CAPE CANAVERAL, Fla. - On Sept. 12, 2001, the day after the terrorist attacks on the World Trade Center and the Pentagon, someone in Afghanistan using the name "newboy1" registered at a NASA website that publicly distributes Air Force satellite tracking data.

That same day, and again on Sept. 18, 2001, two other computer users in China, again giving the name "newboy," also signed up to access NASA's Orbital Information Group website, according to the Government Accountability Office.

Even though the spacecraft in the OIG database were unclassified and as such, U.S. military spycraft were not listed, the newboys and other questionable users stood out like red flags in a review to determine if the website posed any threat to national security.

Air Force Space Command, using a network of more than 40 radars, optical sensors and radio monitoring stations around the world, routinely tracks some 10,000 objects in Earth orbit, including active and dead satellites, rocket bodies and pieces of spacecraft debris.

Since the early days of the space program, NASA, with Air Force assistance, has made unclassified tracking data available to academics, commercial users and hobbyists. Those data include presumed spy satellites launched by Russia and other nations, but not those operated by the United States.

Commercial satellite operators use the data to monitor civilian spacecraft, to predict - and avoid - collisions or close encounters, to determine when maneuvers might be required and to monitor space debris.

Researchers and educators use the information to train future satellite operators, to develop more efficient tracking techniques and to monitor space debris, which poses a threat to all satellites. Radio enthusiasts need it to determine when amateur satellites will be above their horizons.

And in the internet age, even casual hobbyists using widely available Macintosh and PC tracking software can find out when a given satellite will be visible from their location.

Satellites can be seen just after sunset and just before dawn when the spacecraft are still in sunlight but the viewer is in shadow. The international space station, which can be as bright as Jupiter or even Venus, is a popular target.

Mainstream astronomy programs now automatically retrieve satellite data over the internet and plot a spacecraft's path across the sky. Hobbyists who don't want to bother with even that minimal level of effort can simply visit a website like Heavens-Above in Germany (http://www.heavens-above.com), which uses NASA-supplied data to provide pass predictions for virtually any town or city on Earth. Tens of thousands of users access Heavens-Above every day.

NASA managers have never seen the OIG data as a security risk and even the Air Force, in a 1999 review, "assessed the NASA web site data and found no threat to national security," the GAO observed.

But at least one unidentified intelligence agency apparently disagreed and in the post-9/11 environment, NASA and the Department of Defense agreed a more thorough review was in order.

"DOD officials told us that users who have access to certain space surveillance data could have enough information to attempt to damage or jam satellites or move military and other assets at appropriate times to avoid detection," the GAO said in a letter to Rep. Christopher Shays, chairman of the House subcommittee on national security.

How an adversary might damage a spacecraft more than 100 miles up and moving at five miles per second - eight times faster than a rifle bullet - was not specified.

But unclassified military or civilian communications satellites could, in theory, be jammed. And an adversary could use the unclassified data to know when a commercial imaging satellite, possibly operating under contract to the Department of Defense, would be flying overhead.

It might even be possible, through the process of elimination, for knowledgeable amateurs to ferret out the orbit of a classified spacecraft by comparing actual observations with the list of known, unclassified satellites.

Even so, many in the amateur and commercial tracking community viewed the Air Force concern as misguided. While a small group of sophisticated amateurs do, in fact, track presumably "classified" spy satellites, they do it the old fashioned way: by monitoring military launches, looking for new satellites in the night sky and computing their orbits.

"At one level, most of us are trying to be responsible," said Jonathan McDowell, an astrophysicist who provides data on unclassified satellites to a broad internet audience. "On the other hand, there's not a lot of understanding within the military establishment, the political establishment, about how much of this stuff is obvious anyway."

In the post-9/11 environment, "there's this idea that if a piece of information is dangerous for the bad guys to know, we should be able to make it secret," he said. "And that's just not true, because sometimes a piece of information, like the bright satellites, they go overhead. It's futile to try to hide it."

"So sometimes you go through these big hurdles trying to make things secret that are, in an open society, things you just can't. All you end up doing is gumming up the works for everybody living ordinary lives, which makes the terrorists win."

The government is not attempting to black out data on unclassified satellites, Air Force officials say. But based on feedback from the Pentagon and the intelligence community during the OIG review process, the government is making major changes to more tightly monitor and oversee how those data are used.

Public Law 108-136, Section 913, a provision in the 2004 Defense Authorization Act, called for a three-year pilot program "to determine the feasibility and desirability of providing to non-United States Government entities space surveillance data support."

The result was a new Air Force website known as Space Track (http://www.space-track.org), which went on line Jan. 3. The original plan called for a three-month transition period, running through March 31, after which the OIG site would cease operations.

But NASA's computer system at the Goddard Space Flight Center in Greenbelt, Md., suffered a crippling failure in early February and while it is still in operation, its capabilities are limited. For most users, Space Track is now the only game in town.

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