The space shuttle Discovery made a flawless landing Saturday after a five-day mission that was hailed as the ideal beginning for an ambitious launch schedule in 1989 and beyond.

The shuttle and its crew of five glided onto the surface of a dry lake bed to the cheers of an estimated 450,000 spectators - the second largest to watch a shuttle landing.

"I was amazed," Rear Adm. Richard Truly, NASA associate administrator, said of the public's support. "I think the country realizes we're back."

It was the third successful mission since the Challenger disaster, which killed all seven astronauts and grounded the shuttle program for 32 months.

The program, which was relaunched with Discovery's flight in October last year, is now back in high gear. Six more shuttle flights are planned for this year, the most since 1985.

"Now the fun really begins," Truly said at a news conference, referring to the ambitious launch schedule for the rest of the year and 1990.

Discovery, an 87-ton spaceship, was in space for four days, 23 hours and 39 minutes. It landed at 7:36 MST, and crew members, led by Navy Capt. Michael Coats and dressed in orange space suits, stepped onto the runway 50 minutes later.

The return home appeared to be trouble free. The shuttle reduced its orbiting speed of 17,500 mph and passed through a heat barrier as it re-entered the Earth's atmosphere.

The crowd at Edwards Air Force Base in the California desert, second in size only to a July 4, 1982, Columbia landing audience of more than 500,000, was swollen by college students on spring break.

"It was exciting to be able to say, `I saw the shuttle land,' " said Dawn Smith, one of those who fought the traffic to get to Edwards. "It was well worth getting here at four in the morning."

The main purpose of the mission was the deployment Monday of a $100 million communications satellite.

The 2-ton TDRS-D satellite completes a network that will enable NASA to keep track of more than 20 spacecraft from a single ground station in New Mexico.

But the crew also shot dramatic film of the Earth's environmental damage for a wide-screen movie to be produced by a Canadian company.

The environmental damage included ocean pollution, African floods, burned areas of the Florida Everglades and parts of South America where the tropical rain forest has been destroyed.

The astronauts spent their flight cooped up with four laboratory rats and 32 chicken eggs on which they performed experiments designed to study the effects of weightlessness.

The crew dubbed themselves "the rat patrol" in honor of their furry rodent companions.

The rats' legs were broken before the flight. The animals are to be killed so that scientists can study the effects of zero gravity on the bone-healing process.

Arnold Aldrich, director of the National Space Transportation Program, said the mission "had perhaps the smallest number of in-flight anomalies of any flight we've flown."

"This flight of the shuttle again shows what a marvelous and capable vehicle it is," Truly said.

The most notable problem was a faulty fuel cell in a system that generates part of the power used on the shuttle. It forced the crew to turn the lights down for a day.

The fuel tank was successfully restarted Wednesday, and Aldrich said it was never a serious problem..

NASA officials were also happy over the apparent lack of damage to Discovery's heat-resistant tiles. On the previous shuttle mission, that of Atlantis in December, some of the tiles were badly charred.

"The vehicle is as clean as any I have personally ever seen," Truly said. "There is almost no visible tile damage at all."

The next shuttle flight is planned for April when Atlantis will ferry the $500 million Magellan probe into orbit on the first leg of its voyage to Venus. The probe, which has its own rockets to propel it out of Earth's orbit, is designed to provide high-resolution radar maps of the surface of Venus.

Discovery's flight was the 28th of the shuttle program.

Mission commander Coats, 43, flew aboard Discovery on its maiden voyage in 1984. Air Force Col. John Blaha, 46, a shuttle rookie, was the pilot.

The mission specialists were Marine Col. James Buchli, 43, who had flown twice before; Marine Col. Robert Springer, 46, a first-time shuttle flier; and physician James Bagian, 37, who was also on his first space flight.