The prospect boggles the mind: A starry night, a full moon, an affectionate companion - and a mile-long billboard in space, proclaiming the merits of McDonald's hamburgers.

What an advertising monstrosity. Yet a firm called Space Marketing Inc. of Roswell, Ga., sees potential for profit in space and is planning to launch just such a big billboard in the sky, starting in 1996. Says Chief Executive Officer Mike Lawson:"We could actually fly (a corporate logo such as McDonald's) Golden Arches in space." It might appear as large as the full moon. Scripps Howard News Service reports that the City of Atlanta is looking into it as a promotional gimmick for the 1996 Olympics.

To be sure, nobody objects to the space program paying for itself. But surely scientists and entrepreneurs ought to think long and hard before launching billboards into space. Some states already ban highway billboards because of their unsightliness.

Imagine that unsightliness in the sky, not to mention the headaches for astronomers and common folk. We run the risk of raising generations of people who confuse the Golden Arches with the Big Dipper.

Let's go slow on this spacey idea - then scrap it!