WASHINGTON -- America's highly classified intelligence-gathering satellites were given new tasks in the wake of Tuesday's attacks on New York's World Trade Center and the Pentagon, a source told SPACE.com.

However, the terrorist strikes have called into question the utility of spacecraft to provide early warning of such threats.

Space-based assets of both the National Reconnaissance Office (NRO) and the National Security Agency (NSA) are on task, a SPACE.com source said, to snag information that could prove helpful in identifying culprits in the attack.

NRO designs, builds and operates the nation's reconnaissance satellites. The NSA is the lead agency responsible for code-breaking and eavesdropping. It produces foreign intelligence information and is expert in Signals Intelligence (SIGINT).

To what extent the NRO and the NSA satellites are now being specially tasked is not immediately clear. An NRO spokesman declined to respond to SPACE.com's question.

"It's not something we talk about whether there has been or hasn't been," said Rick Oborn, Director of Corporate Communications at the NRO. He said that other intelligence and government agencies request tasking of NRO assets.

A type of satellite critical for monitoring terrorist actions is geared for electronic intelligence gathering. These ELINT spacecraft eavesdrop on communications links, ostensibly in use by terrorist organizations. Oborn said he could not speculate on ELINT satellite use.

"In this context, I'll reserve any kind of comment," Oborn told SPACE.com.

But according to one expert in satellite intelligence operations, ELINT satellites often don't work against terrorist organizations. Such groups shy away from overt use of radio communications, the source said. However, it is likely that these orbiting satellites are on task to intercept potential radio traffic by terrorist organizers, he said.

But relying too heavily on satellites is not advisable, said Robert Steele, Chief Operating Officer for Open Source Solutions in Oakton, Virginia.

"The entire U.S. intelligence community, including all of its expensive satellites, is helpless against any enemy that practices operations security. That means, if they dont use the phone, don't use a computer, and if they do all their business face to face with single-trusted companions, there is no way the existing intelligence infrastructure can anticipate this kind of coordinated attack," Steele said.

Steele is a 25-year veteran of the national security community. He is author of the recently published book: On Intelligence: Spies and Secrecy in an Open World.

"I am terribly concerned the President and his Cold War mandarins will attempt to trivialize this as a terrorist attack. Instead, this should be seen as this century's Pearl Harbor. Even more so this should be seen as the equivalent of the burning by fire of a thousand monks and Quakers in front of the White House," Steele told SPACE.com.

"There's no way to defend ourselves against this kind of thing. We actually have to spend money on plowshares instead of swords," Steele said.

Jeffrey Richelson, a noted Washington, D.C.-based expert on military and intelligence satellite told SPACE.com that photo reconnaissance and intelligence-gathering satellites are presumably on full alert. He is author of the authoritative book, The U.S. Intelligence Community.

"I presume they are targeting any sort of terrorist facility or camp with everything that goes over. So whatever the frequency was previously, I'm sure every time anything that goes over in terms of imagery satellites -- such as sites in Afghanistan or any place else -- they are producing imagery. I'm sure that's being reviewed immediately. I presume that the NSA is sifting through any of the intelligence communications that would relate to terrorism," Richelson said.

"Beyond that, there's a limited amount they can do from space," Richelson said.

Richelson said it is extremely difficult to obtain visible signs of what terrorist groups are planning. In recent years, he said, there has been a growing issue with collecting data, but not having enough time and money to process satellite-gleaned information.

"If you collect and you don't know what's there until weeks after something like this happened, it doesn't do you any good. It's really a question of assessing why didn't we know about this and what could we possibly have done," Richelson said.

"Just throwing money at a problem isn't necessarily going to help. You actually have to penetrate these groups," Richelson said. "The first thing to do is ask exactly what happened. How did they evade detection, security, and how can you prevent that in the future," he said.

Still to be determined, and likely to involve satellite assets, Richelson said, is what to do in terms of retaliation from an intelligence point of view or a military point of view.

Taking satellite photos of terrorist facilities can only go so far, Richelson said.

"But what's going on inside those buildings in terms of planning is not something you can detect by satellite, unless they actually go out and practice. I don't think they would have practiced smashing jets into tall towers," Richelson said. Even if the United States had 24 hours-a-day, real-time surveillance of every place on Earth, simultaneously, he said, detection of such terrorist planning is doubtful.

"It's not obvious that would have made any difference. Pumping up the budget in that area wouldn't necessarily solve the problem," Richelson said.

"The only immediate lesson is kill them first, before they do anything. That's the obvious lesson learned," Richelson said.