Pasadena, Calif. — The golden decade of US planetary exploration is over.
Bruce Murray, director of the Jet Propulsion Laboratory, which oversees the nation's unmanned space shots, calls it ''the end of the beginning'' - a glorious beginning in which the United States realized some of mankind's oldest dreams when it landed a man on the moon, searched for life on Mars, and explored the rings of Saturn and the moons of Jupiter.
Where the US has been is history. Where the US goes next is what worries people like Dr. Murray. In Washington, D.C., a major reassessment of the space program is under way with George Keyworth, director of the Office of Science and Technology Policy, in charge.
''The big question is, will we invest in (new planetary missions) for the '90 s during the '80s,'' Murray told a crowd of several hundred who turned out to hear him speak on a recent rainy night at the California Institute of Technology. ''If we don't, we won't be a significant player in planetary exploration. Other countries will.''
''The decision to be made is do we care about the future,'' he continued. ''It's the same decision we blew in the '70s. . . . The future is under our control if we choose to influence it.''
Because planetary missions take years to plan and execute, funding decisions must often be made a decade in advance. It was decisions made in the 1960s, for example, when the US was caught up in the space race with the USSR, that fueled the extraordinary period of exploration in the 1970s.
In contrast, only one new major US planetary mission, Galileo's trip to Jupiter in the late 1980s, is planned for this decade--a result of the slacking off of the government's financial commitment to the space program during the 1970s, a decade marked by pressing national issues such as the war in Vietnam, Watergate, and the oil crisis. In addition, the space shuttle has also gobbled up most of NASA's funds.
Equally worrisome to planetary scientists is the fact that under a budget-conscious Reagan administration several smaller, long-planned missions already have been canceled, including a probe of Venus and US involvement in a joint exploration of the sun's poles with the European Space Agency. A rendezvous with Halley's Comet, never officially a part of the NASA program, has also been canceled.
What these cutbacks mean for the 1980s, says Dr. Murray, is that the US will abandon its lead in space exploration. Although the US will dominate exploration of the outer solar system with its Galileo mission and the planned Voyager fly-bys of Uranus and Neptune in 1986 and 1989, the Russians, Murray says, ''will be the major player'' in exploration of the inner solar system with planned or possible missions to Halley's Comet, Venus, and Mars.
The Europeans and Japanese will be more involved. ''The cold-war mentality that launched the space race is changing. What we've got is a very important trend. Planetary exploration is becoming more multilateral,'' he says.
Because of that, he warns, the US must realize it can no longer act as it pleases when it comes to planetary exploration, but must work as an international coordinator--and must soothe the bitter feelings it provoked among its European friends when it pulled abruptly out of the joint ''solar polar'' mission.
''Our own national role will have to be part of a larger global scenario,'' he explains. ''We can't see planetary exploration strictly in US terms, especially once we've abandoned the leadership role, as we are doing.''
One impetus for adopting a more international stance, he says, already has been provided by the Reagan administration, which has voiced support for future space programs but only if missions can be done at a substantially lower cost.
Internationally planned and funded projects, explains Murray, would give the US the opportunity to work on the large-scale missions it has been used to launching at only a portion of the cost. In addition to big international missions, he says, planetary scientists will consider proposing smaller, less expensive national missions like a Mars polar orbiter project or a 1987 rendezvous with the asteroid Anteros.
Murray suggests that Americans may lose touch with ''the race of heroes'' that triumphed in space, just as modern Greeks ''lost accountability with their heroes.'' But he adds, ''I believe that in another 100 or 200 years, the solar system will be very familiar territory to our descendants.''