News FocusAstronomy

Radio Astronomers Take Arms Against a Sea of Signals

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Science  22 Oct 2010:
Vol. 330, Issue 6003, pp. 444-445
DOI: 10.1126/science.330.6003.444

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Over the past decade, radio telescopes have faced increasing interference from mobile wireless devices, including Wi-Fi modems and Bluetooth, satellite radio channels like XM and Sirius, and global positioning systems. Last year, the switch to all-digital television broadcasting in the United States—a bigger cause of interference than analog signals—added to the troubles. Meanwhile, traditional sources of interference such as airplanes and satellites continue their barrage. Intrusive emissions routinely contaminate data from cosmic radio sources and in the worst instances can wipe out several hours of observation in a single stroke. Astronomers have been developing a slew of solutions including electronics that help radio receivers tolerate power surges, filters to avoid frequencies at which interference is likely to occur, and ways of making telescopes and telescope arrays selectively blind to signals coming from certain directions in the sky to cancel out interference from satellites and airplanes. In addition, astronomers and radio engineers are coming up with new and improved techniques for subtracting interference from data after it has been collected. And observers are also working out human solutions: negotiating with local communities to reduce interference and silence it altogether for short durations to allow key observations.