Astronomy and Engineering: The Phased Array Feed Receiver

Engineering Excellence

The annual Engineering Excellence Awards exhibition, a partnership between the Sydney Division of Engineers Australia and the Powerhouse Museum, was recently opened to the public. As an awards display, the aim is to present to the public a small number of projects that have been peer reviewed and selected to merit an Engineering Excellence Award within a range of categories. One of the projects entered in the Research and Development category brought together astronomers and engineers from the CSIRO’s Astronomy and Space Science Radiophysics Laboratory at Marsfield in Sydney. Named the Wideband Multibeam Phased Array Feed Receiver for the Australian Square Kilometre Array Pathfinder (ASKAP), the project (and the exhibition) is concerned with radio astronomy, devices receiving radio signals, and Australia’s place in what is one of the world’s major scientific programs in astronomy – the Square Kilometre Array (SKA) project.

A view of the Phased Array Receiver display in the 2014 Engineering Excellence exhibition at the Museum. The ‘chequerboard’ array receiver can be seen on the right and a 1:20 scale working model of the ASKAP telescope, which was made by the Museum, can be seen on the left.

A view of the Phased Array Receiver display in the 2014 Engineering Excellence exhibition at the Museum. The ‘chequerboard’ array receiver can be seen on the right and a 1:20 scale working model of the ASKAP telescope, which was made by the Museum, can be seen on the left.

Prior to 1932 when radio astronomy began to emerge as a serious tool for the modern astronomer and stretching even further back in time famously to the Italian astronomer Galileo Galilei (1564-1642), the most important and time-honoured instrument that was used by the astronomer was the optical telescope. The optical telescope gathers and focuses light from the visible part of the electro-magnetic spectrum and from the time of Galileo many improvements have been made to its light gathering and focusing tasks, thus allowing astronomers to look further into space to study very distant objects clearly.  At one end of the electro-magnetic spectrum there are the gamma rays, with their very short wavelengths, and at the other end there are the radio waves, with their very widely spaced wavelengths. Visible light wavelengths are to be found around the middle of the spectrum

Exhibition view of the Wideband Multibeam Receiver, Powerhouse Musuem, 2014. Photo Rita BIla

Exhibition view of the Wideband Multibeam Receiver, Powerhouse Musuem, 2014. Photo Rita Bila

In Australia, the development of radio astronomy did not arise from the astronomical community but rather by radio engineers and skilled technicians with well-equipped workshops, who gained experience in developing radar during World War 11. Studies of the radio emissions from the Sun dominated the first major radio astronomy work in Australia, with a field station and aerials established at Dover Heights, Sydney. Australian engineers and astronomers have continued to play a major role in radio astronomy ever since, both in regard to theories on the structure and scale of the universe and the objects at its edge, and the design and development of the receiving devices for the detection and analysis of the radio waves from those cosmic objects.

Example of the ‘chequerboard array’ phased array receiver. Photo Rita Bila

Example of the ‘chequerboard array’ phased array receiver. Photo Rita Bila

On display in the current engineering awards program at the Powerhouse Museum, is an example of the recent ‘chequerboard array’ phased array receiver, which is located at the focus of the telescope.

One of several Australian Square Kilometre Array Pathfinder Telescopes at the Murchison Radio-Astronomy Observatory, about 350 km northeast of Geraldton in Western Australia. There is an array of 36 dishes, each 12m in diameter and equipped with the ‘radio cameras’ called Phased Array Feeds (seen, in close-up, in the top right of the picture).

One of several Australian Square Kilometre Array Pathfinder Telescopes at the Murchison Radio-Astronomy Observatory, about 350 km northeast of Geraldton in Western Australia. There is an array of 36 dishes, each 12m in diameter and equipped with the ‘radio cameras’ called Phased Array Feeds (seen, in close-up, in the top right of the picture).

This innovation is the core technology for the ASKAP.  The demonstrated performance and the technological advance of the CSIRO PAF system was critical to the May 2012 decision of the SKA organisation to award two components of SKA Phase 1 to Australia: SKA1 – low, the array of several hundred thousand dipole antennas, and SKA1 – survey, a PAF equipped dish array of 60 new antennas building on the capabilities of ASKAP.

Model of the Australian Square Kilometre Array Pathfinder (ASKAP). Photo Rita Bila

Model of the Australian Square Kilometre Array Pathfinder (ASKAP). Photo Rita Bila

So, what are the advantages of the PAF? The chequerboard style receiver sits inside a standard radio astronomy dish antenna but allows for multiple electronically configurable beams that increase the field of view by a factor of 30 over an octave of frequency bandwidth. This will allow radio astronomers at the Murchison Radio-Astronomy Observatory, which is located in a remote mid-west region of Western Australia, to capture radio images from deep within the universe with unprecedented clarity over large areas of the sky. The large number of chequerboard designed squares in each array have tremendous receiver, filtering, and amplification capacities that will allow astronomers to remove much of the unwanted radio noise that continually streams in from all regions of the universe, thus enabling only the useful radio noise to be captured and analysed. And what you get are some extraordinary images of the galaxies within the universe.

Shown here is ‘our’ galaxy, the Milky Way, in the radio spectrum with a large amount of gas flowing between individual stars and nebulae clusters.

Shown here is ‘our’ galaxy, the Milky Way, in the radio spectrum with a large amount of gas flowing between individual stars and nebulae clusters.

The Phase Array Feed for the Australian Square Kilometre Australian Pathfinder Telescope is one of five displays in this year’s Engineering Excellence Award exhibition and it will be on display at the Powerhouse Museum until mid-January 2015.