Tacsat Credit - USAF

TACSAT was designed to experimentally test and develop tactical communications concepts for all US military services.

As part of an Air Force program aimed at eventual development of a military tactical communications system to complement the IDCSP system, Hughes built the largest experimental communications satellite ever constructed to that time. The mission evaluated the feasibility of using satellite communication repeaters with small surface terminal communication equipment for highly mobile land, sea and air forces. The project was led by the USAF Space and Missile Systems Organization (SAMSO). The satellite featured a then-unique antenna array extending from the top of the drum-shaped spacecraft. The five-element antenna array consisted of UHF antennas, each nearly 2.5 m long. Beneath them were 2 microwave horns. At the extreme top was a biconical horn used for telemetry and command. Technology and concepts originating in this satellite would later make Hughes the leader in commercial communications satellites.

The satellite was spin-stabilized, with the solar panels rotating while the antennas and inner structure remain in a fixed position. The spacecraft was a cylindrical shaped aluminum structure with passive thermal control, spin stabilized (54 rpm) to 0.1 deg using a new gyrostat technique. Body mounted solar cells generated 980 W max and recharged three NiCd batteries of 6 AHr capacity each. The vehicle carried two transponders, one at X-band and one at UHF. The X-band transponder had a bandwidth of 10 Mhz and a maximum RF power of 30 watts. The UHF transponder had a bandwidth of 10 Mhz and a maximum RF output of 230 watts. Provision was made for cross strapping the UHF and X-band up and downlinks with a reduced usable bandwidth of 425 kHz. Earth coverage horn antennas were used at X-band, bifilar helices were used at UHF.

Design Life: 46 months. Typical orbit: Geosynchronous. Length: 3.40 m (11.10 ft). Maximum Diameter: 3.00 m (9.80 ft). Mass: 730 kg (1,600 lb). Associated Launch Vehicle: Titan 3C.

• 1969 February 9 - Tacsat 1 - Launch Site: Cape Canaveral. Launch Vehicle: Titan 3C. Mass: 730 kg (1,600 lb). Perigee: 35,939 km (22,331 mi). Apogee: 36,044 km (22,396 mi). Inclination: 1.00 deg. Period: 1,446.60 min.

  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.

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