From: DOXSEY@avion.stsci.edu
Date: Mon, 31 Mar 1997 22:32:10 -0500 (EST)
Subject: HST entered software sunpoint Monday evening


HST Software Sunpoint safemode entry.

	The HST entered Software sunpoint safemode on Monday evening
at about 6:40 pm eastern time (90:23:39 UT).  The safemode entry
was due to a Solar Array torque test failure on the - Array.  The
safing occured during a routine Solar Array maneuver as a part of 
the slew to the next target.  The + Array performed properly, the
- Array got ahead of the planned profile and tripped the torque 
limit.  The safemode entry was nominal, with FOC and STIS going into
safemode, WFPC-II staying in standby and NICMOS staying in Boot.
The safemode entry shuts off both SADEs, then commands the backup
SADE (SADE 1R) on and uses it to maneuver the arrays to the normal
sunpoint orientation.  These Array slews performed as expected.

	The very early analysis indicates possible similarity with
a safing event in January 1995.  The event took place just before
entry into the SAA.  In is possible that there was an SEU and 
a bit hit in SADE-2 which caused the rotation of the - Array to be
more than planned, tripping the torque limit.  There will be a
more extensive analysis overnight and the ESA engineers will be
contacted.  An analysis review will be held Tuesday at 10:00 am.

	The SPST team will start building a Health and Safety SMS
for execution starting Tuesday at 1:00 pm Eastern.  Unless the analysis
dictates otherwise, we are likely to pick up with the observing program
sometime Wednesday afternoon.