Just before 2 a.m. today, astronauts Robert L. Crippen and Paul L. Weitz flew their weather reconnaissance plane over Launch Pad 39A on a first sweep of the area before launch of the space shuttle Challenger. They found sheets of rain.

Fewer than 15 minutes before the scheduled liftoff, they made their second flyover as five astronauts waited inside the shuttle for news about the storms delaying the flight.

Back from Crippen and Weitz came word that rain had stopped but freezing moisture lingered in clouds, a dangerous condition that could help spark lightning if the 100-ton spaceliner tried to punch through.

Crippen and Weitz were told to make a third pass and, within minutes, determined that the murky skies had cleared. So Challenger roared away from Kennedy Space Center at 2:32 a.m., 17 minutes late.

The delayed liftoff, also 17 minutes before the launch "window" would have closed, climaxed several hours of worry and weather-watching by everyone connected with this eighth shuttle launch.

The "window" marks the earliest and latest possible launch times that would enable the shuttle to reach various orbital destinations in time for its crew to carry out assignments, particularly placement of a weather satellite to be put in orbit early Wednesday.

As the clock ticked right up to the scheduled liftoff time of 2:15, Crippen and Weitz got their first look at Challenger bathed below in searchlights. Not only had the rain stopped, but clouds that had blanketed the area from 9,000 to 20,000 feet for almost four hours also had begun to break up and the freezing precipitation had disappeared.

"One minute, we were being told we had three launch-commit violations, and we were very pessimistic and getting ready for a scrub," Launch Operations Recovery Director Thomas Utsmann said here early today. "Suddenly, we were hearing we had no violations at all."

Utsmann was referring to rain, excess cloud cover and freezing precipitation and violations of NASA rules governing the controllers' final commitment for a launch.

Challenger soared aloft, its two booster rockets and three main engines providing a long, brilliant tongue of orange flame that turned night into day and carried into space astronauts Richard H. Truly, Daniel C. Brandenstein, Dale A. Gardner, Dr. William E. Thornton and Guion Stewart Bluford II.

Challenger's night launch made space history, and so did Thornton and Bluford. At 54, civilian physician Thornton is the oldest astronaut, and Air Force Lt. Col. Bluford, 40, is the first black American to fly into space.

Despite the weather miseries, the crew breezed through its first day in orbit. The only hitch was failure of a hydraulic circulation pump feeding warm fluid through cold plumbing on the underside of the shuttle's fuselage when it is pointed away from the sun.

"We don't need that circulation pump on this flight," Flight Director Harold Draughon said at the Johnson Space Center in Houston, which took control of the mission as Challenger cleared the launch tower. "We know from past experience that's not going to be a problem."

The astronauts are to spend five more days in space, with another first scheduled Monday when Challenger is to make the first shuttle landing in darkness. The event is planned for 3:40 a.m. at Edwards Air Force Base in California's Mojave Desert.

The crew's first major task, scheduled about 4 a.m. Wednesday, involved deployment over the Pacific Ocean of a $43 million satellite for the government of India.

The satellite is to aid in weather forecasting, broadcast radio and television programs and speed telephone calls to as many as 100,000 villages in India that have never had television or telephones.

The satellite is to be dropped out of Challenger's cargo bay, then propelled on a path that should carry it in about 10 days to a permanent position over the Equator and keep it hovering over India for 10 years.

Fewer than three hours after they attained orbit, the astronauts communicated for the first time to Earth through a $100 million communications satellite orbited during the sixth shuttle mission last April. That Tracking and Data Relay Satellite was almost lost after its major onboard engine failed to push it into proper orbit.

Three months of patient rescue work involving thousands of radio signals and almost 50 radio-controlled firings of its 24 thruster engine finally moved the TDRS to its final destination above the Equator just east of northern Brazil.

Flight Director Garry Green said today from Houston that the highlight of this mission's first eight hours "has got to be that first TDRS pass" in which the astronauts switched from communicating to Earth through ground relay stations and talked through the TDRS.

When the Indian satellite is deployed, the astronauts are to begin using the 50-foot-long robot arm in the cargo bay to exercise an 8,500-pound device shaped like a dumbbell.

The arm was tested on two previous shuttle flights but never lifting as much weight. On future missions, the arm is to be used in deploying and retrieving satellites that weigh as much as 10,000 pounds.

If today's liftoff proved a spectacular reward to crowds who stayed up to watch it along the Florida coast, the sight was even more remarkable to shuttle astronauts leaving Earth in darkness for the first time.

"Boy, you should have seen it from up here," flight commander Truly, a Navy captain on his second shuttle flight, told controllers after Challenger entered orbit. "It was blue light almost all the way up."

Navy Lt. Cmdr. Gardner said he "looked back and darned near blinded myself. It looked like we were totally enveloped in a ball of flames.

"I guess it was the light reflecting off aerosols in the air, but the flame appeared to be all around us like we were in the center. Later on, I turned around again and just the main engines were making a much brighter flame than I ever expected, and it was pulsating almost as if an engine was running back there unstable . . . .

"I asked Dan pilot Brandenstein, a Navy commander if all the engines looked OK, and the flame was going out all around the vehicle and pulsating.

"The last thing I remember was when the external tank separated, which was the biggest surprise of all. It looked like we were inside a ball of flame for about 15 seconds, in fact it looked like it was never going to stop. The night situation is really different . . . ."