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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 SDS classified communications/data relay satellites, and identification of a launch in either series as 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.

In their elliptical orbits they would move very slowly over the northern hemisphere for most of their orbital period, allowing 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.

Nation: USA
Type / Application: ELINT
Operator: USAF
Contractors: Hughes
Equipment: ?
Configuration: ~ 20 m dish antenna, HS-318 bus
Propulsion: ?
Power:
Lifetime:
Mass: 700 kg
Orbit: Molniya Orbit
Satellite COSPAR Date LS Launch Vehicle Remarks
Jumpseat 1 (OPS 4788) 1971-021A 21.03.1971 Va SLC-4W Titan-3(33)B Agena-D
Jumpseat 2 (OPS 1844) 1972-F 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 ELINT missions:

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