Radio Quiet Zones(RQZ)

Tasso Tzioumis

ATNF, CSIRO

RAFCAP

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

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

RQZ selection - Population?

Sydney: population 4 million

Narrabri: population 4000

Mileura: population 4

Where are the Quiet areas?

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

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

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

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)

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.

“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)

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

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!

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?

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.

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

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.

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

South Africa Astronomy Reserve

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

Australia + NZ

SKA RQZ in Australia• Studies & definition by ACMA & CSIRO

• RALI MS32 - in force since 24/9/2007

Oz RQZ procedures• From RALI MS32

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

Inner core

Station

Reference Design

Wide-angle radio camera +

radio “fish-eye lens”

RA. 769 thresholds