Rosat status report #82

[REQUEST@rosat.gsfc.nasa.gov]

			ROSAT Status Report # 82
			    Jan 27th 1994


ROSAT is Safe-hold Mode

Due to difficulties with its attitude control system, ROSAT has been 
in safe hold mode almost continually since the end of last year.  Any
attempt to restart pointing operations has led to a return to safe mode
after a short time.  The primary sypmtom of the problem is that the
satellite drifts off target during orbit night, when the attitude
solution is based exclusively on input from the magnetometer and
the S-gyro.  In the most recent instance, the satellite drifted 100 degrees 
off the nominal pointing position.  The cause of this drift is still being 
investigated; it is hoped that a solution involving an attitude control
software update can be found.  Given the potential danger to the satellite,
ROSAT will remain in same mode while the problem is investigated, which
is expected to take a few weeks.  Contingency plans are also being 
developed in the event it is necessary to return to a one-target-per-day
mode reminiscent of the "reduced pointing mode" after the first gyro 
failure.

*****Note*****

Please send ROSAT questions, requests for documentation etc to 
rosat@rosserv    *NOT* ROSAT::REQUEST.

Thankyou