karn@eagle.UUCP (06/17/83)
A report from Karl indicates that we have a serious problem with the attitude of the spacecraft. Apparently, our spin axis is very near the sun, which has created a spacecraft emergency. The sun angle is beyond the range of the sun sensor, but is estimated to be ~+70 from the solar array current, +Z axis sensor, and the 40C temperature gradient between the top and bottom of the spacecraft. Karl reports that we have a breakeven or slightly negative power budget with the GB on, a NEGATIVE budget with the EB on, and positive budget with both beacons off. We are therefore going to be keeping the GB off most of the time except for short intervals to check telemetry. Battery charging current is currently 540 ma; load with beacons off approximately 235 ma. It is not yet known why the attitude is so far off (nearly 90 deg from where it was supposed to be put by the launcher); we have also ruled out the possibility of the launcher having put us in the same attitude as ECS-1. We are currently brainstorming ways around this problem, and hope to have a corrective strategy soon. Since the spin axis is so close to the sun, almost any direction you move it should be an improvement. It therefore might be possible to command the spacecraft to reorient "blind" to improve the sun angle, with the computer monitoring the array current to halt the maneuver if it gets worse. We'll keep you advised. The beacons will be kept off for long periods of time to aid in battery charging, so don't be alarmed if you don't hear it. Phil Karn, KA9Q/1