Project Overview

Traditional radio astronomy receivers are constructed out of discrete components and can be expensive to build; radio telescopes are, therefore, usually equipped with one receiver at a given frequency providing only one beam with which to examine the sky. But if receivers can be fabricated more cheaply, a range of exciting possibilities opens up, involving the integration and operation of multiple beam (array) systems. If the telescopes can collect data much more quickly than now, and these data can be easily analysed, then a wider range of astronomers can gain access to scientifically valuable amounts of observing time on the leading national facilities. At the heart of the project is the development of complex monolithic microwave integrated circuits (MMICs) using levels of integration not previously employed for cryogenic applications in the band 20-40 GHz or for non-cryogenic phased arrays in the 2-5 GHz band. The project is focussed on three innovative array configurations:

• Horn arrays for large-area continuum surveys at ~30 GHz. The effects of receiver gain changes and variations in atmospheric attenuation will be reduced by signal comparison strategies involving switching the signal between independent receivers and closely-spaced horns. The deliverables are an 8-horn prototype array (to be tested on the Torun radio telescope) and a feasibility study for a 100-horn continuum array.
• Horn arrays for spectroscopy in the band 21-26 GHz a heterodyne design will be adopted with a down-converter integrated into each channel; this enables the spectrum of the signal to be obtained and the operating frequency to be varied. The deliverables are a 5-element prototype array (to be tested on the Medicina or Noto radio telescopes) and a feasibility study for a 50-horn spectroscopic array at 40-50 GHz.
• Actively phased arrays at 2-5 GHz. In this concept the receivers are interconnected so that multiple beams can be synthesised and steered electronically by phasing; the aim is to improve the efficiency of individual telescopes and to open up the widest possible field-of-view. The deliverables are a 16-element 2-beam prototype array to work in the frequency range 2.5 to 5 GHz (to be tested on a Westerbork telescope and on an ATNF-designed Luneberg lens) and a feasibility study for a 16-beam phased-array in the band around 5 GHz, generically suitable for any large European telescope.

The project also involves the design of flexible data analysis software tools for the acquisition and analysis of data from horn arrays. The software will be written within the international astronomical standard AIPS++ environment. Since the astronomical aim of this RTD programme is the making of much larger radio surveys we are conscious of the need to link this work in with both National and Europe-wide initiatives for data archiving and Virtual Observatories.