SOT Shift Report

Shift H208
Duration:	17 Feb 2000 01:00 EST - 17 Feb 2000 05:00 EST
		17 Feb 2000 06:00 GMT - 17 Feb 2000 10:00 GMT

SOT Lead:           Tom Aldcroft
Spacecraft/Aspect:  Rob Cameron
FOT/Science Liason: Eric Martin
HRC:                
ACIS:               

========================================

Plan
----
Execute CAP 557 to perform ACA dark current calibration (via SAP 6A014)

Events
------
06:47	AOS on DSS-66.  Lock is solid, but data flow to OCC spotty
07:18	Uplink command loads for procedure
07:30	Disable dither
07:34	Set up for maneuver to "reference star field" via SCS 240
07:39	SCS 213 to update target quaternion
07:40	SCS 170 to update star catalog
07:42	SCS 211 to set ACA integration time
07:45	SCS 241 to execute maneuver
07:46	SCS 38 to clear stars
08:04	Enter NPM, acquire 3 acq. stars, 5 guide stars
08:06	SCS 240 to setup for manuever to dark field reference
08:08	SCS 214 to update target quaternion
08:08:53	Format 5: SAFE MODE

Notes/Issues/Problems 
--------------------- 
Chandra entered safe mode at 048:08:08:53.4 while performing procedures prior
to the ACA dark current calibration.  The safe mode entry was triggered
immediately after issuing a target quaternion update while still in normal
point mode.  This would be expected to trip the attitude error monitor and put
Chandra in safe mode.  However, telemetry shows that the only OBC fault monitor
which tripped was the "commanded attitude monitor", which checks if the
commanded attitude violates sun constraints.  This fault alone would NOT
trigger a safe mode.  PCAD FOT and SOT are therefore still investigating the
precise cause.

All indications are that Chandra is safe.  Commencement of normal safe-mode
recovery is planned for today (2/17).  DSN support with DSS-46 was added.  The
current comm schedule is:

 DSS-34  14:15 - 15:15
 DSS-46  15:36 - 19:20