Transcript Radio Quiet Zones Past, Present and Future

Radio Quiet Zones (RQZ)
History and Current Activities
Tasso Tzioumis
ATNF, CSIRO
Need for RQZ?
• Radio Astronomy (RA) systems must be
extremely sensitive as cosmic emissions very faint
 very susceptible to Interference (RFI)
• RA allocated very little spectrum (~2% at cm
bands) but operates over full radio spectrum (no
control of cosmic emissions)
 RFI from radiocommunication services
• Must start as radio-quiet as possible - RQZ
Radio Quiet?
• Radio Quiet is NOT Radio Silent
• “Passive” bands (e.g. 1400-1427 MHz)
– “all emissions are prohibited” (ITU-R Fn. 5.340)
– but Noise present e.g. Out-of-Band emissions
• Quiet means NO “detrimental” RFI
• RQZ  prevent “detrimental” (harmful) RFI
RQZ definition?
• Define threshold levels for “detrimental” RFI at
the antenna(s)
– ITU-R defines “detrimental” RFI levels for RA bands
• Survey radio transmitters (present and planned)
– Likely RFI levels in the area
• Define distance that transmitters no longer affect
the telescope
– “line-of-sight” – almost always problems
– Propagation models for “over-the-horizon” - complex
– Terrain shielding & other RFI mitigation
RQZ History
• National RQZ
– Within an administration
– Sovereign rule – can depart from ITU
– Regulate terrestrial services
– Little or no impact on satellite services
• International RQZ
– Special areas only
National RQZ characteristics
• 2 distinct areas of RQZ protection
1. EMC protection
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RFI from electrical/electronic equipment
Protect to few kms (5-20) – 30 for heavy industry
Local/State Governments
2. Coordination zone
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Coordinate with radio transmitters
100s of km
Communications administration
Green Bank NRQZ
• The original RQZ - model
• 1956 – West Virginia Radio Astronomy Zoning
Act
– Graded EMC restrictions to 10 miles
• 1958 – NTIA & FCC  National RQZ
– 34000 sq km area
– Coordination of all Tx with RA telescope
– (Also protects Naval Research station)
• Excellent protection in practice
Other National RQZs
• Arecibo PRCZ – Puerto Rico & islands (USA)
– Coordination Zone over entire island area (1996)
• European telescopes
– Mainly EMC (local) & some National coordination
• Indian GMRT
– EMC – 10 km (light)30 km (heavy industry)
– National coordination up to 400 km (bands)
• Also protection zones around other sensitive
antennas and laboratories.
– Mainly EMC protection
International RQZs
• Shielded Zone of the Moon RQZ
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Entire radio spectrum - “back-side” of Moon
No levels defined – coordination
But some RFI from spacecraft (e.g. Mars)
Prohibitively expensive
• Sun-Earth Lagrangian Point L2
– 1.5 million km from Earth & away from Sun
– Excellent RQZ – WMAP (CMB) already there!
– Space missions necessary
“Radio Sensitive Zones”
• Australian Productivity Commission
– Review of Radiocommunication Acts
– Report in 1992
• Recommendation: “radio sensitive zones”
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Around existing radio telescopes
NOT protection zones
Notification and Consultation
Mutually agreeable solutions
• ACA & ATNF working towards implementation.
Methodology & Progress
• Survey of RQZ principles and practices worldwide
(ACA)
• Summary of transmitter characteristics in Australia
(ACA)
• Define RFI thresholds at telescopes (ACA&ATNF)
– ITU-R Recommendations
– Telescope characteristics
• Thresholds + Propagation models  possible “radio
sensitive zones”
– Parkes and Narrabri area maps (150 km)
• Next step: Appropriate regulatory implementation
OECD Global Science Forum
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OECD “Task Force on Radio Astronomy and
the Radio Spectrum” (Report 2004)
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Recommendations:
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4.
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Radio Astronomy and Satellite Operators
Technical consultations
“Controlled Emission Zones”
ITU-R efforts
Operational consultation
Towards international RQZ?
RQZ for SKA?
• SKA to operate 100 MHz – 25 GHz
– Wide unprotected frequency range
– Must have some RQZ protection
– RFI thresholds defined at SKA2004
• National efforts towards SKA RQZ(s)
– Australia PMSEIC - RQZ in WA?
– South African efforts – “SKA Act”?
• SKA site selection criteria
– Include need for RQZ
– Government support critical
Summary
• RQZs important for Radio Astronomy
• Quiet  Silent – no “detrimental” RFI
• National RQZs (e.g. Green Bank) provide
successful protection for telescopes
• International RQZs for L2 and Moon.
• Australian “radio sensitive zones”
– Methodology applicable to RQZ
• OECD initiative – “controlled emission zones”
• SKA – RQZ critical siting criterion