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Date: Sat, 18 Mar 2006 19:58:37 -0500
From: Thomas Wheeler
To: opm@stsci.edu
Subject: [Fwd: ACS Suspend Flash Update #2]

Date: Sat, 18 Mar 2006 19:17:20 -0500
From: Nzinga Tull
Subject: ACS Suspend Flash Update #2

ACS 926/917 STB and Suspend : Flash Update #2

At 4pm EST, 03/18/06, a tag-up meeting was held to discuss investigation
into why ACS suspended after a series of status buffer (STB) messages were
issued (HSTAR #10173). While the root cause of the anomaly is still under
investigation, it is suspected that the ACS FIFO pointer was somehow
corrupted. The last valid command processed by ACS was a transition from
"observe" to "operate" at 077/00:51:10 GMT. The first anomalous message
(926 STB), was received at 077/04:52:41 GMT. Invalid commands and STB
messages were continuously received for ~5 hours until ACS suspended at
077/09:44:10 GMT.

As there are no indications of damage to the instrument prior to ACS
suspending on orbit, SI SEs recommend bringing ACS back up to "operate."
In addition, the 926 and 917 commands should be patched so that ACS will be
suspended if these commands are issued. This will prevent ACS from
receiving multiple invalid commands before suspending in the event the FIFO
corruption occurs again.

After ACS suspended, a NSSC-I status buffer message 202 was received at
077/16:23:59 GMT (HSTAR#10175). Payload FSW engineers are currently
reviewing a NSSC-I dump to investigate the source of the 202 message and to
verify that the contents of NSSC-I memory before proceeding with ACS
recovery.

Another tag-up meeting will be held at 10pm EST, 03/18/06, to provide a
status of the NSSC 202 error and, if advised, proceed with the ACS recovery
and patching of 926 and 917 commands at approximately 11:30 pm EST.



GSFC Attendees: N. Tull, P. Pataro, M. Prior, L. Dunham, T. Cruz, E.
Ruitberg, P. Coleman, Holly Richardson, Darryl Dye, Keith Kalinowski

Call-in Attendees: Rodger Doxsey, Colleen Townsley, Greg Goulet, Tom
Wheeler, Alan Welty , Lisa Mazzu ca, Art Rankin, Ken Carpenter






=============================
Nzinga Temple Tull
Hubble Space Telescope
MOSES Systems Management
Jackson and Tull