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GLONASS and Radio Astronomy. R. J. Cohen. 13th June 2002. Jodrell Bank Observatory University of Manchester. Outline of Presentation Historical background GLONASS – Radio Astronomy Joint Experiment Current status. GLONASS in the 1980s

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GLONASS andRadio Astronomy

R. J. Cohen

13th June 2002

Jodrell Bank Observatory

University of Manchester

Outline of Presentation

Historical background

GLONASS – Radio Astronomy Joint Experiment

Current status

GLONASS in the 1980s

GLONASS was a big problem at a time of great interest in 1612MHz OH-IR sources (OH shells resolved 1981; IRAS catalogue published 1985)

Transmissions overlapped 1612MHz OH line

GLONASS artefacts seen through 0dBi sidelobes typically 5K (5Jy on 100m dish; 50Jy on 30m dish)

Sensitivity eqn

Rapid variations as satellites traverse sidelobes

Null spikes look like masers (seen even at 1667MHz)

More than 100MHz “occupied”

Military “secret” so difficult to establish dialogue

Lovell telescope
Lovell Telescope

  • 250 ft fully steerable

  • Prime focus

  • 150MHz – 5 GHz

  • Upgrade in progress

  • Interference from Satellites - I

  • Line of sight: can’t shield against them!

  • Global coverage: all terrestrial sites affected

  • Spread spectrum: radio pollution of passive bands

  • Many examples (GLONASS, Astra, Tex, Iridium, … )

  • Malfunctions are difficult to repair in space

  • Long timescale for change, once launched

  • More than 100 satellites launched per year

  • No pre-launch check on total emissions (environmental impact)

  • Historical Landmarks

  • 1968 Discovery of OH-IR sources

  • 1979 OH 1612-MHz line given secondary allocation

  • First GLONASS satellite launched (military)

  • 1983 Coordination of GLONASS begins

  • Interference identified and published IRAS catalogue published (~104 OH-IR sources)

  • First IUCAF-GLONASS meeting

  • Worldwide experiment to test possible cures Radio astronomy band made primary

  • GLONASS-IUCAF Agreement signed in Moscow

  • 2006 Projected completion of “clean-up” plan


Coordination is possible with radio astronomy

1993 onwards, no satellites in channels 16-20

1999 onwards, satellites confined to channels 1-12

New GLONASS frequency plan is needed

Filters will be installed on GLONASS-M satellites, sufficient to protect 1660-1670MHz band

GLONASS administration will investigate ways to fully protect 1612-MHz band and will communicate their proposed solution at a future meeting

IUCAF will coordinate further joint experiments as needed

Current Status and Prospects

Last launch 1st December 2001

7 operating satellites at 30th May 2002

Only channels 1-12 used (since ~2000)

No evidence of filters on new satellites

New GLONASS administration in place

IUCAF is gathering information on current levels of interference from GLONASS, deadline 1st Nov 2002

Possible further negotiations and further joint experiment

Complicated by newcomers: Iridium, Globalstar?, etc.