A high-level panel of aerospace experts yesterday called for a sweeping reform of the nation's space program that, if adopted, would shift NASA's primary goals away from engineering feats for their own sake and toward scientific research on Earth's environment and the cosmos.

Space science activities such as interplanetary probes and studies of global change on Earth "rank above space stations, aerospace planes, manned missions to the planets and many other major pursuits which often receive greater visibility," the panel said in its report.

The Advisory Committee on the Future of the U.S. Space Program, appointed by the administration, recommended specifically that the government:Shift cargoes away from the space shuttle to a new unmanned rocket as soon as possible. Redesign the proposed space station to make it cheaper and simpler, and to make its primary focus the study of life in space. Slow manned exploration of Mars to a "go as you pay" approach. Either exclude highly skilled NASA employees from civil service limits on pay and management flexibility or begin converting certain facilities to university-operated research centers.

Within that framework, the two keystones of the panel's recommendations are "Missions to and from Planet Earth." The first, already being planned at NASA, is part of a vast international effort to use orbiting robots to study humanity's impact on the global climate and environment. The second -- missions from Earth -- embraces an initiative by President Bush, to be pursued at a pace limited by the availability of money, to develop the technology and scientific knowledge required eventually to send humans to Mars.

The panel, chaired by Norman Augustine, chairman and chief executive officer of Martin Marietta Corp., a major NASA contractor, was appointed by the administration last summer to help restore credibility and strength to the space program after a season of trouble. The committee spent 120 days holding sessions to hear from more than 300 witnesses.

NASA Administrator Richard C. Truly said that the report is "supportive of many of the directions we have been going" and that he expects some recommendations "will be implemented" while others "may not be."

The committee's report met a more uniformly favorable welcome outside NASA.

"We're absolutely delighted. It's a very strong report," said Louis Friedman, executive director of the Planetary Society. "It is critical in both senses of the word."

Sen. Albert Gore Jr. (D-Tenn.), chairman of the Senate science, technology and space subcommittee, praised the report as "a reasoned view of the space program and the changes that are needed to restore confidence and support in NASA." Gore said he will hold hearings on it soon.

John Logsdon, head of the Space Policy Institute of George Washington University, said the report is "an intense, comprehensive job

. . . . We're unlikely to get a better set of recommendations out of any other set of people . . . . I hope NASA will not fight a rear-guard action, but will recognize the common sense and consensus behind them."

Persistent technical and budget problems, as well as a dependence on the shuttle, had already forced NASA to begin another in a series of redesigns of the orbital facility. The panel recommended that the design make possible "end-to-end testing" of most of its components before launch and that the agency take "whatever time may be required to do {the redesign} thoroughly and innovatively."

The manned space program "is at a crossroads," the panel said in its 11-page executive report. "A focus must be given to this program now if it is not merely to drift through the decade ahead."

Noting the controversy swirling around the manned program, the panel said, "It can be argued that much of what humans can perform in space could be conducted at less cost and risk with robotic spacecraft -- and in many instances we believe it should be."

But the panel rejected arguments that astronauts be eliminated entirely. "There is a difference between {Sir Edmund} Hillary reaching the top of Everest and merely using a rocket to loft an instrument package to the summit," the report said.

Perhaps the most controversial recommendation from NASA's point of view is that the shuttle be downgraded in favor of a new rocket that can carry large cargoes and, when needed, people.

Rather than build another shuttle after the Endeavour -- which will replace the destroyed Challenger -- the panel said NASA should invest several billion dollars to develop an alternative expendable rocket as rapidly as possible, which would take at least a decade.

"The civil space program is overly dependent on the space shuttle for access to space," the panel said. It "has yet to demonstrate an ability to adhere to a fixed schedule. And although it is a subject that meets with reluctance to open discussion, and has therefore too often been relegated to silence, the statistical evidence indicates that we are likely to lose another space shuttle in the next several years."

Truly yesterday acknowledged, as he has before, that the shuttle entails inevitable risks. But he said, "The unbelievable capability and reliability of this system is something we really believe in."

The panel also recommended that highly skilled NASA employees, such as "rocket scientists," be excluded from existing civil service rules. Failing that, it said, NASA should convert some of its facilities around the country to research and development centers operated by universities under contract to NASA.

The administration and Congress should provide NASA with "predictable and stable funding . . . . The essential role of this support cannot be overemphasized if the U.S. is to have a successful civil space program," the panel said.

Because the panel is made up of aerospace insiders from government and industry, some critics predicted it would avoid the tough and divisive issues that beset the space program. For the most part, it did not. Among the members were former NASA administrator Thomas O. Paine, Edward C. Aldridge Jr., former secretary of the Air Force, former astronaut Joseph P. Allen and former House members Edward P. Boland and Don Fuqua.

Vice President Quayle, chairman of the Space Council, said, "The review has been thorough and now it is our challenge to begin its implementation."

It "is not a buy-everything wish list," he said, but proposes serious reforms as well as "charting a new path." Quayle said the Augustine committee will be reconvened in six months to assess progress in its implementation.

But the recommendations may face a gantlet of debate and resistance within NASA and on Capitol Hill, according to analysts.

An administration spokesman who did not want to be identified said, "The chances are better than ever we will implement a great proportion of these recommendations," if not in specific detail, at least "in spirit."

The president is still committed to his Mars exploration initiative but "obviously some sorting out of priorities was in order."

He also said the next presidential budget will give "a strong sense of where we're going to go" on developing an unmanned booster to supplement the shuttle.