Now that people and machines go regularly into space, can advertising and art be far behind? That's what worries astronomers who want to keep the nighttime skies from becoming background for orbiting billboards or burial grounds for the dead.

"Once we let it get started, the next thing you know there'll be Golden Arches up there," astronomer David Crawford said Wednesday. "We have to keep an eagle eye out for this type of thing."Astronomers gathered for the 20th assembly of the International Astronomical Union are concerned that what Crawford calls "the unproductive uses of space" will block observations of the universe by ground-based telescopes and possibly damage astronomy instruments that will be launched into Earth orbit.

Crawford, a Kitt Peak National Observatory astronomer, and Sidney van den Bergh, an astronomer for the National Research Council of Canada, are on an international committee that is attempting to keep space free of "frivolous uses."

Among the proposals that worry them:

-A group of artists in France wants to build a kitelike object the size of a football field and place it in orbit as an art object. The work of art would be designed to catch and reflect the sunlight so it could be seen from Earth.

"Astronomers are appalled," van den Bergh said.

-Celestis Corp., a Melbourne, Fla., company, wants to orbit a satellite containing the cremated remains of 10,300 people, thus using space as sort of a mausoleum in the sky. Plans call for the satellite to be gold-coated so it would reflect sunlight, enabling customers to look up and see the remains of their dead relatives pass overhead.

"It would be like building cemeteries in wilderness areas on Earth," Crawford said.

A plan to create an orbiting salute to the 100th birthday of the Eiffel Tower already has been canceled. Van den Bergh said the plan called for launching a ring of 100 lights that would remind people of the century of the tower.

"That would have been the first advertisement in space," he said. "Once that happens, you don't know where it will stop."

Van den Bergh said such uses of space would add to the already serious light pollution problems astronomers are having in the study of the stars.

Astronomers take thousands of star photographs a year. Most require long exposure times. Satellites orbiting past the field of view can ruin the pictures and perhaps obscure important discoveries.

"Astronomers are being bothered by this problem much more often than other people. Already, a third of all the (photo) plates must be discarded because of satellites," van den Bergh said.

Eventually, though, the crowded orbits of Earth will be a problem for everybody as more and more uses are found for spacecraft, he said.

"The amount of stuff in Earth orbit now is doubling every decade," said van den Bergh. "In a century, all operations near Earth's orbit will be extremely hazardous" due to the possibility of collisions.

Objects in orbit move at about 17,000 miles an hour. At that velocity, even a dime-size object can cause great damage in a collision. Van den Bergh said astronomers are worried about possible damage from space debris to the $1.5 billion Hubble space telescope that will be launched next year by the National Aeronautics and Space Administration.