A radar spy satellite capable of seeing through cloud cover and penetrating the top few feet of the Iraqi desert may be the best bet for locating hidden Scud missile launchers that threaten Israel and Saudi Arabia, a space expert said.

But William Burrows, author of "Deep Black: Space Espionage and National Security," said Friday only one such LaCrosse satellite is known to be in orbit and it only passes over the Middle East every few days. How long it might take U.S. forces to finally eliminate Saddam Hussein's stock of Scud missiles is not known."Radar is their only bet if there's cloud cover," he said. "The problem is, they've got one satellite and it comes over every couple of days."

LaCrosse and advanced Hubble space telescope-class photoreconnaissance satellites undoubtedly have been working around the clock during the Persian Gulf war to locate Iraqi targets, determine which have been destroyed during massive bombing raids and which might need extra attention.

"We have had superb (satellite) intelligence," Burrows said from his home in Connecticut. "Clearly, in terms of targeting, those guys were working overtime. But it's not perfect, it just isn't.

The missiles may be hidden in camouflaged trenches, or ditches, in the Iraqi desert. But radar beams from LaCrosse can be used to penetrate the top few feet of the desert to pinpoint such targets.

"If it's a good, powerful radar satellite, which it's supposed to be, it would be able to go sub-surface in sand 10 feet. Otherwise, you've got to send F-16s and other stuff out to try to find them."

The United States operates a battery of high-tech spy satellites capable of beaming down photos and other data minutes after a high-altitude pass over a given target. Among the spacecraft providing critical information to the commanders of Operation Desert Storm:

- Photoreconnaissance satellites. Burrows said at least two and possibly three satellites once known by the code name KH-11 are in operation. Each KH-11 spacecraft is equipped with a large telescope, an infrared scanner, light-sensitive charge-coupled devices, or CCDs, and a sensor package with "multispectral" scanners capable of detecting materials used in camouflage.

- Advanced KH-11s. Burrows believes one and possibly two of these advanced satellites, launched from NASA's space shuttle, currently are in orbit. Such spacecraft are thought to be capable of photographing details as small as 3 inches across.

- LaCrosse: A radar-reconnaissance satellite believed to have been launched from the shuttle Atlantis during the second post-Challenger mission in December 1988. Such satellites use powerful radar systems to penetrate cloud cover and the first few feet of the ground. A similar system is being used by NASA's Magellan probe to penetrate the clouds shrouding the planet Venus.

- Mentor: One of a series of signals intelligence satellites, or "sigints," capable of intercepting military communications from space.

- Defense Support Program satellites. DSP early warning spacecraft use a large infrared telescope to locate the hot plumes of enemy missiles during the launch phase. A DSP satellite may have detected the Scud missiles launched against Israel Thursday night.