French defense authorities are using information about presumably classified U.S. satellites that they have gathered from their space-surveillance radar to pressure the United States into removing French military satellites from the U.S. Defense Department’s public listing of spacecraft in orbit.

French Defense Ministry officials said a French space-surveillance radar has detected 20 to 30 satellites in low Earth orbit that do not show up

in the regularly updated catalogue of spacecraft and space debris tracked by the U.S. Space Surveillance Network (SSN), a global system of ground-based sensors. French officials conclude that most of them are U.S. reconnaissance satellites whose secrecy classification keeps them out of the SSN reports.

The French Graves radar, whose four transmission platforms are located here, is not

nearly as sophisticated or as thorough as the U.S. network – that is a bit like comparing a small sailboat to an ocean liner, French officials say. But after 16 months of operations, and occasionally complementing the observations with the German FGAN agency’s Tracking and Imaging Radar, French authorities say they have been able to locate some 2,000 objects located up to 1,000 kilometers in altitude. While almost all of those objects figure in the SSN’s regular reports; some do not.

“I was talking about Graves with a U.S. colleague and he said, ‘If it’s not in our catalogue, it doesn’t exist,’” said one French defense official involved in Graves’ operations. “In that case, we have been tracking non-existent objects. All I can tell you is that some of these non-existent objects have solar arrays and are large.”

The U.S. Defense Department’s Space Surveillance Network is the world’s gold standard for cataloguing satellites and debris in both low Earth orbit and the higher geostationary orbit at 36,000 kilometers in altitude, where telecommunications satellites operate.

Data from the U.S. network of ground-based sensors is regularly published and used worldwide by those tracking satellite and space-debris trajectories. The published U.S. information presumably excludes the most sensitive U.S. defense satellites, but regularly publishes data on the orbits of other nations’ military hardware.

In a series of presentations here at the site of the French Graves radar, French defense officials said they are gathering data on satellites and orbital debris in low Earth orbit with the expectation that Graves will be made part of a pan-European space-surveillance program that European Space Agency governments will be asked to approve in 2008.

This program, with a cost of some 300 million euros ($403.7

million), would feature higher-performance radars to track space debris in low Earth orbits and in geostationary orbit. As is true of many European space programs, the space-debris effort would serve European military forces as a secondary market for keeping track of what satellites are flying above European territory.

This new space surveillance program may or may not be approved by European governments. But the Graves radar, and the TIRA system operated by the German government, together already are enough to pinpoint the location, size, orbit and transmissions frequencies of satellites that the United States would prefer not be broadcast worldwide, French officials said.

Col. Yves Blin, deputy head of

the space division at the French joint defense staff, said France would wait until it had acquired, with the help of the German radar, further information about the 20 to 30 secret satellites in question before beginning serious negotiations with the United States on a common approach for publishing satellite orbit information.

“Right now we do not have enough cards in our hand to begin negotiations,” Blin said here at the Graves radar transmitter site June 7. “We need more time to be sure of what we are seeing. At that point we can tell our American friends, ‘We have seen some things that you might wish to keep out of the public domain. We will agree to do this if you agree to stop publishing the location of our sensitive satellites.’”

and other French Defense Ministry officials said they currently have no plans to publish their data.

Graves’ four transmitting platforms here use phased-array radars to sweep the sky. The signals are received at a facility 400 kilometers away in France’s Plateau d’Albion, where 100 omnidirectional antennas are arranged in a circle, each antenna about 1.7 meters tall.

Graves was designed and built by Onera, the French aerospace research institute, for 30 million euros

. The two sites are operated remotely, with no permanent human presence. Annual operating costs are about 1 million euros.