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Radar

In rallying behind the war effort, CSIR (as it was then known) became prominent in aeronautics and the development of radar. In 1939 at the beginning of World War II, the Australian Government was asked to send its most qualified scientist to learn about a scientific breakthrough that the British were developing. CSIR sent physicist David Martyn secretly by plane to London, where, he was given the entire details of a secret radar project by the British Government. He returned to Australia with material to develop the technology in Australia.

Upon his return in 1940, the Australian Government was concerned about the threat of an attack for the sea and immediately began building the first shore defence system. This system would provide advance warning of approaching enemy ships to the Army and Navy. By the end of 1941, the system was further developed to scan the skies for planes. Equipment was sent to Darwin in early 1942, but on 19 February 1942, only days from completion, the city was bombed by Japanese planes. The radar system was operating three days later and detected subsequent raids early enough for them to be intercepted before they reached the coast.

From these covert beginnings was to come the Division of Radiophysics, which during the war initiated over 20 major radar projects and continued after the war with pioneering applications of the techniques to the newly created field of radio astronomy. Other research programs were in cloud and rain physics and the development of Distance Measuring Equipment (DME), the transponder-based radio navigation technology found in all aircraft.

Covert beginnings

On 24 February 1939, the Australian High Commissioner in London sent a cable to the Prime Minister, Joseph Lyons, in Canberra. It read: ‘Conversations have been carried on from time to time with the Air Ministry on the subject of secret research. They culminated today in the disclosure to the High Commissioners of a new development in defence applicable particularly to air but also probably capable of development for other services. The High Commissioners have been informed that if their Governments send their best-qualified physicist to England all information will be placed at his disposal for secret report to Dominion Governments. Utmost secrecy is essential and the choice of a man of the greatest discretion important.’

The secret mission

Prime Minister Lyons called in CSIR and, on the advice of its Chairman Sir David Rivett, chose physicist David Forbes Martyn for the clandestine mission. For a number of years Martyn had been doing research into the upper atmosphere and ionosphere for the CSIR Radio Research Board. He flew to London immediately and was given the entire details of Britain’s secret radar network. He returned to Australia by ship with a great number of reports and essential radio valves locked in a lead-weighted cabin trunk.

Early radar warning systems

Since 1935 Britain had been preparing a warning system of radar ‘ an acronym for Radio Detection and Ranging ‘ under a committee headed by Sir Henry Tizard. When Neville Chamberlain returned from Munich in 1938 with the promise of ‘peace in our time’, five radar stations were guarding the approaches to London. Each station sent out a stream of short-pulse radio waves concentrated by directional aerials. The radio waves scattered on striking an object, such as an aircraft, and some of the energy returned as an echo to be amplified and displayed on a cathode-ray tube. The time between trans­mission and echo reception gave the distance to the reflecting object. The five stations could give warning of aircraft at a height of 3 000 metres out to a distance of 130 kilometres from the coast anywhere between Suffolk and the south of Kent.

Light Weight Air Warning with Height indication radar equipment - circa 1943

LW/AWH Set 1943. Light Weight Air Warning with Height indication radar equipment ‘ circa 1943. [Source: CSIRO Archives]

On Martyn’s return, a conference took place with Sir David Rivett, the Director-General of Posts and Telegraphs, Sir Harry Brown, and electrical engineer Professor John Madsen from Sydney University who had been closely involved in studies of the ionosphere, atmospherics and radio transmission. The conference recom­mended setting up an advisory board representing three major interests: scientific research, development-production and the armed services. A secret Cabinet meeting, of which no records were kept, approved this and voted £80 000 for building a radar research establishment. It was given the cover designa­tion of the CSIR Radiophysics Laboratory.

To attract as little attention as possible, the laboratory was added to the CSIR National Standards Laboratory then being built in the grounds of the University of Sydney. It had sepa­rate entrances, guarded by Commonwealth police, and the first security-cleared staff moved in at the end of March 1940. In time some sixty of the country’s best physicists were recruited to develop radar and make it as accurate as possible including three women, Joan Freeman, Rachael Makinson and Ruby Payne-Scott. They were the first women in Australia to have actual careers in physics and wartime exigencies required that talented young women be hired.

Some of the early work was necessarily trial and error. Electrical engineer Victor Burgmann, (later Foundation Chief of the Division of Textile Physics, member of the CSIRO Executive, and Chairman of CSIRO) recalled how he was given a radar set known as the air-to-surface vessel (ASV). It had been sent out from England with no instructions and he was told to get it working. He knew the broad principles of radar, traced the circuit, and deduced how it worked. He recalled the moment:

It was an interesting moment when I connected it to the mains for the first time and switched it on, hoping I wouldn’t destroy the first ASV set in the southern hemisphere.

He pointed a makeshift aerial out the window ‘ and the set worked. Soon after, Burgmann and a technician from the Post Master General’s Department installed the equip­ment in a DC3 from the RAAF base at Richmond near Sydney and had the pilot fly them out over the ocean. There, in an exciting experiment, they received the first echoes from a real target, a merchant ship steaming off the coast.

Manufacturing begins

From the very beginning there was a strong emphasis on all-Australian manufacture of components because the country was geographically isolated and supply routes were vulnerable. The PMG’s Department made some of the early hardware but commercial electrical firms, which at that time had little experience beyond building wireless sets, were soon called in. They were to produce some remarkably sophisticated equip­ment, particularly in the later years of the war when microwave radar had been developed.

The war years

In 1940 it seemed most likely that Australia would come under sea attack and the Radiophysics Laboratory concentrat­ed on developing a Shore Defence (Sh.D.) set that would warn Army coastal defences of the approach of surface vessels and, by accurate range measurement, assist in gun-laying. This equipment operated on a wavelength of 15 metres (a frequency of 200 megahertz) and gave excellent performance out to 30 to 40 kilometres. Owing to changes in the pattern of war, Sh.D. was never used against the enemy. But the work that had gone into its development on this wavelength had profound effects later.

Towards the end of 1941, it became obvious that air attack would be the real danger to Australia and a group of physicists under Dr Jack Piddington at the Division of Radiophysics worked at top pressure to improvise an air-warning system based on the Sh.D. system but modified to provide the maximum possible range without using more power. Thanks to the background of Sh.D. experience, the first experimental equipment was produced in only 5½ days in late 1941. It had no safety covers and high voltages were a con­stant danger to the operating crew. But in its first week of trials at Dover Heights, Sydney, it detected an aircraft 105 kilometres out to sea. One of the first production models was sent to Darwin in February 1942. RAAF technicians were still installing it when the Japanese staged their devastating bombing raid on the morning of the 19th February. Piddington and his team flew to Darwin and assisted in getting the set operating by the morning of the 22nd February, just in time to detect another Japanese bombing force. It was intercepted and scattered 32 kilometres off the coast.

By 1942 liaison with the services had improved, and a regular exchange of information with the United States was started. In the same year the Radiophysics laboratory developed the Light­Weight Air Warning set (LW/AW) which was to play a vital part in the push north through the islands. It was probably the most reliable and portable set devised by any of the Allies and could detect a twin-engined aircraft at up to 140 kilometres. It was manufactured by the NSW Government Railways (see link below).

During the war, the Division of Radiophysics in Sydney and the PMG’s Research Laboratories in Melbourne developed more than 20 different radar systems. One of the outstanding scientific and technical achievements of the Division came towards the end of the war when Ruby Payne-Scott and a number of colleagues (including BY Mills) designed and tested a prototype high frequency radar operating at 1 200 MHz (LW/AWH, Light Weight Aircraft Warning Height). This sophisticated design represented the major technological achievement of the Radiophysics Laboratory during the war.

Radar photograph of the mass of troop-carrying aircraft gliders leaving England and approaching the Continent on the famous Arnhem raid (Operation Market Garden)

Radar photograph of the mass of troop-carrying aircraft gliders leaving England and approaching the Continent on the famous Arnhem raid (Operation Market Garden). [Source: CSIRO Archives]

Ruby Payne-Scott constructed and tested and later provided the theoretical understanding for the PPI (Plan Position Indicator) used in this advanced radar system. The theory developed by her remained the definitive work for some years after publication in a US journal after the war. Ruby Payne-Scott constructed an ‘analogue computer’ which simulated the use of the 1 200 MHz radar; this setup was used by her and by a number of RAAF radar operators to understand the properties of the advanced system. Payne-Scott’s boss at the time was Dr Joseph Pawsey FRS, FAA, a brilliant team leader who had a positive influence on all who worked with him. Joe Pawsey had led the basic microwave development work in the Division from which these advances flowed. A second late development by the Division of Radiophysics was a flashlight-sized detector used by commandos landing in enemy-held territory to locate Japanese radar installations.

Peacetime research

In 1946 Dr EG (Taffy) Bowen was appointed Chief of the Division of Radiophysics. Bowen was previously a member of the research team which developed radar in Britain in the l930s. Under his dynamic leadership the Division began its transition to peacetime research. The professional staff of Radiophysics had grown to 66 by the end of the war, with several important newcomers recruited from the British and Australian services. Bowen was conscious of his responsibility to them. Two lines of research grew up naturally and became the predominant interests of the Division: radioastronomy and cloud and rain physics. The first grew out of the curiosity of JL Pawsey who repeated the observations of JS Hey in England on the jamming of radar receivers by radiation from the sun. Research on cloud and rain physics was started by Bowen in 1946 when I Langmuir and V Schaefer in the USA reported that rain could be induced by seeding clouds with dry ice. These two programs absorbed the attention of a considerable proportion of the staff until Bowen himself retired from CSIRO in 1971.

Another project was Distance-Measuring Equipment (DME), developed by Brian Cooper, and based on the principle of the RAF’s tactical Rebecca ‘ Eureka system. (An airborne transmitter-receiver, code-named ‘Rebecca’, sent short pulses to a ‘Eureka’ beacon on the ground which responded with a reply pulse. Distance was com­puted from the time interval between the transmitted and reply pulses.) The DME set was more refined, weighed only nine kilograms, and had a graduated distance’indicator dial in place of the cathode-ray screen. This eliminated the confusing multiplicity of ‘blips’ that sometimes appeared on cathode-ray screens.

The single most important factor in the rapid development of DME was that it operated in the 200 megahertz band, using well-established techniques. As a result, the first working trials were possible by mid 1945. An Anson aircraft, on loan from the RAAF, was equipped with a DME set and began overflying the Radiophysics Laboratory where a ground beacon had been built. By January 1947 two commercial aircraft were carrying DME on their regular Sydney ‘ Melbourne runs. The commercial trials of DME were so successful that the Department of Civil Aviation decided in 1947 to go ahead with the design and installation of a nation-wide system. Amalgamated Wireless (Australasia) Ltd made electronic equipment valued at $2.5 million for 95 unattended, automatic ground beacons. The company also made the airborne equipment ordered by the airlines, incorporating the latest developments from the Radiophysics flight trials. In 1953, DME became operational and within four years all domestic airliners had been equipped with sets.

Australia’s choice of 200 megahertz for its system had important technical advantages: the transmissions propagated further around the curve of the Earth than microwave signals, the equipment cost was lower and the transition to transis­torized equipment was relatively easy. In America, powerful commercial-political lobbying accompanied proposals for commercial navigation systems. As a result, America’s 1 000-megahertz domestic DME network was not operating until 1962-64.

In 1956 the Division of Radiophysics began the develop­ment of even lighter and more reliable airborne DME equip­ment based on transistors instead of valves. Using a scheme devised by AWA Ltd, the number of DME channels provided by the new units was increased from 12 to 48, which the Department of Civil Aviation decided would meet all requirements in the foreseeable future.

New directions

Taffy Bowen retired as Chief of the Division in 1971 and reorganization of its activities led its new Chief, Paul Wild, (later Chairman of CSIRO) to look for a major project in the field of applied research. Once again the Division turned to civil aviation where modern needs had thrown up challenging problems to which the Division could apply the know-how gained in 25 years of pioneering research into radio astronomy. Following an approach from the Department of Civil Aviation the Division decided to become involved in the development of an international microwave approach and landing guidance system (MLS) for aircraft. CSIRO’s solution was Interscan.

Sources

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