U.S. Satellites Keep Watch on Reactor

Much of what the world knows about the Soviet nuclear plant disaster comes from the United States, which gets most of its information from spy satellites whose cameras can show objects on earth as small as a grapefruit.

“We were shown satellite pictures of the reactor building from before and immediately after the explosion,” California Rep. George E. Brown Jr. (D-Colton), a member of the House Intelligence Committee, said Thursday after a closed-door briefing by U.S. experts. “They were dramatic, with the roof beams collapsed and debris scattered around the plant.

“No bodies were visible,” he added, although U.S. officials estimate Soviet casualties at 10 times the Soviet admission of two dead and 197 injured.

Despite their capability for detailed snooping, however, U.S. reconnaissance satellites have limitations. And so vast are the regions they monitor and so specialized are some of the satellites’ primary missions that they do not automatically sound the alarm when something unusual happens--even something as dramatic as the explosion of a nuclear power plant.

It took more than a year, for example, for Moscow’s construction of a huge radar facility at Krasnoyarsk to come to the attention of U.S. analysts even though the installation covers an area larger than a football field and is now considered by the United States to be a direct violation of the SALT II treaty.

Some of the satellites’ limitations are technical; they cannot “see” through clouds and darkness, for instance. More important, they collect so much information that relatively little is immediately processed into pictures and analyzed.

Thus it was, according to Pentagon spokesman Robert B. Sims, that this country first learned of the Chernobyl accident through the announcement on the Soviet news agency Tass. The Tass dispatch followed complaints of fallout from Scandinavia.

Only then did CIA analysts go back into their tape files of satellite “imagery” to find the before and after pictures of the Soviet tragedy.

Other space-based sensors help make up for the cameras’ blind spots. Electronic eavesdropping equipment, sometimes in separate satellites and sometimes going along on photo reconnaissance satellites, listen in on Soviet radio and other transmissions. But they, too, provide more information than can be assessed every day.

Earlier Files Used

Back files of these electronic snoopers also were used to try to reconstruct the accident scenario last week.

This somewhat relaxed treatment of reconnaissance data does not extend to early-warning satellites, U.S. officials emphasized. They maintain constant watch on the Soviet Union for missile attacks. Bright flashes from rocket exhausts or nuclear blasts are instantly detected and radioed back to U.S. command posts, where they set off alarm bells. So sensitive are these warning devices that in the past, intense fires at Soviet natural gas wells and even peat bog fires have caused false alarms.

Careful attention is paid to the areas in which Soviet missiles are developed and tested so that their compliance with arms control agreements can be verified.

The U.S. reconnaissance satellites now in orbit--and there are a number of them despite the reported loss of one in the recent Vandenberg explosion--are fourth-generation spacecraft. A fifth-generation version is awaiting its maiden launching when shuttle flights resume.

These spacecraft can take pictures with film--which is periodically dropped from the satellite by parachute and recovered in midair by Air Force C-130s--and with electronic sensors that convert the images into electrical signals that are radioed instantly to ground stations.

In addition to military spy satellites, a U.S. civilian Landsat satellite takes electronic pictures that are normally used for such things as prospecting for minerals, estimating agriculture crop yields and measuring other commercially useful features on earth. Landsat’s camera can resolve objects on earth that measure 90 feet or more in one dimension.

Astonishing feats are claimed for satellite reconnaissance, sometimes falsely. A former secretary of state, for example, wrongly boasted that U.S. spacecraft can watch Soviet targets 24 hours a day, through night and cloud.

Nonetheless, the newest U.S. satellite has been shown to be maneuverable in orbit, as when it was ordered to photograph the underside tiles of an early shuttle mission when damage was feared. It also photographed the U.S. Embassy in Tehran in preparation for the abortive raid to free the hostages, determining the location of guard posts in the compound and scouting rescue routes.