United Space Alliance technicians remove the coverings from a site near the tail of Space Shuttle Atlantis to reveal the power drive unit.

United Space Alliance technicians (left to right) Tod Biddle, Bob Wright and Mark Noel (hidden) remove the coverings from a site near the tail of Space Shuttle Atlantis to reveal the power drive unit (PDU) inside. The PDU controls the rudder/speed brake on the orbiter. Shuttle managers decided to replace the faulty PDU, about the size of an office copy machine, at the launch pad. If successful, launch preparations will continue as planned, with liftoff targeted for April 24 at 4:15 p.m. on mission STS-101. The mission is the third assembly flight for the International Space Station, carrying logistics and supplies to the Space Station, plus the crew will be preparing the Station for the arrival of the Zvezda Service Module, expected to be launched by Russia in July 2000. The crew will conduct one space walk to perform maintenance on the Space Station