STS-125/HST SM-4 Status Report No. 10 (Forwarded)

STS-125 MCC Status Report #10
Mission Control Center, Houston, Texas
Saturday, May 16, 2009, 5 a.m. CDT

Mission Specialists John Grunsfeld and Drew Feustel are preparing to begin
the third spacewalk of Atlantis' mission to the Hubble Space Telescope. The
crew awoke this morning at 4:31 a.m. CDT to "Hotel Cepollina" performed by
Fuzzbox Piranha. The song was played for Grunsfeld.

The first activity for today's spacewalk is the removal of the Corrective
Optics Space Telescope Axial Replacement (COSTAR) and the installation of
the new Cosmic Origins Spectrograph (COS). COSTAR has been on board Hubble
since the first servicing mission in 1993. It has served as a sort of
"contact lens" for Hubble and was designed to correct a problem with the
telescope's optics. The new COS will be the most sensitive spectrograph ever
flown on Hubble and will examine large scale structures in the universe. The
COS weighs 851 pounds and is the size of a phone booth.

The second major task for Grunsfeld and Feustel is the repair of the
Advanced Camera for Surveys (ACS). The ACS is one of Hubble's primary
cameras and was installed during the fourth servicing mission the telescope
in 2002. It stopped working in early 2007 due to a short circuit in its
backup power supply, but it has been responsible for some of the most famous
imagery captured by Hubble. Grunsfeld and Feustel will focus on replacing
some of the camera's electronics, which will require them to remove 32
screws from an access panel. To accomplish this, the astronauts will use a
custom made fastener capture plate that will lie over the top of the access
panel and keep the screws from floating away.

Once complete, the entire crew will review the procedures for tomorrow's
spacewalk, which will be conducted by Mike Good and Mike Massimino.

The crew's sleep period will begin at 8:31 p.m. and crew wake will be at
4:31 a.m. tomorrow. The next status report will be issued at the end of the
crew's day or earlier, if events warrant.