SETI [ASTRO] Radio Astronomers Agree To 6 Year Frequency 'Time Share' With Iridium LLC

Larry Klaes (
Fri, 04 Jun 1999 18:10:01 -0400

>X-Authentication-Warning: majordom set sender to owner-astro using -f >Date: Fri, 4 Jun 1999 1:26:16 GMT >From: Ron Baalke <> >To: >Subject: [ASTRO] Radio Astronomers Agree To 6 Year Frequency 'Time Share' With Iridium LLC >Sender: >Reply-To: Ron Baalke <> > >European Science Foundation >Strasbourg, France > >Press contacts: > >Andrew Smith >Head of Communication and Information >ESF >Tel: +33 (0)3 88 76 71 32 email: >or >Dr Jim Cohen >Chairman of the ESF Committee on Radio Astronomy Frequencies (CRAF) >Jodrell Bank Observatory, UK >Tel: +44 1477 571321 >or >Dr Titus Spoelstra >Frequency Manager, CRAF >PO Box 2, 7990 AA Dwingeloo, the Netherlands >Tel: +31 521 595100 > >ESF news release: Embargoed until 0001hrs Thursday 03 June 1999 > >Radio astronomers agree to 6 year frequency 'time share' with Iridium LLC > >The European Science Foundation has signed a second agreement with Iridium >LLC, the telecommunications satellite operator, providing a further degree >of protection for an important radio astronomy band near to the Iridium >operating frequency. Under the new agreement Iridium guarantees that >unwanted interference from its flotilla of 66 low-earth orbiting satellites >into the 1612 MHz radio astronomy band will be kept to acceptable levels for >up to 50% of the time for the next six and half years. > >This is the frequency used by astronomers to study the distribution of the >hydroxyl radical, one of the most common interstellar molecules, enabling >them to investigate a wide range of issues including the evaporation of >comets and the birth and death of stars. The hydroxyl emissions come from >regions that are hidden from optical telescopes by clouds of dust and gas >and are billions of times weaker than the emissions from an Iridium >satellite. Consequently, the small amount of power that leaks from an >Iridium satellite transmitter outside of its assigned frequency band of >1621.3-1626.5 MHz is strong enough to drown out the faint cosmic >emissions studied by radio astronomers. > >Under a broader framework agreement signed by the ESF and Iridium in >August of last year, Iridium has already pledged to ensure 24 hours a day of >'unpolluted' observation time from 1 January 2006. The new agreement covers >interim arrangements until that date and provides a guarantee that Europe's >extensive and world-leading 1612 MHz research programmes will be able to >continue albeit with a number of operating restrictions. > >Led by Dr Titus Spoelstra, Frequency Manager of the ESF Committee on Radio >Astronomy Frequencies (CRAF), Europe's radio astronomers have won a number >of additional concessions to similar agreements negotiated elsewhere in >the world. The clear times during which interference levels are guaranteed >to be low include not only overnight periods, but also weekends. These are >particularly important to astronomers as they cover full 24-hour periods >allowing them to study objects in any part of the accessible sky. Iridium >has also agreed to make 'quiet' time available on request to cater for >observations of spectacular or unusual events similar to the collision of >Comet Shoemaker-Levy with Jupiter in July 1994. > >However, while Europe's radio astronomers have negotiated a better deal >than many of their international counterparts, CRAF chairman Jim Cohen of >the UK's Jodrell Bank Observatory argues that the Iridium case has set a bad >precedent in several respects, which could threaten the future development >of radio astronomy. He points out that the allocation of the frequency band >1616-1626.5 MHz for space-to-earth transmissions was made by the >International Telecommunications Union (ITU) before technical studies had >been concluded on the possible harmful effects on radio astronomy. And >while radio astronomy has been given regulatory protection by the ITU, in >practice its measurements are now having to be squeezed into those times >when Iridium can guarantee low interference levels. "In effect," says Cohen, >"radio astronomy is time sharing with the radio waste of Iridium satellites. >Given the explosive growth in satellite telecommunications and broadcasting, >radio astronomers have to be worried about the long-term threat to their >science from the unwanted emissions of all these satellites." > >Eighty per cent of frequency bands allocated to radio astronomy on a primary >basis are adjacent to a band allocated for space-to-Earth transmissions, >although most have not yet been taken up. It is expected that the ITU's >World Radio Conference next year will for the first time set limits on >unwanted emissions from satellites. > >Further information and an updated list of cases of satellite interference >to radio astronomy can be found on the web pages of the European Science >Foundation's Committee on Radio Astronomy Frequencies ESF-CRAF > > >Notes for editors: > >1. The European Science Foundation is the European association of 65 major > national funding agencies devoted to scientific research in 22 countries. > The ESF assists its member organisations in two main ways: by bringing > scientists together in its scientific programmes, networks, exploratory > workshops and European research conferences, to work on topics of common > concern, and through the joint study of issues of strategic importance in > European science policy. > >2. The ESF Committee on Radio Astronomy Frequencies (CRAF) was established > in 1988 to coordinate the European efforts for the protection of radiospectrum > bands used by the Radio Astronomy Service and other passive applications. > >3. The criteria defining detrimental levels of interference for radio astronomy > in the 1610.6-1613.8 MHz band have been set by the International > Telecommunications Union (ITU-R RA769-1) at -238 dB (Wm-2Hz-1). Even > this represents a significant concession by radioastronomers to satellite- > enabled industries as current state-of-the-art sensitivities would imply that > these should be several orders of magnitude more stringent. > >4. Further reading: The CRAF Handbook for Radio Astronomy - second edition > (1997), published by the ESF, ISBN: 2-903148-94-5. > >

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