There are currently two significant distributed radio telescopes being planned which require extensive protected areas:
1. LOFAR - the Low Frequency Array, a mini-SKA operating at low frequencies between 10 - 220 MHz. It is an initiative of the NFRA (the Netherlands) and several organizations in the USA including the Naval Research Laboratories (this organisation requested the WA Government to participate in radio-quietness tests for LOFAR as an add-on to the SKA tests). The final date for siting proposals is September 2002.
2. SKA - the frequency range of coverage is assumed to be approx. 150 - 1500 MHz for Mid-SKA, and 1-23 GHz for High-SKA, with a proposal for siting required by 2005.
Both LOFAR and SKA require protection for the closely spaced antennas on the central site. The maximum extent of LOFAR is 350 km, and the SKA extends to continental distances (in its final form). Australia has a number of suitable areas, which could accommodate the SKA and also LOFAR (if requested by the LOFAR consortium).
The ISSC (International SKA Steering Committee) has appointed a Site Evaluation and Selection Committee (SESC) with a representative from each country potentially interested in hosting:
In addition to the interest of Western Australia in providing a site for LOFAR and SKA, South Australia is currently preparing a case for funding to carry out site investigations for the SKA. This will include a radio-quietness testing program. A possible site near Lake Frome, NW of Broken Hill may be investigated first. Broken Hill is also interested in the possibility of being a "base" for engineering services, so that a site in New South Wales between Tibooburra and White Cliffs may be investigated.
Two adjacent areas in the Murchison between Geraldton and Meekatharra have provisionally been set aside by the Western Australian Government as possible sites. Investigation is proceeding for an area east of Kalgoorlie north of the Transcontinental Railway.
The Western Australian Government also appointed a contractor to undertake an intensive three-week high-sensitivity measurement program to determine the amount of "used" spectrum. The program was undertaken on Mileura Station, 100 km west of Meekatharra, during March-April this year. Not all the data has yet been analysed, but the services which are in evidence over the 30 to 1810 MHz frequency range are:
However, the proportion of "unused" spectrum, to the sensitivity limits of the measuring system, is given below (the band 350 - 1060 MHz has not been fully analysed yet). The proportion of unused spectrum is seen to be very high.
It is planned to carry out further tests in the second area in the Murchison, possibly in March 2002. This program will include sample testing the spectrum which appears to be unused, with an equipment configuration having higher sensitivity.
The assistance of Aaron Chippendale in analysing the data provided by the contractor is gratefully acknowledged.
Bruce MacA Thomas
SKA Site Engineer