But with U.S. signal interceptors targeting satphone transmissions to locate Iraqi military commanders, analysts worry that phone calls from civilians could appear as beacons for bombers.
The U.S. military won't discuss how precisely it can track people based on their satphone signals, and the satellite phone companies say they don't know. But military and intelligence experts say U.S. targeting technology is not just possible, it's getting better.
"Any satellite telephone is an emitter," said Loren Thompson, a defense analyst with the Lexington Institute in Arlington, Va. "By detecting the emissions, it should be possible for U.S. intelligence to localize desirable targets."
But distinguishing friend from foe based on a signal alone could prove difficult, he said.
"It's just yet another thing journalists now have to take into account," said Kate Adie, a British Broadcasting Corp. radio journalist awaiting assignment in Iraq.
In Qatar, Central Command spokeswoman Maj. Rumi Nielson-Green said the U.S. military's focus is on structures and equipment – not smaller targets such as individuals.
But she would not discuss the U.S. military's capabilities and could not rule out the possibility that noncombatants could be fired upon by mistake.
U.S. military officials have urged journalists and other foreign civilians to leave Iraq for their own safety.
Iraq's Information Ministry estimates that 300 foreign journalists remain in Baghdad. That does not include those outside the capital, whether traveling with U.S. forces or independently.
Major satellite telephony providers Inmarsat Ltd. of London; Thuraya Satellite Telecommunications Co. of Abu Dhabi, United Arab Emirates; and Iridium Satellite of Arlington, Va. saw subscriptions and usage rise alongside the prospect of a U.S. invasion.
On Tuesday, Inmarsat said it was activating a fifth satellite to help ease congestion caused, in part, by transmissions of news video.
If it wanted to ensure that it was not targeting noncombatants, the U.S. military could ask satellite phone providers for help. After all, the companies must locate subscribers to bill them.
But providers say their technologies aren't precise enough to pinpoint a caller's location closer than a few miles.
In the case of Iridium, chief technology officer Mark Adams said the system can get no closer than an area the size of Arizona.
Thuraya's phones are tied to global positioning technology and accurate to within 100 meters. But company chairman Mohammad Omran said subscribers must activate the GPS function on their phones in order to be tracked.
That leaves the U.S. military, itself a major Iridium client, to rely on eavesdropping or identifying unusual frequencies or call patterns, analysts say.
Wayne Madsen, a former National Security Agency analyst now with the Electronic Privacy Information Center, said U.S. spy agencies listen to phone signals using satellites, aircraft, ground stations and even specially equipped Humvees.
Processing those signals and making use of them is more challenging.
Satellite calls generally carry some sort of identification number, which gets matched to a phone number in company databases. If U.S. intelligence officials can match the ID number to a person, they can monitor the call - assuming they can break any encryption used.
Eavesdroppers can also pinpoint a caller to within several yards - better than phone companies can. The process, called triangulation, typically involves narrowing a signal's source by measuring its intensity from at least three locations – for instance, three surveillance planes, or one making three passes.
But al-Qaeda operatives haven't made it easy for U.S. airborne snoops, and it's not likely Iraqi generals will, either.
Al-Qaeda operatives change phones often and keep calls short to discourage tracing, said intelligence expert and author James Bamford. And phone IDs aren't always static. Iridium's changes with every call to prevent fraud.
Even if a desired target is located, weapons may not be marshaled in time.
You're going to have to move like greased lightning," said Martin Streetly, editor of Jane's Electronic Mission Aircraft in London. "You are going to have the sequence of detection, identification and then calling in a strike."
By Anick Jesdanun
By Anick Jesdanun