Discovery crew continues maintenance and repair operations as shuttle program winds down.
A pair of crewmembers from space shuttle Discovery undertook a lengthy spacewalk early Sunday to swap out a coolant tank on the International Space Station.
Mission specialists Rick Mastracchio and Clayton Anderson spent 7-hours, 26-minutes outside Discovery removing a spent tank and installing a new unit that weighed in at 1,700 pounds.
The astronauts will take another space jaunt Tuesday to activate the tank's fuel lines, move the old tank to Discovery's payload bay, replace a camera light on the ISS's Destiny laboratory, and perform several other maintenance operations.
Meanwhile, ISS crewmembers are set to begin unpacking the 8-tons of cargo the shuttle delivered last week in the Leonardo Multi-Purpose Logistics Module.
The module contains science racks for use in the various labs throughout the station, new sleeping quarters and other supplies. The reusable module will become a permanent part of the space station following the next shuttle mission.
Discovery safely docked with the ISS early Wednesday, despite the loss of a radar system designed to assist with the maneuver.
The shuttle's Integrated Radar and Communications System, or "Ku band" radar, experienced what NASA officials called an "anomaly" shortly after the spacecraft's liftoff early Monday from Kennedy Space Center in Florida.
The space agency, however, said shuttle crews are trained to dock with the ISS without the radar's help. The shuttle's seven-member crew will work jointly with the six astronauts aboard the ISS over the next several days, conducting a series of experiments and maintenance operations.
The shuttle astronauts will also use the ISS's Ku band radar to transmit images of their mission to ground controllers on Earth, at least until the problem with their own system is fixed.
Discovery launched from Kennedy at 6:21 a.m. on April 5th. The 13-day mission, officially known as STS-131, will see the crew perform three spacewalks in total. The astronauts will also collect a Japanese science experiment and switch out a gyro assembly on part of the station's truss structure.
Discovery is commanded by U.S. Navy Captain Alan Poindexter, 48, of Rockville, MD. Three of the crewmembers—pilot Jim Dutton, mission specialist Dottie Metcalf-Lindenburger, and mission specialist Naoko Yamakazi of the Japanese Space Agency—are making their first flights into space.