To Kill a Satellite

The warhead is hardly larger than a coffee can. But jammed inside the 12-in. by 13-in. cylinder are 64 tiny rockets, eight high-powered telescopes and a targeting device so sensitive that it can detect the warmth of a distant star.

This small gem of high-tech miniaturization represents the state of the art in satellite zapping. It is the antisatellite weapon (ASAT) that U.S. scientists have been trying to perfect for more than 25 years, ever since the Soviets launched Sputnik I in 1957 and set off a race to capture what Lyndon Johnson called the "high ground" of outer space.

Termed a miniature homing vehicle, or MHV, the warhead rests on the tip of an 18-ft. missile slung from the belly of a high-flying, specially equipped F-15 fighter. Guided by ground stations tracking enemy satellites, the F-15 climbs several miles into the sky and fires the missile. The two-stage rocket then boosts the warhead out of the atmosphere and into space. The telescopes in the nose of the MHV pick up infrared radiation emanating from the enemy satellite and focus it on a heat-sensitive targeting device. The device is housed in a small refrigerator; just as light is easier to see from a darkened room, heat is easier to sense in the cold. The jets steer the MHV on a collision course with the target. No explosives are necessary: a satellite orbiting at 17,000 m.p.h. would be shattered by a head-on crash with a 35-lb. projectile hurtling 10,800 m.p.h. in the opposite direction.

The American ASAT has been successfully fired into space before, but never aimed at a satellite. In ground tests, the $4 billion project has been plagued by minor technical glitches.

The Soviets already have their own antisatellite weapon, but it is primitive compared with the U.S. model. The Soviet ASAT is a 150-ft., 2-ton rocket designed to climb into orbit and chase down satellites around the earth. After closing with its target, the Soviet missile explodes, destroying the satellite in a hail of shrapnel. But while an F-15 can reach launching position within an hour of takeoff, the Soviets must wait for a target satellite to pass over their fixed missile launch pads, which could take up to twelve hours. The U.S. missile can reach its target within ten minutes of launch. The Soviet rocket takes as long as three hours. Furthermore, the Soviets use a radar homing device that is easier to detect, and thus counter, than the heat sensor employed by the U.S. The Soviets are trying to develop an infrared homing system but their prototype has failed in six tests so far.

Both the U.S. and the Soviet ASATs can reach only satellites flying in low orbit, a few hundred miles high. Reconnaissance or "spy" satellites are < vulnerable, since they hug the edge of the atmosphere for a closer view of earth, but most early-warning and communications satellites--the ones used to fight a nuclear war--float out of harm's way as high as 24,000 miles. Unless, that is, even more effective satellite killers are developed.