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Jumpseat 1, 2, 3, 4, 5, 6, 7

Jumpseat signal intelligence satellites were launched by Titan-3(33)B Agena-D or Titan-3(34)B Agena-D into highly elliptic Molniya-type orbits. These orbits were very similar to those of Quasar (SDS) classified communications/data relay satellites, and identification of a launch in either series as Quasar (SDS) or Jumpseat may differ from analyst to analyst.

The Jumpseat satellites were built by Hughes on the spin stabilized HS-318 bus, very similar to TACSAT and Intelsat-4. Likely they featured a large unfurlable despun dish-antenna.

The primary purpose of this series was to monitor Soviet ballistic missile warning radars in the far north. In their elliptical orbits they would move very slowly over the northern hemisphere for most of their orbital period, allowing interception of the radar signals. It was reported, that these satellites operated in conjunction with P-801 satellites.

Another purpose was reportedly the interception of microwave line-of-sight communications beams. Since they would move slowly through the beams during their orbit, a constellation of such satellites was required to monitor Soviet communications throughout the day.

The satellites also probably integrated ELINT and other SIGINT functions and intercepted up- or down-links from Soviet Molniya strategic communications satellites. An additional early warning payload has also been reported.

They were succeeded by the Trumpet series.

Note: The identification of these satellites beyond the fifth is not definitely confirmed. Some may be in fact Quasar (SDS) relay satellites, which used the same Titan-3(34)B Agena-D launch vehicle and the same orbits.

Nation: USA
Type / Application: SIGINT
Operator: US Air Force (USAF)
Contractors: Hughes
Equipment: ?
Configuration: HS-318 bus
Propulsion: ?
Mass: 700 kg
Orbit: Molniya Orbit
Satellite COSPAR Date LS Launch Vehicle Remarks
Jumpseat 1 (7701, OPS 4788) 1971-021A 21.03.1971 Va SLC-4W Titan-3(33)B Agena-D
Jumpseat 2 (OPS 1844) 1972-F01 16.02.1972 Va SLC-4W F Titan-3(33)B Agena-D
Jumpseat 3 (OPS 7724) 1973-056A 21.08.1973 Va SLC-4W Titan-3(33)B Agena-D
Jumpseat 4 (OPS 2439) 1975-017A 10.03.1975 Va SLC-4W Titan-3(34)B Agena-D
Jumpseat 5 (OPS 6031) 1978-021A 25.02.1978 Va SLC-4W Titan-3(34)B Agena-D
Jumpseat 6 (OPS 7225) 1981-038A 24.04.1981 Va SLC-4W p Titan-3(34)B Agena-D
Jumpseat 7 (OPS 7304) 1983-078A 31.07.1983 Va SLC-4W Titan-3(34)B Agena-D
Further high orbit SIGINT missions:

Geostationary orbit COMINT (Canyon-Chalet-Vortex-Mercury series) Geostationary orbit SIGINT (Rhyolite-Aquacade-Magnum-Orion series) High elliptical orbit SIGINT (Jumpseat-Trumpet series) Other high orbit SIGINT

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