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Date: Fri, 15 Feb 2013 17:18:24 -0500
From: Ken Sembach
Subject: HST Status 5:00 PM, Friday February 15, 2013

Hello Everyone,

Early this morning about 3:12 AM local time, HST entered what is known as
"Software Sunpoint safe mode". This is one of the primary (and relatively
benign) safemodes that Hubble can enter when there is a problem with the
spacecraft or its primary subsystems. It is the same safemode Hubble entered on
Christmas Eve, albeit for a different reason. In today's case, a slightly
off-nominal solar array slew caused the safing. During the solar array slew,
the measured position for one of the two arrays differed by more than 10 degrees
from the commanded position for more than 3 seconds. Hubble's spacecraft
computer recognized that this was not normal, and onboard safing procedures were
executed as expected. The suspected cause of the solar array deviation is a bit
flip in one of the registers in the Solar Array Drive Electronics. Such an
error can be corrected and is not expected to be persistent.

Our STScI and GSFC teams are working on full recovery of Hubble this weekend.
Since this is such an unusual error, recovery procedures are being tested in the
vehicle simulator at GSFC, with an on-orbit test of the Solar Array Drives
tomorrow morning. Onboard health and safety procedures will ready Hubble for
science, and the science instruments (all of which are safe and in their
expected states) will be brought back online accordingly.

I'll send around an update once we recover the science timeline. Thanks to all
involved in this recovery effort here and at GSFC.

Hubble cheers,
Ken