BSAT-1a was a geostationary communications satellite designed and manufactured by Hughes (now Boeing) on the HS-376 platform. It was originally ordered and operated by the Broadcasting Satellite System Corporation (B-SAT). It was used as the main satellite to broadcast television channels for NHK and WOWOW over Japan. It had a pure K_u band payload and operated on the 110°E longitude until it was replaced, along its backup BSAT-1b, by BSAT-3a.^[3][7][8][9] On 3 August 2010, it was decommissioned and placed on a graveyard orbit.^[5]

The spacecraft was designed and manufactured by Hughes on the HS-376 satellite bus. This spin-stabilized platform had two main sections. One, the spinning section, was kept rotating at 50 rpm to maintain attitude, and a despun section that was used by the payload to maintain radio coverage. The spinning section included the Star-30BP Apogee kick motor, most of the attitude control, the power subsystem and the command and telemetry subsystems. The despun section contained the communications payload, including the antennas and transponders.^[3][10]

It had a launch mass of 1,236 kg (2,725 lb), a mass of 723 kg (1,594 lb) after reaching geostationary orbit and a 10-year design life. When stowed for launch, its dimensions were 3.15 m (10.3 ft) long and 2.17 m (7 ft 1 in) in diameter. With its solar panels fully extended it spanned 7.97 m (26.1 ft).^[3] Its power system generated approximately 1,200 Watts of power thanks to two cylindrical solar panels.^[10] It also had a NiH₂ batteries for surviving solar eclipses.^[3] It would serve along BSAT-1b on the 110°E longitude position for the B-SAT.^[10]

Its payload was composed of a four active plus four spares K_u band transponders fed by a TWTA with an output power of 106 Watts. Its footprint covered Japan and its surrounding island.^[3]

Broadcasting Satellite System Corporation (B-SAT) was founded in 1993 to broadcast by satellite the analog signals of NHK and WOWOW, including analog high definition Hi-Vision channels.^[8] In June 1994, it orders two HS-376 satellite from Hughes (now Boeing), BSAT-1a and BSAT-1b.^[3]

During 1997 B-SAT completed its Kawaguchi and Kimitsu satellite control centers. At 23:08:44 UTC, 16 April 1997 the Ariane-44LP flight V-95 successfully launched BSAT-1a, along Thaicom 3, from Kourou ELA-2 launch pad.^[2][10] On 1 August 1997, BSAT-1b entered into commercial service.^[7]

During May 2005, B-SAT ordered BSAT-3a, the replacement satellite for BSAT-1a and BSAT-1b. It was successfully launched in August 2007, and accepted into the fleet the next month. During November, 2007 BSAT-3a took over the broadcasting of analog and digital signals from BSAT-1a and BSAT-1b. On 3 August 2010, BSAT-1a was placed in a graveyard orbit and decommissioned.^[7][11]