The 18th mission of the space shuttle ended in near-flawless fashion today when Discovery and her international crew landed just after sunrise on the dry lakebed runway at Edwards Air Force Base in California's Mojave Desert.

Touchdown came at 9:12 a.m. EDT, ending a seven-day mission that accomplished everything it set out to do in orbit -- including launching three commercial satellites, releasing and retrieving one bargain-basement research satellite and successfully shooting a laser from Hawaii to the shuttle and back in a rudimentary test as part of the so-called "Star Wars" defense against enemy missiles.

Once again, however, the landing gear on the 100-ton spaceliner triggered concern among shuttle managers. All four wheels in the main landing gear dug six inches into the desert floor, three times deeper than is normal for Discovery.

"Parts of the runway were wet and may have been a little soft," Jesse W. Moore, NASA's associate administrator for space flight, said at a briefing, "but I don't have any complaints about the runways out here. They've been good to us so far." Moore said that landing gear is now NASA's chief shuttle worry, adding that a major effort is under way to strengthen the landing gear so crews can resume landing on the concrete runway in Florida.

"We're putting a high priority on all this so it may give us enough confidence to bring our vehicles back to the Kennedy Space Center," Moore said.

Shuttle landings were moved to California when Discovery landed too fast into a Florida crosswind April 19 and blew out a tire. The brakes were severely damaged.

Today's was the second California landing in a row, and the next four landings are all targeted for California. Each landing at Edwards costs $1.8 million, most of it in time lost ferrying the shuttle back to Florida and in paying overtime and travel money to landing technicians, who must be flown in from Florida.

"One difficulty we've had in a crosswind is that the pilot has to use differential braking braking more on one side to stay on the center of the runway, which causes the brake assembly to overheat," Moore said. "We're looking at a plan to tie in the nose gear to the onboard computer so he can use the nose wheel for steering instead of braking one side or the other."

Moore said there is also a move under way to stiffen the landing gear axles and possibly rebuild the shuttle's brake assembly, which was not damaged in yesterday's landing.

"It was a great trip," pilot John O. Creighton said. "I spent the last 24 hours hoping Dan Daniel C. Brandenstein, Discovery commander would get sick so I could do the landing, but it didn't happen. The only bad thing about it is I've got to get to the end of the line now and wait for my next trip."

With that, Brandenstein, Creighton, Fabian, astronaut Steven R. Nagel, scientist-astronaut Shannon W. Lucid, Saudi Arabian Prince Sultan Salman Saud and French Air Force Col. Patrick C. Baudry boarded a plane, where they planned to toast their mission with a bottle of French wine Baudry smuggled aboard Discovery.