A record crew of five men and two women was aboard the space shuttle Challenger today for a predawn liftoff that began an eight-day mission promising to be one of the most ambitious observations of Earth ever undertaken.

The launch went off without a hitch at 7:03 a.m. EDT as scheduled.

Before the day was over, the crew had deployed a radar antenna that can "see" beneath the Earth's soil, and a $40 million scientific satellite designed to study how solar energy influences Earth's climate.

However, the crew fell three hours behind schedule and was forced to put in a 16-hour-plus workday when the two solar panels that supply electricity to the 5,000-pound Earth Radiation Budget Satellite (ERBS) refused to unfold.

While crew members and flight directors at Mission Control in Houston tried to find out why the panels were stuck, the crew went ahead and deployed the 15-foot-wide antenna, called the Shuttle Imaging Radar, to make up some lost time.

The crew for the 13th flight of the shuttle program -- and the sixth by Challenger -- includes Navy Capt. Robert L. Crippen, 47, the commander; Cmdr. Jon A. McBride, 41, the pilot; Lt. Cmdr. David C. Leestma, 35; Dr. Paul D. Scully-Power, 40, and Canadian Navy Cmdr. Marc Garneau, 35, the second non-American to fly aboard a U.S. spacecraft. But today belonged to the two women on board: Sally K. Ride, 33, making her second shuttle flight, and Dr. Kathryn D. Sullivan, 33, who next week is to become the first American woman to walk in space.

Sullivan, a geologist and oceanographer, deployed the radar antenna while flight directors tried to discover why the ERBS solar panels refused to respond to four commands. Sullivan had some trouble with the radar deployment, also; the antenna wobbled when only one of its two "leaves" was erected in space.

"The antenna wasn't too happy about having one wing out and one wing in," Sullivan said after she successfully deployed the antenna. "Right now, though, it looks nice and flat and stable."

Ride saved the day for the ERBS orbiter when she used the shuttle's mechanical arm to place the satellite's two bright-blue solar panels in the sunlight to thaw the hinges, which apparently had frozen and were refusing to let the panels unfold. It took her almost three hours to get the panels warm enough to respond to commands to unlock.

"We're seeing it move," Ride said after the first panel unfolded. "Outstanding!" astronaut David Hilmers replied from Houston's Johnson Space Center. "We have a lock indication" -- meaning the panels had locked in their deployed position. "That's great," Ride replied.

The satellite was deployed on the shuttle's eighth revolution of the Earth (it had been scheduled for the sixth) and was placed into orbit off the west coast of Mexico (instead of south of Bermuda). Flight directors said there was no need for concern about the delay or the change in placement; later, they sent the orbiter new computer instructions to get it to an altitude 380 miles above Earth, from which it will study the planet's atmosphere and oceans.

Before the astronauts ended their day, they powered up the new radar antenna, whose signals can penetrate vegetation and even desert floors.

The radar sends out thousands of pulses every second, in place of the single pulse that conventional radar antennas emit to find and observe a target. The thousands of echoes the radar antenna receives allow it to draw a photograph-like image of the part of Earth its beams strike.

In addition, the radar's wavelength is so long it can penetrate any soil not covered by water. A smaller version of the antenna flown aboard Challenger last year found a previously unknown underground river beneath the Egyptian desert.

The radar antenna is expected to "photograph" 18 million square miles of the Earth's surface during this eight-day mission. The radar will survey deserts in Egypt, Sudan, Saudi Arabia, Oman, India, Peru and Namibia.

"We will also use our radar to look at three of the most dangerous areas of oceans of the world, where waves grow so high they endanger shipping for miles around," said Dr. Charles Alachi of the Jet Propulsion Laboratory in California, where the radar was built.

Today's launch took the 100-ton spaceliner on a path that could be seen as far north as Jacksonville and as far south as Miami. Blazing into the early morning skies, Challenger left a smoke-and-vapor trail that the rising sun turned into brilliant hues of blue, rose red and bright yellow. The shuttle's main engines could be seen burning for almost three minutes, nearly the limit of the naked eye's ability to track the speeding spacecraft.

"Everybody's having fun up here," Crippen said as Challenger streaked into orbit. Some insulating tiles on the craft's engine pod appeared to have been damaged in the launch, but the problem was not thought to be serious.