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– 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