Mission Control Center, Houston, Texas

HOUSTON - The crews of space shuttle Endeavour and the International Space Station spent the afternoon speaking with audiences around the world and preparing for tomorrow's spacewalk to evaluate a shuttle heat shield tile repair technique.

Mission Specialist Takao Doi was joined by shuttle Commander Dom Gorie and station Commander Peggy Whitson for a phone call from Yasuo Fukuda, Japan's prime minister, who conveyed his congratulations for the successful installation of the first component of the Kibo laboratory at the station. The astronauts also answered questions from Japanese students. Afterward, all 10 crew members discussed their flight with CBS News, NBC News and WMUR-TV in Manchester, N.H.

Mission Specialists Bob Behnken and Mike Foreman, along with their spacewalk coordinator Rick Linnehan, configured the tools they will use during Thursday night's spacewalk. Behnken and Foreman will employ a tool called the Tile Repair Ablator Dispenser (T-RAD) - a caulk-gun-like device - to apply a substance called Shuttle Tile Ablator-54 (STA-54) into purposely damaged heat shield tiles. Behnken and Foreman will then smooth the substance in place with foam-tipped tools. Those test samples will be returned to Earth to undergo extensive testing on how STA-54 performs in the environment of space. The demonstration is considered important in advance of the Hubble Space Telescope servicing mission later this year since that flight will be conducted independently of a “safe haven” capability at the ISS in the event the shuttle incurs damage to its heat shield.

Additional objectives of the spacewalk include replacement of a failed Remote Power Controller Module (RPCM) on the station's truss, including the temporary shutdown and spinup of Control Moment Gyroscope-2 (CMG). The RPCM replacement is needed to restore redundant power to CMG-2 and CMG-3.

Both crews reviewed procedures for that spacewalk, scheduled to start at 5:28 p.m. on Thursday and last 6.5 hours. Behnken and Foreman will sleep in the station's Quest airlock overnight for the standard spacewalk “camp out” procedure to purge the nitrogen from their bodies.

The fifth and final spacewalk is scheduled for Saturday to move the shuttle's Orbiter Boom Sensor System (OBSS) onto the station. This is caused by the size of the huge Japanese Kibo pressurized laboratory module, which will be delivered to the station aboard Discovery in May, preventing the shuttle from carrying its own OBSS. Once Kibo is installed, Discovery's astronauts will detach the OBSS left behind by Endeavour, use it to perform tile inspections and bring it home.

The next STS-123 status report will be issued after crew wake-up, about 12:30 p.m. Thursday, or earlier if events warrant.

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