Here’s the second part.
From TACSAT to JUMPSEAT: Hughes and the top secret Gyrostat satellite gamble
by Dwayne A. Day and Nicholas W. Watkins
Monday, December 21, 2020
Starting in August 1968, the secretive National Reconnaissance Office began launching new intelligence satellites into much higher orbits to accomplish their missions. The first was the CANYON series of communications intelligence satellites, followed in 1970 by the first of the RHYOLITE telemetry interception satellites. In spring 1971, the NRO launched a new and enigmatic satellite named JUMPSEAT, which has remained perhaps the most mysterious of these high-orbit satellites. Each of these satellites pushed the state of the art in terms of payloads, antennas, and satellite design. But JUMPSEAT represented a concerted effort by a civil and commercial satellite designer to break into the top-secret world of satellite intelligence by leveraging a new technology and a military contract to demonstrate that it could perform the mission of both detecting signals from the ground, and spotting missile launches with an infrared telescope.
By the late 1960s, the Space Systems Division of Hughes Aircraft Company was already a dominant force in satellite communications, having developed the first geosynchronous orbit communications satellite, Syncom 2 in 1963, and its commercial successor, Intelsat I, better known as Early Bird, in 1965. In early 1969, another new Hughes technology, the Gyrostat, made its space debut. This time it was on the tactical communications satellite, or TACSAT, one of the first geostationary military comsats. The Gyrostat was a damping system which prevented satellites from inevitably spinning around their longest axis. By allowing “long and thin” satellites, the Gyrostat maximized the use of shroud space on the Titan IIIC launcher, enabling TACSAT to be nearly eight meters long and three meters in diameter. TACSAT was a spinning cylinder with a large antenna “farm” on its top, and at over half a ton in mass, and with over 200 watts of power to the UHF antenna array, it has long been known to be a pioneer and record-breaker among comsats. Newly revealed information is, however, only now showing how TACSAT gave Hughes the knowledge and skills to successfully compete for several other key military and intelligence satellite contracts over the next few years, including the JUMPSEAT signals intelligence (SIGINT) and Satellite Data System (SDS) data-relay satellites. The new information also confirms the long-rumored dual role of JUMPSEAT in carrying both signals intelligence (SIGINT) and infrared missile detection payloads, though some puzzles remain.