An update on siting of international distributed radio telescopes

Planned facilities

There are currently two significant distributed radio telescopes being planned which require extensive protected areas:

1. LOFAR - the Low Frequency Array, operating at low frequencies between 10 - 220 MHz. This is an initiative of the Netherlands Foundation for Research in Astronomy (NFRA) and several organisations in the USA including the Naval Research Laboratories. The final date for siting proposals is September 2002;

2. Square Kilometre Array - the frequency range of coverage is assumed to be approximately 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 will require protection for the closely spaced antennas on the central site. The maximum extent of LOFAR is 350 km while the SKA will extend 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 SKA - international activities

The International SKA Steering Committee has appointed a Site Evaluation and Selection Committee with a representative from each country, or region, potentially interested in hosting the SKA. These are:

· northern hemisphere - Europe, China, India, USA;

· southern hemisphere - Australia, South Africa.

Australian siting issues

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, northwest of Broken Hill, may be investigated first. Broken Hill is also interested in the possibility of being a "base" for engineering services, and a site in New South Wales between Tibooburra and White Cliffs may be investigated.

Progress in Western Australia

Two adjacent areas in the Murchison between Geraldton and Meekatharra have provisionally been set aside by the Western Australian Government as possible sites. Investigations are proceeding for an area east of Kalgoorlie, north of the Transcontinental Railway.

The Western Australian Government has 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 - 1810 MHz frequency range include satellite downlinks, TV and FM broadcasts, Telstra phone/fax/email services to homesteads, and aircraft communications (short-period).

The proportion of "unused" spectrum, to the sensitivity limits of the measuring system, is given below and is seen to be very high. (The data for the band 350 - 1060 MHz have not yet not been fully analysed).

Radio-quietness: summary of results. * = night-time operation

Further tests for the second area in the Murchison are planned, possibly in March 2002. This program will include sample testing the spectrum that appears to be unused, with an equipment configuration having higher sensitivity.

Acknowledgement

The assistance of Aaron Chippendale in analysing the data provided by the contractor is gratefully acknowledged.

Bruce MacA Thomas
SKA Site Engineer
(Bruce.Thomas@csiro.au)