Atlantis on track for rescue mission

Shuttle Atlantis will be ready to fly Aug. 21 if sistership Discovery suffers severe damage during its scheduled July 1 launch, forcing NASA to send up a rescue mission.

Atlantis is supposed to be launched Aug. 28 on a mission to resume construction of the International Space Station. But NASA has a plan in place to press the shuttle into service early if damage to Discovery strands its seven-member astronaut crew on the orbiting outpost. NASA engineers estimate that the shuttle astronauts could remain on the station with its current two-man crew for up to 82 days if need be.

The pacing item for an early Atlantis launch: work to ready an external tank for flight. A 15-story tank now is in a checkout cell in the Kennedy Space Center Vehicle Assembly Building. NASA will replace suspect fuel-depletion sensors in the tank; it should be ready to be hoisted atop a mobile launcher platform and mated to twin solid rocket boosters the first week of July.