The first two-TV-channel test broadcast from a satellite: December 1986
On May 12, 1984, the test broadcasting channel, "BS1", began operation amid mixed feelings of expectation and disappointment. While the BS-2a broadcasting satellite, whose design reflected the lessons learned from an earlier experimental broadcasting satellite, had been successfully launched in January of 1984, its two main traveling wave tube amplifiers (TWTAs) had failed by May, leaving only one amplifier, which could not provide the full two-channel service. It was an unfortunate incident for NHK, one which forced a six-month delay in the launch of the BS-2b satellite, which was intended to be only a backup to the BS-2a. After an investigation into the cause of the problem and a thorough ground test of the TWTAs, the BS-2b satellite was launched in February 1986. Test broadcasting over two TV channels started on December 25, with regular broadcasting beginning in June 1989. The bitter experience of the BS-2a TWTA failure was later used in strict space environmental ground tests on the use of TWTAs for broadcasting satellites.

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