From teams of eavesdroppers scattered throughout the Middle East to spy satellites that can identify a Soviet-made T-72 tank from several hundred miles away, U.S. intelligence agencies have an unsleeping circle of assets and alliances to keep watch on the crisis in the Persian Gulf.

They detected sudden activation of a long-distance radar system in southern Iraq four days before the invasion of Kuwait, tracked the increasing flow of troops and supplies toward the border and, U.S. officials say, enabled the Central Intelligence Agency to predict the attack -- though not the exact time and date -- before it took place.

"There were no surprises," CIA spokesman Joseph DeTrani said.

DeTrani would not discuss the assets the U.S. intelligence community is relying on in the tense region, but experts say the KH-11 and advanced KH-11 photo reconnaissance satellites and the Lacrosse all-weather imaging radar satellite are almost certainly the most productive.

Iraqi President Saddam Hussein "would have a very hard time making a move without our seeing it," said John Pike, director of the Federation of American Scientists' Space Policy Project. "We've got a lot of stuff up there. What this translates into is fresh pictures every few hours."

The images are processed by the CIA's National Photo Interpretation Center at the Washington Navy Yard and then quickly distributed to analysts throughout the government.

"You can call up the KH-11 and when it {gets} to the target area, you can get a photo and have it back down here, printed out, in an hour, and have it over to the White House," one person familiar with the system told author James Bamford several years ago.Signals at 22,000 Miles

Saddam and his puppet government in Kuwait will also have to be careful about what they say, according to another source.

In addition to signals intelligence (SIGINT) satellites that intercept communications for the eavesdropping National Security Agency (NSA), the source said, special listening posts are operated by NSA-CIA teams at several diplomatic facilities in the Middle East.

Up above, 22,000 miles over the equator, lurk SIGINT satellites such as Vortex and Magnum, picking up communications and telemetry signals such as radar.

These usually are focused on the Soviet Union and China, said Jeffrey T. Richelson, an expert on U.S. intelligence, but their antennas can be redirected to the Middle East on orders from the SIGINT committee here.

"I'd say there are at least two -- one Magnum and one Vortex -- that are in a position to intercept from that area of the world," Richelson said. Pike said these could aid in "trying to figure out which command posts Saddam Hussein is currently using."

Twice as heavy as the Vortex, the Magnum has bigger antennas that can pick up weaker signals and monitor local traffic, such as radio communications among tank commanders.

"The Magnum can monitor transmissions that are in Kuwait and differentiate between those transmissions and other transmissions halfway between Kuwait and Baghdad," Pike said. "Whereas the Vortex would be monitoring all transmissions on that frequency in all of Iraq and Kuwait put together. It couldn't tell where the tanks are."

Both satellites can pick up any broadcasts, including from car phones. One of these, or possibly a low Earth-orbiting "ferret" satellite, may have picked up signals from the Soviet-built air defense radar system in southern Iraq that, according to Aviation Week, was suddenly detected in operation on July 29 after months of inaction, giving U.S. analysts their first substantive warning of a likely invasion of Kuwait.

The ensuing logistics buildup prompted the CIA to warn, according to officials who read its almost daily reports, that "Iraq could overwhelm Kuwait with little difficulty." Finally, one official said that before the Aug. 2 invasion, "the CIA estimated that the Iraqis would do so."

Those under surveillance, however, can sometimes use that fact to their advantage. Iraqi military forces were spotted earlier this week openly loading what appeared to be poison gas munitions aboard combat aircraft. The news caused consternation here.Messages in Arabic

U.S. agencies face big problems in sifting the huge volumes of raw intercepts to make sure nothing important is overlooked, especially with messages in Arabic. But intercepted communications are valuable simply by showing where the traffic is.

"You may not be able to decrypt what they're saying or you may not even bother to translate it, but just by knowing whether and where their tank commanders are broadcasting tells you something about their operations," Pike said.

Other sources of U.S. intelligence in the Middle East include the British, Israelis and Turks, all of whom have secret agreements to share intelligence with the United States.

Richelson said he was sure the Turks have listening posts focused on Iraq. In addition, he said, the Government Communications Headquarters (GCHQ), the British NSA, operates U.S.-equipped listening posts at the Abut Sovereign Base area in Oman and at the Episkopi Sovereign Base area on Cyprus. Signals they collect are sent to a U.S. post at Bad Aibling, West Germany, and on to NSA headquarters at Fort Meade, Md.

The dispatch of U.S. military forces to Saudi Arabia and the Persian Gulf also brings into play tactical intelligence resources such as specially equipped F-14 Tomcats in each carrier wing. These have pods with special cameras and infrared sensors that can be focused on coastal installations and lines of communication.

Some officials may miss the close-ups provided by the SR-71 Blackbird, the strategic reconnaissance plane that could pick out license plate numbers from altitudes of more than 100,000 feet. It was grounded in January for budget reasons.Oranges and Tanks

The supersonic SR-71 could penetrate clouds, operate at night and take pictures sideways from 80 miles. But the Lacrosse also produces imagery at night and through the clouds. The advanced KH-11s can also work at night, take 12 pictures a minute in any direction -- straight ahead, down or sideways -- from several hundred miles away, with a resolution of a few inches.

"That would mean that if I put three oranges in a row, touching each other, and then took the middle orange away, the KH-11 would be able to see there are two separate objects there," Pike said. "The Lacrosse can do it with card tables.

"In practical terms," he said, "that means the Lacrosse can count tanks and probably tell the difference between a tank and a truck. The KH-11s can tell you exactly what type of a tank it is and whether the truck is carrying troops or ammunition."

By Pike's count, there are five KH-11s and advanced KH-11s in orbit and at least four of them working. He said the oldest went up on December 1984 and the newest was launched from Cape Canaveral in June. There is one Lacrosse at work, launched in December 1988. The Committee on Imagery Requirements and Exploitation (COMIREX), with offices near the White House, decides what pictures and images they take.

"You can be sure that . . . the COMIREX operations subcommittee, which meets 24 hours a day, has been reprogramming satellites for some time to increase coverage in Kuwait, Iraq and along the Saudi border," Richelson said.

"Probably 90 percent of what we're getting is from the {KH-11 and Lacrosse} satellites and 9 percent from the {SIGINT} satellites," Pike speculated. "I would assume we get little bits and pieces from human intelligence sources, diplomatic contacts, debriefing tourists and whatever else there is. But basically there are two things you're going to be interested in: the disposition of Iraqi forces, which you're going to get from satellite, and what Saddam intends to do. I don't know how you figure that out."