Discovery Crew Winds Up Work; Due Home Tonight

Discovery’s astronauts shut down experiments and checked flight control systems Saturday as they prepared to end their secret military mission with a rare night landing in the California desert.

NASA gave no details of the flight, but standard procedure for the day before a landing would call for Commander Frederick D. Gregory and pilot John E. Blaha to run through a series of tests to make certain the shuttle’s computers and control jets were ready for the return to Earth.

Mission specialists Manley Lanier (Sonny) Carter Jr., F. Story Musgrave and Kathryn C. Thornton were expected to pack up the experiments. Some of the tests were believed to be connected to the “Star Wars” missile defense project, and others reportedly tested the astronauts’ capabilities as military observers in space.

Discovery is scheduled to land at 7:02 this evening at Edwards Air Force Base.

Just as Discovery on Wednesday became the third shuttle in 32 missions to be launched after dark, it will be the third to land at night.

The National Aeronautics and Space Administration reported Saturday that conditions at Edwards were expected to be acceptable for landing, with winds gusting from 12 to 20 m.p.h.

Mission rules dictate that the shuttle not land in crosswinds of more than 20 m.p.h. But there are several runways to choose from at Edwards, enabling the shuttle to select one that could avoid the strongest breezes hitting it broadside, officials said.

Otherwise, conditions were expected to be favorable, with scattered clouds at 8,000 feet and visibility of 7 miles.

If the winds interfere, the shuttle generally carries enough food, fuel and other supplies to stay up at least two days beyond the target landing date.

Edwards Air Force Base, which has been host to as many as half a million people for shuttle landings, will be closed to the public today because of the military nature of the flight.

The news blackout was imposed by the Defense Department, which wants to keep the flight’s goals a secret. However, sources who spoke on condition of anonymity reported earlier that the astronauts had achieved their main task on Thursday when they deployed a 2 1/2-ton spy satellite to gather military intelligence over much of the Soviet Union, Europe, Africa and the Middle East.

The next shuttle flight is set for Dec. 18, when Columbia is due to lift off here for a 10-day Christmastime flight.