Radio Telescope on Track

This post was originally published by Australia’s Science Channel on 29th July 2016 but was removed when the website was updated.

David Gozzard is a PhD student who has found himself on an interesting journey to remote Australia. In this blog, he shares some of the fun work he’s been up to!

When I started my PhD in experimental physics, I knew there would be a lot of travelling involved, mostly to conferences, meetings and workshops both in Australia and overseas. What I did not realize was how often I would find myself travelling to remote areas of Australia and South Africa to conduct field work. I’m not complaining. The field work is both challenging and rewarding, it gets me out of the lab, and it means I get to visit some of the world’s premier scientific facilities.

And that’s where I am now. After a four-hour flight from Perth to Sydney, a short hop from Sydney to Tamworth, and a two-hour drive from Tamworth to Narrabri (lugging two heavy cases full of scientific equipment), I find myself at the Paul Wild Observatory, home of CSIRO’s Australia Telescope Compact Array, the largest radio interferometer telescope in the southern hemisphere.

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Antennas 1 – 5 of the Australia Telescope Compact Array.

Built in the 1980s, the Compact Array is a radio telescope comprising six 270-tonne
dish-antennas, five of which can be driven to various positions along a 3 km track in order to change their view of the sky. Although it’s not as famous as The Dish at Parkes, the Compact Array holds the distinction of being the most scientifically productive radio telescope in the southern hemisphere. In radio engineering, the plural of “antenna” is “antennas”. Biologists, calm down.

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Me, driving antenna 3 during an array reconfiguration (see video below).

This is my 3rd trip to the Compact Array. I’m here to test equipment developed for the Square Kilometre Array (SKA) radio telescope. Radio telescope arrays like the Compact Array and the SKA need high-precision reference signals from atomic clocks to be transmitted to each antennas in order for the array to function properly. Over long transmission distances, the precision of these signals can become degraded and when that happens, the array fails.

On something the size of the Compact Array (6 km from one end to the other), this is not a problem; but for the SKA, which will have antennas located up to 150 km away from the centre of the site, signal degradation is a big problem. The equipment I have brought with me is designed to compensate for the degradation of the reference signal by measuring how the reference signal has been perturbed and modifying the transmission to compensate.

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My signal stabilization test equipment setup at ATCA.

My supervisor and I have been developing this stabilization system over the past two years at The University of Western Australia, and we have tested its performance extensively in the laboratory. Now the time has come to plug it into a working radio telescope to confirm that it works in the real world!

Because this is a synthesis imaging telescope, every few weeks the antenna dishes are moved to different positions along a track to change how they image the sky. I was lucky enough to be allowed to take part in one of these array reconfigurations. Each of the six antennas weighs 270 tonnes and has a top speed of 4 km/h. Reconfiguration can take 1 – 2 hours depending on the extent of that day’s changes. Antenna 2 shown in the video was driven nearly 2 km in this reconfiguration job.

The Compact Array is the best facility to perform these tests because it was constructed with an almost unique receiver system that allows us to run the array using both its conventional reference distribution system and our stabilized reference system at the same time. Our system runs over an extra 77 km of fibre-optic cable to a communications hut and back. The telescope data from the conventional reference system can be compared directly with ours to see if the stabilization system is working as designed.

The Compact Array is the best facility to perform these tests because it was constructed with an almost unique receiver system that allows us to run the array using both its conventional reference distribution system and our stabilized reference system at the same time. Our system runs over an extra 77 km of fibre-optic cable to a communications hut and back. The telescope data from the conventional reference system can be compared directly with ours to see if the stabilization system is working as designed.

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Me, sitting in the ATCA control room.

Working with the CSIRO team is an absolute pleasure. Everyone is very professional, they all know the systems they are responsible for insideout, and they are very helpful. The experiments that I have performed at the Compact Array would not have been possible without the efforts they made to accommodate my test schedule and the modifications I needed on some of the antennas.

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This photo is the group of us who contributed to the work on this trip. The people in the photo are left-to-right: David Gozzard, Mike Hill, Sascha Schediwy, Peter Mirtschin, Jamie Stevens and Jock McFee (not pictured – Brett Lennon).

They also took a keen interest in the experiment itself. Many of the staff at the Compact Array reminisce about how it used to be, only a few years ago, when the site was buzzing with astronomers from Australia and around the world. Now, astronomers can operate the telescope remotely from Sydney or, in some cases, from the other side of the world. As a result, the onsite staff have seen their ranks halve as less support is needed. The engineers and other support staff miss being able to quiz astronomers about what they are using the telescope for, and what they are discovering.

Apart from the Compact Array itself, the observatory is home to a lot of Australian science history. The array occupies a site formerly used by the Culgoora radioheliograph (pictured below), which CSIRO used from the mid-60s through to the mid-80s
to perform groundbreaking studies of radio emissions from the Sun and solar outbursts.

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One dish of the Culgoora radioheliograph.

Most of the 96 dish-antennas from the radioheliograph still surround the site in a 3 km wide circle. Within that circle are also the Sydney University Stellar Interferometer, until recently used to make measurements of the size of distant stars; the CSIRO Applied Physics Solar Telescope, which studied the visible light from the Sun in conjunction with the radioheliograph; the Birmingham Solar Oscillations Network Telescope, used to study churning gas inside the Sun; and an IPS Radio and Space Services telescope, which monitors solar outbursts to forecast how they will affect space craft and radio communications.

As I write this, my time at the Compact Array is coming to an end. My experiments have worked, the stabilization system has performed well, and I am preparing to report the results to the SKA Office. And the results are looking good. The system reduces signal fluctuations to one part in ten trillion, over a 1-second period. If your wristwatch
was that stable, after 300,000 years it would be off by less than one second. This is more than 10 times better than the stability required by the SKA.

Now I just have to pack up my equipment and get ready for the journey home.

Further reading

Great Australians — Ruby Payne-Scott

We Australians excel at remembering and celebrating our sporting heroes, from cricketers to particularly successful race horses, but are not so good at celebrating the great people who helped build our civilization, particularly when those builders are Australian. Today, I want to celebrate the birthday of a brilliant Australian scientist, Ruby Payne-Scott.

 

Southern Star

Ruby Payne-Scott is remembered as one of Australia’s most outstanding physicists. As well as contributing to other sciences, she was a pioneer of radio astronomy and made major discoveries about the nature of radio emissions from the Sun. Payne-Scott also has the distinction of being the first female radio astronomer.

Ruby Payne-Scott (28 May 1912 – 25 May 1981) — Physicist, pioneering astronomer

Ruby Payne-Scott (28 May 1912 – 25 May 1981) — Physicist, pioneering astronomer

Early life and education

Ruby was born in 1912 in the town of Grafton, NSW. She demonstrated remarkable talent at school and moved to live with her aunt in Sydney, where she could get a better education. She was awarded honours in mathematics and botany, and won two scholarships to the University of Sydney where she studied physics, chemistry, mathematics, and botany. As was typical of the era, Ruby was often the only woman in her classes.

Research

Despite the prejudice and difficulty in getting a job that female physicists faced at the time (compounded by the Great Depression), Ruby’s excellent academic performance landed her a job as a physicist on the University of Sydney’s new cancer research project. One project she worked on was to determine the effect that the Earth’s magnetic field had on the vital processes of living beings. Working with William Love she cultivated chick embryos in magnetic fields up to 5000 times stronger than the Earth’s field. They found no observable differences in the chicks and determined that the magnetism of the Earth had little or no effect on living creatures.

The cancer research project closed down in 1935, and Ruby was forced to take one of the few career options open to educated women at the time, teaching. She completed a diploma of teaching and started working at a school in South Australia. Ruby was constantly alert for ways to get back into physics and eventually managed to land a job with Australian Wireless Amalgamated, a major hirer of physicists. Although she was hired as a librarian, Ruby managed to get involved in some research projects in the company’s standards laboratory and eventually worked her way into full-time research.

In 1939, Australia, following Britain’s lead, declared war on Germany. The CSIR (the precursor to the CSIRO) was charged with developing an Australian radar capability. As happened in Britain and the USA, mobilization for war created a shortage of trained men and provided women with the opportunity to break into jobs and careers they were previously bared from. Ruby and another woman, Joan Freeman, managed to get hired to work as researchers in the CSIR’s new Radiophysics laboratory. The women excelled in their roles, under the leadership of another great Australian physicist, Joe Pawsey, and both Ruby and Joan later commented that their colleagues treated them as “one of the boys”. The two women mainly had to deal with discrimination from administrators and petty bureaucrats who imposed absurd and unfair rules such as banning women from smoking or wearing shorts, rules which Ruby took the lead in breaking. Ruby even married her Husband, Bill Holman Hall, in secret in 1944 because married women were not allowed to hold permanent positions in government agencies.

Wartime radar research in Britain had discovered that the Sun occasionally produced significant amounts of radio waves. Excited by this, in their spare time Ruby and Joe Pawsey ran some experiments to follow up on this discovery, but did not have the right equipment to make the observations. When the war ended the Radio Physics laboratory was due to be scrapped, so the team put together an application to continue as a radio physics research division, concentrating on rain making and radio astronomy. At the time, radio astronomy was a very new field of research and the astronomy community showed very little interest. Despite this, the CSIR decided to fund radio physics and Australia remains a world leader in radio astronomy to this day.

Along with Joe Pawsey and Lindsay McCready, Payne-Scott used decommissioned radar equipment to make detailed radio-frequency observations of the Sun. This small team was the first to construct a radio-astronomy interferometer. Radio interferometers greatly increase the resolution of their observations by using a long baseline between two or more radio antennas. The CSIR team managed to construct an interferometer using only one antenna.

Great TV reception... Just had to wait for Australia to get TV.

Decommissioned radar antenna at Dover Heights, run by CSIR Radiophysics.

The radar antenna they were using was a coastal installation mounted on a sea-cliff. The antenna received radio signals directly from the Sun but also from reflections off the sea below. This simulated a baseline of around 200 metres between two antennas and allowed Payne-Scott, Pawsey and McCready to determine that solar radio radiation was coming from patches of the Sun that had sun-spots, a major discovery that boosted Australia’s international scientific reputation. The team also showed that the Sun’s corona has a temperature of over a million degrees centigrade, a phenomenon that remains a mystery to astrophysicists. Payne-Scott is also credited with the discovery of type I and type III solar outbursts.

Built to defend against the land of the rising Sun.

Dover heights sea-cliff interferometer — used to study the Sun

Workplace activist and career cut short

Throughout her time at the CSIR and its successor the CSIRO, Payne-Scott was an active advocate of equal rights and pay for women. She fearlessly and vocally opposed women’s workplace restrictions and pay reductions, clashing with CSIRO chairman Sir Ian Clunies Ross on several occasions. Eventually her secret marriage was discovered by CSIRO administrators and she was demoted to a temporary position. Payne-Scott left the CSIRO for good in 1951 (aged 39) to give birth to her son Peter.

Later life

Payne-Scott had a second child, a daughter named Fiona, and in 1963 returned to teaching. She retired in 1974 and died in 1981 at the age of 69.

Today, Ruby’s legacy is remembered in the CSIRO by the Payne-Scott award which is given to support the careers of women researchers. Her influence on radio astronomy and her discoveries means that her name is known by a large section of the Australian astronomy community, though they may not be completely aware of how hard Ruby had to fight to be able to do her ground-breaking research.

Who comes up with these Google doodles?

Google celebrated Ruby’s 100th birthday.

In 2012, on what would have been her 100th birthday, Ruby Payne-Scott was celebrated with a Google doodle. However, this great Australian is still completely unknown to the majority of Australian people. Ruby, her research, and her fight for women’s rights deserves greater recognition.

More information on the life and work of Ruby Payne-Scott can be found at the CSIRO Staff Association, National Archives, or Payne-Scott’s Wikipedia page.