The Atlantis astronauts radioed greetings to the "brave warriors" of operation Desert Shield and packed up for landing Monday, presumably leaving a mysterious Pentagon satellite behind in orbit.

Flying upside down over the Indian Ocean, shuttle commander Richard Covey and co-pilot Frank Culbertson planned to fire Atlantis's twin braking rockets one orbit early, sources said, to kick off an hourlong glide to a 1:48 p.m. PST landing at Edwards Air Force Base, Calif.Breaking three days of official radio silence Sunday, the astronauts sent greetings to U.S. troops stationed in Saudi Arabia, the first time comments from the crew of a military shuttle mission have been released.

"To the men and women of Desert Shield," Covey said. "Whenever we've passed close to Saudi Arabia, we could not help but think of our soldiers, sailors, airmen and Marines deployed there for Desert Shield.

"As the holiday season approaches, the multi-service crew of Atlantis wishes those brave warriors peace and a speedy return home. Our prayers are for them and their families."

The mysterious satellite launched from Atlantis Friday may one day be used to spy on the Persian Gulf region, although the purpose and capability of the Pentagon payload are far from clear.

The shuttle was clearly visible to observers at the Cape Canaveral, Fla., launch site Sunday evening as it sailed overhead, a brilliant, swift-moving "star" that slowly disappeared from view as it passed into Earth's shadow.