Two months from now the International Telecommunications Union will hold its World Radio Conference in Turkey. Radio astronomers are hoping for new regulations to curb emission from satellites that are polluting their observations.
Man-made radio emission has increased dramatically over recent years with the advent of satellite telecommunications and digital broadcasting - so much so that radio astronomy now finds itself under threat from the very technology that it nurtured. Even microwave ovens and car remote locking systems contribute to the rising noise that pollutes astronomical observations.
Radio astronomy has revolutionized our understanding of the universe, revealing, among other things, radio galaxies, quasars, pulsars and the cosmic background radiation. Indeed, radio is the only wavelength other than optical that is not blocked by the Earth's atmosphere. Radio waves pass through the clouds of gas and dust that block out light waves, revealing parts of the universe that would otherwise remain hidden.
Very long baseline interferometry links radio telescopes around the world to give the highest resolution available anywhere across the entire electromagnetic spectrum - 10 microarcsec - which is equivalent to the angle subtended by a golf ball on the moon, 400 000 km away.
Several organizations protect the interests of radio astronomy and negotiate with the governing bodies and communications giants. However, many compromises have to be made along the way. In May 1999 an agreement was concluded between radio astronomers and Iridium, which uses a network of satellites transmitting in the 1616-1626 MHz frequency range. These transmissions seriously pollute observations of the 1612 MHz spectral line of the hydroxyl radical, which gives a unique view of stellar evolution and galactic dynamics. The agreement, which was signed by the President of the European Science Foundation on behalf of the various radio observatories and their funding agencies, guarantees low interference from Iridium up to 50% of the time, which allows limited 1612 MHz research to continue.