HOUSTON - After successfully
docking with the International
Space Station (ISS), the Discovery astronauts interrupted their scheduled
tasks to perform a brief inspection of heat shield panels on the shuttle's left
wing leading edge.
The
unscheduled inspection was prompted by the detection of a very minor impact on
the shuttle wing early this morning and was a precautionary step done in order
to avoid a time-consuming focused inspection on the fifth day of an already
busy flight.
Sensors on
the wing designed to detect vibrations from impacts reported the ding at about
5:30 a.m. EST (1030 GMT) this morning, while the seven STS-116 astronauts were
still asleep.
During the
inspection, mission specialists Joan
Higginbotham and Sunita
Williams used the station's 57-foot camera-equipped robotic arm to scan
four reinforced carbon-carbon (RCC) panels on the shuttle's wing. Preliminary analyses
of the images reveal nothing of concern, said NASA deputy space shuttle manager
John Shannon in a news briefing today.
"The team
has looked and gone through and done their first pass on all of the wing
leading-edge RCCs and the nose cap and has identified no issues," Shannon said. "It is a very rigorous process."
He added
that the impact detected by the wing sensors was only about 0.12 gravity root
mean square (GRMS), about 1/100th of what would normally generate concern.
It takes about a 10 GRMS impact to create a scuff on a heat shield tile, and a
20 GRMS collision to make a crack or hole.
Images shot
by ISS crewmembers during Discovery's rotational
pitch maneuver (RPM) before docking--during which the orbiter performs a
360-backflip--also revealed minor
scuffs and discoloration on some of the tiles, particularly around the external
tank (ET) umbilical cord doors on Discovery's port wing, but these are not
expected to be of concern either, Shannon said.
Led by
STS-116 commander Mark
Polansky, the STS-116 crew will participate in three spacewalks over the
next week to install a new $11 million Port 5
(P5) spacer segment to the ISS, switch on a thermal cooling system and
rewire the orbital laboratory's electrical grid so it can draw power from a new
set of solar
panels arrays installed last month.
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