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Examples of spin-stabilized and gravity gradient stabilized ferret spacecraft.

Robotic ravens: American ferret satellite operations during the Cold War

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Program 989, on the trail of ABMs

One of the early Navy DYNO satellites had detected signals from a Soviet anti-ballistic missile site. Over the next several years the CIA occasionally detected these signals through other means. They developed a method for detecting signals that had bounced off the moon during the few hours each month when it was simultaneously visible in the Soviet Union and the United States. In addition, during a series of Soviet atmospheric nuclear explosions the signals from ABM radars had been reflected down to the ground far away and picked up by American listening posts.

Beginning in the early 1960s the US intelligence community became increasingly concerned with Soviet ABM capabilities, particularly after the development of a new missile site near Tallinn, Estonia. The missiles at the site were obviously designed for high altitude operation, although just how high remained unknown.

But there was a problem, because Tallinn itself was not a high priority target worth defending. So why did the Soviets build a 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 detected at various spots within the USSR, but nowhere near Tallinn. (See “Ferrets of the high frontier: US Air Force ferret and heavy ferret satellites of the Cold War”, The Space Review, April 20, 2009)

But there was a problem, because Tallinn itself was not a high priority target worth defending. So why did the Soviets build a missile site there?

Disagreements within the intelligence community were common. A few of these became legends outside of the secretive community such as the bomber and missile gaps of the 1950s. But many other bitter battles remained secret, such as a dispute over the SS-8 missile and this dispute over the ABM 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. By 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 stood for anti-Earth satellite, the 1960s term for anti-satellite. 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 AES] 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.”

Ultimately the National Reconnaissance Office decided that the best method of gathering this urgently needed information was to modify the existing ferret subsatellite design, derived from the earlier P-11 satellites. In December 1968 a new class of subsatellite ferret began flying to focus on Soviet ABM radars. They had orbits of about 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.

In addition to these satellites, the NRO also began deploying subsatellites from a classified communications intelligence satellite known as JUMPSEAT and launched into highly elliptical 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. The combination of JUMPSEAT and Program 989 operated under the codename YIELD until 1982, when it was changed to WILLOW. Satellite observers remain somewhat skeptical of the claim that Program 989 satellites piggy-backed 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 the code names referred to the collective intelligence information collected by the systems, and one of these sources has confirmed that subsatellites 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.

The original image of a Titan II on the launch pad (left) and a poorly-airbrushed version released by the Air Force (right).

Titan II ferrets

Stanford’s research on signals intelligence payloads for subsatellite ferrets continued throughout the 1960s. According to de Broekert, “Of all the payloads we built at Stanford, all but one of them worked perfectly to the end of the vehicle life. One vehicle blew up on launch and went into the water. Consequently, we were generally pleased with the reliability of our systems.” The one that was lost during launch was the first satellite, launched alongside a KH-6 LANYARD reconnaissance satellite that also fell into the Pacific Ocean.

Lockheed built two basic types of these subsatellites. They were either gravity gradient stabilized with the assistance of a long, deployed boom, or spin-stabilized. The spin-stabilized satellites were regularly observed by people on the ground who noticed that they flashed at a very high rate, approximately five times a second. Assuming that a flash occurred every time a side of a satellite caught the sun, this would mean that they rotated more than sixty times a minute.

The last known ferret subsatellite was launched in 1984 from a KH-9 HEXAGON reconnaissance satellite. A failed KH-9 HEXAGON launch in 1985 also probably carried one of these satellites.

According to de Broekert, “Of all the payloads we built at Stanford, all but one of them worked perfectly to the end of the vehicle life. One vehicle blew up on launch and went into the water. Consequently, we were generally pleased with the reliability of our systems.”

On September 5, 1988 the US Air Force launched a classified payload atop a Titan II rocket from Vandenberg Air Force Base. It deployed a satellite into an 85-degree 500-mile (800-kilometer) circular orbit. Ground observers noticed that the satellite spun at approximately the same rate as the subsatellites deployed by the KH-9 satellites. A second launch took place exactly one year later on September 5, 1989. This satellite apparently suffered some kind of failure, however, and broke into several pieces. A third launch took place on April 25, 1992.

It is likely that these Titan II satellites were the direct linear descendent of the earlier subsatellite ferrets. With the retirement of the large KH-9 reconnaissance satellite in the mid-1980s, the NRO had to find another means of placing its ferret satellites in orbit. The Titan II Space Launch Vehicle, constructed from refurbished decommissioned ICBMs, was the answer.

The Titan II was capable of placing a 4,200-pound (1,905-kilogram) payload into a 90-degree 100 nautical mile (185 kilometer) circular orbit. But the ferret payloads were placed in 500-mile orbits, so the payload capability would have been lower, although not necessarily by much. It is possible that a new type of ferret was inaugurated at this time, perhaps based upon the earlier design. What is known is that the Titan II ferret satellites had a flash rate of about five times a second, nearly identical to the earlier deployed subsatellite ferrets.

At the time of these launches the Air Force still operated the Scout launch vehicle from SLC-5 at Vandenberg, and NASA operated the Delta from SLC-2W at Vandenberg as well. The Scout would have been too small to lift such a payload to the higher orbit, but the Delta would have been capable, as it regularly lifted medium-sized meteorological satellites to similar orbits. At the time, Martin also had proposed two upgraded versions of the Titan II. One, known as the Titan IIS, would be equipped with anywhere from two to ten Castor solid rocket motors around its periphery and could carry up to twice the payload of the standard Titan II launched out of Vandenberg. The other proposal was even more radical, and would have involved strapping three Titan II rockets side-by-side, enabling the vehicle to launch up to four times the payload of the baseline Titan II into polar orbit. But neither rocket was ever developed.

It is possible that the Air Force determined that refurbished Titan IIs would be cheaper than NASA-supplied Deltas and used them even though they were more powerful than necessary to carry the small ferrets. Or alternatively, Air Force leaders simply did not want to use NASA rockets. The story will probably not be declassified for many years.

Before the third launch took place a military official testified before Congress that the intelligence community had combined two of its strategic intelligence missions into a single platform. In addition there were soon reports that three of the six classified Titan II launches had been canceled. Apparently the ferret mission that was descended all the way from the P-11s of the early 1960s and which had been transferred to the Titan IIs was soon combined into another satellite platform.

In recent years a humorous postscript to this program has emerged. Apparently at the time that these spacecraft were being launched some Air Force official determined that the payload shroud might reveal information about the classified payload. So he or she chose to clumsily airbrush the shroud in several publicity photos. The effect was undone, however, by the fact that an identical non-airbrushed photo was also released by Martin Marietta, the contractor that refurbished the Titan ICBMs. Undoctored photos of later launches were subsequently released and the airbrushing remains puzzling, for the shrouds reveal nothing of the payload they contained.

The Lockheed P-11s and their descendents were not the only subsatellites deployed from classified American reconnaissance missions. During the early 1970s the U.S. Air Force also contracted with Boeing to develop a larger and heavier scientific satellite for deployment from several KH-9 spacecraft. These Small Secondary Satellite payloads, abbreviated as “S3” were apparently entirely scientific. They were spin stabilized and had a mission lifetime of six months and weighed 590 to 650 pounds (268-295 kg). They looked similar to the P-11s undoubtedly because they occupied the same space on the KH-9 satellites and required an angular shape to fit underneath the payload shroud. Three of these satellites were launched, in October 1974, December 1975, and July 1976.

Although these satellites were at least twice as large as the P-11s, they are not a likely choice for the payloads launched aboard the Titan IIs starting in 1989. By that time they would have been out of production for over a decade.


One of the many ironies of Cold War history is that today far more is known about Soviet and even contemporary Russian signals intelligence satellites than is known about American Cold War systems that ceased operating decades ago. In recent years the NRO has admitted that it operated a multitude of systems for gathering up the elusive electronic whispers of Soviet radars during the Cold War, but American officials still remain reluctant to reveal what these satellites looked like or were capable of doing. What is clear is that James de Broekert’s little battery-powered signals intelligence receiver, the one that he carried in his pocket and held up to airliner windows to log radar signals, had a long legacy.