Crew Attaches Final Station Solar Array
Frank Morring, Jr. 
The crew of the space shuttle Discovery installed the fourth and final solar array on the International Space Station (ISS) during a spacewalk March 19.
Spacewalkers Steve Swanson and Richard Arnold bolted the S6 truss element onto the starboard end of the truss, completing the station's 310-foot long backbone and providing a platform for the last 240-foot-long solar array wing, which is folded into the truss.
Rated at 66 kilowatts overall, the S6 arrays can add 21-30 kilowatts of usable power for the station's systems, of which 15 kilowatts would be for science. That would effectively double the power available to run scientific experiments as the station crew doubles to six in May.
However, problems with the 10-foot-diameter geared mechanism designed to rotate the two starboard arrays for maximum sunlight continue to limit the amount of power available from that end of the truss. Known as the solar alpha rotary joint (SARJ), the device remains crippled by the failure of its original dry lubrication.
Discovery must undock by March 25 to make way for a Russian Soyuz capsule bearing the next station crew and space tourist Charles Simonyi. As a result, a couple of chores that would have taken place during a dropped fourth extravehicular activity (EVA) -- installation of a GPS antenna on the Kibo laboratory module needed to guide Japan's new H-II Transfer Vehicle in September, and reconfiguring connectors on a patch panel that provides power to station control moment gyros -- were moved into EVA 2. The third EVA of the mission is scheduled for March 23 to reconfigure the truss after the array installation and lubricate the end effector on the station's Canadian robotic arm.
The station crew will handle other outside work left undone because of the dropped spacewalk after Discovery and the old Soyuz depart. Inside, the combined shuttle and station crews were concentrating on getting a new water recycling unit working before the crew grows to six.
Photo: NASA TV
