February 4, 2003

Secretary of State Colin Powell will be laboring under the burden of a generation's worth of spy novels and movies when he comes before the United Nations Security Council tomorrow to unveil some of America's intelligence secrets about Iraq. In the popular imagination, spy satellites can tell the president of the United States anything he wants to know at any time about America's foreign enemies. Turn on TV almost any night and you'll see Bondian agents ferreting out the bad guys with the help of satellites that follow their every move like security cameras in a bank. It's an appealing concept, but it isn't true.

Anyone expecting an Adlai Stevenson moment tomorrow ó that dramatic occasion in October 1962 when Stevenson showed the Security Council irrefutable photographs of Soviet missile sites in Cuba ó is likely to be disappointed. The reasons have to do not only with the limitations of spy satellites but also with the ability of foes like Saddam Hussein to shield their activities from America's prying eyes in the sky.

Stevenson's star turn before the Security Council is itself a somewhat misleading point of comparison, because the pictures he showed were recorded by spy plane, not satellite. In those early days of space espionage, America's first-generation photo reconnaissance satellites, code-named Corona, operated only for a day or two before they ran out of film, and the images they produced were not detailed enough to show missile components on the ground in Cuba. The intelligence officials who briefed John F. Kennedy during the missile crisis found their new technology all but useless during the crisis.

Today's high-powered satellites can show objects as small as a football. They remain in orbit for years and transmit imagery data back to earth almost instantaneously in digital form ó no more rolls of film that must survive re-entry through the atmosphere and then be processed. Yet for all the advances of the last 40 years, the satellites remain prisoners of some basic laws of physics ó and human failings.

For better picture taking, for example, a satellite has to orbit the earth at a relatively low altitude ó several hundred miles up. That means it is constantly circling the planet in polar orbit every 90 minutes or so, leaving it over any particular target of interest, like an Iraqi military base, for only a few minutes each day. (In the real world, those TV secret agents might get information from the sky on where their enemies were hiding, but the satellite would have flown on without noting whether they moved.) If Baghdad knows the orbit, which is not hard to learn from public sources, it can time the movement of suspicious munitions when no satellite is passing overhead.

India perfected these deceptive arts in 1998 when it was secretly preparing to conduct a series of underground nuclear tests. Work at the test site in the desert southwest of New Delhi was suspended whenever an American satellite flew overhead. That subterfuge ó along with a lack of attentiveness by analysts in Washington ó left the Clinton administration without any warning that the tests were coming. Top officials learned about the blasts on CNN.

The best protection from American monitoring is to work indoors. Imagery satellites were ideally suited for cold-war espionage because the things Washington wanted to see ó Soviet missiles, aircraft, tanks and troop movements ó were clearly visible from space. Satellites were helpful even in monitoring missile construction because they could keep count of new weapons as they emerged from manufacturing plants and were loaded aboard railroad cars or trucks.

Saddam Hussein's weapons of choice ó chemical and biological arms ó are smaller and far more difficult to detect. Biological agents are especially elusive because from afar bio-weapons labs are almost impossible to distinguish from more innocuous facilities like dairies, and germs can be transported in microscopic amounts. Nuclear weapons, though harder to conceal, can be developed out of sight until they are tested.

Imagery satellites are also only as good as the analysts who study the pictures. Since the development of digital systems in the 1970's, which provided Washington with a torrent of images, spy agencies have had a hard time keeping up with the data. The National Imagery and Mapping Agency, created in 1996 to consolidate the government's photo interpretation work, has been busily recruiting new analysts and modernizing its computer systems, but it can't handle the flood of pictures that pour in from space every day. That means that analysts can easily miss something important, particularly if it is happening in some corner of the world that hasn't been singled out for attention.

Even when they do spot something suspicious ó like trucks pulling away from a site in Iraq not long before U.N. inspectors appear ó the scene may be open to varying interpretations. Pictures don't reveal intent. If the trucks are covered, it may be impossible to know whether they are carrying garbage or chemical warheads.

In places like Iraq, where deception has been turned into a fine art, intercepted communications can be more revealing. The Reagan administration made highly effective use of intercepts to make a public case against a foreign foe on Sept. 6, 1983. On that day, another American representative to the U.N., Jeane Kirkpatrick, played recordings of Soviet pilots as they prepared to attack a commercial South Korean airliner that had strayed into Soviet airspace.

Mr. Powell is expected to have some intercepted conversations on hand, but like the spy satellite photos he brings, they may suffer from comparison with those moments in the past. Mr. Powell will be fighting both Security Council suspicions and the memory of the times when the United States was lucky enough to nail the case with perfect evidence.