Wednesday, December 23, 2009

Silent Skies for Radio Astronomers

With the ever-increasing expansion of radio-frequency mobile telecommunication chatter via cellular / mobile phones and other wireless devices, will our skies be “silent” enough for radio astronomy?

By: Ringo Bones

The International Astronomical Union and the International Dark Skies Association had made significant progress recently in stamping out the scourge of urban light pollution during the celebration of the UN sponsored 2009 International Year of Astronomy. Especially when the Galloway Forest Park in Scotland was established as a protected dark sky area for stargazers and amateur astronomers. Unfortunately, nothing has been done for radio astronomers when it comes to the “trivial” problem of the increasing radio-frequency traffic that denied a chatter-free silent sky condition for astronomers who explore the cosmos in the radio portion of the electromagnetic spectrum. Especially in radio frequencies of interest used in exploring our universe like galactic structure and evolution to signs of “extraterrestrial technology”.

As far back as the 1970s, astronomer Carl Sagan raised concerns over the US Department of Defense’s heavily encrypted DARPA Net “Hotline” operating so close a frequency to the hydroxyl radical radio frequency. In 1995, the Strasbourg-based European Science Foundation issued a warning that the rapid expansion of the mobile communications / mobile phone / cellular phone industry’s excessive “radio-frequency pollution” – a.k.a. RF pollution - was a serious threat to radio astronomers worldwide. Back then, Dr. James Cohen of Britain’s Jodrell Bank observatory decried the ongoing deployment of numerous low-Earth-orbit telecommunications satellites used to serve the mobile / cellular phone industry.

Around that time, Dr. James Cohen stated that even if the sideband emissions from satellite / mobile / cellular telephones were small, they would still devastate radio telescopes equipped with large dishes which are so sensitive they can detect extremely weak and distant RF signals on the sub-nanovolt level. Like urban light pollution plaguing astronomers who work in the optical portion of the electromagnetic spectrum, Dr. Cohen likened the problem to a professional photographer having a light shining into his or her lens every time he or she tried to snap a picture. Dr. Peter Napier of the US National Radio Astronomy Observatory concurred with Dr. Cohen, saying that the problems of excessive RF pollution in the radio spectrum of our skies were severe and getting worse as the years go by. Dr. Napier characterized common telecommunications engineering practices as “inadequate” to prevent severe disruption to radio astronomy.

Due to a lack of a legally binding international treaty designed to protect the world’s radio astronomers against excessive RF frequencies reaching into their astronomical instruments or radio frequency pollution. The International Telecommunications Union (ITU) had assigned a frequency of 1410MHz – previously the sole domain of the US DoD during the height of the Cold War to send heavily encrypted data streams – available for civilian use for satellite / mobile / cellular phone systems. Unfortunately, this radio frequency band is dangerously close to the 1412MHz signature of the hydroxyl radical – a hydrogen / oxygen molecular fragment widely distributed in space and is used by radio astronomers to map our universe.

In the time since the European Science Foundation issued its warning against excessive radio frequency traffic ruining radio astronomy, “celestial traffic” via telecommunications satellites around the Earth had increased tremendously. These now support an ever-growing market of dedicated ISDN modem / broadband modem lines / wi-fi / and mobile / cellular phones – not to mention an “experimental” system intended to prevent auto collisions. Not only do these satellites contribute to the RF frequency pollution that spoils radio astronomy - their highly reflective Teflon-coated antennae can also be a source of light pollution to astronomers working in the optical spectrum. These satellites – like the various Iridium satellites and the 24-satellite Global Positioning System in geosynchronous orbits - are probably the only “stars” visible in urban areas plagued by sodium-vapor street-lamp light pollution.

The radio frequency pollution problem shows no sign of abating. Mike Cousins, who runs the Stanford Research Institute’s radio-telescope research program, told the San Francisco Examiner that the problem is “constant, sometimes severe”. There is now a cellular phone tower just over the hill from Stanford’s 150-foot dish, Cousins told the San Francisco Examiner’s science writer Keay Davidson. “There is nothing we can do about it” Cousins says. The Stanford dish is sensitive enough to pick up radar reflections from ships in the Western Pacific and Citizen’s Band radio transmissions from as far away as Florida. Even Seth Shostak of the SETI Institute in Mountain View, California, characterized the radio frequency pollution problem in radio astronomy as “science versus heavy-duty commerce”. Scientists at Seth Shostak’s institute search for radio frequency signals from extraterrestrial civilizations.

Will the radio frequency pollution problem that plagues radio astronomers like urban light pollution problems plaguing astronomers using optical telescopes ever be solved? Most radio telescopes, like their optical counterparts, stand in once-remote and once-uninhabited locations that are now surrounded by highly urbanized civilization with their inherently light and RF polluting lifestyle. Even the International Dark Skies Association had failed to solve the increasing light pollution problem around Mount Wilson Observatory in Pasadena, California.

Recently, radio astronomers have developed a few techniques for separating the extraterrestrial radio signals of interest from the more mundane RF pollution noise. One is by computer correlation of signals received by two or more dishes spaced hundreds of miles apart. Using this technique, radio astronomers can filter out the transmissions of cellular phone “yakking yuppies” and concentrate on the spectrum of interest. The better – if not the best technique – for radio astronomers to beat radio frequency pollution is to build a radio astronomy dish as far away from the earthbound RF noise as possible – like on the dark side of the Moon. Sadly, this project won’t be getting any US Congressional funding anytime soon after the Bush-Cheney Consortium ran their “Global War on Terror in a malfeasant manner that left the US Government mired in a 12 trillion dollar debt burden. Some gifted scientist now smoking weed in Amsterdam could have built a faster-than-light capable spacecraft that carries a crew of 150 with that kind of money.

1 comment:

May Anne said...

Given the radio frequency chatter won't die down anytime soon, radio astronomers' only viable resort to solve this dilema is a radio observatory - Arecibo sized - on the far side / dark side of the Moon.