Parkes radio telescope construction

By the late 1940s and early 1950s it was clear that the days of improvisation in radio astronomy were over, and that the next steps had to be big ones. In turn, this implied that much planning and lots of money would be required. At the time the two strongest countries in radioastronomy were the UK and Australia. Given the UK were building the large 250-ft (77-m) telescope at Jodrell Bank, the Chief of the CSIRO Division of Radiophysics, Dr EG (Taffy) Bowen, proposed that Australia needed one as well.

With considerable funding from the Carnegie Corporation, the Rockefeller Foundation and the Australian Federal Government, the project went ahead. After a preliminary planning stage, the design study was carried out with Freeman Fox and Partners, London from 1955 to 1956 and the design contract from 1956 to 1959. Construction started in 1959 and the telescope was officially opened on the 31 October 1961 by the Governor-General, Viscount De L’Isle.

John Bolton’s association with the project began in November 1958 when he made a commitment to Taffy Bowen to return to CSIRO Radiophysics to stand by the construction and commissioning of the telescope and to direct its subsequent operations. Other key CSIRO players in the telescope’s construction and commissioning were Frank Kerr and Harry Minnett.

Almost half a century later, it is still one of the most advanced telescopes of its kind. A gigantic structure of steel and concrete, the telescope soars nearly 55 metres into the sky near Parkes, NSW. As reported in the commemorative volume Parkes: Thirty Years of Radio Astronomy, Betty Siegman, from the Australian Telescope National Facility, penned the following tribute to celebrate its thirty year anniversary on 22 November 1991:

 ‘Thirty years or so ago
Men of vision had a wish,
And they worked upon a plan,
And the plan became a dish.
And she served them long and well
As they probed the endless sky,
Seeking answers to the riddles,
What was out there, where and why?
And they gather here today
Having come from near and far,
To wish her happy birthday,
For today she is the star.’

The initial idea gets little support

Australia got off to a good start in radio astronomy just after the Second World War. Staff of the CSIRO Radiophysics Laboratory (later the Division of Radiophysics) made use of radio-receiving antennas and other equipment left over from war-time, and turned them from their original purpose of receiving man-made radio signals to studying the natural radio waves produced by objects in the cosmos. The equipment located on the coast at Dover Heights in Sydney was rough and ready, and often improvised (see Radio astronomy at Dover Heights). But by the late 1940s and early 1950s it was clear that the days of improvisation were over, and that the next steps had to be big ones. In turn, this implied that much planning and lots of money would be required.

The first proposal was to build a large air-warning antenna that would double as a radio telescope. The Radiophysics Laboratory had close links with the Royal Australian Air Force (RAAF): during the war it had worked for all three services (army, navy and air force) and just after the war it was advising the RAAF on radar and navigation equipment, including air-warning equipment. At the time it seemed that the best way to extend that technology would be to build larger radio-receiving antennas. Radiophysics staff began thinking in terms of dimensions of hundreds of feet. At one stage they proposed to build a wooden antenna, 100 feet in diameter, rotating on a track and costing all of A£365. A large antenna like this could be used for both air-warning and for radio astronomy. But the RAAF was even more strapped for cash than CSIRO, and had no money to put towards such a project.

In 1952 it became clear that CSIRO too had no chance of getting a large capital sum to fund such an instrument. Some way had to be found to squeeze it out of the existing Radiophysics budget. So a proposal was drawn up for a cylindrical antenna, lying on its back, 1 000 feet long and 200 feet wide, made up of five adjoining elements. Each element would be 200 feet square, lying on an east-west line and scanned by cable and winches in the north-south direction. The total cost was to be about A£125 000, spread over five years. But once again the answer was no

The tide changes

Now a new factor appeared. Unlike Australia, the USA had been slow to take up radio astronomy after the Second World War. The leader of the Division of Radiophysics, Dr EG (Taffy) Bowen, had many contacts in science and industry in the USA, and he urged them to help the USA to take up radio astronomy, mainly by building a large radio-receiving antenna. The proposal fell on receptive ears. The Division of Radiophysics wrote a detailed specification for such an instrument and a program of scientific activities that it could be used for. It was tacitly understood that this telescope would go ahead at the California Institute of Technology, and that the Carnegie Corporation might provide up to US$5 million for it.

About the time that these plans for a telescope were being drawn up, the large American foundations such as Ford, Rockefeller and Carnegie were changing their emphasis in supporting science, giving less to the US and more to other parts of the world. Vannevar Bush (President of the Carnegie Corporation) and Alfred Loomis (a Trustee of both the Carnegie Corporation and the Rockefeller Foundation) suggested that the proposed large telescope be built in Australia, with financial assistance from the USA. The Carnegie Corporation had accumulated US$250 000 that it was obliged, for certain reasons, to dispose of in the British Commonwealth, and the Corporation’s trustees granted this money towards the construction of a telescope in Australia. This grant was followed by another US$250 000 from the Rockefeller Foundation.

The last hurdle was that the overseas bodies required that their own grants be met, dollar-for-dollar, by the Australian Government. The Australian Government rose to the occasion (the money actually came from other CSIRO sources) and contributed to not only the capital costs but the running costs as well. A year later the Rockefeller Foundation gave a further US$130 000. The telescope now had an assured future and work began on ideas of what a giant radio telescope should look like.

What should it look like?

As Frank Kerr recalled in Parkes: Thirty Years of Radio Astronomy (p.9):

One of our bibles was a little book called A Proposal for a Giant Radio Telescope. It’s not exactly in the style of engineering proposals, but was meant to interest the fund-raising people and parliamentarians. I was heavily involved in writing this document, which describes radio astronomy in general, goes on to talk about astronomical and technical considerations connected with a possible giant radio telescope, and ends with a cost estimate. At the time the most interesting thing in the book was a presentation of eight or nine alternative designs. One was a sketch of the UK Jodrell Bank design (Fig. 1a, which came into operation in 1957), a dish to be suspended on two towers. We now regard most of the others as rather wild ideas. Fig. 1b shows one version of an alternative design in which the dish was carried on a sphere in different ways and the sphere either floated on oil or was carried around on rail tracks. I don’t think anybody had considered how to stop the thing from blowing away! But it was all good fun. Fig. 1c is yet another design which runs around a great big hole and finally, in Fig. 1d, we have a design which is starting to evolve towards the ultimate one ‘ a single tower, a single support.

Preliminary planning begins in 1954

In his recollections of the proposal to build the Parkes telescope Frank Kerr, at the symposium that marked the 30th anniversary of its opening, recalled:

One thing that is striking if you stop to think about it, is that the real start of radioastronomy was in 1945, and it was a mere nine years later that Taffy Bowen and others began thinking about a new telescope.

In 1954 there was no-one in Australia capable of building the Parkes telescope or even doing the engineering design. So Joe Pawsey went to Britain for advice (it was thought to be cheaper than the USA). The first person consulted was Barnes Wallis (of ‘dambusters’ fame), who was then the Chief Engineer of Vickers. Wallis was quite excited by the challenge of the proposed telescope but warned that: the design of a giant radio telescope is a venture into the unknown

Taffy Bowen was very conscious of the dangers of this new venture and was also very good at seeking expert advice. He formed a Technical Advisory Committee (TAC) to help select the consultants for the design study, to specify exactly what they had to do and to assess their recommendations. The TAC included a distinguished English engineer John Roderick, Professor of Civil Engineering at Sydney University and Arthur Wills, an experienced engineer at the Aeronautical Research Laboratories in Melbourne.

The design study 1955-1956

Freeman Fox and Partners (FF&P) in London, was the design firm chosen. The top people involved from FF&P were Ralph (later Sir Ralph) Freeman Jnr and Gilbert (later Sir Gilbert) Roberts, FRS, a brilliant if somewhat idiosyncratic bridge engineer for the project. Roberts was the partner directly responsible for the project and had been first assistant in the 1920s to Freeman’s father, Sir Ralph Freeman Snr who was design consultant to Dorman Long in their successful tender for the Sydney Harbour Bridge and was afterwards responsible for its detailed design. Robert’s first assistant for the telescope study was MH Jeffrey. Harry Minnett was the Radiophysic’s representative at FF&P in London, available for consultation on CSIRO’s requirements, especially the radio and electrical aspects and to liaise with Sydney on problems and progress.

Bowen had arranged for Barnes Wallis to collaborate with FF&P. Wallis advised on the problems of deflection of the telescope’s structure, first by thinking of incompressible columns (he held the patent to this device) and then by recommending automatic compensation for changes to the dish’s parabolic shape (which was in fact used in the telescope). In a significant departure from the design of previous telescopes, Wallis recommended that the telescope’s mounting system (the way in which it is turned and pointed to different parts of the sky) be ‘alt-azimuth’, rather than, for instance, the equatorial mount used on the earlier radio telescope at Jodrell Bank in the UK. And just for good measure, Barnes Wallis came up with the idea of the telescope’s guidance system, the ‘master equatorial’. Wallis’ contributions far exceeded his very small retaining fee ‘ which, in any case, it seems was never paid.

One issue was that FF&P had no servo expertise and, aware of its importance, tried to interest companies with such expertise in the project. All the capable firms approached were engaged at the time in big defence contracts and were not interested in a ‘one-off’ job. As Harry Minnett recalled in Parkes: Thirty Years of Radio Astronomy (p.15):

The impasse lasted many months and in that period I looked into the basic servo problem myself. Perhaps because I was new to the field and unconstrained by any knowledge of gun servos, I hit on the solution which was ultimately adopted. This system could track or scan celestial objects accurately, even in gusty winds because it strongly resisted all the components in the wind torque spectrum without, however, interacting with structural resonances.

Finding a site

Another important step was to find a suitable site. The people involved in the search were Lindsay McCready, Joe Pawsey and Frank Kerr. The first consideration was that it needed to be accessible from Sydney but shielded from Sydney’s radio noise. Initially they felt a distance of about 30 miles would be sufficient, but with Sydney’s subsequent expansion that would have been unsatisfactory. Areas considered in NSW were Camden, Canberra, the Kangaroo Valley near Nowra, Cowra and Parkes. In the end the Cowra/Parkes options were the only possibilities considered feasible. The Cowra site was at a point beside the Macquarie River and looked promising but the Parkes site was better because it had more flat ground. As Frank Kerr recalled in 1991 in Parkes: Thirty Years of Radio Astronomy (p.10):

Probably the most influential factor was that the Cowra authorities were not interested in our project and wouldn’t give us any assistance in road-building, or anything else, whereas the Parkes’ people saw the possibilities for their town. The then mayor of Parkes, Cec Moon, was a real enthusiast and proceeded to play a role in bringing the telescope to Parkes.

During recent discussions I am reminded that the first site we chose was not as far out of town as the present one. It was Taffy Bowen who urged us to go a bit further from Parkes, which we did. We marked out the present site, which was attractive for a different reason. The land-owner at the time, Australia James Helm (born on Federation Day in 1901) was very sympathetic to our project and this turned out to be very valuable in those early days.

Cec Moon and the Parkes Council’s vision has been justified. Over 120 000 members of the public visit the Parkes telescope annually. The observatory has an excellent visitors’ centre with two audio-visual theatres and a café ‘ a great vantage point for viewing the telescope.

Design contract (1956-1959) and construction (1959-1961)

The design contract was placed in 1956 and completed in 1959. John Bolton’s association with the project began in November 1958 when he made a commitment to Taffy Bowen to return to CSIRO Radiophysics to stand by the construction and commissioning of the telescope and to direct its subsequent operations. From that point on Bolton was kept up to date with design progress or lack of same and the constant battles with FF&P.

In mid-1960 Bolton and Bruce Rule (Caltech’s ‘Dean’ of telescope construction), went to London to have a close look at the FF&P design. They had a mandate from Bowen that what they felt were definite errors had to be modified and what they felt could be improved was to be debated. In the first category was the cross-section of the tripod legs, which they felt were far too small and would lead to torsional oscillations of the entire tripod and cabin structure ‘ they won that argument. Their second objection was that there was insufficient isolation between the main telescope and the master equatorial column. FF&P again gave in but Bolten felt that the modifications did not go far enough and 30 years later believed that the interactions between the main telescope and the master equatorial tower probably accounts for some of the random changes seen in the telescope pointing.

After the design contract was completed, the search for a construction contractor commenced. CSIRO finally settled on the MAN Company (Maschinenfabrik Augsburg-Nürnberg AG) in Germany with Askania-Werke in West Berlin and Metropolitan Vickers, UK as sub-contractors for the master equatorial and servo-drive systems respectively. The contract was placed in 1959 and the telescope completed in 1961.

The base tower was started only months after finalising the contract with MAN in July 1959 and with Mike Jeffery as supervising engineer, the telescope construction proceeded very smoothly in time for the opening ceremony in October 1961. Harry Minnett recalled two special events in his chapter on the construction published in Parkes:Thirty Years of Radio Astronomy (p.16):

The first was when the aerial cabin had been secured in position on the tripod, it was suggested that a photograph be taken from the erection crane to mark the occasion with some human figures in it to add human interest. It was not a case of not looking back, but rather of not looking down ‘ something I would not care to repeat all these years later. The second was tilting the dish from the zenith for the first time ‘ a dramatic event.

Following the Opening, Mike Jeffery supervised the acceptance tests before the instrument was handed over to CSIRO in March 1962.

Commissioning

It took nine years after the dedication before all the major faults in the design and construction of the telescope surfaced, and were finally overcome and commissioning considered complete. However for the major part of those nine years, the users of the facility were rarely conscious of the work going on behind the scenes and produced hundreds of scientific papers.

The major faults found during and after construction, are discussed in detail by John Bolton in Parkes: Thirty Years of Radio Astronomy (pp.19-26) and were as follows:

• The counterweight was insufficient as the weight of the dish had increased substantially between the preliminary and actual construction drawings.
• The production of the master equatorial and the control desk fell badly behind schedule. When finally delivered the former was an excellent piece of mechanical design and precision engineering while the control desk in John Bolton’s view was ‘pathetic’.
• The variable speed control for the alt-azimuth part of the telescope did not work and the variable control for the equatorial burned out the motors in less than 12 hours of operation.
• The first attempt to move the dish in zenith angle produced two large bangs as the dowels locating the zenith angle’s gear boxes on their mounts shot out. The mesh of the pinions to the racks, preset in Germany, was now far too close. This was solved by increasing the clearance and fitting larger dowels into the reamed out holes.
• At the next attempt to move the dish, the counterweights were seen to be slipping relative to their support arms. Bolton and Mike Jeffery reinforced the bolts by welding.
• At the next trial the counterweights walked ‘ as predicted by Bruce Rule. Harry Minnett provided an ingenious electrical solution ‘ back-to-back motor/generators which sat in the motor room for years. As John Bolton observed: Many people probably saw them wobble occasionally but never really understood what they were doing ‘ neither did I.
  Parkes identities (left to right) Cliff Smith and Ben L tightening the azimuth track bolts. [Source: Bolton J, 1994, ‘Commissioning the Parkes radio telescope ‘ a retrospective view’, In: Parkes: Thirty years of Radio Astronomy, Goddard DE, Milne DK (eds), CSIRO, Melbourne, Australia, pp.19-26]