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.


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.


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.


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.


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.


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.


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

Measuring Up for World Metrology Day

This post is a modified version of a World Metrology Day article I wrote for Australia’s Science Channel.

Saturday 20th May is World Metrology Day.

I’m not surprised if you hadn’t heard of it. I was three years in to a PhD in metrology before I found out we had a day for it.

Metrology is the science of measurement. It is an important foundation of other experimental sciences and is also a critical component of a nation’s ability to conduct business. Metrology considered to comprise three different fields:

Scientific metrology focusses on the definition of units of measurement (e.g. the kilogram, the metre, etc), how to actually make the measurements, and how to reliably trace a measurement back to an official reference.

Industrial metrology is about the application of measurement to manufacturing and other industrial and social applications. Industrial metrology is a very important factor in a nation’s engineering capability.

Legal metrology concerns the statutory requirements of measurement for trade, taxation, and protection of the public. Whenever farming produce is weighed, petrol is pumped, or shares are traded, the measurements (in these cases; weight, volume, and time) need to meet strict government controls on accuracy and precision.

Nearly every country has a metrology institute, involved in all of these important aspects of measurement. In Australia, we have the National Measurement Institute (NMI). America has the National Institute of Standards and Technology (NIST) and the UK have the National Physical Laboratory.

World Metrology Day is an international event commemorating the signing of the Metre Convention on 20th May 1875. The Metre Convention established international cooperation to develop the metric system and the International System of Units (SI).


Signatories of the Metre Convention. Technically, America uses the metric system. Somebody should probably tell them.

Measure for measure

For the past three-and-a-bit years I have been pursuing a PhD in optical metrology — I use light to measure stuff.

In particular, I work on the transmission of atomic clock signals for use by radio telescopes and other space science experiments. Over the years, atomic clocks have become more and more precise, and today we need new technologies in order to transmit the atomic clock signals to another location for use in scientific or industrial measurements.


My metrology lab.

Measuring up

The next few years hold some exciting developments for metrologists. We will soon re-define two of the most basic measurements we use every day, the kilogram, and the second.

The SI system has seven basic units of measurement. These are: the metre, the kilogram, the second, the ampere, the Kelvin, the mole, and the candela. All other units that we use to measure stuff, such as volts or kilowatts, a derived from these basic units.

The second is currently defined using caesium atomic clocks. The caesium within the atomic clock emits microwaves at around 9 GHz, and this frequency is used as the “tick” from which the second is defined.

As atomic clocks have got better, another type of atomic clock that uses atoms of ytterbium have proved to be more stable and precise than caesium-based clocks. These clocks emit light at a frequency around 518 THz, that is, they tick at around 518 trillion times per second. In a few years’ time, ytterbium clocks might become the new way to define time.

The second, and most of the other SI base units, are defined using physical constants. For example, the metre is defined as the distance light travels in 1/299792458th of a second. However, the kilogram is the only unit that is still defined by a physical object. A platinum-iridium ingot in a vault in France is defined to be the kilogram.


NIST’s copy of the kilogram.

Metrologists are working to find a better way to define the kilogram in terms of fundamental constants so that any metrology laboratory around the world can more easily make a precise and accurate measurement of the mass of the kilogram.

The leading contender is a device called a Watt balance that uses electromagnets to convert the mass of the kilogram into units of electrical power, Watts, which can be traced back to fundamental physical constants.

You can even download plans to build your own Watt balance. The US NIST released plans for a DIY Watt balance made out of LEGO. It’s millions of times less precise than NIST’s Watt balance, but about 10 to 100 times more precise than your kitchen scales (depending on how good your building skills are).


NIST’s LEGO Watt Balance

Metrology is an important part of our modern civilization. It is as fundamental to our way of life as electricity, or the internet. The progress of science and technology depends on the progress of our ability to make accurate and precise measurements.

50 Rules for Postgrads

This list was originally published as a humorous article in the UWA Postgraduate Student Association’s year book PostscriptIt was inspired by the famous (infamous?) Skippy List. I have only done some of the things on the list, I’m not going to say which ones though…

50 things today’s postgrad is no longer allowed to do at university

  1. Not allowed to imply that senior professors’ careers pre-date the discovery of the atom.
  2. Not allowed to tell prospective students that “PhD” stands for any of the following:
    – Parents have Doubts
    – Probably half Dead
    – Project half Done
    – Permanent head Damage
    – Potential heavy Drinker
    – Probably hopelessly Deranged
  3. No longer allowed to perform experiments on undergrads (even if rats are expensive and you grow attached to them).
  4. Must stop telling new students that the Reid Library was actually a spelling error and everyone is too embarrassed to change it.
  5. It is considered very unprofessional to add “in accordance with the prophecy” to the end of answers I give to questions when presenting at a conference.
  6. “It is easier to beg forgiveness than ask permission” does not apply to getting ethics approval for an experiment.
  7. The large rolls of aluminium foil in the lab are for experiments, not for making tinfoil hats to block government mind-probes, and I should stop telling students this.
  8. No longer allowed to set joke questions in exams.
  9. No longer allowed to create obvious patterns in the multi-choice exam answers
  10. No longer allowed create an obvious pattern in the multi-choice answers for the first half of an exam, and then break that pattern in the last half to watch the students freak out (even if it would be hilarious).
  11. Not allowed to attempt to purchase anyone’s soul using grant money.
  12. When giving a reason for the failure of an experiment I must put forward a reasonable hypothesis, not:
    – God
    – Gods
    – Witches
    – Gnomes (there is no physics, it’s all gnomes)
  13. Not allowed to sacrifice a chicken (or goat, suckling calf, mule, or virgin) to Odin so that He may look favourably upon my work (even if virgins are easy to come by in the physics department).
  14. When visiting German colleagues, don’t mention the war.
  15. Laser safety briefings must contain more than “Don’t stare into laser beam with remaining good eye.”
  16. Drug running and prostitution are not acceptable ways to raise research funding.
  17. Not allowed to ask “Do you want fries with that?” when given instructions by supervisors.
  18. Must stop trying to hide Dr Seuss quotes in paper manuscripts.
  19. Not allowed to turn my office into a ball pit…
    Not allowed to turn anyone else’s office into a ball pit…
    Plastic balls are no longer allowed on campus.
  20. Despite the fact that people with a PhD are called “doctor”, they are not allowed to prescribe any form of medication.
  21. When asked to attend a meeting in formal attire, I am not allowed to turn up in jeans and hoodie claiming that it is “the cultural dress of my people”.
  22. Not allowed to wear costumes in the lab unless it is Prosh.
  23. Office decorations must be limited and practical. I am not allowed to fill the room with inflatable novelties. (And not allowed to try and convince anyone that the Kiwi PhD student owns the inflatable sheep.)
  24. When asked to “give a few words” to new postgrads, I am to assume that I should say more than a “few” words. (“Run you fools!” is also inappropriate.)
  25. The correct course of action for an asphyxiating gas leak is not “hold my breath and hope for the best.”
  26. Crucifixes do not ward off supervisors.
  27. Stop sticking large googly eyes on laboratory equipment.
  28. Not allowed to make liqueurs out of lab-grade ethanol.
  29. No drinking in the lab.
  30. No drinking in the office.
  31. No drinking while teaching.
  32. I may not trade laboratory equipment for any of the following:
    – cigarettes
    – booze
    – sexual favours
    – bootleg DVDs
    – magic beans
  33. Using an old Smirnoff vodka bottle as a water bottle and taking large, regular gulps is disturbing and I should not do it around new students or while teaching.
  34. Putting red skittles in a prescription medicine bottle and swallowing regular handfuls while teaching is not appropriate.
  35. I should not taunt humanities students just because they are doing “easy” subjects.
  36. No longer allowed to scare international visitors with tales of how dangerous Australian fauna is (even if it’s true).
  37. “No drinking of alcohol” is not a challenge to find other ways to imbibe.
  38. Correct technical terms are to be used when teaching or preparing manuscripts. “Thingy”, “doohickey”, and “piece of shit” are not appropriate terms.
  39. I must stop sending new students to the lab supply stores to ask for things that don’t exist.
  40. Stop telling new students that Petri dish agar is edible (even though it is).
  41. Wearing shorts under a lab-coat is disturbing because it looks like I am not wearing pants.
  42. Do not replace the coffee in the lab coffee machine with decaf “to see what happens”.
  43. No cooking in the lab.
  44. Lab safety inductions do not need to begin with the “Safety Dance” song.
  45. “To conquer the Earth with an army of flying monkeys” is not an appropriate response to being asked “what is this research for?” during a media interview.
  46. Do not suggest to a colleague who has just had twins to name them “Alex, and the control.”
  47. Beers are not to be stored in the specimen fridge. (Beers do not count as specimens.)
  48. Magic eight-balls are not to be consulted for experimental procedures.
  49. Student plagiarism is to be referred to the Head of School, not resolved “at dawn, on the field of honour.”
  50. I am not allowed to start a betting pool on how long before the PSA president finally snaps and actually goes insane.

The Value of a PhD

Stop telling me to “get a real job”: PhDs drive economic growth, as well as the progress of human knowledge

As a PhD student, questions I am often asked very shortly after “What do you do for a living?” include “What’s the point of that?” and “So when are you going to get a real job?” Science communication practice over the past couple of years (such as competing in 3-Minute Thesis and FameLab) has helped me to come up with concise answers to the first of these questions that satisfy the majority of my interrogators. I am also quick to point out that studying for a PhD is a real job and to explain the benefits of PhDs and academics to the nation. However, people often seem to disagree with my assertions about the contribution of PhDs to the public and to the economy, to the extent that many will repeat the question the next time they see me.

PhDs in your life

Everywhere you look you will find technology that was invented or developed by people with PhDs. The technologies your smartphone and computer are based on cannot be built without a working knowledge of quantum mechanics, GPS would fail without knowing how to apply Einstein’s General Theory of Relativity, and the medical practices that keep you healthy are only possible due to our understanding of the immensely complex system that is the human body. Tens, hundreds, or thousands of PhDs have contributed to the technologies and services that you rely on and enjoy every day. You owe your health and wellbeing to the diligent research of generations of PhDs.

A PhD student has many similarities with a tradesman’s apprentice. The apprentice/student learns the tools and skills of their trade guided by the knowledge and experience of their master/supervisor, producing useful work as they learn. Just as we expect an apprentice electrician or machinist to quickly gain a measurable level of competence, we expect PhD students to make significant contributions to scientific and technological progress from early on in their candidature (continuing this analogy, PhDs have a “post-doc” period similar to an apprentice’s journeyman years).

A common accusation I received before I learned to explain the significance of my work quickly (and still receive on occasion) is that my chosen field of research is so narrow that it is of no use or interest to anyone else. It is often the case that one scientist’s research can seem so focussed on one objective that it has no impact elsewhere. This is a matter of necessity. We live in such a rich and complicated cosmos that, today, the only way one person is able to make significant progress is to pick a direction and attack it. However, the accusation that their research is of no wider significance fails to take into account that we scientists do not work alone. We work in a team, playing our individual part in a global human effort to understand the world we live in and to improve our quality of life. No science exists in isolation, and each narrow field of research contributes to the growing expanse of collective human knowledge and progress.

But the accusation of narrowness is false too. The seemingly tight focus of my research is built upon a broad foundation of other skills and knowledge. I view my growing expertise in my field as something resembling a pyramid, with the narrow apex supported by a broad and sturdy base. When I finish my PhD, I will be the world expert in optically-sensed stabilized microwave reference dissemination systems, I will be a world expert in stabilized time and frequency transfer, an expert in microwave and optical transmission, fibre-optics, and radio-telescope engineering, all supported by a strong competence in electronics, computer aided design and simulation, and a variety of fields of physics including wave mechanics and General Relativity.

This only took slightly less effort than the Giza one.

Focused research is supported by a broad background of skills and expertise.

The job of a researcher is to seek answers and improve our understanding of the world we live in, to look forward and drive our progress as a species. Scientific research is the only defence humanity has against threats to our way of life, or even our survival.

The economic argument

I have met many people who, disconcertingly for me, view PhDs as a waste of taxpayers’ money. Indeed, government treasuries are often keen to see proof that their investment in research and in PhDs is not being wasted, or couldn’t be better spent elsewhere. In the United States, Congress has demanded that the National Science Foundation “better articulate the value of grants to the national interest.” Recognizing that failure to communicate the return-on-investment of grants places us at risk of losing government and public support, researchers have challenged themselves to come up with scientific evidence on the impact of government investment in research. Late last year, a study published in Science demonstrated a significant way in which PhDs (and thus, the government grants that supported them) make an impact on the economy.

The study showed that PhDs disproportionately gained jobs in high-productivity, high-payroll establishments performing research and development, firms that that typically have a much greater economic impact. The study also showed that the majority of PhDs gained jobs close to where they had studied. Together, the evidence shows that PhDs make a substantial contribution to the economy that supported them, and that investment in PhD funding and research grants is well-founded.

More broadly, there is much historical evidence to show that research drives economic growth. Scientific and technological research produces new technology and ideas, that create new products and services, that create new jobs.


PhDs are no less real jobs than a trade apprenticeship. PhD students work hard to contribute not just to the economy, but to increasing knowledge and progress for the benefit of all humanity.