karn@eagle.UUCP (10/04/83)
Over the weekend, a "software fuse" in the Oscar-10 onboard software tripped several times, shutting off the Mode B transponder. A routine which checks several vital parameters in the spacecraft detected that the battery voltage was below a specified limit and shut the transponder off. This caused quite a bit of concern among the users, as the beacon could be heard but no stations could access the transponder. The problem was that the satellite began experiencing solar eclipses for the first time since launch, starting about 20 September. As the eclipse durations increased (they will reach a maximum of about 35 minutes later this month), the battery, which then has to supply the entire spacecraft load, dropped below a trip point of 13.0 volts. This was clearly too high and has since been reduced to 11 volts. The satellite went back into normal operation yesterday and no more problems are anticipated. Phil Karn