STS-125/HST SM-4 Status Report No. 14 (Forwarded)

STS-125 MCC Status Report #14
Mission Control Center, Houston, Texas
Monday, May 18, 2009, 5 a.m. CDT

As Atlantis' crew begins their eighth day in space, astronauts Drew Feustel
and John Grunsfeld are hours away from conducting the final spacewalk on the
Hubble Space Telescope. The STS-125 crew awoke this morning to "Sound of
Your Voice" performed by Barenaked Ladies. It was played for Commander Scott
Altman.

There are two major focuses for today's spacewalk. The first objective for
Feustel and Grunsfeld is the removal of the battery module from Bay 3 on the
telescope and the installation of a fresh module. Each battery module weighs
460 pounds and contains three batteries. Each of the nickel hydrogen
batteries weighs 125 pounds, and they provide power to the telescope when it
passes into orbital night and the solar arrays are not exposed to the sun.
All of the batteries on Hubble are original equipment, and they were only
designed to operate for five years. The batteries in Bay 2 were replaced
earlier in the mission.

The second task is the removal and replacement of Fine Guidance Sensor (FGS)
2. Hubble has three of these sensors, and FGS 2 has degraded over time. The
three sensors are parked at 90 degree angles around the circumference of the
telescope, and two are used to point and lock the telescope on its targets.
The third can be used for astrometry, which is measuring the distances
between different celestial objects. The refurbished FGS that will be
installed today previously had been removed and returned on the third
servicing mission in December 1999. It has since been enhanced and upgraded.

After these two tasks are accomplished, Feustel and Grunsfeld will turn
their attention to the New Outer Blanket Layer (NOBL) on the outside of the
telescope's Bay 5. The NOBL on Bay 8 was due to be installed during
yesterday's spacewalk, but the crew was unable to accomplish it during the
spacewalk. If time permits, Feustel and Grunsfeld may be asked to install a
partial or full set of NOBLs on Bay 8.The team in Mission Control will make
the decision in real time based on the progress of the spacewalk.

The crew's sleep period will begin at 7:31 p.m. CDT, and the crew is due to
wake up tomorrow at 3:31 a.m. to begin procedures to release Hubble. The
next status report will be issued at the end of the crew's day or earlier if
events warrant.