Space Systems Division selected the Hughes Aircraft Company as the contractor to proceed with research and development of the experimental communications satellite for the U. S. military services. With a target price of $23.5 million, the contract called for design, engineering, assembly, and testing of what became the Tactical Communication Satellite (TACSAT I).

Air Force Titan IIIC, Vehicle #17, was launched from Cape Canaveral and placed the 1,600-pound experimental Tactical Communications Satellite, TACSAT I, into a near-synchronous orbit at an altitude of 19,300 nautical miles above the equator. TACSAT I, built by Hughes Aircraft Company under SAMSO management, was the largest communications satellite yet launched and placed in orbit by the United States. It was to determine the feasibility of using satellite communications repeaters with small mobile ground tactical communications equipment. In addition, using the technology already developed with earlier Despun Antenna Test System (DATS) and Lincoln Experimental Satellites (LES) test spacecraft, TACSAT I would test the feasibility of satellite communications over great distances while also testing the new gyrostat stabilization system. The satellite could handle transmission of television or multiple telephone/ teletype communications channels. Experimental commsat. Space craft engaged in investigation of spaceflight techniques and technology (US Cat A). Positioned in geosynchronous orbit over the Americas at 107 deg W in 1969?-1970; over the Pacific Ocean 173 deg W in 1970; over the Pacific Ocean 179 deg W in 1971-1972; over the Pacific Ocean170 deg E in 1972 Last known longitude (9 June 1995) 176.44 deg E drifting at 0.150 deg E per day.

Tactical Satellite Communication (TACSATCOM) reached interim operational capability, consisting of the Tactical Communications Satellite (TACSAT I) and the Lincoln Experimental Satellite LES-6. TACSAT I was initially designed to demonstrate the feasibility of handling tactical communications by satellite. The tests had been so successful with both satellites that tri-service traffic was added for relay through the system.