Shuttle Atlantis on Schedule for Landing Today

Neither a troublesome auxiliary power unit nor bad weather posed any threat to today’s scheduled landing of the shuttle Atlantis, NASA officials said Saturday.

The spacecraft was set to touch down at Kennedy Space Center at 5:24 a.m. PDT, ending a nine-day mission that included the deployment of a $120-million communications satellite.

Three auxiliary power units operate the shuttle’s wing flaps, rudder and landing gears. Only one would be needed for Atlantis to touch down safely, NASA said.

Flight director Jeff Bantle told reporters at Johnson Space Center in Houston that the faulty power unit’s cooling system malfunctioned during a routine pre-landing test of the shuttle’s steering controls Saturday.

The same malfunction was originally spotted shortly after launch Aug. 2, but NASA engineers had hoped it was caused by ice that would melt during the mission.

The unit, one of three on board that power the shuttle’s steering and braking systems, would still be used during descent, but would be started later than usual to avoid overheating, Bantle said.

“I don’t think it is going to have a significant impact on the mission at all. We’ll probably land exactly where we want to land,” he said.

Atlantis could land with only one functioning power unit, but in that case it would do so at Edwards Air Force Base in California, where there is more margin for steering error on the base’s vast runways, Bantle said.

He said the weather was expected to be good at both Kennedy and Edwards.

The five astronauts spent Saturday completing medical and technical experiments and stowing gear in preparation for landing.

Earlier Saturday, shuttle communicator Bill Shepherd on the ground woke the crew to the sounds of chirping crickets and croaking frogs.

“We hope to be back there (on Earth) soon, but we’re in no rush,” mission specialist Shannon Lucid said.

Atlantis is attempting to make the first scheduled landing in Florida since 1985.

Kennedy was relegated to secondary status because of safety concerns raised by the Challenger explosion in January, 1986. Its smaller runways and trickier weather were thought to make landings there more risky.

Two shuttles have landed here since the Challenger explosion because of poor weather conditions at Edwards. NASA is improving the shuttles in an effort to return more of the spaceships to Kennedy and avoid piggybacking them across the country on jumbo jets.