The Endeavour crew completed a routine inspection and completed the third of four planned spacewalks, NASA reports.
Space shuttle Endeavour's crew completed an inspection of the
shuttle's thermal protection system the morning of May 26, NASA reported. The
crew began the inspection early and used the 50-foot-long Orbiter Boom
Sensor System to conduct a high fidelity, three-dimensional scan of
areas of the shuttle that experience the highest heating during entry -
the wing leading edges and nose cap.
The late inspection occurred earlier in the mission than normal,
prior to undocking. As a consequence, the risk of re-entering with
undetected micrometeoroid debris is increased but deemed acceptable.
Managers and engineers in Mission Control will review the data to
validate the heat shield's integrity and assure it has suffered no
significant micrometeoroid and orbital debris damage, the space agency
The inspection is a routine precautionary check for any damage that
may have occurred during the docked phase of the mission, although this
is usually done after undocking. Because the orbiter boom will be left
on the space station, it is necessary to perform the inspection while
the two vehicles are still mated.
During the mission's fourth and final spacewalk scheduled for May 27, the boom
will be left at the space station to extend the robotic reach. Mike
Fincke and Greg Chamitoff will prepare it for its stay by replacing its
grapple fixture with a power data grapple fixture to enable its use as
the new International Space Station Boom Assembly. Once on station
without power and in the extended exposure to the vacuum of space, the
boom's imagery sensors will cease functioning.
Endeavour Mission Specialists Drew Feustel and Mike Fincke installed
a power and data grapple fixture on the Russian Zarya module during a
6-hour, 54-minute spacewalk early May 25, bringing the International
Space Station's Canadarm2 closer to having a new base of operation,
giving it access to much of the orbiting laboratory's Russian segment.
The arm can "inchworm" its way to the new base by grasping it and
then releasing the hand holding the old base to become the new end
effector. A cable to provide power to that new operating base is on the
to-do list for the fourth spacewalk of the mission. The spacewalkers
also installed a video signal converter on Zarya and ran power cables
from the U.S. segment to Zarya, which provides a backup for
transmission of power from the solar arrays to the Russian segment.
Feustel and Fincke used a new procedure to prepare astronauts for
spacewalks. They breathed oxygen for an hour, then put on spacesuits
and did "light exercise" for 50 minutes, standing and doing slow
intermittent movements. The procedure avoids the overnight stay in the
Quest airlock that had become standard, according to a mission overview
provided by NASA.
The spacewalk brought the total time spent for station assembly
construction and maintenance to 995 hours and 13 minutes during 158
spacewalks. The mission's fourth spacewalk is expected
to break the 1,000-hour mark. It will also be the last spacewalk by
space shuttle crewmembers. A spacewalk during the program's final
mission, STS-135, is to be conducted by space station residents.