BRIGHT Venus is fading from the evening sky. But as you admired its display this spring, did you also remember the long-lasting spacecraft that orbits it? The Pioneer Venus Orbiter has just celebrated its 10th birthday. It was launched from the Kennedy Space Center May 20, 1978, and its continuing service reflects the sturdy engineering that has kept the United States in the space science game even when all its launch capability is down.
There are 18 American scientific spacecraft still operating. Besides Pioneer Venus, they include Voyager 2, which will pass by Neptune next year, and Pioneers 6 and 8, 23 and 21 years old, respectively, this December.
Some of these hardy craft orbit Earth, keeping our planet and its space environment under scientific scrutiny. Some, like Pioneers 6 and 8, explore the interplanetary environment as they orbit the sun. Three craft, having intersected Jupiter and Saturn, are heading out of the solar system altogether. Pioneers 10 and 11 - launched respectively in March 1972 and April 1973 - and Voyager 1 - launched in September 1977 - are groping for the heliopause, as astronomers call the boundary zone between the sun's domain and interstellar space.
Taken together, these spacecraft have maintained a minimum level of US space research while NASA prepares for a new burst of activity when the shuttles orbit again and new expendable launch rockets become available. While the United States can be grateful for this, it should not be complacent. Its space science effort - indeed its entire civil space program - is in jeopardy. Lack of a consistent long-term strategy, reflected in roller-coaster support, has virtually brought that program to its knees.
``The fact is that the American civil space program - your space program ... faces a crisis unparalleled in its lifetime,'' NASA administrator James C. Fletcher said in a public address in Washington earlier this month. He added: ``It is not a pretty prospect to imagine the United States as a second-rate, or even a third-rate, power in space. But that is what this country will quickly become if Congress doesn't act responsibly and give NASA the resources it needs to do its job.''
Congress's own budget office has given a comparable warning. If NASA is to accomplish its present goals - including the space station, eventual lunar base occupation and manned Mars exploration, and a vigorous space science program - it needs increasing resources. To maintain the present $9 billion-a-year budget level indefinitely would mean drastic restructuring of the NASA civil program with major curbs on its activities, the budget office said.
Thus the current debate over whether to give NASA the full $11.48 billion it has requested for fiscal 1989 is no mere budget squabble. It involves strategic decisions that affect the long-term nature of the US civil space program.
Pioneer Venus is a symbol both of past glory and of the present challenge to decide what the United States is to do in space. The craft's maneuvering fuel will last until 1991, when its successor Magellan craft is scheduled to reach Venus. But will NASA be able to keep that date?
A Tuesday column. Robert C. Cowen is the Monitor's natural science editor.