MY parents went out that weekend in 1969 and bought a television set so they could watch it. Like the rest of the nation, they were enthralled and enraptured by the prospect of a human being setting foot on the surface of another world.

I was only four months old at the time, but I'm told that I watched the event as well, comfortably ensconced in the laps of one or the other of the friends and relatives who came over to watch, blissfully unaware of what was taking place.

But even 20 years later, looking with a more observant eye at the live footage of the first landing on the moon, it is easy to see why the Apollo mission captured the imagination of the nation as it did. Twenty years (and more) of science fiction movies have been unable to recreate the silent majesty of the lunar landscape on the day it was first marred by human footprints.

It is easy to understand the sense of pride the nation took in its accomplishment. After all, hadn't America been founded on just the same spirit of adventure and exploration? Didn't the sheer effort required to catapult three astronauts millions of miles beyond their native sphere attest, once and for all, to the dominance of American technology.

It is easy to understand--and yet it is precisely these feelings that poses the greatest threat to the U.S. as it reevaluates our role in space.

TWENTY years after Neil Armstrong and Buzz Aldrin first walked on the moon, President Bush now wants the U.S. to return there. His plan calls for the establishment of a permanent lunar base, which would serve as a way-station for an expedition to Mars, and eventually as a stepping stone for further exploration of the solar system.

It sounds like a noble goal. But what reasons does the president give for launching the nation on a mission that will almost certainly take decades to complete, at a cost of billions of dollars?

"America should never stop seeking distant frontiers," Bush tells us. "We dream of distant shores we've not yet seen... A dream to be realized by future generations must begin with this generation."

Such a dream may be seductive, may sound sexy to the ears of millions of Americans, but it is a fairly tenuous thing for any nation to be risking so much time and money on.

Over the past three decades, our space program has had its share of ups and downs, with the greatest triumph being the moon landings and the greatest failure being the death of the seven astronauts aboard the space shuttle Challenger in 1986.

The monetary costs are easy to figure: $25 billion for the Apollo program, more than $35 billion for the fleet of four space shuttles. Not so easy to assess are the benefits that we have gained by sending people into space.

Admittedly, we have gained knowledge about our planet and our solar system, but the question is by no means settled as to whether we could have accomplished the same using robot craft.

And in recent years, our reliance on the astronaut-piloted programs may even have hindered the march of progress. The shuttle program, consuming about 40 percent of NASA's annual budget, has often detracted from smaller, less glamourous efforts.

Programs like the Galileo probe to Jupiter and the Hubble space telescope have been delayed more than three years since the Challenger explosion because NASA never planned on using conventional rockets to launch them.

The Hubble telescope has been sitting in clean storage since the Challenger tragedy--initially at a cost of $18 million a month. The cost has been declining, but by the time Hubble is ready to go in January, the total cost of the delay will be approaching $468 million.