I cacciatori di interferenze del radioosservatorio

Il ronzio generato da un televisore o un computer nella cuffia di un radioamatore è una "minor nuisance" se confrontata con gli stessi disturbi percepiti dalla parabola (da chissà quanti milioni di dollari) di un radiotelescopio. Associated Press dedica un articolo molto divertente al mestiere dei "cacciatori di rumore" che agisono per conto del National Radio Astronomy di Green Bank in West Virginia, andando in giro a bordo di furgoni attrezzati di ricevitori ad ampio spettro e spettrometri per l'identificazione delle fonti di disturbo in RF. A Green Bank è stata istituita una area di 13mila miglia quadrate, la National Radio Free Zone dove non vengono tollerati disturbi e rumori elettrici e ogni attività in radiofrequenza deve essere concordata con i responsabili dell'osservatorio.

Shhh! Gadget racket threatens pulsar research

By TOM BREEN - December, 31st

GREEN BANK, W.Va. (AP) — Of all the threats to scientific research Wesley Sizemore has stymied over the years, satellites and cell phone towers don't stick in his memory quite like the possessive old hound and its treasured heating pad.
Sizemore is an interference hunter, vigilantly pursuing stray electromagnetic signals that bedevil researchers at the National Radio Astronomy Observatory, which sits on 13,000 square miles tucked away in the nation's only radio-free quiet zone.
Radio observatories need interference-free zones like optical observatories need clear night skies.
Though buffered by ridgetops in a West Virginia mountain valley, 50 miles from the nearest town of any size, the Green Bank observatory is under an audio assault unlike any it's faced in the 50 years since Congress created the quiet zone. Wireless computers and other gadgets are cluttering the same frequencies occupied by signals from neutron stars.
Researchers, mostly looking at pulsar waves that have traveled through space for billions of years, pursue signals so weak they can be easily foiled by anything from power locks on cars to a broken wire inside a heating pad that kept a nearby dog warm in the winter.
"There was enough arcing inside the heating pad that it caught our attention," Sizemore said, again telling what he affectionately calls "that damn dog story."
Over several days, Sizemore — who has a specially equipped truck and gear that can pinpoint an interference source the size of a 50-cent piece — tracked it to a doghouse about 10 miles from the observatory.
He bought a new heating pad and all was resolved, although not necessarily amicably.
"It was a nasty little dog," Sizemore said. "He wasn't real happy with me snooping around his doghouse, put it that way."
Astronomer Scott Ranson, whose ongoing study of neutron stars has been destroyed more than once by bursts of interference, said collecting data in today's technology-dependent world is like trying to look at stars while a neighbor is shooting fireworks.
"We were completely swamped and our data was useless," he said of one particularly frustrating episode. "We didn't know where it came from. It was there for several hours over a course of a few days."
The observatory's origins hail from the 1950s when Congress and the West Virginia Legislature created national and state radio quiet zones to protect and promote the relatively new science of radio astronomy.
While Green Bank is one of many radio telescope observatories around the world, it's unique because it features the world's largest steerable radio telescope. Completed in 2000, the ultra-sensitive scope is taller than the Statue of Liberty and heavier than a fleet of Boeing 747s, with a reflective dish that could hold 60,000 people.
"We have to have a radio-quiet environment for the radio telescope to work," assistant site director Karen O'Neil said at a recent open house at the observatory. "If we start to lose radio frequency bands, the point of having a telescope here diminishes rapidly."
The observatory goes to great lengths to prevent interference from its own grounds, adopting "Stay Quiet to Promote Science" as its motto.
Visitors must walk, bike or ride to the giant telescope in a diesel-powered bus because diesel motors rely on compression instead of spark plugs to ignite. Guests must turn off digital cameras and use film to take pictures.
Even the signals from space received by the telescope are sent to computers via fiber-optic cable rather than wirelessly to prevent interference. Inside the observatory, walls are lined with copper, and computer equipment is housed in metallic cages that block radiation and protect the telescope.
While the observatory can weigh in on the proposed placement or upgrade of any fixed transmitter within the 13,000-square-mile National Radio Quiet Zone, it doesn't have control over electronic interference from passing planes or satellites.
The 10-mile radius of the West Virginia Radio Astronomy Zone gives researchers the authority to crack down on wireless modems and speakers and cordless phones. The scientists try to be good neighbors, and residents have generally accepted the precautions taken to reduce electromagnetic noise, but some are starting to chafe against the limitations placed on their tools of the digital age.
"We feel we're a bit discriminated against because they created the zone around us," said County Commission President James Carpenter, who lives within Green Bank's extra-restricted 10-mile radius. "Our children can't have a wireless computer when everybody else in the state can have one." Sizemore said the observatory's staff want to accommodate residents, but there may come a day when the researchers start "knocking on doors and asking people to get off their wireless devices."
"Without interference protection," he said, "we might as well close up shop and go home."