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Iridium is in trouble with Indian radio astronomers

Motorola subsidiary, Iridium Inc, is setting up a network of 66 low-earth orbit satellites to offer a global voice and paging service, beginning September 1998. It has already launched 39 satellites.

Astronomers at the Giant Metre Wave Radio Telescope in Pune claim Iridium satellites are a threat to Indian radio astronomy because the

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down-link frequencies at which the satellites will communicate with individual telephones are too close to the observational band of the telescope.

Spurious signals from the satellites will interfere with GMRT's observations of the universe in the crucial range of 1610 MHz to 1613.8 MHz, says V K Kapahi, GMRT director.

Astronomers of the Tata Institute of Fundamental Research in Bombay have urged the Department of Telecommunications to not clear the Iridium operation in India until they see the results of experiments to be conducted later this year at the National Radio Astronomy Observatory at Grenbank, US.

The Rs 600 million telescope built by TIFR is, at present, the most sensitive telescope in the world in the 38-1427 MHz frequency range. There are plans to extend the range of to 1670 MHz over the next two years.

"These bands are also important for potential searches for extra-terrestrial intelligence," says Govind Swarup, creator of the GMRT project, and its director until he retired from TIFR a year ago.

It is therefore necessary that the Indian Radio Astronomy Group protect itself against expected interference from Iridium satellites, he says.

Negotiations between TIFR astronomers and Motorola on how to avoid interference are in progress but the conflict has not yet been resolved, says Kapahi.

An Iridium spokesman has said that his company is trying to find ways "so that we both can co-exist".

Indian astronomers are reportedly asking Iridium to switch off telephone traffic during weekend daytime in addition to four hours every night. This condition, Iridium says, will severely cut into profits.

Indian scientists are also demanding that there be regulated use of hand-held telephones within 300 km of GMRT. They want a written commitment from Iridium that their future satellites will provide full protection to radio astronomy services in the frequency band at all times of the day.

In contrast, TIFR has already cleared the Globalstar System, Iridium's rival, whose constellation of 48 satellites will downlink at a frequency that will not pose any problem to GMRT.

"Unfortunately, Motorola has chosen to make space for earth transmission in the 1619.35-1626.5 MHz band which is relatively chose to the radio astronomy band of 1610-1613.8 MHz," TIFR scientists said in a statement.

The statement added: "Indian radio astronomers are extremely unhappy about the high level of spurious emission from the Iridium systems. In spite of assurance given in 1991 prior to the allocation made by the International Telecommunication Union in 1992, Motorola is continuing to launch Iridium satellites."

The Indian astronomers' battle with Motorola is likely to be an uphill task, given the fact that a dozen public financial institutions of the country have invested Rs 2.5 billion in Iridium Inc and that India's own telecommunications company, the Videsh Sanchar Nigam Limited, is a business partner.

There is fear that economic pressures may find place in future negotiations with Motorola but Kapahi points out that the wireless planning and coordination groups in DoT have been very supportive of GMRT in the past and is confident that they will not give in now.

Indian astronomers are not alone in their battle against Iridium. Astronomers in the UK, Australia and Europe are also fighting against the telecom giant.

The International Telecommunication Union allows satellite companies to use the 1610-1626.5 MHz frequency range for mobile telephone service but prohibits companies from causing any harmful interference to radio astronomy.

Swarup says that Motorola could have avoided interference by choosing a downlink frequency far away from the radio astronomy band, but it did not do so to save money.

- Compiled from the Indian media

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