Shuttles get limelight, Venus probes just get data

While national attention has been focused on the glitch-plagued but ultimately successful space shuttle Columbia, scientists involved for more than two decades in planetary exploration have been quietly celebrating their own achievement.

At ''an International Conference on the Venus Environment'' here Nov. 1-6, some 200 participants summed up findings from 20 years of flybys, landings, and orbits of Venus by various Soviet and American spacecraft. The meeting was sponsored by the National Aeronautics and Space Administration's (NASA) Ames Research Center at nearby Moffet Field .

Since Dec. 4, 1978, the Pioneer Venus orbiter has been sending back data collected in more than 1,000 elliptical orbits around the planet. A second Pioneer, which arrived at Venus on Dec. 12, 1978, delivered five probes which entered the cloud-draped Venusian atmosphere, sent back their data, and disappeared.

The Soviets, who have sent a dozen ''Venura'' probes to Venus since 1961, were expected to have representatives at the conference here - but none showed up. Nevertheless, reports utilizing Venura findings were presented by participants.

Ames spokesmen said the time seemed right for a wrapup of this sort, since Pioneer data interpreted in the past two years have yielded significant findings - and questions. A ''compendium textbook'' to be issued by the University of Arizona after the conference is being described as ''the definitive work on Venus for years.''

Reports at the Nov. 1-6 meeting dealt with subjects such as the overall circulation patterns of the massive Venusian atmosphere; the pattern of atmospheric changes and the sun's contribution; surface characteristics, including volcanoes, and the ratios of rare gases in the atmosphere and what they indicate about the planets of the solar system.

Most relevant to environmental concerns on Earth was proof that the ''greenhouse'' mechanism keeps the Venusian surface temperature at 900 degrees F. In a Monitor interview, Dr. James B. Pollack, one of several Ames scientists studying the Venusian atmosphere, explained why he and his colleagues are confident they have the right explanation for the greenhouse effect and why it is of enormous import on Earth.

Data from Pioneer on the components of the Venusian atmosphere that created the greenhouse effect have enabled NASA scientists over the past two years to produce a totally convincing model of how the searing heat of that planet has been produced.

Now Dr. Pollack and his colleagues feel that the world must act on the warnings they and others have been issuing over the past several years. Earth's inhabitants, he says, must make some decisions on the burning of fossil fuels.

The amount of carbon dioxide in Earth's atmosphere has risen 10 percent in the last two decades. Sometime fairly soon, there could be enough CO2 in the atmosphere to cause a greenhouse effect that would be harmful to agriculture and melt enough of the polar icecaps to flood coastal areas.

Earth's residents, says Pollack, need to consider the ''right mix'' of energy sources and environmental controls to prevent this.

He and his fellow scientists are not saying that Earth faces exactly the same fate as Venus. Each planet has characteristics that make it unique. Earth, for example, has huge oceans that apparently have absorbed 50 percent of the CO2 so far added to the atmosphere by the burning of fossil fuels. There are other components of Earth's atmosphere that might cause variations in the greenhouse effect - but the overall effect could still be calamitous.

''There is a real possibility,'' Pollack notes, that early in its history Venus had a moderate climate and even an ocean. That being so, ''There is no reason Venus couldn't have had life that was done in by a runaway greenhouse effect.''

Pollack and others here assert that much more of benefit to Earth can be learned from Venus, and NASA's long-range plans include at least one more Pioneer Venus vehicle. More visits by the relatively inexpensive Pioneer-type spacecraft to other planets are also planned.

NASA and the Jet Propulsion Laboratory are planning a more-sophisticated Venus flight, with launch set for 1988. Called the Venus Orbiting Imaging Radar (VOIR), this craft will be positioned in a circular, polar orbit so that its sensitive radar can scan the entire surface of the planet. It will pierce the cloud cover and send back to Earth detailed, high-resolution images - perhaps even three-dimensional topographical ''maps.''

The Pioneer Venus orbiter is expected to send data to Earth until 1992, when its orbit will degrade and it will burn up in the planet's atmosphere.

The Soviets recently launched their 13th Venera probe, and a joint French-Soviet spacecraft will rendezvous with Venus in 1985. It will send a probe toward the surface, then continue on to a meeting with Comet Halley in 1986.