The first space salvage mission ended in triumph here today when the five Discovery astronauts returned to Earth with two wayward satellites they had plucked from orbit for repair and reuse.

Falling out of pink-and-blue skies at 7 a.m., Discovery was flown to a perfect landing on the three-mile-long concrete runway at Kennedy Space Center by shuttle commander Frederick H. Hauck and pilot David M. Walker.

"Two landings in a row at Kennedy, and this time with a cargo bay as full as it was when it took off," Jesse W. Moore, NASA associate administrator for space flight, told reporters an hour after landing. "It's hard to believe those two satellites are sitting out there on the runway after being in space for more than eight months."

The recovery and return of the Palapa and Westar VI satellites took a lot of the sting out their loss last February, which forced insurance companies to pay $180 million to their owners, the government of Indonesia and Western Union Corp.

"I'm proud to be a part of the crowd that put this mission together in just six months," said Stephen Merrett, chairman of Merrett Syndicates, an affiliate of Lloyds of London, which helped to underwrite the insurance on Palapa and Westar.

"We expect Palapa to be resold for between 30 and 40 million dollars and Westar for $30 million, and we expect those sales to be concluded very soon."

Merrett declined to identify potential buyers of the two satellites. The governments of Thailand, Pakistan and Indonesia reportedly are interested in Palapa, a more advanced satellite than Westar with a concentrated signal designed for use in Southeast Asia. Possible buyers of Westar include most U.S. companies in the communication satellite business.

To National Aeronautics and Space Administration planners, the importance of the shuttle's 14th mission lay in the almost routine way that Discovery's crew handled the recovery and return of the two satellites.

"We have begun to reap the almost 25 years of experience we've had in space," shuttle program manager Glynn S. Lunney said in an interview. "It may have looked easy this time because we're experienced. The whole experience process, even among crews, has been so accumulative that we have begun to benefit by the lessons we've learned."

Lunney said the next candidate for repair in space is the Landsat satellite that is out of fuel and has been orbiting aimlessly for more than two years because it can no longer be positioned to point its instruments at Earth. Lunney also said that two large and expensive space observatories yet to be launched will be periodically refurbished in orbit by shuttle crews to prolong their lifetimes.

"I'm talking about the Gamma Ray Observatory and the Space Telescope," Lunney said. "These expensive machines must enjoy lifetimes of at least 10 years and the only way to ensure those lifetimes is through astronaut maintenance in orbit."

Apparently in good condition, Palapa and Westar VI will remain in Discovery's cargo bay until Sunday, when they will be carefully removed. The hazard that NASA foresaw in possible leakage of toxic hydrazine fuel still aboard the two satellites never materialized during reentry and landing.

The five crew members who landed with Discovery today were on their way back to Houston's Johnson Space Center before noon. Walking in their blue flight suits to the T38 jet trainers they use for transportation on Earth, the crew waved to a crowd of well-wishers and smiled for cameras.

Said Hauck: "We had a wonderful time up there and we worked very hard to do it, and these people you see behind me, David Walker , Dale Gardner , Anna Fisher and Joe Allen , all made it work."

The next space shuttle flight again will be aboard Discovery and will take place no earlier than Jan. 21. Its cargo is secret and its flight will be the first full shuttle mission for the Pentagon.

Meanwhile, NASA said it had "no knowledge" of a report published today in The Washington Post that the United States and the Soviet Union are discussing a demonstration rescue mission that could take place as early as next year. Said NASA's Jesse W. Moore: "I have no knowledge of this and the report did not come from my office."

The Post obtained a copy of a NASA document dated June 28, 1984, which states that President Reagan told the Soviets, "We have proposed a joint simulated space rescue mission in which astronauts and cosmonauts would carry out a combined exercise in space to develop techniques to rescue people from malfunctions in space vehicles."

Reagan signed legislation on Oct. 30 that renews the space agreement between the United States and the Soviet Union, which had been allowed to lapse in May 1982 in response to the events in Poland. It is understood that a NASA delegation is in the Soviet Union discussing possible plans for a joint demonstration rescue mission.

"Both countries want it and both want to demonstrate it," a high-ranking official at the Johnson Space Center told The Post.