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40 Years of the Australian Astronomical Observatory
FRED WATSON
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40 Years of the Australian Astronomical
Observatory

FRED WATSON
AUSTRALIAN ASTRONOMICAL OBSERVATORY

ORIGINS AND GOVERNANCE

Half a century ago, Australian astronomy was a very different endeavour from what it is today. With the Parkes Radio Telescope having been recently completed, radio astronomy was in the ascendency, and optical (visible light) astronomy was mostly limited to the facilities of the Australian National University (ANU) at Mount Stromlo in Canberra.

But observing conditions in Canberra were less than ideal, with the gradual spread of the suburbs and their associated light pollution. An ANU outstation at Mount Bingar in the Riverina region of New South Wales had a small telescope that was used by the Stromlo observatory's Director, Professor Bart Bok, and when Bok initiated the quest for a permanent dark-sky site for the observatory in the early 1960s, he favoured Mount Bingar. That was not to be, however. Extensive site testing revealed that Siding Spring Mountain in the Warrumbungle Range in north-western NSW boasted observing conditions that were at least as good as Bingar, but with a small nearby town - Coonabarabran - to provide infrastructure and an attractive home for staff.


Fig. 1: David Sinden, Grubb Parsons' Optical Shop Manager, contemplates his handiwork in 1973. The 3.9-m Anglo-Australian Telescope mirror sits on the company's 6-m polishing machine. (C A Parsons & Co)

Thus it was that Siding Spring became Mount Stromlo's dark-sky site and, eventually, Australia's national optical observatory. The first telescope there, the ANU 1-metre, was opened in February 1964, and was used extensively by Bok and his wife Priscilla in their landmark studies of the Milky Way. Other smaller telescopes followed, but when the Australian and British governments decided in the late 1960s to build a major instrument in the 4-metre class, Siding Spring became the favoured site. This 3.9-m Anglo-Australian Telescope (AAT) was eventually inaugurated at Siding Spring by HRH Prince Charles on 16 October 1974, when he famously 'declared this aperture open'.


Fig. 2: Fred Hoyle greets HRH Prince Charles at the opening of the telescope, with Australian Prime Minister Gough Whitlam looking on. Hoyle later said of his welcoming speech that 'every syllable was blown clean away in the roar of the wind, so that I was instantly reduced to the grimaces of primitive man.' (Official photographer)

The occasion was not without incident. The Prince's arrival at the telescope was accompanied by the bone-rattling gales that have since become familiar to generations of Anglo-Australian astronomers. And, flapping wildly on their identical poles, the three flags demanded by protocol had seemed reluctant to maintain their prescribed order of ascendency - the Prince's standard highest, the Australian flag next, and the banner of the ANU lowest. Somehow, the University flag always seemed to be at the top, despite repeated adjustments. History reveals the clandestine flag-raiser to have been Olin Eggen, Director of the Mount Stromlo Observatory, who had previously campaigned vigorously in favour of ANU proprietorship of the new telescope. By the time the Prince arrived, however, the halyards had been secured beyond his reach, and order was restored.


Fig. 3: The cavernous void of the AAT dome is exaggerated in this modern wide-angle view, but it remains one of the largest telescope enclosures in the world. (Ben Wrigley)

Eggen's audacious gesture was a final dig at the decision to operate the telescope through an independent Anglo-Australian Telescope Board, a position that had been strongly advocated by the UK's Secretary of State for Education and Science - Margaret Thatcher. Eggen had learned the hard way that Mrs Thatcher was not a person to be swayed, and had resigned his position on the Board in August 1973. In the event, the AAT Board turned out to be the ideal governance arrangement for the telescope, and quickly led to the establishment of the Anglo-Australian Observatory (AAO), with equal funding by both nations in return for equal access to the telescope. This arrangement was frequently held up as a model for multinational scientific projects, until its supporting Act of Parliament was repealed on 30 June 2010, following the UK's staged withdrawal from the AAO. That event signalled the rebirth of the organisation as the Australian Astronomical Observatory, a division of what is now the Commonwealth Department of Industry and Science.

PRODUCTIVE TELESCOPES

In the AAT's early years, it had to be all things to all users. It was by far the biggest telescope available to British and Australian astronomers and, then as now, they had to apply competitively for observing time through an independent time-allocation committee. For its part, the AAT had to fulfil all their requirements for imaging, photometry, spectroscopy and polarimetry. Indeed, it had been built with versatility in mind, a set of three interchangeable 4-tonne top-ends for the telescope providing a range of focal ratios from f/3.3 to f/36 at prime, Cassegrain and coud챕 focal stations. The auxiliary suite of more than a dozen instruments that was built to take advantage of this ranged from a large intermediate-dispersion spectrograph to advanced infra-red instrumentation, built at the AAT's own laboratory in the northern-Sydney suburb of Epping. And because the telescope operated completely under computer control (it was the first large telescope to do so), it was gifted with a pointing accuracy of better than 2 arcseconds. That was nothing short of astonishing in 1974, when 1 arcminute was considered the norm.

The telescope was originally designed with the idea that photographic plates would be the main detectors, both for imaging and spectroscopy. For large-format astronomical imaging, that indeed turned out to be the case, and one of the unexpected contributors to the telescope's early reputation was the profusion of remarkable astronomical images made by its photographic specialist, David Malin. When, in the late 1970s, David pioneered a technique for recording faint celestial objects in true colour, the impact was dramatic, rocketing both the telescope and himself to world fame. For spectroscopy, however, new electronic techniques were emerging, and the mid-1970s saw the installation of several ground-breaking two-dimensional detectors, culminating in the cooled charge-coupled devices (CCDs) that are ubiquitous today in both professional and amateur astronomy.


Fig. 4: Robert Dean, Telescope Operator, at the control console of the AAT in 1974. (Official photographer)

Two other circumstances conspired to increase the AAT's potency as a discovery machine. The first was that that the southern sky was essentially unexplored by large telescopes. Even such significant targets as the Galactic Centre and the Magellanic Clouds had been observed only at low elevations by northern-hemisphere instruments. The second was that the challenge presented by this virgin territory had been met by the British when they had decided, in 1970, to go ahead with the construction of a wide-field photographic survey instrument, the 1.2 m UK Schmidt Telescope (UKST). That instrument was opened at Siding Spring on 17 August 1973, and entered service some two weeks later. Its initial task was to photograph the whole of the southern sky not covered by its near-twin on Palomar Mountain in the USA during the 1950s, a job that eventually took the better part of a decade. (The survey is now available on-line, and has even found its way into Google Sky.) In June 1988, the UKST became part of the AAO, having previously been an outstation of the Royal Observatory, Edinburgh.


Fig. 5: Robert Dean, AAO Telescope Systems Manager, at the console rather more recently. Minor changes may be noted. (Chris McCowage)

From the beginning, scientists and engineers at the AAO showed themselves to be adept at building novel instruments for use with the telescope. For example, the use of fibre optics in astronomy (which allows the spectra of hundreds of celestial objects to be recorded simultaneously), while not invented at the AAO, was transformed from an interesting novelty into a most effective technique at both the AAT and the UKST during the early 1980s. Subsequently, robotic fibre positioners were developed for both telescopes - the 2-degree field (2dF) and 6-degree field (6dF) systems respectively. These instruments immediately transformed the collection rate of spectroscopic data, allowing surveys to be undertaken on a scale never before imagined.

The first major project of that kind - the 2dF Galaxy Redshift Survey - measured 221,000 galaxies and was completed in 2002, quickly becoming the richest source of AAO scientific papers to date. In 2005 it was used to find the "missing link" between the temperature fluctuations in the Cosmic Microwave Background Radiation and today's distribution of galaxies. This remarkable work highlighted the importance of large-scale astronomical surveys and confirmed that survey-type astronomy would continue to be a major element of the AAO's work.


Fig. 6: About half a kilometre from the AAT is the elegant building of its smaller sibling, the UK Schmidt Telescope, seen here at the start of a night's work. (Ben Wrigley)

Since then, a number of other major surveys have been undertaken on both the observatory's telescopes. With 6dF replacing photography on the UKST in 2001, this telescope completed the largest three-dimensional map of galaxies in the southern sky in 2005, and followed it with a survey of the velocities and physical parameters of 500,000 stars in our own Galaxy, completed in 2013. All these surveys have provided fundamental data for astronomers, constraining parameters such as the proportions of dark matter and dark energy in the Universe, and details of the evolutionary history of our Galaxy in the new discipline of galactic archaeology.

Other instrumentation includes a large echelle spectrograph at the telescope's coud챕 focus, which is used to obtain very detailed spectra of objects one at a time. It is perhaps most famous for its contribution to our knowledge of planets in orbit around other stars. The Anglo-Australian Planet Search (AAPS) programme has discovered some 5% of all confirmed extra-solar planets by means of the "Doppler wobble" technique. AAPS obtains a velocity precision of about 1 metre/sec - a slow walking pace - by means of an iodine calibration cell, whose temperature is controlled to within 짹 0.1 K.

Together, these instruments have propelled the AAO into an enviable position regarding its scientific productivity. A 2007 survey showed that the AAT was the first-ranked 4 m telescope in the world in both productivity and impact, achieving 2.3 times as many citations as its nearest competitor. Moreover, among optical telescopes of any size, on the ground or in space, the AAT was ranked fifth in productivity and impact. These are remarkable achievements, given that the telescope is now only half the size of the world's largest.

THE AAO TODAY

In recent years, the AAO has faced significant challenges, of which unquestionably the most dramatic was the Wambelong bushfire of January 2013. With its cause still the subject of a Coronial Inquiry, the fire swept through the Warrumbungle National Park, enveloping Siding Spring Mountain, and racing eastwards towards the town of Coonabarabran 20 km away. It stopped short of the town, but destroyed 55,000 hectares of bushland, and more than 50 homes. Mercifully, there was no loss of life. And thanks to the water-bombing efforts of the Rural Fire Service, none of the Observatory's telescopes were damaged, although the ANU lost the Siding Spring Lodge.

Meanwhile, in Sydney, the AAO had recently relinquished its ageing laboratory accommodation in Epping in favour of new purpose-built government offices in nearby North Ryde. The bushfire prompted plans for a remote observing suite to be brought forward, since access to Siding Spring was restricted for some months after the fire. That facility at North Ryde is now well-used by visiting astronomers, working in a room that looks more than a little like the AAT control room. Another significant change was the appointment in 2013 of Warrick Couch, formerly of Swinburne University, as the AAO's Director. Warrick's long association with the observatory made him an ideal and most welcome candidate.

The AAO is currently enjoying further instrumental and scientific growth. Its HERMES multi-object spectrograph was commissioned on the AAT in 2013, and is now delivering spectra for the million-star GALAH survey (Galactic Archaeology with HERMES). Other fibre-fed instrumentation is under development, including the TAIPAN multi-object spectroscopy system to replace 6dF on the UKST. This system uses miniature autonomous fibre-positioners called 'Starbugs', and is a prototype for a similar multi-fibre instrument to be built by the AAO for the 25-m Giant Magellan Telescope.

It was against this exhilarating background that in October 2014, the AAO celebrated its 40th birthday, along with Siding Spring Observatory's 50th. A weekend of birthday celebrations gave everyone a chance to join in the festivities, with telescope visits, presentations, a celebrity 'Science in the Pub', and Australian astronaut Andy Thomas talking about his experiences in space. The Observatory even received a letter of congratulation from Clarence House in London, expressing HRH Prince Charles' great pleasure at the success of the AAO.


Fig. 7: Bedecked with a birthday ribbon around its high walkway, the Anglo-Australian Telescope dome braces itself for another 40 years. (Anna Tenne)

A few things have remained unchanged over the years. Thanks - in part, at least - to the efforts of the Siding Spring Dark Skies Committee, the site's average zenithal night sky brightness is still a very dark 22.7 magnitudes/sq. arcsec in the visible waveband, as it was in the early days. The wind still whips around the front door of the telescope, surprising the unwary. And, despite the formal withdrawal of the UK from the operation of the observatory, British accents are still frequently heard in its control rooms. Clearly, the UK has a very soft spot for Australian astronomy.

FURTHER READING

AAO: http://www.aao.gov.au/
AAPS planet search: http://newt.phys.unsw.edu.au/~cgt/planet/AAPS_Home.html
GAMA galaxy survey: http://www.gama-survey.org/
2dF Galaxy Redshift Survey: http://magnum.anu.edu.au/~TDFgg/
6dF Galaxy Survey (UKST): http://www.6dfgs.net/
RAVE Stellar Survey (UKST): https://www.rave-survey.org/
GALAH Stellar Survey: http://www.mso.anu.edu.au/galah/home.html
TAIPAN instrument and surveys (UKST): http://www.taipan-survey.org/

 

Fred Watson is an astronomer at the Australian Astronomical Observatory, where he is Head of Lighting and Environment. Fred is best known for his radio and TV broadcasts, talks, and other outreach programs, which earned him the 2006 Australian Government Eureka Prize for Promoting Understanding of Science. He has also written a number of award-winning books, and was made a Member of the Order of Australia in 2010. Fred has an asteroid named after him (5691 Fredwatson), but says that if it hits the Earth, it won't be his fault.

 
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