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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