IT will be months and years before experts assimilate all the new data on Neptune. But even laypeople know how extraordinary is the fact of seeing an unknown sovereign world 2.5 billion miles away roll past on their living-room TV screens. Voyager's triumphant 12-year tour of Jupiter, Saturn, Uranus, and Neptune is an event that can't be repeated for another 160 years. That's how long it will be before the orbits of the outer planets line up so that space probes can hop from one to the other - ``surf the great cosmic wave'' as it is known among astrophysicists.
Voyager wasn't expected to make it to Uranus, let alone Neptune. Yet despite a half-functioning transmitter and computer memory problems, scientists at the Jet Propulsion Laboratory reprogrammed Voyager en route. Thus, the new facts about Neptune are something of a gift - one that couldn't be duplicated for a decade, even if a Neptune-bound probe were launched tomorrow.
Neptune is very different than expected. Its rings are fuller and ``clumpier.'' Its rotation rate is faster. It has eight moons - six more than were known in 1977. Further, Neptune, thought to be much like Uranus, is not as bland as that planet. It has spectacular weather - winds of up to 450 miles an hour creating huge centuries-long storms. Since weather is considered dependent on heat, what heats this planet so far from the sun, scientists wonder?
The ability to ask such questions accentuates the importance of unmanned missions. For now, probes are the best means of exploring the solar system and the stars. Congress and NASA should keep such exploration on the top of the space priority list - though not framing the issue counterproductively as ``unmanned versus manned'' missions.
The fact is, future manned missions will depend on information secured from unmanned probes - whether it's a lunar orbiter designed to find ice or moisture at the moon's poles that would help sustain life on a moon base, or a Mars reconnaissance.
The Galileo probe exploring Jupiter's atmosphere will be launched in 1995. The Craf-Cassini probe talked about as a joint NASA-European Space Agency venture (a fly by of Saturn and a comet) is worth funding.
New space telescopes already built but as yet unlaunched - the Hubble scope for unfiltrated photography, a gamma-ray scope for information about black holes and neutron stars, an X-ray scope, and a cosmic radiation scope - all will yield rich information.
Voyager has shown that such enterprises deserve high priority.