Space


BS

A year after the first CS-class satellites were launched, the BS (Broadcasting Satellite) program was inaugurated with the flight of BSE (Experimental) also known as Yuri. As the name implies, BS satellites are designed for television broadcasting and were initially developed for the Japanese Ministry of Posts and Telecommunications and for the Japan Broadcasting Corporation (NHK). All BS satellites have been located at 110 degrees E and have been of the same basic configuration: 3-axis stabilization of a rectangular spacecraft bus with two elongated solar arrays.

The 350-kg BSE was followed in 1984 and 1986 by the operational and essentially identical BS-2a and BS-2b, respectively. Each spacecraft carried two active and one spare 100 W. 14/12 GHz transponders. Built by Toshiba with assistance from General Electric, the BS-2 series were designed for five years of operations. BS-2a was moved to a graveyard orbit in 1989, followed by BS-2b in 1992.

After losing two BS spacecraft in launch accidents (Ariane in February, 1990, and Atlas Centaur in April, 1991), the BS constellation from 1990-1994 consisted of BS-3a (August, 1990) and BS-3b (August, 1991). The BS-3 class satellites, which have experienced some difficulties, have an initial on-station mass of 550 kg and are based on the Lockheed-Martin (GE) 3000 bus. The 15-m span solar arrays provide slightly less than 1.5 kW at beginning of life. The payload includes three active and three backup 14/12 GHz transponders and a single 14/13 GHz unit. A third BS-3 named BS-3N was finally launched by Ariane on 8 July 1994. Co-located with its predecessors and with a similar payload, the spacecraft possessed a higher on-station mass of 700 kg. A more powerful B-SAT (formerly BS-4) generation spacecraft is under development for a maiden launch in 1997. The Hughes-built, 1.25 metric-ton spacecraft are being developed by the newly formed B-SAT (Broadcast Satellite System) Corporation (References 175, 186-194).



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