radio quiet zones (rqz) history and current activities tasso tzioumis atnf, csiro
TRANSCRIPT
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– RFI from electrical/electronic equipment– Protect to few kms (5-20) – 30 for heavy industry– Local/State Governments
2. Coordination zone– 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– 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”– 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
• OECD “Task Force on Radio Astronomy and the Radio Spectrum” (Report 2004)
– Radio Astronomy and Satellite Operators
• Recommendations:1. Technical consultations2. “Controlled Emission Zones”3. ITU-R efforts4. 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