Radio Quiet Zones (RQZ) Tasso Tzioumis ATNF, CSIRO RAFCAP.
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Transcript of Radio Quiet Zones (RQZ) Tasso Tzioumis ATNF, CSIRO RAFCAP.
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Radio Quiet Zones(RQZ)
Tasso Tzioumis
ATNF, CSIRO
RAFCAP
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Why? -- Need for RQZ?
• RA systems extremely sensitive
very susceptible to RFI• RA allocated very little spectrum (~2% at cm )
– Still RFI from out-of-band (OoB) emissions • RA operates over full radio spectrum
RFI from radiocommunication services• “prevention better than cure”
RQZ is 1st step of mitigation
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What? -- Radio Quiet?
• Radio Quiet Radio Silent
• “Passive” bands (e.g. 1400-1427 MHz)– “all emissions are prohibited” (Fn. 5.340)– but OoB emissions still a problem
• RQZ prevent “harmful” (detrimental) RFI
• RFI mitigation – minimise “harm” may influence RQZ limits & area
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RQZ selection - Population?
Sydney: population 4 million
Narrabri: population 4000
Mileura: population 4
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Where are the Quiet areas?
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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– Moon & L2 point
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National RQZ characteristics
• 2 distinct areas of RQZ protection1. 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
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Greenbank 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
• Excellent protection in practice
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Other National RQZs
• Arecibo PRCZ – Puerto Rico & islands– Coordination Zone
• Jodrell Bank & other European telescopes– Mainly EMC (local) & some National
coordination
• GMRT– EMC – 10 km (light)30 km (heavy industry)– National coordination up to 400 km (bands)
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ALMA Quiet Zone -- Chile
• Central Quiet zone: 30 km radius, no transmitters in ALMA bands (variously 31 to 950 GHz)
• 120 km radius coordination zone
– AUI/ESO may comment on xmit applications
• > 31 GHz, comply with 769 at site boundary
• < 31 GHz, 769 + limit on transmitter power
– Eirp such that pfd at ALMA border <2x10-6 W/m2
• Formal recognition is needed to avoid future changes in policy.
• Need to educate the general public and politicians about radio astronomy and the need for radio quiet zone.
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“Radio sensitive zones” in Australia
• Radio Act review 2002 – “radio sensitive zones”– Notification and coordination - no protection
• Regulatory RALI (2006) to cover all Oz RA sites
• Studies by ACMA (administration)
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Notification Zone Parameters
• Limits derived from RA.769 (+ ~10-15 dB)
• Propagation models from P.526 (Diffraction) and terrain models.
Notification Zones (km radius) Band (MHz)
Parkes Narrabri Mopra Hobart Ceduna Tidbinbilla
1 250-1 780 200 250 150 100 n/a 120
2 200-2 550 180 180 130 80 120 80
4 350-6 700 160 160 120 70 120 70
8 000-9 200 150 110 100 50 120 50
16 000-26 000 110 90 80 30 80 30
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International RQZs
• Shielded Zone of the Moon RQZ– ITU-R Rec RA.479 - Entire radio spectrum
– No levels defined – coordination
– But some RFI from spacecraft (e.g. Mars)
– Prohibitively expensive
• Sun-Earth Lagrangian Point L2– ITU-R Rec RA.1417
– 1.5 million km from Earth
– Excellent RQZ – WMAP (CMB) already there!
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OECD Global Science Forum
• OECD “Task Force on Radio Astronomy and the Radio Spectrum” (Report 2004)
– RA and Satellite Operators
• Recommendations:1. Technical consultations2. “Controlled Emission Zones”3. ITU-R efforts4. Operational consultation
• Leverage for international RQZ?
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ITU-R Question
• Question in WP7D to initiate studies
• Strong opposition from satellite operators
• Question delicately framed i.e.1. Characteristics of existing RQZ?
2. RAS characteristics stimulating RQZ?
3. environment characteristics stimulating RQZ?
• Work still to be done.
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Square Kilometre Array
~ 1 km2 collecting area in an interferometer array sensitivity ~50 x EVLA (current largest radio array) survey speed >10000 x faster than EVLA
wide frequency range: 0.1 – 25 GHz
configuration: longest baselines >3000 km; 50% collecting area<5km
wide field of view: 50 sq. degree at <1 GHz (250 x
moon)
total cost 1 B€; operating costs 70 M€/year
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RQZ for SKA?• SKA to operate 100 MHz – 25 GHz
– Wide unprotected frequency range
– Must have some RQZ protection
• National efforts towards SKA RQZ(s)– All site proponents must define progress towards RQZ protection.
• Protection now for SKA demonstrators / pathfinders– Preserve “quiteness” of sites
– e.g. Australia started with a “spectrum embargo” for 100-150 km radius around Mileura site.
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RQZ guidelines -SKA Regulatory “Task Force”
• Report covers Protection criteria and general discussion on methodology.
• Threshold levels:– “Central site” - RA.769 levels (cont & line)– Up to 150km - RA.769 Table 1 +15dB (array levels)– Remote sites - RA.769 VLBI levels
• Radio propagation modelling (ITU Recs)• Complex and many assumptions
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South Africa Astronomy Reserve
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South Africa Legislation: Astronomy Geographical Advantage Act
• Empowers the Minister for Science and Technology to declare protected areas around strategic astronomy sites by publication in the Government Gazette.
• The Act empowers the Minister to prohibit over-flights• The Act covers both radio and optical astronomy• Three tiers of protected areas:
– Core area – the physical area of the observatory / instrument– Central area – surrounds the core area. Minister prohibits certain activities
/ categories of activities in this area– Coordination area –Minister sets standards which activities must comply
with
• Protected areas apply to existing and new activities
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Australia + NZ
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SKA RQZ in Australia• Studies & definition by ACMA & CSIRO
• RALI MS32 - in force since 24/9/2007
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Oz RQZ procedures• From RALI MS32
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Summary & lessons learned
• RQZs important for RA – 1st step in mitigation– National “RQZ”s - coordination only– Weak enforcement
• RQZ essential for SKA– Exclusion and coordination zones– Strong Enforcement
• Lesson from Oz experience:** Work closely with national administration **
• ITU Question on RQZ – towards IRQZs?– Inputs from SKA RQZ experience
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Inner core
Station
Reference Design
Wide-angle radio camera +
radio “fish-eye lens”
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RA. 769 thresholds