On the south end of the tarmac at a British air base on the Indian Ocean island of Diego Garcia, two portable maintenance shelters for B-2 stealth bombers sit like high-tech cocoons, erected by the U.S. Air Force in anticipation of the possibility of war with Iraq.

While no American reporters have been allowed on the base for more than a year, a think tank in Alexandria posted a commercial satellite photograph of the shelters on its Web site last week, confirming that they were in place, and raising a host of national security issues about the privatization of spy satellite images.

The think tank, GlobalSecurity.org, purchased the satellite photo from an Israeli company, ImageSat International, for $200. It has also posted even higher resolution satellite photos from two U.S. companies, Space Imaging and Digital Globe, of the Air Force's growing Al Udeid base in Qatar, which would be a major staging area for warplanes in any military campaign against Iraq.

Some military analysts argue that these photos could possibly endanger national security, tipping off Iraq and other adversaries about U.S. military abilities and plans.

But the CIA and the Pentagon have voiced no such objections, largely because they benefit more than anyone else from these new high-resolution commercial imaging satellites. With a small fleet of highly classified spy satellites overtaxed and the next generation satellites over budget and behind schedule, their commercial counterparts are beginning to help shoulder the burden, and offer an important insurance policy against any future interruptions in service.

In fact, the National Imagery and Mapping Agency (NIMA), an intelligence organization inside the Pentagon, has increased its spending on commercial images this year by 10 times to about $100 million, according to defense and intelligence officials.

What's more, the government has absolute "shutter control" under licensing agreements with the satellite companies and can stop them from photographing particular countries for national security reasons.

A year ago, when the war began in Afghanistan, NIMA exercised what some analysts have called "checkbook shutter control" by agreeing to buy all imagery of Afghanistan produced by Space Imaging, then the only American company operating a high-resolution satellite.

Bobbi Lenczowski, a senior NIMA official, said Friday that the agreement wasn't a form of shutter control: NIMA needed the commercial imagery, she explained, to keep commanders supplied with battlefield maps made from the satellite photos.

But beyond this government utility, the availability of commercial satellite images has had a far more visible impact in the public debate over national security issues. Think tanks and media organizations have begun obtaining photographic intelligence that was, as recently as three years ago, the exclusive preserve of the CIA and the Pentagon.

As GlobalSecurity.org published the ImageSat photo of the B-2 shelters on Diego Garcia last week, MSNBC, CNN, ABC News, CBS News and the BBC were all using commercial satellite pictures to buttress stories about growing concern in the Bush administration over nuclear facilities in Iran and North Korea.

Ann Florini, a senior fellow at the Brookings Institution, said that commercial imagery is likely to have a far greater impact "democratizing" public policy debates than jeopardizing military operations.

With images showing renewed activity at Iranian and North Korean nuclear facilities openly available, she said, the U.S. government can no longer respond by saying no comment. "And that," she said, "is the way policies are supposed to be debated in this country."

John Copple, chairman and chief executive officer of Space Imagining, based in Thornton, Colo., said that the commercial satellite industry must "practice a reasonable amount of restraint in producing and analyzing these images when there is the possibility that it could threaten or harm in some way U.S. interests; otherwise the U.S. government has shutter control."

But Copple argued that the ability of nations all over the world to obtain high-resolution satellite pictures of conditions along their borders serves to increase global transparency and "reduce fear of what's going on."

"There is a long-term benefit that could come from having this transparency, and we're seeing it happen already in the news media," Copple said.

Space Imaging launched the first high-resolution commercial satellite with "one meter resolution" -- meaning it can capture objects as small as one meter (39.37 inches) in size -- in September 1999. It was followed into space in October 2001 by Digital Globe, based in Longmont, Colo., which launched a satellite with 0.6 meter resolution. (The capabilities of U.S. spy satellites are highly classified, but they are believed to be capable of 0.1 meter resolution.)

In June, CIA Director George J. Tenet signed a memo directing NIMA to use commercial imagery to "the greatest extent possible." Commercial imagery, Tenet said, should become the "primary source" of data for use in military mapping.