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Passengers expect to use cell phones after 911 { June 9 2005 }

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Astronomers criticise plans to allow cellphone use on planes

11:05 09 June 2005 news service
Maggie McKee

Using cellphones on aeroplanes could drown out faint radio signals from space, astronomers are warning. They told a US agency considering lifting in-flight restrictions on cellphones that special devices should be installed on planes to limit damage to research if the regulations change.

US law currently prohibits aeroplane passengers from using cellphones because they may interfere with critical aircraft electronics. But the dramatic use of cellphones by passengers on the planes hijacked on 11 September 2001 spurred many people to petition the government to change this policy.

"It was not the cellphones that caused those planes to crash," says Paul Feldman, a telecommunications lawyer at the firm Fletcher, Heald and Hildreth in Arlington, Virginia, US. "For better or worse, there's an increasing expectation that people can use their cellphones everywhere, all the time."

Now two government agencies - which would probably both have to agree to lift the ban - are reviewing the issue. The Federal Aviation Administration may reverse its policy depending on the results of a study on how cellphones affect flight safety. The study should be finished in January 2006.

Meanwhile, the Federal Communications Commission (FCC) has asked for public comments on the possibility of lifting its restrictions, which were originally put in place because of the strain that cellphone use could put on ground-based wireless networks.
Newborn stars

In late May 2005, the National Academy of Sciences' Committee on Radio Frequencies submitted comments on the proposed FCC changes. It pointed out that, as well as emitting radiation at their fundamental operating frequencies, cellphones leak radiation at integer multiples of these frequencies, called harmonics.

The second harmonic happens to fall in a frequency band that reveals the molecular signature of newborn and dying stars and is among the 2% of frequencies in this part of the electromagnetic spectrum "reserved" for use by radio astronomers.

Cellphone use on planes "could be a disaster for us", says Michael Davis, director of projects at California's SETI Institute, which searches for signs of extraterrestrial intelligence, and former chair of the NAS committee. "We have incredibly sensitive radio telescopes - even a single cellphone on a single plane 100 miles away could cause pretty serious damage", he told New Scientist. It would exceed recommended "noise" levels by 10 times.

That is partly because cellphone signals from planes are not blocked by trees or buildings as they are on the ground, allowing them to travel straight into astronomers' telescopes. "Putting cellphones in a plane is like building a cellphone tower 40,000 feet high," says Davis.
Turn it down

Compounding the problem is the fact that, in order to save on battery power, cellphones adjust the strength of their signals according to the distance of the nearest transmitter. But the NAS committee says the FCC could co-opt this feature to render cellphones harmless to astronomy.

A device called a "picocell" could act as a local transmitter on a plane, telling cellphones, "I'm right nearby, so turn your output power down," explains Davis. The picocell would then transmit the signals from within the plane to a station on the ground over a single frequency that would not endanger radio astronomy with its harmonics.

A single-frequency system already transmits signals from the phones installed on the back of seats in some planes.

However, another factor may be more important in the decision. Among the nearly 8000 comments submitted to the FCC, many - including one from flight attendants - echo a sentiment by Michael Traynor of Lakewood, California. He writes: "Being in an aeroplane seat for a four to five-hour flight is arduous enough in itself without additional annoyances such as a plane full of cellphone yakkers. Keep the ban as it is!"

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