Astronauts aboard Space Shuttle Discovery gathered valuable new data during the third spacewalk today as part of an ongoing evaluation of repairing a damaged orbiter.

Mission Specialists Piers Sellers and Mike Fossum began the spacewalk at 6:20 a.m. CDT and prepared a foot restraint on the end of the International Space Station's Canadarm2. Sellers rode the arm, commanded by Mission Specialists Lisa Nowak and Stephanie Wilson, to the starboard wing of Discovery where he used an infrared camera to shoot 20 seconds of video of selected reinforced carbon carbon panels on the wing's leading edge. Infrared imagery may aid in identifying damage on the inside of those panels.

Fossum translated to the aft of Discovery's payload bay to join Sellers and help prepare a box containing 12 RCC sample panels for the EVA's primary task of testing a repair material known as NOAX. Non-oxide adhesive experimental is a pre-ceramic polymer sealant containing carbon-silicon carbide powder, and is being evaluated for repairing damage to RCC panels.

Data gathered from tests on mission STS-114 last year indicated NOAX is most effective when applied while the temperature of an RCC panel is falling between 120° F and 30° F, so today's spacewalkers were directed to apply NOAX to the pre-damaged RCC panels based on the temperatures of the panels. Over the course of almost two and a half hours, Sellers and Fossum completed three gouge repairs and two crack repairs with NOAX, and provided Mission Control a running dialogue describing the repair activity and how the NOAX responded. They also imaged four of the samples with the infrared camera, which Fossum also used to gather video of an area of Discovery's port wing while riding Canadarm2 back to the airlock.

Near the end of the EVA, Mission Control added a task to the spacewalk. Since the spacewalkers were on schedule and had plenty of supplies, Sellers carried a Pistol Grip Tool to the Integrated Cargo Carrier in Discovery's payload bay and removed the fixed grapple bar used during delivery of the Pump Module during the second spacewalk. He carried it to the S1 Truss where Fossum helped him install it on an ammonia tank inside that truss so that the tank can be moved on a later shuttle assembly mission.

Repressurization of Quest began at 1:31 p.m., completing a 7-hour, 11-minute spacewalk, the 68th in support of ISS assembly and maintenance. The cumulative duration of the three spacewalks on this mission is 21 hours and 29 minutes. Sellers' total spacewalking time of 41:10 on six EVAs ranks him 4th among U.S. spacewalkers and 9th in the world all-time.

ISS Expedition 13 Commander Pavel Vinogradov and Flight Engineers Jeff Williams and Thomas Reiter concentrated on packing the Multipurpose Logistics Module today with returning experiment samples, unneeded hardware and trash. The Leonardo module is scheduled to be returned to Discovery's payload bay on Friday.

The next STS-121 mission status report will be issued Thursday morning, or earlier if events warrant.

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