,

4

3

2

1

0

Figure C-l—Notional Costs of Inspections and

Violations (detected and undetected violations)

Cost of flying and violation (billions) . .

. — —

0 2500

Open skies flying time (hours)

‘

-- Open skies only ~ Other means

7

5000

+1

added

The expected sum of the cost of the inspections and the imputed

costs of violations represents the total cost to the Nation. An

amount of flying can be chosen to minimize this total. The upper

curve depicts a situation, described in the text, in which only Open

Skies flights can detect a violation. The lower curve shows the

contribution of some other means of detection that, albeit at a cost,

greatly increases the probability that a violation will be detected.

SOURCE: Office of Technology Assessment, 1991.

including the prior distribution of the probabilities of the

various violations, we find an expected cost of $3 billion

without the flights and one of $2.17 billion with them so

that the flights save us $830 million net, including the

costs of the flights.

More generally, we may find the worth of various

numbers of aerial monitoring flights by finding their

expected net cost and comparing it to the expected $3

billion cost of not having any flights at all, always keeping

in mind that the result depends upon all of our assumptions, including our a priori estimates of the likelihood of

various levels of violation and our dollar-cost characterizations of the harm done by countered and encountered

violations.

8cmy he ~mcision of some of Ow asswptiom does not jus@ the retention of four decimal places in the resdt, as ks ken done for tie s~e

of clarity in illustrating the structure of the calculations.
Appendix D

NATO’S PROPOSED BASIC ELEMENTS FOR OPEN SKIES

Open Skies: Basic Elements

The following text outlines the basic elements of

NATO’s Open Skies negotiating position. These elements

were agreed to by the North Atlantic Council Meeting in

Ministerial Session at NATO Headquarters, Brussels, on

14th and 15th December 1989.

1. INTRODUCTION

1. On 12th May 1989, President Bush proposed the

creation of a so-called ‘Open Skies’ regime, in which the

participants would voluntarily open their airspace on a

reciprocal basis, permitting the overflight of their territory

in order to strengthen confidence and transparency with

respect to their military activities.

This proposal expanded on a concept that had already

been proposed during the 1950s but had failed to reach

fruition because of the unfavorable international political climate prevailing at the time.

Today, this new initiative has been made in a very

different context as openness becomes a central theme of

East-West relations and the past few years have been

marked by important advances in the areas of confidencebuilding and arms control.

2. The provisions for notification and observation of

military activities specified in the Helsinki Final Act were

strengthened and made obligatory by the Stockholm

Document concluded by the CDE [Conference on Disarmament in Europe] in 1986.

With respect to arms control, in 1987, the INF

[Intermediate-Range Nuclear Forces] Treaty, apart from

its immediate goals, represented a very important precedent because of the extent of its verification provisions.

All this leads one to expect today that even more

spectacular advances will be achieved in the near future.

In particular, a two-pronged effort is under way in Vienna:

on the one hand, to deepen the measures for confidencebuilding and transparency among the 35 countries of the

CSCE [Conference on Security and Cooperation in

Europe], and the other, to reach an unprecedented

agreement between the countries of the Atlantic alliance

and the Warsaw Treaty Organization on the elimination

of large numbers of conventional arms.

Furthermore, one awaits important developments in

other sectors of disarmament such as chemical weapons

and the Soviet-American strategic arms negotiations.

3. All of these agreements will naturally require their

own verification regimes, often of a highly intrusive

nature. Moreover, the specific provisions of each verification treaty will be supplemented by the habitual means by

which countries verify compliance with agreements

(National Technical Means).

It seen is useful, however, particularly in the prevailing

context of improved East-West relations, to reflect on

other ways of creating a broadly favorable context for

confidence-building and disarmament efforts.

In this context, the Open Skies concept has a very

special value. The willingness of a country to be

overflown is, in itself, a highly significant political act in

that it demonstrates its availability to openness; aerial

inspection also represents a particularly effective means

of verification, along with the general transparency in

military activities discussed above.

This double characteristic of an Open Skies regime

would make it a valuable complement to current EastWest endeavors, mainly in the context of the Vienna

negotiations but also in relation to the other disarmament

efforts (START [Strategic Arms Reduction Talks], chemical weapons).

It would seem desirable to focus now on the European

region, while also including the entire territories of the

Soviet Union, the United States, and Canada. Accordingly, we will be ready to consider at an appropriate time

the wish of any other European country to participate in

the Open Skies regime. This element could be complementary to their efforts at confidence-building and

conventional arms control and would conform to the

objectives of those negotiations.

4. To this end, the Open Skies regime should be based

on the following guidelines:

the commitment of the parties to greater transparency through aerial overflights of their entire

national territory, in principle without other limitations than those imposed by flight safety or rules of

international law.

the possibility for the participants to carry out such

observation flights on a national basis or jointly with

their allies.

the commitment of all parties to conduct and to

receive such observation flights on the basis of

national quotas.

the establishment of agreed procedures designed to

ensure both transparency and flight safety.

the possibility for the parties to employ the result of

such overflights to improve openness and transparency of military activities as well as ensuring

compliance with current or future arms control

measures.

–113–
114. Verification Technologies: Cooperative Aerial Surveillance

Il. PURPOSE

The basic purpose of Open Skies is to encourage

reciprocal openness on the part of the participating states

and to allow the observation of military activities and

installations on their territories, thus enhancing confidence and security. Open Skies can serve these ends as a

complement both to National Technical Means of data

collection and to information exchange and verification

arrangements established by current and future arms

control agreements.

Ill. PARTICIPATION AND SCOPE

Participation in Open Skies is initially open to all

members of the Atlantic Alliance and the Warsaw Treaty

Organization. All territories of the participants in North

America and Asia, as well as in Europe, will be included.

IV. QUOTAS

1. Open Skies “accounting” will be based on quotas

which limit the number of overflights. These quotas will

be derived from the geographic size of the participating

countries. The duration of flights can also be limited in

relation to geographic size. For larger countries, the quota

should permit several flights a month over their territory.

AU of the parties will be entitled to participate in such

observation flights on a national basis, either individually

or jointly in co-operation with their allies.

2. Effective implementation of a quota system requires

agreement that a country will not undertake flights over

the territory of any other country belonging to the same

alliance.

3. Quota totals for participating states should be

established in such a reamer that there is a rough

correspondence between totals for NATO and the Warsaw Treaty Organization and, within that total, for the

USSR and the North American members of NATO.

4. Every participant, regardless of size, would be

obligated to accept a quota of at least one overflight per

quarter.

5. Smaller nations, that is, those subject to the

minimum quota, may group themselves into one unit for

the purposes of hosting Open Skies overflights and jointly

accept the quota that would apply to the total land mass

of the larger unit.

V. AIRCRAFT

The country or countries conducting an observation

flight would use unarmed, freed-wing civilian or military

aircraft capable of carrying host country observers.

Vi. SENSORS

A wide variety of sensors would be allowed, with one

significant limitation-devices used for the collection and

recording of signals intelligence would be prohibited. A

list of prohibited categories and types of sensors will be

agreed among the participating states which will be

updated every year.

VII. TECHNICAL CO-OPERATION

AMONG ALLIES

Multilateral or bilateral arrangements concerning the

sharing of aircraft or sensors, as well as the conduct of

joint overflights, will be possible among members of the

same alliance.

Vlll. MISSION OPERATION

1. Aircraft will begin observation flights from agreed,

pre-designated points of entry and terminate at predesignated points of exit; such entry and exit points for

each participating state will be designated by that state

and listed in an annex to the agreement.

2. The host country will make available the kind of

support equipment, servicing and facilities normally

provided to commercial air carriers. Provision will be

made for refueling stops during the flight.

3. An observing state will provide 16 hours notification

of arrival at a point of entry. However, if the point of entry

is on a coast or at a border and no territory of the receiving

state will be overflown prior to arrival at the point of entry,

this pre-arrival period could be abbreviated.

4. The crew of the observation aircraft shall file a flight

plan within six hours of its arrival at the point of entry.

5. After arrival and the filing of a flight plan, a 24 hour

pre-flight period will begin. This period is to allow time

to determine that there are no flight safety problems

associated with the planned route and to provide necessary servicing for the aircraft. During this pre-flight

period the aircraft will also be subject to intrusive but

non-destructive inspection for prohibited sensors and

recorders.

6. Prior to the flight, host-country monitors will be able

to board the observatory aircraft. During the flight they

would ensure that the aircraft is operated in accordance

with the flight plan and would monitor operation of the

sensors. There would be no restrictions on the movement

of the monitors within the aircraft during the flight.

7. The flight will be from the agreed point of entry to

an agreed point of exit, where the host country observers

would depart the aircraft. The points of entry and exit

could be the same. Loitering over a single location will

not be permitted. Aircraft will not be limited to commercial air corridors. Observation aircraft may in principle

only be prohibited from flying through airspace that is

publicly announced as closed to other aircraft for valid air

safety reasons. Such reasons would include specific

hazards posing extreme danger to the aircraft and its

occupants. Each country will make arrangements to

ensure that public announcements of such hazardous

airspace are widely and promptly disseminated; each
Appendix D—NATO’s Proposed Basic Elements for Opent Skies ● 115

country will produce for an annex to the agreement a list

of where these public announcements can be found. The

minimum altitudes for such flights may vary depending

on air safety considerations. The extent of ground control

over aircraft will be determined in advance by agreement

among the parties on compatible rules such as those

recognized by ICAO [International Civil Aviation Organization]. In the application of these considerations and

procedures, the presumption shall be on behalf of

encouraging the greatest degree of openness consistent

with air safety.

8. The operation of the Open Skies regime will be

without prejudice to states not participating in it.

IX. MISSION RESULTS

Members of the same alliance will determine among

themselves how information acquired through Open

Skies is to be shared. Each party may decide how it wishes

to use this information.

X. TRANSITS

A transit flight over a participating state on the way to

the participating state over which an observation flight is

to be conducted shall not be counted against the quota of

the transitted state, provided the transit flight is conducted

exclusively within civilian flight corridors.

Xl. TYPE OF AGREEMENT

The Open Skies regime will be established through a

multilateral treaty among the parties.

XII. OPEN SKIES CONSULTATIVE BODY

To promote the objectives and implementation of the

Open Skies regime, the participating states will establish

a body to resolve questions of compliance with the terms

of the treaty and to agree upon such measures as maybe

necessary to improve the effectiveness of the regime.

U.S. GOVERNMENT PRINTING OFFICE ; 1991 - 29.2.90 0