American spy satellites have been credited with helping to keep the Cold War cold, but if a hot war breaks out in the Persian Gulf, these space robots and their human interpreters will face an unprecedented test in monitoring their first large-scale combat.

Some experts say the satellites do not provide enough coverage to meet the demands of a Persian Gulf war -- even though the United States has a record number of them watching the region and the amount of data they collect already outstrips the human ability on the ground to analyze and redistribute it.

"The level of coverage needed, intelligence-wise, for this situation is far greater than anything in the past because of the possibility of combat and because of the American concern -- on a minute-to-minute, hour-to-hour basis -- about what the Iraqis are doing," said analyst Jeffrey Richelson, author of "America's Secret Eyes in Space" and other books on intelligence.

He predicted a push by field commanders for more information. "There's a feeling that . . . the level of coverage needed is far, far greater than what is needed during peacetime."

While the numbers and capabilities are highly classified, independent analysts such as Richelson describe a clandestine fleet led by photo reconnaissance satellites code-named Keyhole.

The satellites can't quite read a license plate from hundreds of miles up, experts say, but they can see the plate. They may not be able to read a newspaper headline held by a citizen on a Baghdad street corner, but they can distinguish which newspaper it is by the type style. And they use newly developed night-vision technology to "see" in the dark.

The orbiting fleet may not be able to find Americans held hostage, or reveal what Iraqi leader Saddam Hussein is thinking, but some satellites use radar or infrared eyes to distinguish between real and dummy tanks, or see through camouflage and clouds.

By all accounts, the spy fleet already is providing more information than field commanders have ever had in any war. "This is one of the big space stories of all time. These guys are finally getting their chance at bat," said John Pike, space policy analyst for the Federation of American Scientists.

In a sense, the space intelligence community has been at war since late July, he said. Although it is not yet a shooting war, "This is as real as it's ever going to get for them. . . . It's the 21st century against the 20th century."

Only the United States, the Soviet Union and China have such satellites, whose main purpose for years was to detect violations of superpower arms control agreements.

Over the past 10 to 15 years, they have been integrated gradually into tactical military planning, according to Paul Stares of the Brookings Institution. They played a role in conflicts in Lebanon, Grenada, the Falkland Islands and Panama, and some say the Iran-Iraq war.

But this is the first crisis in which the spy satellites are being used on such a large scale to supply U.S. field commanders with continuous information about the positions of enemy troops, tanks, gun emplacements, missiles and other activity.

In July, the satellites helped document the buildup of Iraqi military units on Kuwait's border. But only after they indicated that the Iraqi army was mobilizing support and supply units -- just a day or two before the invasion -- did intelligence analysts reportedly conclude that the Iraqis intended to invade, rather than merely intimidate, Kuwait. Political officials in the United States, Saudi Arabia and Kuwait refused to believe it until the invasion was in progress.

Satellite information reportedly has fed presidential decisions in the aftermath of that invasion and provided the impetus for Operation Desert Shield.

Richelson, Pike and other analysts estimate there are four to seven photo reconnaissance satellites of the Keyhole, or KH-11, series in operation, each costing $1 billion to $1.5 billion. These are huge instruments based on the same technology used in the Hubble Space Telescope: a combination of television cameras, sensors, a precision pointing system and a telescope, aimed at Earth instead of the heavens. In addition to collecting images in visible light, the more advanced Keyhole craft use infrared instruments to detect heat.

The satellites, originally intended to monitor the Soviet Union, are in orbits inclined at high angles (between 62 and 98 degrees) relative to the equator and pass over different regions on each orbit as Earth rotates beneath them. They have maneuvering engines that can be used to raise or lower their altitude.

In addition, a $500 million satellite known as Lacrosse sees through cloud cover and smoke using advanced radar similar to that of the Magellan probe currently mapping the planet Venus.

"The disposition of Hussein's forces is an open book; you can see everything," Pike said.

There are also two types of signals intelligence, or "sigint," satellites with the code names Magnum and Vortex that are parked in geosynchronous orbit -- a fixed spot over the globe -- about 22,000 miles out. These are giant "ears" that listen to Iraqi radio communications, and they reportedly helped locate trailers from which U.S.-Saudi AWACS radar planes were being jammed.

But the bulk of information is believed to come from the Keyhole satellites. The deluge of digital data is relayed by communications satellite to Fort Belvoir, near Washington, and from there to the National Photographic Interpretation Center (NPIC) at the Washington Navy Yard, where interpreters from various intelligence agencies use computers to analyze it.

The information can be forwarded to commanders in the field virtually instantaneously but more typically reaches them within minutes or hours, analysts said. "My impression is they're updating target folders every three days, and for high-priority targets, maybe several times a day," Pike said.

But "the collection end has clearly gotten out in front of the system management and dissemination end," he said. According to published reports, the photography of Iraq pouring in from the satellites initially overwhelmed the NPIC analysts, keeping them working 18 hours a day.

A former Army chief of staff recently told the industry newsletter Defense Daily that Army units in Saudi Arabia are frustrated over a lack of "timely" imagery intelligence.

Pentagon officials will not comment on the capabilities of spy satellites. Martin Faga, assistant secretary of the Air Force for space, said U.S. forces rely on an array of "many tens" of orbiting spacecraft that supply troops with weather information, precision navigation in the desert and the bulk of their communications with the states, among other things.

The armed services are struggling to develop a system that will make information about enemy movements derived from all national intelligence sources, including ground stations, radar planes and satellites, rapidly available to field units on their personal computers.

Rebutting complaints that satellite data are not always available to commanders who need it, Faga said, "Every satellite we own that has an application of value in that part of the world is employed for that purpose."