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Historical Essay: GAMBIT 4352

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The NRO has declassified details of NRO's GAMBIT-3 mission 4352,
launched on 1982 Jan 21 and deorbited 1982 May 23. The analysis
in this essay is based on comparison of the newly declassified documents
with existing information on the mission and on the GAMBIT program.

This 52nd GAMBIT-3 flight was the only 'Dual Mode' GAMBIT mission, with
both high and low orbit (search and surveillance) mission phases.
Previous GAMBIT flights used only low orbits. The mission observed
Soviet and Chinese military targets as well as assessing their agricultural
output; I will leave others to discuss details of the intelligence mission
and broader programmatic issues (for example, see Dwayne Day's article
The Space Review: Higher Look: A top secret reconnaissance mission in 1982 )
and here focus on the orbital history of the vehicle.

British Interplanetary Society analyst Tony Kenden spotted the mission
as unusual and wrote an article about it later that year (JBIS 35, 441),
basing his analysis on two-line element (TLE) data which at that point
were publicly available even for NRO satellites. (That changed a few
months after Anthony's article came out, possibly not coincidentally).
However it now turns out that the TLE data for the later part of the
mission is bogus, which prevented analysts from understanding the full
story until now.

The 4500 kg Mission 4352 spacecraft was launched by Titan 34B Agena D
from Space Launch Complex 4-West at Vandenberg AFB at 1930 UTC on 1982
Jan 21 and reached a 147 x 543 km x 97.3 deg sun-synchronous orbit ten
minutes later. It was cataloged as object 1982-06A. Another object,
1982-06B, reentered quickly - it was probably a camera aperture cover.
At around 0500 UTC on Jan 22, the Gambit orbit was boosted slightly to
189 x 563 km; a series of three burns the next day boosted it to a 571 x
659 km orbit - unprecedented for the normally atmosphere-surfing Gambit
series - and it began its high orbit mission. Orbit maintenance burns
were performed once a week, slowly raising the orbit to 636 x 672 km by
Mar 9 and then lowering it to 616 x 630 km by Apr 22.

The Gambit-3 consists of an Agena stage connected via a rotating joint
to the PPS (Photographic Payload Section), which in turn is connected
to a fairing containing two SRVs (Satellite Recovery Vehicles). Each SRV consists of a capsule
with a film container, a heat shield, a thermal cover, and a `thrust cone'
with a solid rocket to deorbit the system for mid-air recovery over the Pacific.

On Mar 20 SRV-1, now full of film, was commanded to eject from the nose
of Gambit 4352 in its 633 x 666 km orbit. But the pyro failed to fire
and a backup timer separated the capsule from the thrust cone. The
capsule, heat shield and thermal cover were stranded circling the Earth
in high orbit, while the thrust cone remained attached to the spacecraft
fairing. The objects were cataloged as 1982-06C (possibly the heat shield; reentered
1999 Feb), 1982-06D (possibly the thermal cover; reentered 1998 Sep per estimate
by Ted Molczan in SeeSat-L Jan-13 : Decay date of a KH 8-52 SRV revealed)
and 1982-06E (the SRV-1 film capsule, reentered 2002 Sep 28). All the film from
the first part of the mission was lost, and it was decided to continue high
orbit operations a little longer than had originally been planned.

On around Apr 27 the spacecraft fairing, with SRV-1's thrust cone
attached, was ejected from the spacecraft. It was cataloged as 1982-06F
and per Ted Molczan's estimate may have reentered in about 1995 Apr.
Then, on 1982 Apr 28-29, Gambit 4352 made a series of five burns to
lower its orbital perigee to only 155 km. Two more burns on Apr 29-30
lowered apogee to 343 km and low orbit operations began; a final burn on
May 3 set the orbit at 152 x 308 km. These orbit changes are NOT
reflected in the published NORAD tracking data, which shows the
satellite remaining in a 633 x 645 km orbit until the end of the flight.
My first assumption was that this discrepancy was an inadvertent error,
with NORAD tracking the wrong object and not communicating with NRO,
rather than deliberate disinformation (which would be out of character
for that era). However, it is a bit mysterious - did NORAD really fail to
spot a 5 ton satellite in very low polar orbit for almost a whole month?
Isn't that the sort of thing they were set up to spot in the first
place?

Daily reboosts from May 3 to May 20 maintained the low orbit, and at
around 1700 UTC on May 20 the photographic mission was concluded and
attempts to recover SRV-2 began. Since it was thought to have the same
pyro problem, the only way to get it down was to deorbit the entire
spacecraft and then separate the capsule during descent. The Agena main
engine was to be used for the deboost, but when the propellant valves
were opened the spacecraft oscillated out of control. That plan was
abandoned in favor of using the Agena's integrated secondary propulsion
system (ISPS) for the deboost. On May 22, with control recovered, the
orbit was only about 140 x 250 km, and four more reboosts put the
perigee back up to 160 km to keep the spacecraft in orbit for another
day. Finally at around 2225 UTC on May 23 the ISPS fired to send the
spacecraft into the atmosphere, and the SRV-2 capsule was successfully
recovered in mid-air over the Pacific at 2246 UTC, completing the
unusual mission.