Spacechronicle: JBIS. Vol.59. Suppl.1. pp.56-62, 2006

RELAY IN THE SKY: THE SATELLITE DATA SYSTEM

DWAYNEA. DAY SpaceSlLidies Boatd,500 Fifth Street, NW, Washington,DC 20001,USA. Era : [email protected]

One of the key developments in real-time satellite reconnaissance was the Satellite Data System, or SDS.The SDSis a constellationof communicationssatellites placed in highly-elliptical,highly-inclined that relay imagery from low-altitude reconnaissance satellites back to the United States. The original concept for satellitedata relay datesto the late 1950s,but the modernconcept of the systemwas conceivedin the mid- '1960sand the satellitesentered development in the early 1970s.The satelliteswere built by Hughesand at leasta dozenof them were builtand launchedthrough the mid-1980s.They have apparently been replaced by newerand largersatellites starting in the early 1990s. Ket/words! Data-relay,reconnaissance, National Reconnaissance Office, communications

1. INTRODUCTION

In fall '1963Albert "Bud" Wheelon was sitting in his overcome: getting the data back to a ground station. living room in a suburb of Washington, DC,watching "This was a major issue because the opticaldata were a football game being played in San Francisco.At the so vast in each frame thatwe could not afford to store it time Wheelon was the Deputy Director for Science on board the satellite", Wheelon explained. "The data and Technology at the Central Intelligence Agency. simplywould pile up and overflowthe limitedavailable He was building his directorate into a powerful re- storage devices". In fact, an early attemptatdoing this search and development organization that initiated with the E-1 and E-2 satellites was limited to the and funded aerial and space reconnaissance sys- transmission of only a few photographs during each tems for the United States [1]. pass over a ground station, "We could notdownlink the data as it was being collected, because it would have While watching the football game Wheelon had an to be received in denied territory". But Wheelon had a epiphany. "lt suddenly struck me that if I could do that, solution for that as well. "The rightway to do this was to the technology was available to view the Earth's sur- uplink the data to a relay satellite in much higher , face from orbit and to observe that scene as it was which could then pass it on to the ground station" [2]. being received in the spacecraff', Wheelon said. "ln other words, to develop a near-real-time imagery sys- 2. THE BEGINNINGSOF tem". The nextday Wheeloncalled one of his deputies DATA RELAY and assignedhim to work fulltime on the development of such a system "This turned outto be one of the best Wheelonwas not the first person to develop the idea decisionsof my career", Wheelonsaid. "We ended up of a data relay satellite. In August 1958 Lockheed creating a new class of satellite imaging systems that Missile Systems Division prepared a slide depicting revolutjonized intelligence collection". a "Sentry Data Relay Concept". The slide depicted data and commands being relayed between three It took a decade to develop the technology for satellites in and a ground station. such a near-real-timesystem, known as the KH-11 This was a means of connecting a satellite with a KENNAN and first launched in late 1976. The clA ground station that was far below the horizon. But helped fund work at Bell Telephone Laboratories on this method of relaying data between satellites in what eventually became charge-couple devices, or low Earth orbit was not practical in 1958 with satel- CCDS,which today are readily available in commer- lite communications and electronics in their infancy. '1990s cial digital cameras. In fact, it was not until the late that the tech- nology was perfected and utilizedfor the lridium low But there was anolher hurdle that thev needed to Earth orbit communicationssystem [3].

56 Belay in the Sky: The Sate ite Data System

The biggest problem was that of locating another in a 12-hour would spend eight hours satellite to relay data through. Because all of the satel- flying above the northern hemisphere, but only four lites were in low orbitand moving relativelyfastto each hours flying over the southern hemisphere.From the other, no satellite would be visible to another for very satellite's perch approaching apogee, it could see long before moving below the horizon. Before the days much of the northern hemisphere.A satellite in such of sophisticated computers it was impossible to com- an orbit could maintain a line of sight with both a pute what satellites would be in range, where they low over the Soviet Union would be located, and then point an antenna at them, and a ground station in the United States. The Soviet switching to the next available satellite when needed. communacations system required three satellites for a full day of coverage, but because the American Another problem at the time was bandwidth, or reconnaissance system only operated during the day, the amount of information that could be sent over a only two SDS satellites would be necessary to sup- data link, somethingthat every user of the Internet is port a reconnaissancesatellite in low Earth orbit. familiarwith. The communicationssystems used with the early Samos satellites were severely limited in 3. THE KH-II REGONNAISSANGE how much information they could transmit. lt took SATELLITE many minutes to transmit a single photograph. For the remainder of the '1960sthe CIA sponsored Intelligence officials desperately wanted a,,near the developmentof new technologies to make "near real-time" reconnaissance satellite that could take real-time" reconnaissance possible. Until the basic pictures and relay them to the ground within a few image creation and processing technologies were minutes because itcould be used to warn of immedi- developed,there was not really a need for communi- ate events, such as Soviet tanks about to roll into cations systems to relay the imagery to a distant Czechoslovakia.But without a relay system, a satel- ground station. lite over the Soviet Union would have to travel a quarter of the way around the world or more before ln June 1971 President Richard Nixon approved the coming within range of an American ground station. development of what was soon designated the KH-11 KENNAN reconnaissance satellite. The KH-11 was a Wheelon's original idea was to place the relay big telescope with an image-forming electronic device satellite in above the equator. at its focal point. The tirst KH- l1s launched used light But the problem with this solution was that a single sensitive diodes, but the later ones used a linear CCD relay satellite would be insufficient to beam the data array [6]. Once the KH-11 was appmved, a data relay back to the United States and it would have to trans- system was also necessary mit it through another satellite or a ground station. The key was finding a way of sending the information The exact origins of the relay satellite are not through only a single relay satellite before sending it currently known due to continued classification.Ap- back to the ground. parently in the early 1970s the U.S.Air Force devel- oped a requirementfor providing command and con- According to Wheelon,Alexander Flax,the Direc- trol informationto nuclearforces in the Arctic where tor of the NationalReconnaissance Office from 1965 the propagation of radio waves is poor. The Air Force until 1969- after Wheelon had left the government - proposed a Data Relay Satellite System, or DRSS, came up with a superior solution. Although it is not which would transmit data to nuclear forces ooerat- clear how Flax got the idea, it is possible that he had ing in the Arctic, such as Strategic Air Command B- help from the Soviet Union [4]. 52s attacking the Soviet Union during a nuclear war, and also relay data from satellites over the horizon In April 1965 the Soviet Union taunched its first to a ground station. The early Defense Support Pro- successful Molniyacommunications satellite [5]. The gram missile warning satellites were proposed as satellite was placed in a new orbit, which was soon candidates for this data relay mission [7]. named the Molniyaorbit. lt was highly inclined to the equator, but also highly eccentric, meaning that it At the same time, the CIA component of the Na- swung low over the Earth in the southern hemisphere tional ReconnaissanceOffice required a relay sateF before heading toward a distant apogee high over lite for its KH-11 data. This satellite, known as the the northern hemisphere - like tossing a tennis ball Satellite Data System, or SDS,was undoubtedly ap- high into the air, it would slow down on its way up and proved sometime in late 1971 and it is possible that speed up on its way down, but appear to spend most for a short period of time the American military was of its time in a small area above one sDot.A satellite studying both DRSSand SDS simultaneously[8]. Dwayne D. DaY

satellitesand was DRSSwas formally cancelled in May 1973, but it sible for developmentof Air Force from Program A. lf the seems likely that its missions were transferred over located across the street SAMso, it would provide to the SDS by early 1972. DRSS had formally been satellite was developed by mission. An early plan designated "Program 313" and this designation was useful cover for the classified was that it could be apparently then given to the SDS [9]. One mission for the near-real-time system previous satellites, that was not given to SDS was that of relaying DSP covert. Unlike reconnaissance to drop recovery vehi- missile warning satellite data. Instead, the Air Force the KH-11 would never have giving away its mission' continued to utilize an overseas ground station in cles containing film, thereby an effective cover story, Australia for several decades to perform the relay lf the data relay system had its link to the highly function. then nobody would know about secret imaging satellite. The first payload added to SDS was an Air Force to giving the management Satellite CommunicationsSystem (AFSATCOM)UHF There was a drawback SAMSO and the NRO transDonder used for communicating with strategic of sDS to SAMSO, however. rules and regulations The forces in northern regions.Another payloadthatwas operated under different chain of com- added to the satellite was known as the "Mission-22 NRo's Program A had a simplified procuremenf' system, packet." ltwas essentiallya high data rate communi- mand and a "streamlined to abide by the same cations system for connecting the Air Force Satellite meaning that it did not have as the rest of the Air Force' Control Facility at Sunnyvale, in California, and its paperwork requirements to obey standard procure- seven remote tracking locations situated around the In contrast, SAMSO had significant red tape----and globe[10]. ment regulations-meaning all major decisions had to be approved by various One key question about the SDS concerned committees and senior leaders. whether it would be managed by the intelligence to select a contractor community or the Air Force now that it included both The original schedule was 1972. This selection was highly classifiedand relativelyunclassified missions. to build the SDs by 1 March of Defense Kenneth This decisionwas inextricablyentwined with the com- delayed until Deputy secretary the programme plex way that the United States managed satellite Rush decided who would manage signed the SatelliteData system reconnaissance. The National Reconnaissance Of- [ 11].On 3 May Rush placed the Space and Mis- fice, or NRO, was a Department of Defense agency ManagementPlan, which in charge of SDS development headed by a civilian Air Force official. That official, sile Systems Office management,secu- the Undersecretary of the Air Force, had dual re- and also described streamlined procedures to be used in sponsibilities.On intelligence satellite issues he an- rity and public release programme.According to a cover letter, swered to the Secretary of Defense as well as the running the plan the potential need to devi- Director of Central Intelligence.But he was also re- the "also recognizes Department of Defense soonsiblefor purely Air Force satelliteissues as well, ate from or waive certain which conflicf'with the and on these questions he reported to the Secretary Directives and Instructions procurement' In other of the Air Force. requirement for streamlined words, although the NRO'SProgram A was not for' could operate much The NRo was composed of three offices known mally managing SDs, SAMSO the details remain classi- as "Programs." Program A was an Air Force office like Program A. Although managedthe intelligence basedin Los Angelesalongside unclassified Air Force fied, presumablyProgram A payload for SDS space offices. Program B was the CIA office' based communications [121. in Washington, DC,and Program C was a small Navy board selected a contractor in office, also in Washington'The CIA's Program B man- A source selection then briefed senior Air Force offi- aged the developmentof the KH-l1, which was then early April and was not announced until I May being built by Lockheed. cials, but the winner '1972.The announcementwas classified atthe "con' of security classifi- Both the AFSATCOM and Mission-22 payloads fidential" level-the lowest level public of the award were standard Air Force missions,notan intelligence cation.The formal announcement were completed and community requirement. But once they were added was delayed until negotiations realigned and the to the satellitethey created a question and an oppor- "the programme objective was policy tunity. Should the SDS development be managed by public release established" [13]. the Air Force Program A component of the NRo, or Klass wrote in AviationWeek & by the Air Force's Space and Missile Systems Or- fn June 1972 Philip Force was procuring a ganization (SAMSO)?sAMSO was normally respon- Space Technologylhat the Air

58 Relay in the Sky: The Satellite Data System

new class of data relay satellitesthat would ,'enable search-and-findtype reconnaissance satellite pho- tos to be transmitted directly to the U.S. for speedy analysis and the transmission of commands back to the reconnaissance satellite to take closeJook oic- tures of targets of opportunity discovered on the earlier photos." Klass also quoted the USAF'Spre- pared statementforthe service,s fiscal 1973 budget request indicating that it was developing a relay sat- ellite. He reported that TRW and Hughes were com- peting for the satellite contract. In reality, Hughes had already won it. Nevertheless, his article prob- ably unnerved members of the intelligence commu- nity who were not used to seeing their missionsmen- tioned in publicly released statements,or the pages ot Aviation Week 114J.

The first launch was scheduled for January j 926, followed by a second launch in March, with $17.8 million allocated immediately,and $23 million for fis- cal year 1973[15].

4. HUGHESBUILDS THE SATELLITES Fig. 1 TheTACSAT experimentat . Hughes'successful Inielsat lV seriesof communications satelliteswasbased upon TACSAT TheSatellite Data System On 5 June 1972 HughesAircraft Company was given satellitesweie basedupon Intelsatlv. (usAF) a "Letter of Intent" from the Air Force indicating that the government would formally sign a contract with ably the most significant difference was that the SDS the company in the near future and which allowed did not require an apogee kick motor to place it in its Hughes to begin working on satellite development. final orbit. The Molniya orbit that SDS operated in On 7 July the Air Force publicly announced the con- was similar to the initial transfer orbit that tract, worth $36 million [16]. The initiat plan was to geosynchronous comsats were placed in by their launch the first two satellites in January and March upper stages. But this was the final orbit for the SDS 1976. and no powerful rocket was necessary to circularize it. The apogee kick motor had considerable mass, Almost nothing is known about the technical de- and eliminating it from the SDS undoubtedly had a sign of these satellites other than that they were major impact on the satellite's design, allowing it to cylindrical, weighed approximately700 kg, and were carry extra mass for other purposes, such as station apparently based upon Hughes' commercial Intelsat keepingfuel. lV satellite. The Intelsat lV which weighed approxi- mately 730 kg, was derived from an experimental Another major change was that SDS operated in .1960s comsat developedfor the Air Force in the late an orbit that repeatedly took it in and out of the Van known as Tacsat and some reports at the time stated Allen RadiationBelts, which regularlycooked its elec- that SDS was based upon Tacsat (Fig. 1). However, tronics. This required extra radiation hardening. Hughes had a policy of designing its commercial comsats to military specifications and the differences But undoubtedly the most important change in between Tacsat and Intelsatwere not major.lt seems the satellite from its commercial Dredecessor was likelythat advancesincorporated into IntelsatlV were the communications package. The KH-11 also adopted for SDS.The satellitewas drum-shaoed KENNAN'sdesigners wanted to make the satellite ,,farm,,or and spun in orbit. At its top was an antenna as covert as possible and one means of accom- platform that was de-spun by an electric motor so plishingthis was to preventits transmissionsover that its antennas pointed at the Earth [1 7]. the Soviet Union from reaching the ground. The way they achieved this was to use an uplink trans- Because the SDS satellite operated in a consider- mitter that operated at 58 GHz, a frequency which ably different orbit than Intelsat lV, it undoubtedly was absorbed by the oxygen in Earth's atmosphere had numerous differences from its progenitor.prob- and could not reach the ground. The KH-11would Dwayne D. Day transmit up to the SDS satellite at this frequency The Air Force also initiateda study to upgrade the and the SDS would then retransmit the information satellites for Survivable Satellite Communications, down to a ground station al22 GHz [18]. Because known as SURVSATCOM.Although the specifics are the SDSwas alreadybeing usedto transmit KH-11 unknown, this probably involved nuclear hardening imagery, which would have taken much bandwidth, of the electronics and other systems [25]. it probably was also used for less bandwidth-in- tensive telemetry, command and control, relaying ln the second half of 1974 refurbishmentof the Y- commands and satellite health data back and forth 1 spacecraft as a flight spare was slipped from fiscal to a ground station. In addition, all of this informa- year 1976 to 1977. The first flight spacecraft, desig- tion would have to be encrypted [ 19]. nated F-1,was under construction, with F-2 starting construction and F-3 scheduled to start in fiscalyear 5. SATELLITESCHEDULES 19751261.

Although little is known about the technical design In the first half of 1975 testing of X-1 was com- of the SDS satellite, more is known about its early pleted, assembly of Y-1 was completed and testing administrativehistory. In the second half of 1972 the was started, and fabrication and assembly of F-1 launch dates for the first two satelliteswere slipped continued. During this period the budgets were in- to June and August 1976, with ihe system achieving creased slightly due to increased costs for the operational availability by November. Funding was booster and some increases in the costs of F-2 and also realignedas better cost estimatesbecame avail- F-31271. able. The Air Force had initially allocated $49.'l mil- fion for fiscal yea( 1974, but reduced this to $43 In August 1974 the Secretary of the Air Force million and then to $40 million [20]. But $1.9 million approved a change in spacecraft to "augmenf'the was later added back to the budget [21]. However' polar coverage of the Atomic Energy Detection Sys- althoughthese numberswere declassified,it is highly tem which warned of nuclear explosions in the at- likely that additional money was also provided mosDhere. The F-3 and F-4 spacecraft were to be through classified channels to support the develop- retrofitted with nuclear detection (or NUDET) de- ment of the communications package devoted to the vices known as "bhangmeters." NUDETwas already intelligencemission. carried aboard DSPmissile warning satellitesby this time [28]. The communications subsystems Critical Design Reviews (CDRS),an intensive review of all aspects By late 1975 system level qualification testing on of the communications payload, were conducted in the Y-1 spacecraft was completed, with all critical November and December 1973 [22]. specifications met or exceeded and the overall de- sign validated. Assembly of the first flight space- Hughes initially started work on two satellites. craft was also completed and final acceptance test- The first, designated X-1, was a structural model, ing was started [29]. designed to prove that the spacecraft structure was sound during launch. The second, Y-1,was the quali- ln November of 1975 the Secretary of the Air fication model, which was equipped with most of the Force for Research and Development approved a electronic systemsand intended to demonstratethat plan to procure two additional spacecraft, F-5 and F- the satellite could perform the functions it was de- 6 in fiscal 1978 and 1979 respectively.These space- Space signed for. The system CDR was accomplished in craftwere to be modified to be compatible with anti-jamming pro- March'1974 [23]. Shuttle launch. In addition, their tection features and other aspects of their The initial plan was apparently to procure four AFSATCOMpayload were also to be improved. Fund' flight spacecraft plus to refurbish Y-1 to serve as a ing atso included launch support '1982 flight-qualifiedspare if any of the production space- through fiscal year [30]. craft was destroyed. 6. LAUNCH AND OPERATIONS Early in 1974 the production schedule for the on schedule in spacecraft was revised to accommodate delays ex- The first two satelliteswere launched perienced in the delivery of some equipment as well June and August 1976 from Vandenberg Air Force The as increased manufacturing and testing costs. De- Base atop lllB Agena D launch vehicles. in December1976 livery of the first flight vehicle was slipped from No- first KH-11 KENNANwas launched 1977. Satellite F-3 vember 1975 to February l9T6 [24]. and was operational by January

6U Relay in the Sky: The SatelliteData System was launched in August 1978. The fourth and fifth satellites were apparently not in their proper posi- satellites were delivered in May and October 1980. tions when the KH-11s were uplinking data. This ulti- Satellite Y-'l, the configuration test model, was ap- mately resulted in the NROtaking over management parently redesignated as F-sA and delivered in May of the SDS system by 1983. Apparently it was Pro- 1980 [31]. gram B, the CIA component of the NRO and not the Air Force component, that took over management The launch dates of the satellites after F-3 are not authority from SAMSO. accurately known because the National Reconnais- sance Otfice launched a classified signals intelligence Instead of procuring a new batch of identical sat- satellite known as JUMPSEATinto the same orbit. There ellites, in the early 1980s the Air Force chose to were six classified American launches into Molniya or- develop a new and more capable "SDS-B" class of bit during the 1980s. In 1981 the Air Force proposed satellites based upon the larger IntelsatVl commer- buying an additional SDS satellite, F-7. This meantthat cial satellites. Congress appropriated money for a the Air Force had a total of four SDS satellites, plus the "shuttle-comoatible"SDS satellite in the fiscal 1984 F-5A spare to launch during the 1980s, although it is budget. The first launch of this bigger satellite took not clear how many of those five satellites were actu- place aboard the Space Shuttle Columbia on STS-28 ally launched during this period. in August1989. Two satelliteswere placed in Molniya orbit, although a third was placed into Two different sources have indicated thatthe early geosynchronous orbit [33]. That class of satellites operations of the data-relay system were troubled. was probably replaced by a new class of satellites Apparently the KH-11 KENNAN satellites had prob- beginning in 2001. lt remains to be seen if further lems with the TravellingWave Tubes that generated information about the early years of this programme the 58 GHz signal used to send data to the SDS will be released by the National ReconnaissanceOf- satellites. The KH-1'1TWTS burned out earlier than fice, or whether they will remain partially obscured expected [32]. Another problem was that the SDS in the remaining shadows of the Cold War [34].

TABLE 1i Launch historv of SDS Block I Satellites

F -'l June'1976 August l9T6 August 1978 F-4 13 December'1980? 24 April 1941? 31 July 1983 28 August 1984 F-sA (ex Y-'l) ??

Othet Possible Launch Dates

8 February1985 12 February 1987 x-1 Structu.alTest Article

TABLE 2: Funding Protile for SDS Satellites.

74 78 79 8t'

RDT&E 41.9 36.5 30.2 4.0 25.5 15.0 20.4 25.0 30.0 Plocurement 35.0 35.8 9.6 107.5 85.0 50.0 45.0 40.0

*Plannedamounts as of FY 1980.Actua amountsare not knownat this time

References

1. "Albert D. Wheelon", in Robert A. McDonald. ed., 2. Ibid. Beyond Expectations-Building an American National 3. Lockheed Missile Systems Division [Slide], "Sentry Reconnaissance Capability, American Society for Data RelayConcept",'19 August 1958. [declassifiedin Photogrammetryand Remote Sensing,2003, p.333. responseto NRO FOIA requestl The name Sentry was DwayneD. Day

changed to Samos only a few months later. based crosslink instead, which proved impossible to 4. "Afbert D. wheelon," RobertA. McDonald,ed., Beyond devefop atthattime. See: Jeffrey T. Richelson, Ameica's Expectations-Building an Ame can National Space Sentinels, University Press of Kansas, 1999, Reconnaissance Capability, American Society for pp.278-279 , tn . 55 . Photogrammetry and Remote Sensing, 2003,p.333 20. "Semi-Annual History of the Directorate of Space, 1 5. Bart Hendrickx, "The Early Years of the Molniya January 1972-30 June 1972", [declassified excerpt], Program", Ouest 6, pp.28-36, t998. AFHRA, pp.19-20; the operational date is from "Two 6. Jeffrey T, Richelson, The Wizatdsof Langley,Weslview Spacecraft Planned for USAF Satcom Syslem", Aviation Press, 2001, p.199. Week & Space Technology,6 August 1973, p.'16. 7. 'DMS Market Intelligence Report, Satellite Data 21. "Semi-Annual History of the Direotorate of Space, 1 System,"Greenwich, CT, 1979, p.1. July 1972-31 December1972", [declassified excerpt], 8. See: Jeffrey T Richelson, "The satellite Data system", AFHRA.p.31. 'l JBI S, 37, pp.226-224, 1944. 22. "Semi-Annual History of the Directorate of Space, 9. "DMS Market Intelligence Report, Satellite Data July 1973-31December 1973", [declassifiedexcerptl, System,"Greenwich, CT, 1979, p.1. AFHRA,p.4t. 10. Both the AFSATCOMand Mission-22 payloads were 23. "Semi-Annual History of the Directorate of Space, 1 publicly acknowledged in congressional budget January 1974-30 June 1974", [declassified excerpt], documents. see: Jeffrey T. Richelson, "The Satellite AFHRA, p.40. Data System", JBIS, 37, pp.226-228,1944. This article 24. lbid.. p.41. contains many oontemporarycitations concerning the 25. lbid., p.42. openly acknowledgedmissions. 26. "SemiAnnual History of the Directorate of Space, 1 11. "SemiAnnual History of the Directorate of Space, I July'1974-3'l December 1974", [declassified excerpt], January 1972-30June 1972", [declassified excerpt], AFHRA. p.30. Air Force Historical Research Agency, Maxwell Aar 27. "Semi-Annual History of the Directorate of Space, 1 '1975", Force Base [hereafter AFHRA],pp.18-19. January 1975-30 June [declassified excerpt], 12, Kenneth Rush, Memorandum for the Assistant AFHRA, p.37. Secretary of Defense (Comptroller) el al, "Satellite 24. lbid.,p.38. 'i972. Data System (SDS) Management Plan", 3 May 29. "Semi-Annual History of the Directorate of Space, 1 [declassified in response to FOIA request to the J uly 1975-31December 1975", [declassifiedexcerpt], Departmentof Defense.The SDs ManagementPlan is AFHRA. p.37. currently under declassification review and has not 30. lbid., pp,37-38.One document lists as a "milestone" been releasedas of July 20061. the upgrade of vehicle #6 in September1978, but this 'l 13. "Semi-Annual History of the Directorate of Space, was long before the delivery ot the fourth vehicle. January 1972-30 June 1972", [declassified excerpt], 31.The launch dates for the first three satellites are from: AFHRA, pp.19-20. "satellite Data System (SDS)", c3l Program '14. Philip J. Klass, "USAF Plans Data Relay Satellite", Management Structure and Major Programs, Aviation Week & Space Technology,l9 June 1972, p.12. USDR&E(ASD/C3l),10 December 1980. 15. "Semi-Annual History of the Directorate of Space, 1 32. The KH-l ls had another problemas well. Theircontrol January 1972-30June 1972", ldeclassified excerpt], Moment Gyros, which were used not only to point the AFHRA,pp.19-20. satellites but io slew the satellite in order to remove 16. "Hughes to Develop USAF Data Relay Syslem", Aviation image smearfrom the photographs, burned out earlier Week & Space Technology,lT July 1972, p.'14. than expected. comments of a former intelligence 17. USAF Brigadier General Henry B. Stalling testified official. before the House Armed Services committee that the 33, Dwayne A. Day, "Out of the shadows: The Shuitle's SDS would be based upon Tacsat. "Two Spacecraft Secret Payloads", Spacellight,41, pp 78-84, 1999. Pfanned for USAF Satcom Syslem", Aviation Week & 34. Craig covault, "Launch Surge Begins for Secret NRo Space Technology,6 Au g u st 19 73, p.16. Missions". Aviation Week & Space Technology,'lo '18.comments ol a former intelligence official. September 2OO1,p.43i Craig Covault, "Secret Relay 19.These radio crosslinks had apparently been proposed Satetlite Launched as USAF weighs Surge Options", for the Defense Support Program satellites in the Aviation Week & Space Technology,15 october 2001' 1980s, butthe DSP programme office selected a laser- o.44,