The Space Reviewin association with SpaceNews

HEXAGON with secondary payload
Declassified image of a bus-sized HEXAGON reconnaissance satellite showing the location of a subsatellite riding "sidesaddle" on the forebody of the reconnaissance spacecraft. These satellites were deployed from HEXAGONs in the 1970s and 1980s. Some HEXAGON missions carried two of these spacecraft. (credit: NRO)

The wizard war in orbit (part 4)


Bookmark and Share

In August 1968, Soviet forces invaded their captive ally Czechoslovakia. The invasion began with an intense electronic warfare campaign against the Czech air defense network. A declassified secret US Defense Intelligence Agency report, titled “Soviet Electronic Countermeasures During Invasion of Czechoslovakia” and produced in October 1968, provided substantial detail on Soviet electronic warfare actions. It stated, “Electronic countermeasure activity was concentrated southeast and east of Prague to screen and protect Soviet air movements.” It added, “Jamming apparently was not targeted in the radio frequency range of NATO radars; the locations of chaff seeding suggests that it was not intended to screen Soviet air operations from Western observers.”

They were evolved versions of a series of satellites known as P-11, and by 1968 had become a major part of the American low altitude signals intelligence program. They remain one of the few bigger mysteries about the early American SIGINT satellite program of the 1960s.

The report was stamped for no foreign distribution “except Canada/UK.” Although it is only a few pages long, it contained significant information on Soviet jamming efforts. It noted that some of the jamming might have been directed at the SA-2 surface-to-air missile fusing system—a subject of considerable interest to the American military because SA-2 missiles had been blowing American combat aircraft out of the sky in Vietnam. Other jamming might have been intended for land-based guided missile systems that could have been fired at invading Soviet forces. The electronic warfare effort was successful, the Soviet invasion took place without a hitch, and the Czechs enjoyed another two decades in the workers’ paradise.

The report does not indicate the sources of its information, but because much of the activity took place far inside Czechoslovakia, it seems likely that American signals intelligence (SIGINT) satellites flying over Eastern Europe gathered much of the data. In fact, this would have been an intelligence bonanza for the United States military, because the Soviets understood best how to jam their own equipment, and monitoring what they were doing in Czechoslovakia could have provided information that the American military could use against similar weapons systems in Vietnam.

Several American signals intelligence satellites were in low Earth orbit at this time, including the large Agena-based MULTIGROUP 3 (see “The wizard war in orbit (part 3)”, The Space Review, July 5, 2016) and multiple POPPY 5 satellites launched in May 1967 that may have still been operational in summer 1968. But two small satellites launched off the back of photo-reconnaissance satellites in June 1968, designated Mission 4413 and Mission 4420, were the newest satellite assets in orbit. After being pushed off the back of their host satellites with springs, cold gas jets spun them around at a very high speed and then a solid rocket motor fired to push them into higher orbits, where they would more slowly cross over Soviet territory, recording signals for later transmission to American ground stations.

The satellites were squat rectangles about one and a half meters on their long sides, no more than a meter wide, and perhaps half a meter thick. As they spun rapidly, their antennas stretched out to their sides by centrifugal force. They were evolved versions of a series of satellites known as P-11, and by 1968 had become a major part of the American low altitude signals intelligence program. They remain one of the few bigger mysteries about the early American SIGINT satellite program of the 1960s.

More than 40 of these small satellites were launched over a period of nearly 30 years, from 1963 until 1992. Although the overall program remains classified, significant information about it has been declassified in documents and oral histories over the years. In addition, the author has obtained information such as the mission numbers and the identity and frequency ranges of many of the individual satellite payloads.

The P-11s were followed by updated satellites under the designation Program 989, which were eventually given code names such as URSULA, FARRAH, and RAQUEL. Like AFTRACK before them as well as the large Agena-based SIGINT satellites, these spacecraft carried multiple SIGINT payloads focused on different frequency bands. The payloads themselves had names such as TIVOLI, TRIPOS, SOUSEA, and LAMPAN. Despite significant amounts of available information, understanding the overall 30-year program is like trying to assemble a jigsaw puzzle with two-thirds of the pieces missing and no photo on the box. The P-11 program and its successors remain the most obscure and difficult to understand of the American low-altitude SIGINT satellites first deployed in the 1960s. However, their origins are clear.

subsatellite illustration
Early drawings from a low quality reproduction of a document declassified in the 1990s showing Lockheed Missiles and Space Company's proposal for a subsatellite that could be deployed from the aft rack of an Agena spacecraft. The actual spacecraft was rectangular, to take advantage of the available volume under the rocket's shroud. (credit: NRO)
subsatellite illustration

From AFTRACK to P-11

The first effort to launch a smaller satellite off the aft rack of an Agena spacecraft carrying a photo-reconnaissance satellite took place in March 1963 and ended in failure when the Thor first-stage rocket suffered engine problems and the vehicle broke up in flight before either spacecraft reached orbit. The next launch took place in summer 1963, when a subsatellite was deployed off its host satellite and quickly boosted to a higher orbit. Initially designated as Program 11, or “P-11,” these small satellites were soon being deployed on a regular basis of about two per year. The P-11s had their own small rocket motors that could boost the satellites to different orbits and they could keep operating for weeks or even months.

Although most details of the P-11 satellite program remain classified, it is clear that they were a direct evolution of the AFTRACK program that was started in 1960 and ended by 1965. (See part 2.) By summer 1962 approximately a dozen AFTRACK payloads had been launched into orbit. The first two of the larger Agena-based Program 102 signals intelligence satellites had also been launched. The Agena satellites were large multi-purpose satellites, intended to collect many different signals at many different frequencies. In contrast, the AFTRACK payloads were more focused and simple, targeting specific types of emitters in the Soviet Union. But they also had severe limitations. Because they were attached to their battery-powered host satellite, they operated only as long as the host did, usually no more than five to seven days. They were also in relatively low orbits, which limited the time that they were over their targets gathering signals.

By summer 1962 Lockheed engineers came up with a new concept: a small independent satellite that could be deployed from the rear of the Agena upper stage and operate at higher altitude and significantly longer than AFTRACK, at least a month at first. This alone would have significantly increased the amount of intelligence they collected. But rather amazingly, there is evidence indicating that several of the later satellites eventually operated for decades.

The spin-stabilized satellites were regularly observed by people on the ground who noticed that they flashed as they spun.

The P-11 operation was apparently run by Air Force Major John E. “Jack” Kulpa, Jr., who reportedly directed a classified “research subsatellite project” that ended in 1964. The satellite’s sensitive signal detectors were most likely developed by James de Broekert and his colleagues at the Stanford Applied Electronics Laboratory, who were also developing the AFTRACK payloads. If the P-11 program followed the AFTRACK example, the Stanford group would design the initial prototype payloads and then a contractor—most likely Lockheed or one of the small companies started in Silicon Valley by ex-Stanford and ex-Lockheed engineers—then produced the follow-on versions of the payloads. Lockheed’s 1962 proposal featured a disk-shaped satellite, but when the P-11s were developed they were rectangular, with payload bays on each of their longer sides. Each payload bay could contain one or two payloads about the size of a plumber’s toolbox, for a total of up to four. The satellites were approximately 1.5 by 1 by 0.5 meters—tiny compared to the Agena-based satellites. But one of the major differences between the P-11s and earlier satellites was that the satellites were covered with small solar panels that extended their lifetimes.

According to a former engineer who worked on the early P-11 satellites, each P-11 initially had two “black boxes,” representing two payloads. Like with the AFTRACK payloads, usually a payload engineer would individually design each black box for a satellite. In the early years there were about six payload engineers working at Lockheed Missiles and Space Company.

The P-11 satellites were spin-stabilized, and this design feature was important for the deployment of the satellite antennas. At least some of the satellites had two types of antennas. One type was like a tape measure, with the antenna spooling out from the side of the spacecraft due to centrifugal force. The other was a spiral antenna pattern. This was cut or printed onto a thin piece of metal fabric that rolled up. The engineers referred to these as “window shade antennas.” A cold gas system ejecting through nozzles on the sides of the spacecraft would spin it up prior to the rocket motor firing. Once the motor burned out and the spinning satellite had reached its operating orbit, the rolled up fabric unfurled. From their high perch, the satellites gathered up signals within their field of view on tape recorders. Lockheed apparently also built a second version that was gravity-gradient stabilized with the assistance of a long, deployed boom. The spin-stabilized satellites were regularly observed by people on the ground who noticed that they flashed as they spun.

Each satellite flew over an American ground station and downloaded its recorded data. But if it was doing a short pass (i.e. not high overhead but lower near the horizon, giving it less time in line of sight with the ground station) it was possible that the satellite would go “over the hill, hot” and still be transmitting as it went over the horizon. This was a bad thing to do because there was no automatic cutoff for the transmitter and when the satellite then flew over the Soviet Union, somebody on the ground could intercept the transmissions. When it came to the next American ground station, controllers would command it to stop transmitting.

Seven P-11 satellites were launched between March 1963 and October 1964, ejected from the aft rack of Agena upper stages carrying photo-reconnaissance satellites. Three of the P-11s were scientific satellites intended to study the Earth’s magnetic fields, although only two of these reached orbit. Apparently their scientific payloads were constructed at The Aerospace Corporation, where the scientists’ work was unclassified, but they knew they were hitching a ride on a classified satellite. Although the specific radar and other emitter targets for the SIGINT payloads remain classified, it seems likely that they focused on many of the same things that the AFTRACK payloads did—detecting and characterizing radar emitters and collecting communications intelligence (COMINT) from various targets. As the AFTRACK program wound down, with fewer launches, the P-11 program ramped-up, and because the solar-powered P-11s lasted longer, eventually fewer and fewer new payloads were required. The first satellite, designated 4051, was strapped to the side of an Agena carrying a KH-6 LANYARD satellite, but neither spacecraft reached orbit due to a booster failure.

According to a source who worked on the program for many years, the next seven satellites had different mission sequence numbers: 4001, 4101–4102, 4201–4202, and 4301–4302. However, the 4000 series mission numbers were used by the National Reconnaissance Office (NRO) for the GAMBIT-1 (KH-7) photo-reconnaissance satellites, and the 4300 series were used for the GAMBIT-3 (KH-8) satellites. GAMBIT mission numbers have been officially declassified, whereas the P-11 mission numbers have not been declassified. Therefore, these numbers for the P-11s are possibly in error.

According to a recently-published oral history on Air Force satellite reconnaissance programs, the satellites weighed approximately 68 kilograms (150 pounds). A former satellite official, Don Thursby, who worked in the Air Force component of the National Reconnaissance Office at Los Angeles Air Force Base stated in the oral history, “They were ‘HeathkitSats’ delivered to the base in a box of parts, assembled, tested and readied for launch under the Launch Services Contract… it was a very successful cost-effective program.”

Two views of the first P-11 satellite mounted on the aft rack of the Agena spacecraft carrying a KH-6 LANYARD spacecraft. This spacecraft apparently carried scientific experiments built by The Aerospace Corporation. It was launched on March 18, 1963, but the launch vehicle failed and neither the LANYARD or the P-11 reached orbit. (credit: Paul Gatherer)

P-11 and A-11

One of the tactics that Soviet radar crews used to deny American signals intelligence aircraft their data was turning off their radars when the American aircraft were in the vicinity. This sometimes prompted the Americans to take provocative actions, like flying directly toward Soviet airspace before suddenly turning away. In July 1964, shortly before the P-11 program ended, a CIA official proposed a more exotic version of this tactic: using an actual high-speed aircraft overflight of Soviet territory to provoke the Soviets into activating their air defense network while American P-11 satellites flew overhead. The CIA considered using three P-11 satellites in concert with the Mach 3 A-12 OXCART reconnaissance plane—the predecessor to the SR-71 Blackbird. At the time the A-12 was still referred to as the A-11. According to a declassified memo, an NRO official “sketched a plan whereby three P-11 satellites spaced 120 degrees apart in polar orbit would make north/south passes across the Soviet Union progressing say East to West but with 500 miles cross spacing between each trace at intervals of 30 minutes.” The writer, whose name has been deleted from the document, proposed, “The A-11 could fly diagonally across the Soviet Union stimulating the defense networks while the P-11s gathered the resulting elint data.” He speculated that such a mission could gather data on Soviet radars that the intelligence community had designated TOKEN, TALL KING, and SPOON REST.

When American SIGINT satellites flew over the Soviet Union they encountered dozens, sometimes hundreds, of air defense and surface-to-air missile radars during their missions. ABM radars were different. There were only a few of them. The bigger problem was capturing their signals.

Sending a high-altitude Mach 3 aircraft deep inside the Soviet Union might not be very risky for the pilot—the OXCART would have been relatively invulnerable on a single surprise flight—but it would be highly provocative, especially in light of American promises in the wake of the May 1960 Gary Powers U-2 shoot down incident to no longer fly spyplanes over the Soviet Union. It could possibly even result in a nuclear war if the Soviets suspected that the aircraft was a bomber sent on a sneak attack. The mission, which was apparently only a theoretical proposal, never occurred. The window of invulnerability for the OXCART was also closing as intelligence analysts became concerned that the Soviets were networking their radar systems, enabling one radar to automatically alert another one downrange that an aircraft was approaching so that missiles could be prepped and ready to shoot down the intruder.

The P-11 follow-on and the ABM radar hunt

Starting in April 1965, a new series of subsatellites entered service with Mission 4401. This series continued until the mid-1980s. But the Mission 4401 series satellites may have consisted of multiple different designs and maybe even a major upgrade of the satellites.

In March 1968, Mission 4411 was launched off the back of a CORONA photo-reconnaissance satellite. According to one account from someone who worked on it, this small satellite was the first to be equipped with a six-foot (two-meter) diameter parabolic dish, which itself was significantly larger than the satellite. Mission 4420, launched in June 1968 off another CORONA satellite, had 1-meter and 0.5-meter dishes. Mission 4417, launched in March 1969, again had a two-meter dish antenna. Mission 4407, launched in September 1969 along with a POPPY general search signals intelligence satellite, actually used its rocket to lower its orbit after deployment instead of raise it.

Beginning in the early 1960s, the US intelligence community became increasingly concerned with Soviet anti-ballistic missile (ABM) capabilities. When American SIGINT satellites flew over the Soviet Union they encountered dozens, sometimes hundreds, of air defense and surface-to-air missile radars during their missions. There was little difficulty in gathering these signals because the radars were everywhere throughout the Soviet landmass, and the Soviets did not turn all of them off when American satellites were overhead. The primary challenge for the Americans became precisely locating all of them.

ABM radars were different. There were only a few of them, and their locations were soon well known to American intelligence analysts. The bigger problem was capturing their signals. The radars did not operate often, and the Soviets could turn them off if they thought that an American satellite was trying to collect their signals. One of the primary targets for the US signals intelligence collection effort at this time was the Soviet Union’s large HEN HOUSE anti-ballistic missile radar located on the shores of Lake Balkash at Sary Shagan. The first HEN HOUSE had been spotted in a U-2 reconnaissance aircraft photograph, and eventually the Soviets built several more of the radars, which were used to track ballistic missiles for interception. American intelligence analysts believed that the HEN HOUSE could also be used to track satellites, but gathering data on this capability took time.

One time one of his colleagues called him in to listen to the latest HEN HOUSE signal. Instead of the typical “zzip zzip” they got a very strong continuous “ZZZZZZZZZZ” that indicated that the HEN HOUSE had locked onto the satellite and was tracking it.

A former Lockheed engineer who worked on the early satellites mentioned that the typical HEN HOUSE signal was recorded as an audible “zzip zzip” sound as the signal swept past the satellite. Lockheed would get the recording from the ground station and make a copy; one recording would go to the National Security Agency and one to the CIA. The Lockheed engineers could listen to the recording for engineering purposes, but early on the Air Force decided that the contractors would not perform any signal processing themselves. According to the engineer, that decision was later reversed when the amount of data coming in from the various satellites became so great that the NSA was overwhelmed and had to enlist contractors to process it.

One time one of his colleagues called him in to listen to the latest HEN HOUSE signal. Instead of the typical “zzip zzip” they got a very strong continuous “ZZZZZZZZZZ” that indicated that the HEN HOUSE had locked onto the satellite and was tracking it. This gave them proof that HEN HOUSE could be used to track orbiting targets and also provided them a very strong signal to analyze.

By the mid-1960s, the American intelligence community became interested in the development of a new missile site near Tallinn, Estonia, that looked like it might have an ABM mission. Tallinn itself was not a high priority target worth defending, raising a question as to why the Soviets were building a new missile site there. Some intelligence analysts in the US Air Force soon claimed that the Tallinn site was for conducting “area defense” against American ICBMs. Equally confusing was the fact that no phased-array radars capable of directing ABMs were anywhere near the launch site. Several massive HEN HOUSE ABM radars were eventually located at various spots within the USSR, but nowhere near Tallinn.

Disagreements within the intelligence community were common. A few of these became legendary outside of the secretive community, such as the bomber and missile gaps of the 1950s and the dispute over the range of the Backfire bomber during early 1970s arms control negotiations. But many other bitter battles remained secret, such as a dispute over the SS-8 ballistic missile, and this dispute over the suspected anti-ballistic missile site at Tallinn. In an all-too-familiar pattern, CIA analysts argued that the Tallinn site was not an ABM site, whereas Air Force officials argued that it was, or at least could be, and pointed out that there were still many radars within the Soviet Union that the US had little information about.

By summer 1966, this dispute resulted in a call for a revision of satellite signals intelligence collection efforts. In October, the Committee on Overhead Reconnaissance, known as COMOR, which selected targets to be viewed by American photo and SIGINT satellites, discussed a “requirement for collection against ABM/AES.” AES refers to “Anti-Earth Satellite,” now known as ASATs. By November the committee discussed this subject again and it became an “urgent requirement for SIGINT satellite collection against Soviet ABM/AES systems.”

A few days later, Director of Central Intelligence Richard Helms wrote a letter to the Deputy Secretary of Defense, Cyrus Vance, stating: “On 17 November the United States Intelligence Board (USIB) approved an urgent requirement for information on [Soviet Anti-Ballistic Missile radar and anti-Earth Satellite] systems. It is essential that every effort be made to meet this requirement within the next twelve months. In evaluating the chance of early fulfillment of that requirement, I am convinced that, among the various SIGINT satellite systems presently available, the best hope lies in a concentrated [deleted] program. This program would involve qualitative improvement, as well as an expanded launch schedule, probably to as many as [deleted] per year. I believe that immediate steps should be taken to develop such a program and to make the necessary NRO funds available.”

By December 1966, a group of senior scientific intelligence advisors to the government met to discuss SIGINT issues. According to a letter by the two senior advisors, Edwin Land and Edward Purcell, “the Panel spent considerable time discussing systems which might meet the urgent requirement to determine the characteristics of the Soviet ABM systems. We believe that the Panel in general would agree that the decisions that would be influenced by the information gathered about these defenses are of such magnitude that we ought not be satisfied with any collection system [deleted more than 25 lines of text].”

In addition to these satellites, the NRO also began deploying subsatellites from a classified SIGINT satellite known as JUMPSEAT that was launched into highly elliptical high inclination orbits.

In January 1967, the National Reconnaissance Office launched the large Agena-based MULTIGROUP 3 satellite. According to the declassified official history The SIGINT Satellite Story, this satellite had enhanced equipment for intercepting ABM and anti-satellite radars. The meeting of the advisory group one month earlier undoubtedly included a briefing about this upcoming launch, and the group may have found it inadequate, prompting their recommendation for “immediate steps” to develop a response.

Ultimately, National Reconnaissance Office officials decided that the best method of gathering this urgently needed information was to modify the existing subsatellite design, derived from the earlier P-11 satellites, and launching them into even higher orbits. In December 1968, a new class of SIGINT subsatellite began flying to focus on Soviet ABM radars. They had orbital altitudes of 1200–1400 kilometers at about 80.3 to 96.9 degrees inclination—significantly higher than their predecessors and requiring an additional kick motor to place them in the proper orbit. These satellites were apparently given the designation Program 989, although it is also possible that the designation had been applied to the earlier low-altitude successors to the P-11 as well.

The higher orbit undoubtedly resulted from the need to keep the targets in view for a longer period of time and maximize the amount of signals the satellites could record. Satellites focused on surface-to-air missile sites and general search radars had many targets to locate and analyze throughout the Soviet Union and its allies, but satellites designed to detect ABM radars only had a few potential targets, so time over target was more important. Seven satellites of this type were launched from KH-4A CORONA and KH-9 HEXAGON reconnaissance satellites between 1968 and 1983.

In addition to these satellites, the NRO also began deploying subsatellites from a classified SIGINT satellite known as JUMPSEAT that was launched into highly elliptical high inclination orbits. Seven of the JUMPSEAT launches took place between 1971 and 1981, but it is unknown how many of these may have included subsatellite payloads. JUMPSEAT, according to a former senior intelligence officer, was a relatively large satellite built by Hughes and similar to that company’s military TACSAT and civilian Intelsat IV comsats: a large spinning drum with a nest of antennas on top. JUMPSEAT’s focus was on Soviet ballistic missile warning radars in the far north. JUMPSEAT’s orbit allowed it to spend much of each orbit in the northern hemisphere collecting signals from these radars as they pointed their radar beams over the north pole and their signals traveled out into space.

The combination of JUMPSEAT and Program 989 operated under the codename YIELD until 1982, when it was changed to WILLOW. Independent satellite observers remain somewhat skeptical of the claim that Program 989 satellites piggybacked on the larger satellites. They note that no additional deployed payloads were cataloged by NORAD, which regularly released orbital information on classified satellites until 1983. One possibility is that it was simply Program 989 signals intelligence equipment that was carried on the much larger satellites, rather than an actual separate satellite. But two sources have confirmed YIELD and WILLOW referred to the intelligence information collected by both systems, and one of these sources has confirmed that subsatellites, not simply attached payloads, were indeed carried aboard JUMPSEAT.

Although detecting and characterizing ABM radars had been an urgent requirement in late 1966, the urgency began to fade soon after the launch of the first satellite in late 1968. By that time Air Force officials had essentially conceded that Tallinn was not an ABM missile site; it was in fact intended to shoot down high-altitude, high-speed XB-70 Valkyrie bombers, which had been canceled before the site was even built. By the early 1970s, the United States and Soviet Union had also entered into a treaty to ban ABMs.

This changed situation was reflected in the deployment of the lower-altitude satellites. Four were deployed between late 1968 and 1973, but only three more were deployed in the next ten years. The number of payloads deployed from JUMPSEAT is unknown.

page 2: Stanford Electronics Laboratory and the Vietnam War comes to SIGINT >>