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Radio Quiet Zones Carol Wilson, CSIRO 3 rd Summer School in Spectrum Management for Radio Astronomy 31 May – 4 June 2010, Tokyo
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Radio Quiet Zones

Jan 08, 2016

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Radio Quiet Zones. Carol Wilson, CSIRO 3 rd Summer School in Spectrum Management for Radio Astronomy 31 May – 4 June 2010, Tokyo. Outline of talk. What is a radio quiet zone? Why are they needed? Methods to achieve a radio quiet zone Examples Conclusions. What is a Radio Quiet Zone?. - PowerPoint PPT Presentation
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Page 1: Radio Quiet Zones

Radio Quiet Zones

Carol Wilson, CSIRO3rd Summer School in Spectrum Management for Radio Astronomy

31 May – 4 June 2010, Tokyo

Page 2: Radio Quiet Zones

• What is a radio quiet zone? • Why are they needed?• Methods to achieve a radio quiet zone• Examples• Conclusions

Outline of talk

Page 3: Radio Quiet Zones

What is a Radio Quiet Zone?

“Prevention is always better than a cure.” Best strategy is to “prevent” RFI rather than mitigate it after the fact.

• Radio Quiet Radio Silent• RQZ = prevent “harmful” (detrimental) RFI• Various ways to achieve this – a combination of tools

depends on frequency, telescope, location…

“…any recognized geographic area within which spectrum management procedures are modified to reduce or avoid interference to radio telescopes, thereby maintaining the required standards for quality and availability of observational data” WP 7D Draft New Report on RQZ

Page 4: Radio Quiet Zones

Challenges in radio quietness protection

• Range of potential interferers:• Terrestrial licensed services (fixed, mobile, TV/radio, CB

repeaters)• Class-licensed services (mobile devices, short-range devices,

etc)• Aircraft and satellites• Noise from non-communication systems (vehicles,

households, industrial activity, power lines)• On-site noise

• Rigorous demands of radioastronomy• Time frame (telescope life of 50 years or more)• Technical + political + economic implications

Page 5: Radio Quiet Zones
Page 6: Radio Quiet Zones

Extending the limits of science exploration

“Observations of significance in radio astronomy are those which result in new knowledge of astronomical phenomena, which either require making observations of objects not previously studied, or observing known objects with increased precision. Both such cases call for observations at the highest achievable sensitivity. As radio astronomy has matured, the usefulness of data which is limited in accuracy by the presence of interference has declined, and it is the usual practice of astronomers to delete data for which there is any evidence of interference.” Rec. ITU-R RA.1513-1

Page 7: Radio Quiet Zones

Interference thresholds

Interference threshold levels from Recommendation ITU-R RA.769-2

-300

-280

-260

-240

-220

-200

-180

-160

10 100 1000 10000 100000

Frequency (MHz)

Sp

ec

tra

l p

fd (

dB

(W/(

m2

Hz)

))

Continuum

Continuum +15

Line

VLBI

Page 8: Radio Quiet Zones

ITU-R Question & Report

Question in WP7D to initiate studies1. Characteristics of existing RQZ?

2. RAS characteristics stimulating RQZ?

3. Environment characteristics stimulating RQZ?

ITU-R Correspondence Group • Inputs from many countries

• New Draft Report – comprehensive

• Finalised in 2010 (?)• WP7D meetings; June and October 2010

Page 9: Radio Quiet Zones

Methods to achieve a RQZ

• Geographic location – remote• Site shielding• Control of interference sources

• Notification, coordination, restriction (intentional radio devices)

• Physically control access to site• Legislative control of activities near site (industrial,

mining, use of electrical appliances, etc)• Provide alternative technology to replace interference

source

• Requires commitment from government and ongoing maintenance.

Page 10: Radio Quiet Zones

Choosing a quiet site to start with!

SydneyPop. 4 million

NarrabriPop. 6,000

MurchisonPop. 4

40dB ?

Measurements with a swept spectrum analyser

Page 11: Radio Quiet Zones

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

Page 12: Radio Quiet Zones

Examples of national RQZs

•Arecibo PRCZ – Puerto Rico & islands• Natural site shielding by surrounding hills• 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)

Page 13: Radio Quiet Zones

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.

Page 14: Radio Quiet Zones

“Radio sensitive zones” in Australia

• Radio Act review 2002 – “radio sensitive zones”• Notification and coordination - no protection

• Regulatory RALI (2006) covers all Oz RA sites (MS31)• Studies by ACMA (administration)

Page 15: Radio Quiet Zones

Notification Zone Parameters

• Limits derived from RA.769 (+ ~10-15 dB) & VLBI• 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

Page 16: Radio Quiet Zones

RALI MS 32 distances and thresholds

• Restricted – no new apparatus licences (except in extraordinary cases)

• Coordination – if power at MRO is above threshold, consultation with CSIRO required

Page 17: Radio Quiet Zones

RALI MS 32 distances

100-230 MHz coordination

100-230 MHz restricted

>230 MHz restricted

Page 18: Radio Quiet Zones

Comment on the SKA RQZ in Australia in a speech by the chairman of the Australian Communications and Media Authority:

Page 19: Radio Quiet Zones

Conclusions

• Radio Quiet Zone increasingly important for existing and (especially) new radiotelescopes to extend science goals

• Number of mechanisms, procedures to address different types of interference

• Starting with a naturally quiet site simplifies both technical and regulatory problems

• Important to work with national and local authorities and with the community.

Page 20: Radio Quiet Zones

Contact UsPhone: 1300 363 400 or +61 3 9545 2176

Email: [email protected] Web: www.csiro.au

Thank you!

Questions?

Carol Wilson, Research [email protected]