Square Kilometre Array program report

The major recent event on the SKA calendar was the international meeting held in Groningen, The Netherlands. Prior to the meeting the International Engineering and Management Team (IEMT) had initiated and managed a process, which led to seven SKA concept descriptions being publicized shortly before the meeting. These descriptions, or whitepapers, formed the basic of the Groningen discussions. Four of the whitepapers were "end-to-end" expositions, while the remaining three outlined only antenna technology. The Australian SKA Consortium submitted two full descriptions, one based on Luneburg lenses and one using cylindrical reflectors. Both were prepared by CSIRO engineers in consultation with science colleagues from the University of Sydney and the ANU.

The whitepapers, and the ensuing discussions, raised many astronomy and radio science issues. The descriptions were slices through problem and solution spaces and, not surprisingly, the conceptual designs proved excellent vehicles for extending understanding of SKA requirements and practicalities. No concept selection was made but a shortlist will be compiled in 2004, after a stage-2 (and more rigorous) whitepaper process. Some key points to emerge from Groningen are:

• No single concept meets all science goals;

• Concepts give good high frequency (>20 GHz) or multibeaming operation, but not both;

• The SKA science community currently divides into camps favouring either high frequencies or multibeaming;

• The Australian concepts offer unique compromises in the "10 GHz - 10 beams" parameter space and it behoves us to assess our R&D directions given the recent international discussions;

• The comprehensive Australian submissions made contributions in a number of system design areas apart from antennas, including new receiver concepts and SKA data transport requirements.

Following my suggestion of an international 100-m class, cm-wave, multibeaming demonstrator in establishing the scientific credentials of multiview interferometers, and the wish to ensure that Australia remains a key player in SKA activities, an opportunity for an increased CSIRO involvement in LOFAR (the low-frequency SKA equivalent and an SKA system demonstrator) is being pursued. Initially, this involves assistance to the WA Government in submitting a LOFAR siting proposal. In the slightly longer term, it will involve working with LOFAR proponents to incorporate the idea of a cm-wave demonstration platform.

In practice, re-assessment of R&D directions could amount to fine-tuning the demonstrator programs proposed under MNRF 2001, with the ATCA New Technology Demonstrator project offering the most scope to incorporate exciting new developments.

Despite the enormous efforts that went into the whitepapers, our SKA group has been active on a number of other technical and outreach fronts. The prototype 2 - 7-GHz GaAs LNA chip is now back from the foundry and Aaron Chippendale is busy with on-wafer diagnostics prior to the wafer dicing operation. In collaboration with ASTRON, CSIRO has been testing an 8x8 Vivaldi horn array. The picture below shows the antenna being used as a focal surface array with our prototype 0.9-m Luneburg lens, giving a "cluster" beam feed and using the lens as a first-stage quasi-optical beamformer. In the outreach area, the SEARFE project continues to grow in strength, with a notable recent event being a foray by the Storey family to the Eyre Peninsula in SA; a highlight was an exhibit at a local agricultural field day. Outreach with a different thrust - that aimed at professional engineers and industry - has produced some fascinating contact with professionals experienced in financing and managing multi-billion dollar international projects; interesting lessons relevant to the SKA are emerging.

Figure 1: Luneburg lens and focal plane array being tested in the CSIRO near-field test facility.

Figure 2: The response plots show typical computed far-field responses for a central array element.

The next meeting of the Australian SKA Consortium Committee (ASKACC) will be held on 6 November. On the preceding day, 5 November, there will be a joint ATUC/SKA symposium at Marsfield and we invite everyone to attend. Finally, we have had a significant departure in that Graeme James, who has been associated with Radiophysics and CTIP for many years, has recently retired from CSIRO. On behalf of the SKA community I'd like to record my thanks to Graeme for his invaluable contributions, to wish him well in his retirement, and to assure him that we look forward to his continuing participation as part of his post-retirement fellowship.

Peter Hall
SKA Program Leader