When In Doubt, Check It Out

By Philip Elmer-DeWitt

Interest in Mikhail Gorbachev's long goodbye speech to the American press last month was starting to flag when the General Secretary made an offhand remark that brought heads up with a snap. The technology exists, he said, that would permit the superpowers to spot nuclear weapons on each other's ships and submarines without having to climb on board. According to Gorbachev, this technique would "identify not only the presence but also the capacity of the nuclear warheads aboard such vessels." Come again? Have the Soviets managed to develop a spy satellite that can peer through the hull of a Trident submarine?

Not exactly. Senior Administration officials close to the negotiations say the capability claimed by the Soviets is based on familiar, not revolutionary technology. The Soviet proposal is to approach suspect vessels by helicopter or ship and bombard them with high-energy neutrons emitted by portable particle accelerators. These neutrons would provoke fission reactions within any nuclear warheads on board and release detectable streams of neutron and gamma-ray emissions. The scheme is feasible, say U.S. experts, but could be foiled by shielding the warheads with thick layers of water and wax. "We looked at that technology very, very carefully a couple of years ago," says one U.S. official, "and we are skeptical."

But Gorbachev's proposal, and the reaction it stirred in Washington, served to underscore the role that surveillance technology plays in arms control. Glasnost is nice, but the success of an agreement like the new ban on intermediate-range nuclear weapons depends upon electronic eyes and ears that make sure both sides keep the deal. "Verification has always defined the outer frontiers of what we can achieve in arms control," says Kenneth Adelman, former director of the Arms Control and Disarmament Agency and a prominent adviser to President Reagan. "We can control effectively only what we can verify."

The U.S. spends an estimated $15 billion a year on high-tech snooping techniques that can monitor Soviet activities in fine detail. Among them:

PHOTO RECONNAISSANCE. Satellites in the top-secret Keyhole series and high- flying aircraft like the U-2 and SR-71 scour the Soviet countryside with sharp-eyed optical and video cameras that can pick out a football-size object from 500 miles. Beamed to earth electronically, the satellite images are enhanced by computers that can compare them with earlier pictures and show only those objects that have entered or left the area.

INFRARED SENSORS. Several satellites, including an advanced craft called Teal Ruby that is being prepared for launch, have detectors that are sensitive to the infrared frequencies of the electromagnetic spectrum. These sensors can determine the size and shape of Soviet test warheads from the radiation they emit as they streak through the atmosphere. Pictures taken with film sensitive to infrared emissions are especially useful for spotting missiles or launch vehicles that have been camouflaged on the ground to look like vegetation.

RADAR. Powerful ground-based radar stations can track objects the size of basketballs from up to 2,000 miles away. The Cobra Dane station in Alaska monitors missiles launched from the Soviet mainland, while Pave Paws radar systems from California to Cape Cod watch for sea-launched warheads. The new Lacrosse satellite will carry lightweight radar systems that can penetrate heavy cloud layers and monitor Soviet ground activity at night.

LISTENING POSTS. Whenever the Soviets launch test missiles, ground controllers monitor and direct the flight by sending and receiving signals in the form of radio waves and microwaves. Those signals can be picked up by a variety of listening posts, including low-flying "ferret" satellites, ships loaded with antennas and a network of ground stations in countries that are close to the Soviet Union, such as Norway and China. By monitoring radio frequencies and telephone calls carried on microwaves, the listening posts can also eavesdrop on a broad range of Soviet military communications. Information can be gleaned, for example, on the movement of mobile weapons systems.

SEISMIC DETECTORS. The U.S. has set up a worldwide network of seismic detectors, like those used to measure earthquakes, that can gauge the explosive force of large underground nuclear tests in the Soviet Union. Later this month an American science team will travel to Moscow to begin working out an agreement under which the U.S. could install a more accurate detection , device near the test sites. The new system, called Corrtex, would allow the U.S. to measure nuclear blasts that are too small to be clearly identified from seismic data alone.

How does Soviet verification hardware stack up against this sophisticated array? Western experts say the Soviets use most of the same technologies but in cruder form. Some of their spy satellites still parachute film to earth for processing, instead of beaming pictures electronically. But the Soviets make up with quantity what they lack in quality. The U.S. has only two Keyhole satellites in operation, while Moscow orbited 31 Cosmos surveillance satellites in 1986 alone.

The Soviets insist, and most U.S. experts agree, that the technology both sides have in place is capable of adequately verifying compliance with the current arms-control treaties. But some troublesome shortcomings remain. For one thing, future agreements will have to deal with mobile weapons and sea- launched cruise missiles, both of which are particularly difficult to monitor. Figures supplied by the Kremlin in connection with last month's summit revealed 84 Soviet ground-launched cruise missiles that the U.S. did not know existed.

Detecting weapons in space -- or documenting their absence -- raises more verification obstacles. The U.S. has begun preparing a new generation of satellites whose sensors will be aimed not at the earth but at the vast expanse beyond its atmosphere. One of the first due off the drawing board is an experimental bird called Starscan, scheduled for launch in 1991. It will approach orbiting objects and test for the radiation given off by nuclear devices. But the new satellites will have a harder time establishing the presence of space-based lasers and particle-beam weapons like those proposed as part of President Reagan's Star Wars missile defense initiative. Says John Pike, a space-technology expert with the Federation of American Scientists: "Effective verification of space-based defense virtually requires cooperation from the Soviets."

Ultimately, technology can take arms control only so far. The biggest concern raised by negotiators of the recent treaty was the verification of those provisions beyond the scope of surveillance technologies. Satellites can count missiles and silos and bombers, but they cannot monitor the disassembly of nuclear warheads. To be assured that this is done, both sides were forced to rely on on-site inspections and the most sophisticated technology of all: the human eye.

With reporting by Jay Peterzell and Bruce van Voorst/Washington