It is believed that 6 Jumpseat satellites were successfully launched from Vandenberg Air Force Base on Titan IIIB launch vehicles with Agena D boosters between 21 March 1971 and 31 July 1983. The 700-kg Jumpseat satellites were manufactured by Hughes Aircraft and were inserted into highly elliptical Molniya orbits with an inclination of 63 degrees and orbital periods of close to 12 hours. These were in similar orbits to the Satellite Data System relay satellites. The successors to the Jumpseat series are the Trumpet satellites.