WASHINGTON — The director of the U.S. National Reconnaissance Office (NRO) confirmed Sept. 26 that at least one American satellite has been illuminated by a ground-based laser operating in China.

“It was a test,” NRO Director Donald Kerr told reporters following a speech here at the Air Force Association’s annual conference. The NRO operates America’s spy satellites.

Kerr did not specify the spacecraft that has been illuminated by the Chinese laser. The incident was first reported in the Sept. 25 edition of Defense News.

During his speech, Kerr said the United States has concerns about freedom of action in space. “I think you’re aware from the press, for example, that the Chinese have tested an [anti-satellite] capability,” he said.

Asked if the test degraded U.S. monitoring capabilities in any way, Kerr said: “No, it was a test … It makes us think.”

Kerr declined to provide additional details.

Richard Oborn, a spokesman for the NRO, declined to say when the test took place or whether there had been just one.

The Department of Defense has been saying for several years that China is developing anti-satellite capabilities. In its “Annual Report to Congress: Military Power of the People’s Republic of China 2006,” the Pentagon said that “at least one of the satellite attack systems appears to be a ground-based laser designed to damage or blind imaging satellites.”

Kerr said there are a number of ways the United States can protect itself against anti-satellite threats. “Actually, my favorite way would be to have a hot production line,” he said.

China’s test is not the first publicly acknowledged incident involving the firing of a ground-based laser at a satellite. On Oct. 17, 1997, the Pentagon conducted a test in which the U.S. Army’s Mid Infrared Advanced Chemical Laser was fired at an experimental U.S. Air Force satellite dubbed Multi Sensor Technology Integration 3.

In the months leading up to the test, U.S. defense officials offered different rationales for conducting the test, with some saying it was intended to determine the feasibility of using lasers to disrupt or disable satellites and others saying the purpose was to assess the vulnerability of U.S. spacecraft to such attacks.

Following the test, then-Pentagon spokesman Ken Bacon said data from the satellite and from ground-based sensors confirmed that the laser illuminated the satellite but added that information was lost that could have helped determine the laser power levels necessary to disable or damage the satellite’s sensor.

Philip Coyle, who was the Pentagon’s director of operational test and evaluation at the time of the experiment, said that two tests were conducted: a 1-second firing designed to simulate an accidental illumination; and a 10-second firing that was supposed to be more representative of a deliberate attack.

In an interview, Coyle, now an advisor to the Center for Defense Information, a think tank here, said a ground-based laser with sufficient power could in theory overheat and damage a satellite or its sensitive optics.

But temporarily disrupting a satellite’s optics without causing permanent damage is a difficult thing to do with a laser, Coyle said. To be able to do that, the laser must operate in roughly the same wavelength as the sensor, he said. If the sensor operates in multiple wavelengths, it would take several lasers — one for each wavelength — to effectively render it temporarily blind, he said.

Michael Krepon, co-founder of the Henry L. Stimson Center, a Washington think tank, said the incident involving China illustrates the need for what he called a code of conduct among space faring nations.

“The illumination of somebody else’s satellite for destructive purposes would be a huge provocation and could lead to war,” Krepon said in an interview Sept. 27. “The illumination of somebody else’s satellite for nondestructive purposes is unwise and unhelpful for those who wish to keep space as a friendly environment for satellites.”

One of the dangers, Krepon said, is that it is difficult if not impossible to determine the intent of a nation that is firing a laser at a satellite. He said satellites are as vital as they are vulnerable. Similar types of incidents, such as when nations have trained missile-guidance radars on another country’s aircraft — a practice known in military parlance as painting — have led directly to overt hostilities, he noted.

“To me this episode, assuming it occurred, underlines the importance of rules of the road that permit satellites to operate as intended,” Krepon said. “This is noteworthy because it’s so unusual.”

Phone calls placed Sept. 27, 28 and 29 with the press office of the Chinese embassy in Washington were not returned.

News of the incident surfaced during a long-anticipated trip to China by NASA Administrator Mike Griffin. Over the last year, Chinese space officials have publicly expressed interest in cooperative projects with nations including the United States.

At least one U.S. lawmaker thinks wider cooperation with China in space is a bad idea in light of the revelations about China.

“It is unfathomable this Administration has decided to engage China on space policy or any other technological endeavor,” Rep. Dana Rohrabacher (R-Calif.), a former chairman of the House Science space and aeronautics subcommittee and a strident China critic, said in a Sept. 26 press release. “…This latest revelation of the Chinese firing ground-based lasers to blind our reconnaissance satellites while high level officials from NASA are participating in an alleged exploratory visit is the highest level of contradiction.”