The Soviet Union has perfected its space weapons to the point they could intercept and destroy "some" American satellites. Defense Secretary Harold Brown disclosed yesterday.

"I find that troublesome," Brown said at a Pentagon news conference which coincided with the 20th anniversary of Sputnik, the Soviet satellite that opened the space age.

Although U.S. officials have previously acknowledged that the Soviet Union appeared to be testing anti-satellite weapons, Brown's statement yesterday marked the first time the weapons were officially upgraded to operational status.

"There is a fact of Soviet anti-satellite, not only development, but operational capability," Brown said. "That is something of concern to me because we rely a good deal on our space system" to support the military.

The United States is not far along as the Soviet Union in anti-satellite weapons, but has recently launched an effort to catch up. The Air Force last month contracted with the Vough Corp. to build a test version of a satellite killer.

Brown's remarks yesterday represented the latest evidence that the character of the American space program is changing from such scientific adventures as landing a man on the moon to preparing to fight in this newest battle zone.

Other revidence of militarization includes a growing proportion of the American space dollar going to the Pentagon and executives from three running the civilian spave agency.

Defense officials said after Brown's news conference that the U.S. satellites now vulnerable to Soviet space killers are those that fly low - the picture-taking spy satellites.

Besides reconnaissance, today's American military relies heavily on satellites for sending messages around the world: for positioning missile-carrying submarines: and for detecting any launch of Soviet missiles, thus providing warning time.

"I would hope that we could keep space from becoming an area of active conflict," Brown said yesterday.

Earlier this year, Gen. George S. Brown, chairman of the Joint Chiefs of Staff, told Congress that "in view of increased dependency on space systems and the Soviet Union's demonstrated ASAT [anti-satellite] capabilities, the heretofore accepted sanctuary of space may be jeopardized."

Malcolm R. Currie, former Pentagon research director, warned Congress in his posture statement this year that it would be "catastropic" to the U.S.-Soviet military balance to allow the Russians "obtain a military advantage in space through anti-satellite weapons."

In response to such talk from teh Pentagon and the demonstrated advantages of military space systems, Congress has increased the Pentagon's space budget from $489.5 million in fiscal 1959 to a record $277 billion in fiscal 1978.

While the military space budget has been rising, the civilian one has been eclining since the days of the Apollo manned moon landing program. The civilian National Aeronautics and Space Administration budget has gone from its peak of $5.17 billion in fiscal 1965 to $3.6 billion this fiscal year.

Three of NASA's top four executives formerly held Pentagon or military jobs. NASA Administrator Robert A. Frosh was assistant Navy secretary for research; his deputy, Alan M. Lovelace, formerly was the Air Force secretary's research deputy, and fourth-ranking NASA executive Duward L. Crow, associate deputy administrator, is a retired three-star Air Force general.

Military planners have a long list of space projects they would like to pursue, including making it harder for the Soviets to destroy the circuitry aboard U.S. satellites with either explosives or laser beams. There are no big new civilian space projects in sight.

Besides making military satellites harder to destroy, the Air Force is spending $58.7 million on a flying "tomato can" that would lock onto enemy satellites in space and destroy them through collisions at the orbital speed of 17,500 miles an hour.

Rather than rely on collisions in outer space, the Soviet tests of satellite killers indicate the Russians apparently would rely on the hunter satellite to fly close to its quarry and then detonate a nonnuclear explosive to destroy its target.

The United States experimented with a similar idea in the 1960s, basing nuclear-tipped Thor missiles on Kwajalein Island as the satellite killers, but then abandoned the system as impractical.