Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/ops/swat/safing/96195/flash-7-16.txt Дата изменения: Mon Apr 26 17:33:47 1999 Дата индексирования: Sun Mar 2 02:28:43 2014 Кодировка: Поисковые слова: moon

From: "Wolf_Charlie"
Sender: hst-status@stsci.edu
To: miller@stsci.edu
Subject: Safing Event Flash Report
Date: Tue, 16 Jul 1996 09:09:44 -0400

Safing Event Flash Report

On Day 195/17:31, the observatory entered Inertial Hold safemode as a =
result of failing the Earth/Moon Bright Object test. The safemode test =
failed as a result of a step change in the second element of the vehicle =
attitude quaternion, which occurred at 195/16:46:35. This caused a =
change in the expected vehicle attitude of approximately 7 degrees. A =
guide star reacquisition was commanded at 195/17:31 at which time the =
flight computer determined that the vehicle was still in a V1 occultation =
state (based on the erroneous attitude quaternion) and the Earth/Moon =
Bright Object test failed.

The step change in the second element of the vehicle attitude quaternion =
resulted from a bit flip in the 18th bit of the higher order quaternion wo=
rd. Two other bit flips in different memory locations have also been =
identified. These also occurred in bit 18. No other bit flips have been =
identified either at event time or following the event. Investigation is =
currently focusing on the read/write operations in the DF-224 and the =
CoProcessor.

The observatory has been recovered from safemode and is currently =
executing a health & safety SPC load in preparation for re-intercepting =
the science timeline. The onboard recorder configuration will be changed =
to allow for engineering telemetry recording during LOS (TDRSS ZOE) =
periods. Combined with real-time data, this provides 100% engineering =
coverage. This will ensure the ability to detect and analyze a =
reoccurrence of the problem. To accommodate this change, the SMS is =
being replanned using one science tape recorder.