A Radio-quiet Zone for the SKA Michelle Storey CSIRO 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

Licensed transmitter signals 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? n Controlling increase of above-threshold signals over the RQZ n 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 n Need to respect rights of existing license-holders

Protection of the SKA central site n Central site is 5km in diameter, and contains 50% of the SKA array-stations n Close to the central site, tighter restrictions will be needed than further away n 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 n Protection required from radio-communication signals over larger distances ( km) n 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 n Final decision on license approval rests with RQZ Management Group n Consultation at even larger distances

Protection of the SKA central site Required restricted emission zone for SKA

Protection of remote array-stations n 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 n Less stringent protection required for remote array-stations n EMI protection probably required over zone of radius 5km from each remote array-station n Restricted emission zone to “line-of-sight” distances would be desirable

Conclusions n Future radio astronomy requires new forms of protection from background radio-frequency emission n OECD Task Force has recommended that countries examine establishment of radio-quiet zone n Establishment of RQZ is a site selection criterion for SKA siting n Australia is in a position to take a lead role internationally

Conclusions n RQZ proposal will involve all layers of Government (local, State and Federal) n The above proposal satisfies SKA requirements n Government assistance required for implementation