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ARIA aircraft
EC-135 ARIA aircraft like those used in the VAST and VASP controlled reentry tests of American intelligence satellites in the early 1970s. The bulbous noses of these aircraft held large receiving antennas that collected signals from the spacecraft as they disintegrated. (credit: NASA)

Black Fire: De-orbiting spysats during the Cold War

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It’s the basis of a Cold War spy novel: a top secret American satellite falls to Earth and the Soviets race to recover the wreckage, hoping to figure out the technical wizardry that makes the satellites so good. Of course, it was the basis of a Cold War spy novel. Alistair MacLean’s Ice Station Zebra, which later became a movie that obsessed Howard Hughes, used similar elements. But it was a very real possibility. So real, in fact, that the United States government threw a vast set of resources at figuring out just what might survive a spysat’s fiery plummet to Earth.

They only did it after an embarrassing, but secret, accident.

Certainly the possibility that highly classified technology could fall on the vast Soviet landmass must have concerned NRO officials.

In the early 1970s, an English farmer found pieces from a top secret American spy satellite in his field. British and American officials promptly covered up the incident (see “Ike’s Gambit: The KH-8 reconnaissance satellite”, The Space Review, January 12, 2009). But the incident came to the attention of people in the Nixon White House, who were concerned that it had happened at all. What would have happened if that satellite had fallen on the Soviet Union instead of the United Kingdom? They asked some tough questions of the Air Force and the National Reconnaissance Office (NRO)—which managed the spy satellite program—concerned with how much classified equipment could actually survive reentry. According to the reentry models of the time, nothing from the spy satellite should have survived reentry. So the White House suggested that maybe they needed to test their models.

The Air Force and the NRO developed a plan. From 1971 to 1973 they deliberately reentered six different spy satellites, including two of the new, schoolbus-sized KH-9 HEXAGON satellites, over the Pacific in areas where the reentries could be monitored by numerous sensors, including radar, infrared and optical cameras. The tests revealed that the theoretical models were wrong: reentering spacecraft did not get as hot as people thought, and spacecraft therefore did not burn up like they expected. The tests resulted in new policies for disposing of spysats after they were finished with their missions. Two and a half decades later, the Air Force and NRO did it again.

Burning stars

For decades now amateur satellite observers have gone out into their backyards at night and watched classified satellites fly overhead and tracked their orbits. They have noted that after a certain number of years in orbit, the satellites are retired and reentered, sent plummeting into the Pacific Ocean. But it has never been clear when the NRO began this practice. In 1964 the reentry vehicle from a CORONA reconnaissance satellite accidentally fell in Venezuela and was recovered (see “Spysat down!”, The Space Review, February 18, 2008). In 1959, the Air Force was concerned that the second Discoverer vehicle—a developmental version of what became CORONA—could have fallen into Soviet hands (see “Has anybody seen our satellite?”, The Space Review, April 20, 2009.) In the early sixties there was also an incident involving a Samos reconnaissance satellite prototype that apparently fell in Canada, and may still be buried in a forest to this day (see “From cameras to monkeys to men”, The Space Review, July 27, 2009). Certainly the possibility that highly classified technology could fall on the vast Soviet landmass must have concerned NRO officials. But it is unclear if the NRO had a policy of de-orbiting its reconnaissance satellites at their end of life in the 1960s and early 1970s. Why that KH-8 fell on England remains classified.

At White House prompting, the Air Force and NRO initiated a series of tests starting in 1971 known as VAST, for Vehicle Atmospheric Survivability Tests. They had an extensive array of assets that were conveniently already deployed. During the late 1960s the United States was developing an anti-ballistic missile (ABM) system. The goal was ambitious: to shoot down reentry vehicles, which are small, fast targets surrounded by a sheath of ionized gas. In order to shoot down reentry vehicles, it is necessary to know what they look like as they speed through the atmosphere, and so the Air Force had deployed numerous sensors to the Pacific Ocean on islands, ships and aircraft to measure what a reentry vehicle from American ICBMs looked like in space as well as when Soviet reentry vehicles reentered the atmosphere heading toward their target zone on the Kamchatka Peninsula. They also deployed intelligence sensors to track and measure Soviet ICBM reentry vehicles.

The ARIAs were the most bizarre. They were C-135 tankers that had been modified to support the Apollo program and fitted with big receiving dishes inside bulbous noses that made them look like the kind of airplane a clown would fly.

In February and again in May 1971, the NRO conducted reentry tests of KH-8 GAMBIT reconnaissance satellites after they had finished their missions. The KH-8 was by this time equipped with two reentry vehicles, allowing operators to take photos and recover them, put the spacecraft into “zombie mode” for a period of time, and then reawaken it to take more photos, filling up the second reentry vehicle. When that second vehicle was filled, it was jettisoned and recovered. At that point, the spacecraft was useless (unless it had a secondary payload, like a radar signal detector). The pencil-shaped spacecraft was still relatively large, however, at five feet (1.5 meters) in diameter and approximately forty feet (12 meters) long. It was essentially a long thin cylinder, consisting of reinforced sheet metal, aluminum, and similar metals. Much of that tube was filled with empty fuel and oxidizer tanks. But at least part of it contained the camera, and was therefore a maze of metal and glass and the kinds of materials used in a large precision optical system.

For these first two tests, the Air Force employed an extensive array of sensors, including: an ARIS tracking ship equipped with L and C-band radars, optical cameras, and telemetry dishes; at least one TRAP aircraft equipped with optical and infrared cameras; and two ARIA telemetry aircraft. The ARIAs were the most bizarre. They were C-135 tankers that had been modified to support the Apollo program and fitted with big receiving dishes inside bulbous noses that made them look like the kind of airplane a clown would fly. In addition, a ground-based radar in Shemya and the tracking ship USN Watertown was used for the first test, but only a PRESS sensor aircraft was employed for the second test, along with the previously mentioned assets.

The reason the Air Force could bring so much equipment to bear was that it was largely left over from the ABM testing effort. With the United States canceling its ABM program, the testing was ending as well. By the third and fourth VAST tests, in September 1971 and April 1972, the tracking ships and aircraft were not used, largely because they had been retired. But for these tests the NRO decided to do something different. The first two spacecraft were sent down into the ocean. The third was sent to impact in Alaska, and the fourth to impact at Eniwetok, where the Air Force had devices for listening to the impact of ICBM reentry vehicles into the ocean, and for recovering them.

Burning Big Bird

In May 1973, the NRO resumed the testing, this time renamed Vehicle Atmospheric Survivability Program, or VASP. Instead of the long, slender KH-8, they used the bus-sized KH-9 HEXAGON. The HEXAGON had a diameter twice that of the KH-8, and it was also longer. It was such a large satellite that it had earned the nickname “Big Bird” at the Vandenberg launch site. Its camera system and forward section were also considerably bulkier and heavier than the KH-8. The May test used an ARIS tracking ship, two ARIA aircraft, and a land-based radar at Shemya.

According to an unclassified report, the tests resulted in changes in procedures for satellites at the end of their usefulness, although exactly what has not been revealed.

In October 1973 the NRO sent another KH-9 to a fiery end, this time using an ARIS tracking ship, a TRAP tracking aircraft, and three ARIA aircraft. Whereas the May VASP reentry was into the open ocean, this one was into Eniwetok, and was monitored not only by underwater listening devices, but also a submarine. According to a report, the data gathered by the TRAP aircraft on the second reentry “was remarkable and extremely informative.” Apparently, much more of the spacecraft survived reentry for a lot longer than the heating models predicted, and the aircraft’s optical sensors were able to see quite a bit of the vehicle while it was inside the atmosphere.

Not all of the details of these tests have been declassified. After all, the KH-8 and KH-9 satellites remain classified (see “A paler shade of black”, The Space Review, September 20, 2010). But it doesn’t require much imagination to guess why the NRO conducted reentries into Eniwetok Lagoon and even monitored the splashdown with a submarine—after all, if the Soviets wanted to recover parts of an American intelligence satellite, they would use similar methods.

The KH-8s consisted of a camera section and an attached Agena upper stage with its rocket engine and control systems. The KH-9s were essentially a single large piece, but they were also described as possessing a “boattail”—possibly referring to the large solar panels attached to the rear—and this produced lift during part of the reentry and “corrupted” the trajectory. But both types of spacecraft were made of similar materials and both therefore started to melt when they reached a certain temperature. The KH-9s had onboard temperature sensors, possibly included only for testing purposes. This might have been the reason for using so many of the ARIA aircraft—they were there to collect the electronic emissions from a burning spacecraft screaming through the atmosphere and shaking itself apart.

What the six tests revealed was that the reentry heating models were off by an order of magnitude. This must have been startling to those familiar with the program, and it explained why parts of the KH-8 could have fallen in England and not burned up completely. According to an unclassified report, the tests resulted in changes in procedures for satellites at the end of their usefulness, although exactly what has not been revealed. Presumably, the biggest change would have been ensuring that the spacecraft were deliberately de-orbited, and brought down in the deepest part of the ocean possible.

Next: De-orbiting from nearly Earth escape velocity.