SOT Shift Report 2009-08-27 L3687 (retroactive)

This retroactive report (from Mike Juda's e-mail) gives a more extensive description of the MUPS
thruster test performed on August 26, 2009 at 15:30 UT

August 27, 2009 9:59 AM local time:

The MUPS tank pressure reading is 185.3 psia with occasional toggles up to 186.9 psia. 
Based on the diagnostic thruster firing these readings do not represent the actual tank pressure. 
Limits monitoring will no longer performed on the MUPS tank pressure.

The MUPS diagnostic thruster firing was successful an the resulting analysis of a 95% "efficiency" 
is exactly in line with what is expected for a MUPS tank pressure of ~254 psia.

The ops crew is continuing the monitoring with expanded coverage and will do so through 
their normal staffing rotation on Sunday morning. From that time on they will return to 
nominal staffing and we will release DSN comm in the black-out period.

Spacecraft attitude restrictions are now removed. Mission planning will begin to 
schedule attitudes forwar of 130 degrees sun-pitch in the SEP0709 week (sooner only if an 
accepted TOO/DDT requires a replan).

Momentum dumps are now allowed as needed for momentum management in scheduling.

Auto-unloading is still enabled on-board and we plan to leave it enabled for the near-term. 
There are two patches in process to handle the possibility of the thruster "thermal-choking" 
anomaly leading to anomalouly long unloads: the MUPS firing parameters update which should 
prevent the anomalous performance and a stored command sequence that would terminate an unload 
if the anomaly appeared. The firing parameter update patch is ready and awaits scheduling of an 
on-orbit test. The stored command sequence needs to be tested on ASVT.

Several contingency CAPs (1118, 1126, 1132, and 1133) generated for responding to potential 
events are no longer needed and will be archived.

The thruster dump analysis tool will be updated with a new calibration to reflect thruster 
effectiveness at the current pressure.

There are some remaining analysis tasks to finish for the fault tree and the close-out 
flight note for this anomaly.

Future communications on this anomaly will come via the normal channels of the 
Chandra Flight Director's Board and daily operations tag-up.

I'd like once again to thank the team for a job well done