Indian officials hope to strike a deal with a subsidiary of Motorola that would prevent signal interference by company satellites with the country's Giant Meterwave Radio Telescope (GMRT). Astronomers say signals to mobile phones could hamstring the $17 million installation as it prepares to become operational next year.
GMRT, near Pune, India, is designed to be one of the most sensitive instruments in the world for exploring the early universe, with 30 antennae spread over 25 kilometers. GMRT now operates in the 50- to 1420-MHz range, but expansion is planned within the next few years to 1612 MHz. That will bring it near the 1621.35- to 1626.5-MHz range being used by Iridium India Telecom, a collection of 72 low-Earth orbit satellites--of which 39 are in place--that will offer global mobile phone service. A gateway to serve South Asia is being set up uncomfortably close to GMRT at Dighi, about 80 km away.
"Spurious radio emissions because of the cheap circuits and filters being used in the Iridium project can close important windows to view the universe," says Vijay Kapahi, director of the National Centre for Radio Astronomy in Pune. Scientists are worried in particular about interference with signatures from hydroxyl radicals at about 1612 MHz, which are important for exploring star-forming regions.
Iridium officials insist that their system won't cause trouble. "The initial experiments done at the Dighi site give favorable results that meet international requirements," says Jaydev Raja, head of Iridium. He adds that the company "has offered a radio pollution-free window for 4 hours every day very early in the morning." However, former GMRT chief Govind Swarup says "this is highly impractical" and that clear signals are required around the clock.
The interference problem is not new. This month, at the World Radiocommunication Conference in Geneva, concerns were aired about communications companies that are seeking ever higher radio frequency bands for high-capacity mobile phones and Internet services.
