A Radio-quiet Zone for the SKA

Michelle StoreyCSIRO Australia Telescope National Facility

SKA – radio astronomy of the future

International project (16 countries in partnership)

SKA is geographically distributed

Detects cosmic emission over wide, continuous frequency range, including low frequencies (signals propagate further)

What does the SKA need?

Radio-quiet environment over wide frequency range Low population density Low density of incompatible activities Protection from increase (over decades) in background radio-frequency signals

Sophisticated infrastructure and highly trained workforce

Friendly neighbours

Radio-quiet

Radio-quietness determined by amount and ambient noise level of unused spectrum

Licensedtransmittersignals

Unused spectrum

Spectrum usage in inland WA

Frequency (MHz)

Radio-quiet

How do we establish a radio-quiet site?

Self –protection (first find one)

SKA site studies since 1997• Remote• Compatible economic activities• Supportive local community• Radio-quiet• Low mineral prospectivity

How do we establish a radio-quiet site?

Nookawarra Station

Mileura Station

Areas protected from mineral exploration

How do we establish a radio-quiet site?

Controlling increase of above-threshold signals over the RQZ

Thresholds recently determined at international SKA conference– For central site, slightly less stringent than for single dish

– For remote array-stations, relaxed further from single dish levels

Need to respect rights of existing license-holders

Protection of the SKA central site

Central site is 5km in diameter, and contains 50% of the SKA array-stations

Close to the central site, tighter restrictions will be needed than further away

Within 30km, protection from EMI will be required– In US case, managed with State legislation

– For WA situation 30km zone could be entirely within area protected from mining exploration, and far from any towns

Protection of the SKA central site

Nookawarra Station

Mileura Station

60km diameter EMC zone

Protection of the SKA central site

Protection required from radio-communication signals over larger distances (150-200 km)

Within this distance, new applicant should consult with SKA and, if a problem is identified, all stakeholders should work to find solution– Redirecting transmitter, refining beam shape, lower power

– Providing service with SKA optic-fibre network

– Interference mitigation

Final decision on license approval rests with RQZ Management Group

Consultation at even larger distances

Protection of the SKA central site

Required restricted emission zone for SKA

Protection of remote array-stations

25 array-stations within 150 km of central site, 25 more beyond

Large circles give estimate of tolerance in placement of array-stations

Protection of remote array-stations

Less stringent protection required for remote array-stations

EMI protection probably required over zone of radius 5km from each remote array-station

Restricted emission zone to “line-of-sight” distances would be desirable

Conclusions

Future radio astronomy requires new forms of protection from background radio-frequency emission

OECD Task Force has recommended that countries examine establishment of radio-quiet zone

Establishment of RQZ is a site selection criterion for SKA siting

Australia is in a position to take a lead role internationally

Conclusions

RQZ proposal will involve all layers of Government (local, State and Federal)

The above proposal satisfies SKA requirements

Government assistance required for implementation