NASA engineers worked through the weekend to ready the shuttle Discovery for a short trip to the Vehicle Assembly Building, the last stop before the move to the launch pad for the first post-Challenger flight.

A NASA spokeswoman said Sunday engineers and technicians in Discovery's hangar hoped to wind up final work on the shuttle's heat-shield tiles by early Monday.The schedule called for the paperwork used to document and verify processing to be closed out by midnight, clearing the way for "rollover" to the Kennedy Space Center's rocket assembly building Tuesday.

Once inside the giant building, the orbiter is to be be picked up by giant cranes, rotated into a vertical position and attached to its external fuel tank and boosters. After electrical and mechanical checks are completed, the shuttle will be ready for the trip to the launch pad.

A Tuesday rollover would mean a roll out to the pad on June 30.