A Day Late, Atlantis Points Into Wind and Lands Successfully : Space: The shuttle and its five crew members conclude a voyage that was extended because of weather problems at Edwards Air Force Base.

After an extra day in space caused by gusty winds here, the space shuttle Atlantis finally returned to Earth Thursday, touching down at 6:55 in the cold, crisp dawn.

The crowd of 5,000 present Wednesday had dwindled to a meager 1,000 who braved the 37-degree temperature and wind gusts up to 21 m.p.h. to cap a mission that had featured the launch of the second of NASA’s four great observatories and the first American spacewalk in five years.

Atlantis landed on Runway 33, which had never been used before, in order to land into the wind. The successful landing ended 1991’s first shuttle mission, a six-day flight for Atlantis commander Steven Nagel, pilot Ken Cameron and mission specialists Jerry Ross, Linda Godwin and Jay Apt.

Apt was so excited when the astronauts disembarked that “he bounced around,” said ex-astronaut Paul J. Weitz, deputy director of the Johnson Space Center in Houston, who was here for the landing. “He had one heck of a good time.”

After tests are completed next month, the Gamma Ray Observatory launched by Atlantis will start scanning the heavens for gamma rays, which penetrate interstellar gas and dust, allowing astronomers to use the observatory to “see” very distant objects.

The observatory will help astronomers study some of the most violent phenomena in the universe, including exploding stars called supernovas, super-dense black holes, stars called pulsars, the centers of active galaxies and incredibly bright objects called quasars.

Thursday’s landing occurred just one day before the 10th anniversary of the National Aeronautics and Space Administration’s first shuttle launch. Columbia lifted off from Cape Canaveral, Fla., on April 12, 1981, and landed in California two days later with astronauts John Young and Robert Crippen, who now heads the shuttle program.

Reflecting on the shuttle’s first 10 years, Weitz said at a post-landing news conference that NASA has “demonstrated that we do have a reusable system. It’s a little more complex than we had hoped it would turn out to be, but we are learning how to cope with that, how to get the process running smoothly and routinely.”

Today also is the 30th anniversary of the first manned spaceflight: Soviet cosmonaut Yuri Gagarin’s one-orbit ride aboard the Vostok 1 capsule on April 12, 1961.

The next planned launch will be the orbiter Discovery, which will carry the last Department of Defense payload to be orbited by NASA. The experiments on board are intended to provide information that will improve the military’s ability to detect and intercept enemy missiles.

The agency is aiming for an April 23 launch for Discovery, 18 days after Atlantis’ send-off. NASA has not launched two shuttles in the same month since January, 1986. The second ship to go up that month was Challenger, which exploded 73 seconds after liftoff, killing all seven aboard.

Discovery’s trip will be the 40th for the fleet. Discovery was supposed to lift off with its five-member crew and Pentagon cargo in early March. But large cracks were discovered in the mechanisms that open and close doors to the fuel inlet, and shuttle managers decided it was too risky to fly.

The shuttle was hauled from the launch pad back to the hangar last month, and workers replaced the cracked metal hinges with reinforced devices. NASA returned Discovery to the pad in early April.

Smaller cracks were found in the same place on the Atlantis and Columbia shuttles as well as the new orbiter Endeavour, which rolls off the assembly line April 25.

Officials proceeded with Atlantis’ flight despite the cracks after judging them too small to be of concern. The two fuel inlet doors closed tightly after liftoff last Friday and protected against the terrific heat of Thursday’s re-entry.

The delay of Discovery forced NASA to drop one shuttle mission from this year’s schedule. Five more flights are now planned for 1991.