Harry Clive Minnett 1917–2003

Written by Bruce MacA. Thomas and Brian J. Robinson.

In April 1940, Harry Minnett joined the Council for Scientific and Industrial Research (CSIR, renamed CSIRO in May 1949), soon after the establishment of the Radiophysics Laboratory for research into advanced radar systems. He remained with the organization until his retirement in 1981. Harry’s ability as a meticulous engineer with a thorough understanding of the related underlying scientific principles was recognized by his being appointed to leading roles in a number of significant projects. These were to have a long-term impact on Australian science and technology. Among the most important was his role in guiding the design of the Parkes 64-m radio telescope to successful completion, and the establishment of a world-recognized research group on antenna design to support radio telescope design and upgrades. He also had considerable impact on the construction of the 3.9-m Anglo-Australian optical telescope at Siding Spring Mountain, New South Wales, and the ‘Interscan’ aircraft Microwave Landing System being developed by the Division of Radiophysics in collaboration with industry. He was Chief of the Division from 1978 to 1981. Harry died on 20 December 2003 after a short period of illness.

Family background and education

Harry Minnett was born at Hurstville in Sydney on 12 June 1917 and lived there until he married in 1955, just prior to being posted to London in 1956. His parents were Frederick Harry Brook Minnett, a nurseryman (born in Paddington, September 1887) and Elsie May Garnsey (born in Dubbo, July 1891). Following their marriage, they established a delicatessen business at a time when Hurstville was expanding. Harry attended Hurstville Primary School and was Dux in his final year in 1929. He then attended Sydney Boys’ High School, 1930–1934. Harry had a brother Bruce who was nine years younger. At an early age Harry was captivated by technology, and at around the age of 15 built a short-wave radio set to listen to overseas stations. This more than anything is seen to have sparked the passion that marked out his future career and dominated so much of his life.1

Harry then studied science and engineering at the University of Sydney, where the Professor of Electrical Engineering was the far-seeing J. P. V. Madsen. Harry graduated in Science (Mathematics and Physics) in 1939, and in Engineering (Mechanical and Electrical) with First Class Honours in 1940.

The laboratory during the War years2

In April 1940, following graduation, Harry, along with a number of other recent graduates, joined the newly founded Radiophysics Laboratory of CSIR. The Laboratory was established in late 1939 as part of the war effort in collaboration with the UK to develop radar systems for the south-west Pacific region. Of particular importance was the considerable influence that Madsen (later Sir John) had over the period prior to and during the early years of the Laboratory.3 It would have been unforeseen at the time that the Laboratory would have such a long-term influence on Australian science and engineering research. An important factor was the hiring of excellent research staff, many of whom would eventually make their mark outside CSIRO as well as within the organization. Harry could certainly be considered as being in the latter group.

The Laboratory partially grew out of the functions of the Radio Research Board, which was established in 1927 to encourage fundamental research in radio in Australia. The Board, which was responsible to the executive Committee of CSIR, had research groups at Sydney and Melbourne Universities, with Madsen as Chairman of the Board. The expertise that existed in the Sydney group provided a nucleus of senior staff for the newly formed Radiophysics Laboratory in 1939. Unlike the operation of the Board, the work of the Laboratory was clothed in secrecy. One of the senior staff who transferred to the Laboratory was J. H. Piddington who was to have a significant influence on Harry in his radio astronomy endeavours after the war. Because of the need to rapidly expand the activities of the Laboratory, Madsen requested that external candidates be approached to join the Laboratory. One of these was an Australian, J. L. Pawsey, who had been educated at the Universities of Melbourne and Cambridge, and had been engaged in the UK on antenna problems relating to television services. In late 1939, he returned to Australia to take a leading role in the development of radar sets in the Laboratory. Pawsey was to mentor many young researchers such as Harry, and in the latter part of his career – he died in 1962 – was known as the ‘father’ of radio astronomy in Australia.

The other senior scientist who was to recognise Harry’s talents was E. G. Bowen, who in 1956 made Harry responsible for overseeing the design and implementation of the Parkes radio telescope. Bowen had been a member of R. A. Watson-Watt’s team in the Radio Division of DSIR in the UK. The group had carried out pioneering work in radio, and in 1935 had developed a system (which came to be called radar) to detect and define the location of aircraft. Bowen was initially seconded to the Radiophysics Laboratory in January 1944 for a period of two years, but appears to have been made permanent soon after, having been appointed Deputy Chief in July 1944 and then Chief in 1946.

Another member of staff appointed during the war years (1944) was D. E. Yabsley. Although initially supporting Pawsey in a research programme relating to anomalous propagation, he was later to play a significant role in reflector performance studies and upgrades for the Parkes radio telescope under Harry’s general direction.

The need to provide accommodation and research facilities for the rapidly increasing staff of the Laboratory must have put immense pressure on those responsible for its planning (the number of researchers increased from 10 to 51 over the four-year period June 1940 to 1944, the corresponding numbers for the entire Laboratory being 19 and 205 – in 1945 the total was 300!). Madsen had played a significant and active role in planning over the first two years as Chairman of the Radiophysics Advisory Board, which first met in Melbourne in 1939. The Board consisted of influential members including Sir David Rivett, F. W. G. (later Sir Frederck) White4 and Professor M. L. Oliphant. (White was appointed Chief of Division from 1942–1944, and Chairman of CSIRO from 1959–1970.) Accommodation for the Laboratory was found by utilizing part of the National Standards Laboratory (NSL) building then under construction at the University of Sydney. The first occupants (in March 1940) were in fact the staff of the Radiophysics Laboratory because of the priorities set by the war-time requirements.5 The Radiophysics Laboratory (the corresponding CSIRO division was later titled the Division of Radiophysics) was located at the NSL building until 1968 when a new facility was opened at Marsfield in the northern suburbs of Sydney.

Thus the scientific environment had been set for a relatively new and exciting area of high-priority research supported by both experienced and young outstanding researchers. It was in this environment that Harry started his career in April 1940 as an Assistant Research Officer on an annual salary of £344.6

Contributions to War-time radar research7

Harry was immediately attached to Pawsey’s radar research group, and was to play a significant role in developing radio-frequency and antenna-related technologies for radar equipment (or RDF – radio direction finding – the term that was often used at the Laboratory). He was to say much later: ‘So we had some pretty knowledgeable mentors. We knew nothing about the ultra-high-frequency radio techniques. It was all brand new. It was known only in some of the major laboratories in the world, and we had a lot to learn. Pawsey was an ideal teacher as far as I was concerned. In fact, he was for everyone.’8

Harry contributed not only to the design of radio-frequency components such as waveguides, antennas and high-isolation receive-transmit switches for very high-power operation, he also participated in the testing of the radar systems with which he was associated.

The first such antenna system was for Shore Defence (ShD) operating at a frequency of 200 MHz. This unit was intended for ‘laying’ the 9.2-inch (233 mm) guns of the Army’s coastal batteries. The antenna consisted of a 36-element broadside array with a rotating capacitor switch to scan the phase and hence the beam direction. Up to that time, two separate antennas had to be used for radar – one for the 10 kW, 1 µs pulse transmitter, and one to receive the weak reflected echo. Pawsey asked Harry to investigate the feasibility of using the same antenna system for transmitting and receiving. The new switch was incorporated into the equipment. The manufacture of forty sets commenced in late 1941 with installation at Australian ports occurring from 1942.

Harry also played a role in the next major development. The design principles for the ShD system were incorporated into the first Light-Weight Air-Warning equipment (LW/AW Mk1) of which over 200 were built for the support of Australian and US Forces in the south-west Pacific region. The equipment, of wholly Australian design, was transportable by air and readily assembled by personnel working in the field. In addition to air-warning use, later developments included other major functions including height finding (40).

In 1942–1943 Harry became involved in research involving radio-frequency techniques appropriate for air-warning radar operating at the higher, microwave frequency of 1.2 GHz. Under Pawsey’s general direction, he led a group to develop appropriate antennas and related radio-frequency components for the new system. This time the antennas used cylindrical paraboloids fed by waveguide systems. Again, one of the critical items was the receiver–transmitter switch that was successfully developed for the higher frequency. The final outcome was the highly successful high-performance Australian Light-Weight Air-Warning set (LW/AW Mk2). Although this system was later described as ‘perhaps the outstanding technical war-time achievement of the Laboratory’,9 the quantity production order of 47 units was cancelled because of the cessation of hostilities.

Over the period 1940–1946, Harry was author (or co-author) of 23 reports in the Laboratory’s Report Series, dealing with technical topics that arose during the development of radar.10 These reports were generally classified as ‘Secret’ at the time because of the nature of the work being undertaken in the Laboratory.

From June to November 1945, Harry went to the USA to investigate the development of microwave radar at major research laboratories there, including the Radiation Laboratory at MIT, the Bell Telephone Laboratories and the Naval Research Laboratory. In 1946, Harry’s technical achievements were recognized by the Radiophysics Laboratory by making him responsible for two chapters in a textbook on radar that constituted his first publications (1). In January 1946, he was reclassified to Research Officer at an annual salary of £540.

Following the war, the technology developed for radar systems, particularly the advanced research carried out for the final version of the Light-Weight Air-Warning set operating at microwave frequencies, placed Harry in a sound position to contribute to new fields of research. His first significant post-war project related to radio astronomy, a general area of research proposed by Pawsey.

Radio astronomy at microwave frequencies

In 1947, Harry teamed up with J. H. Piddington to carry out the first significant radio astronomy observations at microwave frequencies (37). This programme seems to have functioned independently of the young researchers in Pawsey’s radio astronomy group, who were concentrating on relatively low-frequency observations. One of these areas of interest related to the study of strong solar radio emissions associated with sunspots.

Piddington tended to concentrate on the theoretical aspects of the new, microwave radio astronomy programme. Harry’s main efforts were directed to developing the observing equipment and in observing, although he also participated in the analysis of the results (2–8). In CSIRO’s personal files for Harry,11 there is a letter dated 24 May 1948 from E. G. Bowen (as Chief of Division) to the CSIRO Secretary, requesting authorization for Harry to use his own car to carry out the observations: ‘I should be glad if you would authorise Mr H. C. Minnett to use his private car, which is an 8-HP Standard, for official purposes when required. As part of his work on millimetre wave propagation he is at present making measurements of the moon’s temperature at various phases and this involves his attendance at the laboratory on occasions in the early hours of the morning...’! In recognition of his contributions, Harry was promoted again to Senior Research Officer from 1 July 1948, with an annual salary of £755.

The radiometers that Harry had developed were, at that time, the most sensitive and stable in existence. He had pioneered the successful application of Dicke switching and the use of synchronous detection. These techniques, together with the locking of local oscillators to a high-Q cavity, minimized the impact of noise-level (background) drift, and hence significantly improved sensitivity. The first radiometers were manufactured for 24, 10 and 3 GHz. In a later design operating at 1.2 GHz, Harry developed an efficient rotary capacitor switch operating at 25 Hz to permit comparisons between the antenna output and the reference. The resistive reference was soon replaced by a reference antenna looking at the cold sky, thus ensuring that the signal levels from the reference antenna and the observation antenna were nearly in balance, giving much improved stability. These radiometers made possible the first systematic observations of the Moon, Sun and Galaxy in the microwave region of the spectrum.

The first observations were made in 1948 of the Moon using the 24-GHz radiometer and a 1.1-m searchlight mirror (antenna) located on the roof of the Radiophysics Laboratory building. The thermal radiation from the Moon was measured over three lunar cycles, and they found that the maximum microwave radiation was delayed 45 degrees in phase after the full moon. Harry developed a model for a uniform lunar crust, but could not match the observations. Following some earlier calculations by J. C. Jaeger (University of Tasmania) and A. Harper (CSIRO Division of Physics), Harry and Piddington modified the model to include a thin blanket of dust over the rock crust, giving the predicted observed amplitude and phase of the lunar radio emission (2). This work was directly responsible for the discovery of the dust layer on the Moon’s surface.

Observations were then made of microwave emission from the Sun and these contributed to the understanding of the chromospheric layers of the solar atmosphere, systematic measurements not having been previously carried out for frequencies above 3 GHz. The measured temperature at 24 GHz was found to be about 10,000 K (3). Measurements of the ‘quiet’ Sun were made at a frequency of 10 GHz, and the degree of enhancement with sun-spot activity was established and transient phenomena such as bursts were observed (4). Solar-eclipse observations at a frequency of 3 GHz in November 1948 revealed a small area with a temperature of 1 million degrees, and another small area emitting partially circularly polarized radiation (5). The polarization was measured using a novel rotatable screen placed in front of the antenna aperture. Piddington and Harry developed advanced theories that were far more comprehensive than earlier ones. In particular, Harry considered the magneto-ionic aspects, which led to pictorial representations to assist clarification of the behaviour of the propagating modes (8). These diagrams were used subsequently for solving magneto-ionic problems.

Harry and Piddington then turned their interests to the observation of Galactic and extra-Galactic radiation. They made measurements at 1.2 GHz using a war-time paraboloid with aperture dimensions of approximately 5 m, and at 3 GHz with a 3‑m diameter paraboloid. Measurements were made in the direction of the Galactic centre at both frequencies and, at the lower frequency, of the sources Taurus A, Centaurus A (then thought to be in our Galaxy), and the extra-Galactic source Cygnus A. In particular, the resolution of the measurement system permitted Cygnus to be resolved into a discrete source (Cygnus A) and a second, diffuse source they called Cygnus X, the spectrum of which suggested that it was thermal emission from clouds of ionized interstellar gas (6, 7).

Following their success with their microwave radio astronomy programme using sensitive receiving systems, Piddington and Harry approached Pawsey for funds to build a larger paraboloid of about 20-m diameter. Pawsey’s policy, however, was to support research programmes at relatively low frequencies. His strategy was to build relatively large telescopes in the shape of a cross consisting of arrays of individual elements. Funding had been allocated to B. Y. Mills, who was establishing a cross-style telescope operating at 86 MHz (a ‘Mills Cross’), and W. N. Christiansen, who was establishing a two-armed array at Potts Hill reservoir using small paraboloids for operation at 1.4 GHz.12 One may imagine Harry’s disappointment at not being able to continue the pioneering work he had been doing. However, several years later the tide began to turn, with Harry becoming deeply involved in the concept and design of a much larger, single-dish antenna of 64-m diameter (not 20 m!). This radio telescope would operate at microwave as well as at lower frequencies.

The radio navigation group

In 1952, Harry was appointed leader of the Microwave Navigation Group. Very little information exists on Harry’s activities in the period 1952–1954. However, existing records show that he made an experimental study in collaboration with Don Yabsley on the feasibility of long-range automatic distance measuring equipment for aircraft navigation using ionospheric propagation.13 He was also responsible for the development of microwave radar for the measurement of vehicle speed for the New South Wales Police Department. This development would be interesting to review, given the current interest in such devices; perhaps the work was done before all the underpinning technologies were available to give adequate portability?

Harry was reclassified to Principal Research Officer on 1 July 1954 at an annual salary of £1,366.

The Parkes 64-m radio telescope

Although serious research in radio astronomy commenced at the Radiophysics Laboratory in 1945 under Pawsey, it was not long before, in the early 1950s, there was a major shift in emphasis in instrumentation. The Chief, E. G. Bowen, had up to that time taken the lead in cloud physics and associated rain-making research, leaving decisions about radio astronomy programmes to Pawsey. However, Bowen became increasingly concerned at overseas developments, particularly in the UK at Jodrell Bank (near Manchester), where a large single dish of 76-m diameter was being planned for operation at frequencies up to 400 MHz. Pawsey, on the other hand, had favoured interferometer arrays using a large number of small antennas to achieve higher resolutions. Bowen considered that the era of improvised engineering was drawing to a close and that the era of ‘big science’ was soon to begin. Following extensive lobbying in the US (which up to that period had no serious interests in radio astronomy), Bowen secured considerable funding from the Carnegie Corporation in 1954. This was followed in 1955 by a grant from the Rockefeller Foundation, and these generous donations were matched by the Australian Government. During this period, Bowen had had considerable political support from White, by now CSIRO’s Chief Executive Officer. In 1955, it was decided to proceed with a design study.14 Although this decision was quite contentious among the astronomy community at the time, it is now generally agreed that it was indeed the correct decision.15 It is also recognized that without Bowen’s vision, drive and determination, the Parkes radio telescope and associated observatory would not have been possible (34). However, behind the success of the design and its long service as a state-of-the-art instrument, Harry’s contributions as a meticulous, thoughtful and knowledgeable engineer must also be recognized as a key factor leading to its success.

Work on a proposal for a Giant Radio Telescope (GRT) – as it was then called – commenced in 1954 and it was finally issued on 23 November 1955 by the Radiophysics Laboratory over the signatures of Bowen and Pawsey. Harry had written the ‘Technical Considerations’ section and associated engineering specifications, and had contributed to the ‘Astronomical Considerations’ in association with Mills.16 The lowest maximum operating frequency was specified as 1.4 GHz (corresponding to the hydrogen-line wavelength of 21 cm) with a desired diameter of 76 m (to match the proposed Jodrell Bank antenna). The beamwidth at 1.4 GHz would be 12 minutes of arc, and the pointing accuracy, one minute of arc. To keep the cost within budget, the angular coverage was specified as ‘from the vertical down to a zenith angle of 60 degrees at any azimuth’. This would allow the beam to reach the South Celestial Pole and provide a good overlap with the sky coverage of radio telescopes in the northern hemisphere.

In 1955, Bowen appointed Harry to represent CSIRO’s interests and to participate in the design study for the radio telescope that had been contracted to Freeman Fox and Partners in the UK. Prior to leaving for England, Harry married Margaret (Margo) Betty Rooney in October 1955. At Freeman Fox he was the CSIRO Consultant and Liaison Officer, with responsibility for the radio aspects of the design.

One of the most critical engineering design issues was the type of mount to be used, particularly given the antenna size and high-frequency performance desired. A number of alternatives had been proposed including the more conventional equatorial mount and the altazimuth mount. This was a key issue that Harry obviously saw as a challenge, despite not previously having expertise in the area (35).

The altazimuth mount was favoured by the structural engineers, whereas the scientific community doubted the feasibility of a servo system that could drive the massive mount so that it would respond to the commands of the coordinate converter with the required accuracy and stability. The following summarizes Harry’s major contribution to the design of the Parkes antenna and the resulting influence on the design of large radio telescope antennas generally (35).17

The story commences when Pawsey visited England and made contact with Barnes Wallis at Vickers Armstrong Aircraft Co. Wallis was renowned for his inventions during the Second World War. He now proposed the use of an altazimuth mount for the new telescope with the pointing of its beam locked by a servo system to a small equatorial (reference) telescope – the ‘Master Equatorial’.

Freeman, Fox and Partners did not have ‘in house’ expertise to investigate the master equatorial proposal and the associated servo control for the large telescope, so Harry worked closely on the evolution of a design with Sir Howard Grubb Parsons Ltd in Newcastle-on-Tyne. As Harry was later to describe that project:

In the case of the problem of servo driving the altazimuth mounting, I proposed a design philosophy which was the opposite of that which had been pursued in the US. There a wide band servo system had been investigated in an unsuccessful attempt to correct for the deflections of the rather flexible telescope structures in gusty wind conditions. Instead I proposed that the stiffness of the mounting and drive systems should be of a very high order to be determined solely by dynamic servo considerations rather than static load calculations or economics. This pushed the spectrum of structural resonances as high as possible. Secondly, I proposed that the servo should have a very high gain (static stiffness) but nevertheless a low natural frequency well below the lowest structural resonance. These conflicting requirements could be met by deliberately designing for high drive inertia by means of very high gear ratios and if necessary motor flywheels. The reflected inertia then greatly exceeds the disk inertia and the drive system behaves like a massive flywheel rotating at sidereal rate and unresponsive to even violent wind gusts.

This approach was especially suited to the astronomical requirements and could be demonstrated by some fairly basic sums but aroused some strong opposition initially from within the Parsons’ organisation. Initially I supported the proposal by a very detailed analysis18 which was confirmed by servo consultants at Imperial College and then by the servo specialists at Metropolitan Vickers (now AEI) in Manchester. At the end of the study, I returned to Australia with the Freeman Fox report which I had helped to write. My servo study was a key item in gaining Australian acceptance for the altazimuth mounting. This was finally approved in spite of the fact that the US [for their proposed 42 m diameter antenna] had opted for an equatorial mounting substantially because of opposition to servo control. Completion of the US telescope was delayed several years after that of the Parkes instrument because of the very great mechanical and structural problems in the equatorial mounting and these were only rectified at considerable cost.

Following the evaluation of the Freeman Fox design report in Sydney over the period December 1957 to March 1958, Harry returned to London at the request of Freeman Fox to assist with the detailed design and contracting of the telescope. He continued to monitor the servo development at Metropolitan Vickers and prepared the technical specifications for the complete control system. He also took part in the evaluation of facilities and personnel of potential US, British and German contractors.

The contract called for the construction of a 64-m antenna to operate at frequencies up to 3 GHz (double the original 1.5 GHz). The diameter and upper frequency limit were a compromise based on cost and revised astronomical requirements. A contract was let to Maschinfabrik Augsberg Nurnberg (MAN), with Askania-Werke of Berlin and Metropolitan Vickers as sub-contractors for the master-equatorial and servo-drive systems, respectively.

On returning to Sydney in 1961, Harry interacted closely with the Freeman Fox resident engineer for a period of nearly two years and conducted acceptance testing. The telescope was officially opened by the Governor-General, Lord De L’Isle, on 31 October 1961 – the date being set by the Commonwealth Government. In the same year Bowen attracted J. G. Bolton back from the Owens Valley Radio Observatory in California to be Director of the Parkes Observatory. With strong support from Bowen, Bolton lived in Parkes and took full responsibility for bringing the telescope into operation for radio astronomy observations in 1962.

Harry Minnett on the Parkes radio telescope, May 1964. [Courtesy CSIRO Australia Telescope National Facility.]

At a conference held in Parkes in 1991 to celebrate the thirtieth birthday of the radio telescope, R. H. Frater, a past Chief of Division, stated: ‘This telescope was Taffy Bowen’s vision, a vision taken up enthusiastically by Ian Clunies Ross [Chairman of CSIRO] and Fred White, carried to its initial fulfilment by the efforts of people like Harry Minnett working with Freeman Fox and Partners, and then carried to fame by John Bolton...’.19

Let us now return to 1962. Bowen was obviously very impressed with Harry’s efforts in bringing the design and overview of the construction of the radio telescope to a successful conclusion. On 23 February 1962, he wrote to F. W. G. White (now Chairman of CSIRO) seeking Harry’s immediate promotion to Senior Principal Research Officer:

In this letter I want to recommend the immediate promotion of Harry Minnett to the position of SPRO at the Radiophysics Laboratory...

Although the telescope has not yet been officially handed over to CSIRO, the outstanding success of the instrument is generally recognised. A large measure of the responsibility for the detailed planning of the instrument and, in particular, for the very successful servo-drive system, is directly attributable to the excellent work of Harry Minnett who, as you know, has spent the major part of his time on this device for the past five years.

A reason which weighed heavily with the Executive for not giving Harry Minnett promotion last July was the fact that he did not have recent publications to his credit. As I mentioned several times, this is a point of view which frequently leads in CSIRO to unfair discrimination against people who do the real hard work in some of the larger projects. I believe that this is certainly true in Harry Minnett’s case and that the best monument to his work of the past few years is likely to be the instrument itself and not any papers which he may subsequently write about it.

Finally, it appears that the completion of the telescope is already bringing considerable credit to CSIRO in a variety of forms including favourable notice from other bodies like NASA. The success of this project is also likely to have a profound influence on any submissions we might make to some of the benevolent foundations. It is only right that Harry Minnett should receive a small share of the credit for this.

Bowen received immediate action from this interesting letter, with Harry’s promotion back-dated to 1 July 1961. His new salary was £3,528 p.a. (The approval was actually dated one day prior to Bowen’s letter, so presumably Bowen must have obtained prior verbal approval from the Executive!)

Harry’s excellent reputation had obviously travelled far and wide. His advice was sought by the Canadian National Research Council, which modelled a new 45-m radio telescope for Algonquin Park on the Parkes design. Harry also visited Pasadena twice in 1962 as consultant on the feasibility studies for three second-generation tracking telescopes for the Deep Space Network of NASA. NASA was greatly impressed by the performance achieved in the Parkes radio telescope, compared with any US designs. The master equatorial concept and Harry’s servo design philosophy were to be incorporated in these telescopes. The antennas were to be 64-m in diameter, the same as the Parkes radio telescope, but the elevation range was extended down to the horizon to meet the demands of tracking Earth-orbiting satellites.

In 1962 the Division of Radiophysics received a grant from NASA to carry out engineering measurements on the Parkes dish. Harry led the technical programmes to supply performance data to the Jet Propulsion Laboratory in California, the technical consultants to NASA in the US. The year 1962 could thus be considered the date when Harry established the Antenna Group (then called ‘Aerial Group’) within the Division of Radiophysics. This group was to expand over the years to become a world-recognized centre of antenna research and development. In fact the research function still exists, albeit in a different form so as to participate in CSIRO’s industrial technological research programmes.

In March 1965, Harry moved into his new home at 88 Neerim Road, Castlecove, in Sydney. The house had been designed in association with his brother Bruce, an architect, and Harry skilfully kept a close eye on its construction. Harry and Margo had two children: Adam John (born 1964), and Kate Lucinda (born 1967). Margo, who was ten years younger than Harry, died in 1992 following a prolonged illness.

The Antenna Group at Radiophysics

From 1962, Harry’s initial interest centred on satisfying the requirements of the NASA contract, which required the provision of regular reports.20 One aspect of the contract was the supply of engineering data to NASA on the performance of the Parkes antenna. In addition Harry, with the support of D. Cole, carried out tracking measurements for NASA of the Mariner II spacecraft on its mission to Venus (1962) and of the Mariner IV spacecraft on its mission to Mars (1964–1965). (Further tracking of NASA’s spacecraft under separate contracts were to be made at Parkes in 1969 (Apollo 11, made famous in the movie The Dish), 1986 and 1989 (Voyager II), 1996–1997 (Galileo) and 2003–2004 (Mars tracks). The earlier measurements were used by NASA to help justify the design and building of the three 64-m antennas for their Deep Space Network.

Reflector performance studies and surface upgrades

The first major long-term research project of the Antenna Group under Harry’s direction involved Don Yabsley with the support of the CSIRO Division of Applied Physics (M. J. Puttock and K. J. Loughry). This project required the development of precision instrumentation to enable structural and reflector panel deformations to be determined under various gravitational and wind loads. In addition, the Civil Engineering Department of the University of Sydney participated in vibration tests and analyses.

A semi-automatic rapid survey camera was developed that could photograph nearly 700 small targets on the dish surface in two eight-hour night sessions (18). Harry and Yabsley made periodic surveys with the camera and arrived at a thorough understanding of the deflection of the dish surface and support structure. The ‘best-fit’ paraboloids were determined and compared with observations of aperture efficiency. They showed (22) that it was possible to improve the performance considerably by readjusting the entire dish surface so that the optimum shape occurred midway in the elevation range (55 degrees) rather than at the zenith (where the initial surface adjustment had been made). The surface was accordingly adjusted in late 1965, giving significantly improved performance across the elevation coverage of the antenna.

The survey measurements also demonstrated conclusively that the fabrication accuracy of the reflecting panels, and not the gravitational distortions of the support structure, was the factor limiting the short-wavelength performance of the dish. Harry instigated a programme to develop improved reflector panels using perforated aluminium sheet on a shaped aluminium frame. Yabsley was responsible for this programme with the support of Divisional structural engineers. The reduced weight of the new panels was traded off against increased wind loading due to the smaller holes in the perforated aluminium panels (the reduced ‘open’ nature of the aluminium surface was necessary to give improved reflection at higher frequencies compared with the original wire-mesh panels). Lift and drag measurements were made on aluminium panels in the wind-tunnel at the University of Sydney. The new, low-cost panels were initially installed on the Parkes antenna out to a diameter of 37 m, followed soon after by an increase to 44-m diameter.21 The highest operating frequency of the telescope was increased from 5 GHz to approximately 24 GHz across the upgraded section of antenna surface. Radio astronomers were immediately able to observe emission from interstellar water vapour molecules at 22 GHz, which had just been discovered by C. H. Townes and collaborators in California (25).

In 1972 Harry proposed that the inner part of the Parkes antenna, a welded solid-steel surface 16.5 m in diameter, could be improved. Yabsley made careful measurements of this surface with the survey camera and a precision surface of solid aluminium panels was attached to a network of steel studs welded to the original steel. Each stud was individually fitted with a spacer to correct for the measured surface error at that point. This surface was then used to observe spectral lines of complex interstellar molecules at frequencies up to 43 GHz.22

More recent upgrades of the radio telescope have been made. A major upgrade was made in 1995 when the original focus cabin was replaced by a larger structure to permit a number of alternative receivers to be brought on-line in a matter of minutes.23 Of note was the use of radio holographic techniques to rapidly determine the reflector deformations;24 this technique replaced the need to use the original mechanical survey equipment developed in the early 1960s. In 2003, the diameter of high-precision perforated aluminium panels was increased from 44 m to 54 m, thus further improving the overall efficiency at higher frequencies. (These upgrades were partially funded by NASA as part of contracts to supply tracking services for the Galileo and Mars projects.)

The ‘design life’ for the Parkes radio telescope was 25 years. Now, 43 years later, through the ability to perform upgrades on the antenna, the telescope continues to make a major contribution to world astronomy. This reflects the remarkable underlying design of the telescope, its upgraded precision surface and the servo drive and control system. Its sister NASA antennas at Goldstone, Tidbinbilla (Canberra) and Madrid, now extended from 64- to 70-m diameter, continue to be vital for the exploration of the solar system.

However, the 100-m NRAO GBT (‘Green Bank Telescope’) nearing completion in West Virginia may soon threaten the continuing dominance of the Parkes radio telescope. The GBT will use off-set geometry to eliminate blockage of the focus-cabin, and its designed capability of 100 GHz will be achieved through automated surface adjustment.

High-performance feed research

During the design stage for the Parkes antenna, the Division had carried out a study of appropriate prime-focus feeds using then-current technology. The study concentrated on low-frequency (less than 1.5 GHz) elemental (dipole) feeds optimized to give acceptable feed radiation pattern symmetry and overall antenna efficiency. A feed consisting of parallel dipoles situated over a metallic ground-plane was proposed; this design was an important factor in defining the focal length-to-diameter ratio (f/D) of the antenna. It was also recognized that horns consisting of a rectangular aperture could be designed for frequencies above about 1.4 GHz.

Harry considered that the antenna efficiency using such basic feeds represented a considerable waste in effective collecting area of the antenna, and hence a sub-optimal cost per unit area. To arrive at a solution, he considered that if the received electromagnetic fields could be determined accurately across the focal plane of the antenna, then an optimum feed would exactly ‘match’ these fields and hence absorb the energy incident on the aperture of an ideal feed. Increased antenna efficiency would occur if the diameter of the ideal feed was increased to absorb more energy. Also, he deduced that if the field match across the focal plane were exact, the polarization purity would not be contaminated.

To support these fundamental ideas, Harry commenced a thorough and meticulous theoretical study in late 1963.25 (Presumably Harry had been looking forward to some challenging electromagnetic theory to work on to soothe his mind over the Christmas–New Year break!) The approach that he used entailed determining the complex (vector) fields in the focal region of the Parkes antenna assuming a plane wave from a distant point in space incident on the antenna aperture. (With a short f/D of 0.41 there is considerable ‘distortion’ of the focal plane fields compared with the long f/D case.)

Interestingly, this significant study showed that the field structure, although complex, led to identical electric (E) and magnetic (H) fields, although rotated 90o relative to each other. The two field types were also related through the free-space impedance (377 ohms). Harry called the fields ‘hybrid’ because they were equivalent to in-phase (locked) Transverse Magnetic (TM) and Transverse Electric (TE) fields characteristic of unbounded circular waveguides. Also, later calculations showed that the power flow across the focal plane was symmetric, although the field amplitudes were not. A major question at the time was how these hybrid fields could be bounded so that the energy would be absorbed in the focal plane and passed to a low-noise receiving system. Finally, Harry’s analysis showed that the optimum guiding surface might possibly be approximated by a circular waveguide with internal corrugations, although this still had to be verified. This would certainly be a break from tradition, where only waveguides with a smooth metal surface had been used.

To assist these studies and to extend the initial findings, one of us (BMT) joined CSIRO in mid-1964, having just completed a PhD at the University of Melbourne. In addition to implementing computer studies to enable the characteristics of the hybrid fields and their optimization to improve the efficiency and polarization characteristics of the Parkes antenna, I embarked on an experimental programme to support the theoretical studies. These two aspects of the research programme verified that circumferentially corrugated cylindrical waveguide structures would give the idealized radiation pattern symmetry and pure polarization characteristics, and hence were suitable for use as high-performance feeds.26 This work was initially reported to JPL27 and in the open literature soon afterwards (15, 16, 20). The performance of a feed supporting one hybrid mode was initially tested on the Parkes radio telescope, followed soon after by a feed capable of propagating two hybrid modes to give increased antenna aperture efficiency. This latter feed also reduced the spill-over past the reflector edge. A review paper describing the early period of research at CSIRO and placing it in the context of the world-wide research effort was subsequently published28. This research programme continued to flourish, and further researchers joined this team within the Antenna Group: T. B. Vu in 1966, D. N. Cooper in 1968 and G. L. James in 1976.

The availability of feed systems that were polarization-pure was to have a significant impact on satellite communication systems generally by enabling the overall efficiency to be doubled through the implementation of ‘frequency re-use’ (the use of orthogonally polarized channels). The research programmes within the Antenna Group were soon to provide input into the Division’s support of Australian satellite communications companies and the Department of Defence, including the supporting engineering and manufacturing industries. The first such interaction commenced in 1978 for the upgrade of Australian earth-station antennas for frequency re-use. This was soon followed by the provision of antenna expertise to support Australian industry in the design and manufacture of satellite earth-station antennas for Australia and the Pacific region. Later, the combined expertise of the CSIRO researchers and Australian industry led to the successful design and construction of the seven Australian-built 22-m radio telescopes for the Australia Telescope array. Six of these antennas are located at Narrabri, New South Wales.

Although Harry was not responsible for these projects, his early influence in developing appropriate research strategies laid a firm foundation for future success.

The Anglo-Australian optical telescope project

An Anglo-Australian Joint Policy Committee (JPC) recommended that the UK and Australia jointly fund the construction of a 3.9-m optical telescope in Australia, to be called the Anglo-Australian Telescope (AAT). The project office for the AAT was established in Canberra in 1967.

In November 1967, Harry, having gained extensive experience with the design of the Parkes radio telescope, became a consultant, together with R. L. Ford of the Royal Radar Establishment (Malvern), for the design of the drive and control system for the AAT. It was initially intended to follow well-established design concepts for the telescope, but Harry found that the requirements for the drive and control system were initially lacking. He also considered that optical telescope design had not kept pace with the opportunities that could be provided by technological advances. As Harry related: ‘together we visited the major astronomy centres in Britain and listened to the conflicting and often discouraging requirements of the optical observers. I persuaded the Science Research Council that Ford should accompany me to Kitt Peak where we found a proposal for a digital servo drive to the traditional worm gear system.’

Harry became convinced that the only way to make a major advance in optical telescope drive systems was to eliminate the inefficient worm gears from the servo loop, together with the reverse-torque spur gear system that had gradually evolved for anti-backlash purposes. His proposal29 was to replace these with a precision spur-gear driven by a balanced pair of motors and pinions in the push-pull anti-backlash arrangement that had become common in radio telescopes. Harry’s experience with the design of the Parkes servo system also suggested that the struts connecting the horseshoe structure to the north-end bearing were too flexible and would lead to a low-resonant frequency. The AAT strut structure was completely redesigned for greater rigidity by consultants in Canada.

Harry and Ford recommended to the JPC that the AAT should use a photo-electric guiding system integral with the telescope to relieve the astronomer of this traditional chore. They also recommended a modified digital on-line computer for automatic setting, correction of systematic errors, monitoring and data logging. As Harry stated:

All these changes represented a major rethink in optical telescope drive and control practice and in such a large project could only be advocated after a good deal of anxious soul searching. A great amount of effort by myself and ultimately by many others was needed with the gearing manufacturers and the Japanese drive and control contractors to achieve the high precision required.

Mike Jeffery, the Project Manager for the AAT, died suddenly in September 1969 and Harry was seconded to the JPC as Project Manager. He was responsible for supervising all aspects of the project design and construction, and contracts with local and overseas contractors. This included the optical structure, mechanical and electrical design and manufacturing work on the telescope, its building together with ancillary equipment, and the civil works on Siding Spring Mountain, New South Wales, that were carried out by MacDonald, Wagner and Priddle Pty Ltd. Harry travelled to England and the USA in April–May 1969 and in July 1970. When a new Project Manager took up duty in the last half of 1970, Harry overlapped as an adviser for a further year. He then returned to his consulting role on the drive and control system.

The AAT was, at that time, the largest scientific project undertaken in Australia. Its ease of use and high level of performance put British and Australian astronomers into the forefront in many areas of astronomy. It contrasted very much with the performance of a telescope of similar size built in Chile by the European Southern Observatory Consortium. Harry wrote of the AAT: ‘Its design and construction involved almost all branches of engineering and at crucial points in its evolution, I believe I helped to shape the outcome.’

Harry had, in reality, contributed enormously to the design and construction of both the Parkes radio telescope and the Anglo-Australian optical telescope. These two telescopes were vital steps for Australian astronomy. Both telescopes are still, in 2005, contributing to leading-edge astronomical observations.

Based primarily on his contributions to the two astronomical instruments, Harry was promoted to Chief Research Scientist Grade 1 from 1 July 1971 at an annual salary of $15,370. Interestingly, the recommendation was partly based on a new project that he had commenced: the design for a 30-m mm-wave radio telescope.

Harry was awarded an OBE in the New Year’s Honours List for 1972. The award was in recognition of his services to the astronomical community over a period of many years, particularly his contributions to the Parkes 64-m radio telescope and the Anglo-Australian 3.9-m optical telescope projects.

In early 1972, the new Chief, J. P. Wild, recommended that Harry be appointed Assistant Chief of the Division of Radiophysics. In Wild’s recommendation to the CSIRO Executive, he said (in part): ‘On a personal basis, his maturity of judgement, sound approach and wise counsel on difficult problems arouse confidence and respect in all who have occasion to seek his advice. He also has the personality, diplomatic manner and tact which has enabled him always to enlist the wholehearted cooperation and support of his colleagues in any venture for which he assumes responsibility.’

Interscan – a precision microwave landing system30

When Wild was appointed Chief in 1971, he took the opportunity to participate in an international competition by the International Civil Aviation Organisation (ICAO) to design and construct a microwave landing system (MLS) for aircraft. Wild assembled a small team to propose and develop a new system. The project had financial support from the Commonwealth Department of Transport. Other competing groups were three large teams in the USA and groups from the UK, France and Germany. For decades the aircraft approach system used world-wide had been in the VHF frequency band. The ICAO required a much more precise system operating near 5 GHz. The system was required to define appropriate landing paths that could also automatically land the aircraft. If landing was aborted, it would need to guide an aircraft away safely.

Wild, who had an outstanding grip on the basic principles of physics, was quick to come up with a time-reference scanning-beam system as a possible solution to the MLS; this was called ‘Interscan’. In 1972, he appointed Harry as Engineering Director for the Interscan MLS project. Wild and Harry had complementary expertise and both had enthusiasm.

Harry’s role as Engineering Director continued through the feasibility studies in 1972, and during the design definition phase in 1973 when the Australian company AWA was awarded a contract from the Department of Transport to engineer and manufacture a system for flight trials at Tullamarine airport, Melbourne.

Harry’s antenna expertise was called on particularly for the conceptual and design phases. One of the antennas was an electronically scanned torus reflector. He wrote: ‘The vertical profile of an azimuth reflector was shaped by synthesis techniques to produce a very sharp cut-off along the ground and an optimum shape at other vertical angles. The technology developed for the new surface of the Parkes radio telescope was directly applicable to all the reflector antennas for Interscan.’

During 1974 Harry travelled widely to advocate the Interscan MLS system. At the end of that year, the US Government conducted a four-month evaluation of the British doppler system and the Australian Interscan system. Through negotiation, the US would collaborate with the country that they saw as having the best system. This would then undergo further development prior to submission to ICAO. The US decided in favour of the Australian time-reference scanning-beam technique, giving the US and Australia a common technical platform in preparation for the final submissions to ICAO.

As part of the programme to improve the Interscan system, Harry proposed a concept for correcting the cylindrical aberration of the torus reflector. The correction was implemented in the electronic modulation and switching system that produced the quasi-continuous beam scan. This reduced the overall size of the antenna by almost one-half.

The Department of Transport entered the Interscan MLS system into the international competition conducted by ICAO, and in 1976 it was selected as the winning entry. Unfortunately international politics was later to plague the project, resulting in a reduced role for Australia. One significant spin-off was the formation of a company to commercialize aspects of the Interscan MLS sytem. This Australian company was called Interscan (Australia) Pty Ltd but was later renamed Interscan International to promote the sale of its products, including phased-array antennas, on the international market.

Harry’s technical contributions in the open literature on Interscan consist of two submitted patents31 and three papers (27, 28, 30).

In addition to Harry’s responsibilities in connection with the Interscan project, he also had oversight, in the period 1970–1976, of the 4-m diameter mm-wavelength radio telescope that had been purchased for operation at Marsfield to develop expertise in mm-wave astronomy.

Appointment as Chief of Division

In September 1978, Harry was appointed Chief of the Division of Radiophysics for a period of three years, after which he would reach retirement age.

In addition to his normal duties as Chief, Harry played a major role in guiding a preliminary proposal for the next-generation radio telescope then called the ‘Australian Synthesis Telescope’.32 He was also involved in the search for a new Chief who would not only carry forward the concept of the new telescope, its implementation and funding, but would take a lead in initiating new research directions for supporting Australian industry. (The position was filled by R. H. Frater.)

Harry retired on 26 June 1981. He was appointed a Senior Fellow in the Division of Radiophysics until 23 October 1981, when he was made an Honorary Fellow until 30 June 1982.

In retirement

In retirement, Harry was always busy, whether in undertaking tasks for industry or professional associations, or in connection with personal activities such as investigating family history. We will now briefly consider some of the professional activities.

Interscan Australia

In 1982, Harry became consultant to Interscan (Australia) Pty Ltd at the invitation of the Managing Director (J. Drennan). The Interscan (Australia) engineering team had just spent two years in Kansas City, USA, working with Wilcox Electric developing an MLS using phased-array antennas, which had displaced the original CSIRO reflector antennas. This joint effort was aimed at satisfying the Federal Aviation Admisistration (FAA) specifications followed by submission of a formal response to the FAA’s Request for Tender. It was then a matter of urgent commercial necessity for Interscan to obtain other engineering work to support the team while the tender was being evaluated. As it later transpired, Interscan (Australia) was unsuccessful in being awarded a contract and the need for new contracts became more pressing.

Harry’s task was to search for suitable opportunities. His first success came with a proposal he had written for the Australian Department of Civil Aviation (DCA) for a long-range VOR (Very-high-frequency Omni-Range) antenna.33 By arrangement, the design was based on research that Godfrey Lucas of the University of Sydney had previously undertaken. Harry did some extensive analysis of the related cavity-backed slot radiators and then further optimized the design. This was the first task outside MLS to be undertaken by Interscan (Australia). Some twenty systems were subsequently sold to the DCA.34

An additional task undertaken by Harry was the design of a precision ground-reflection antenna range35 using the old landing strip at ‘Fleurs’, Badgery’s Creek, New South Wales. This range was intended to be used for production testing of MLS antennas. Although Interscan (Australia) was unsuccessful in its bid to the FAA for MLS, it was successful in selling the systems in Spain, China and Taiwan, and in the USA to non-FAA customers. The units were tested on the range to a precision of 0.001 degrees in guidance accuracy.

Another project in which Harry was involved, this time in association with B. B. Jones, was the conceptual design of an electronically scanned TACAN (Tactical Air Navigation) antenna for use by the Royal Australian Air Force. This antenna consisted of a cylindrical array fed from a 36-way Butler Matrix using electronic phase shifters. It was a very successful project both commercially and technically.

Harry became Deputy Chief Executive of Interscan International in 1985. He retired from that position in July 1986 at age 69. As one of his colleagues (Jones) said: ‘Harry’s work was characterized by extreme thoroughness and attention to detail. He had a deep technical insight which he communicated with his work colleagues in a marvellously honest and intuitive way.’

Supporting industry and professional organisations

Harry was involved in supporting the telecommunications industry through consultancies with the Australian Telecommunication and Electronics Research Board (1986–1987),36 and as an adjudicator in the selection of candidates for the annual Overseas Telecommunication Corporation Student Awards (1988–1992).

Harry in the 1990s was invited to contribute to the preparation of three biographical memoirs for the Australian Academy of Science: E. G. Bowen (32), F. W. G. White (36) and J. H. Piddington (37). In 1964, he had also provided input to A. C. B. (Sir Bernard) Lovell for the biographical memoir on J. L. Pawsey published by the Royal Society of London.37 His increasing interest in the early 1990s for recording history relating to radar developments involving the Radiophysics Laboratory during the Second World War led initially to several comunications38 and a paper in the popular telecommunications press (33). In 1999, his natural aptitude for research led to three highly significant contributions to the above subject and these formed part of a special issue of Historical Records of Australian Science.39 The topics addressed by Harry included an overview of the contributions made by the Radiophysics Laboratory (38), a critical study of the impact of the programme’s technical and man-power support during the bombing of Darwin in 1942 (39), and a detailed account of the development of the Light-weight Air-warning equipment (40).

Harry was frequently invited to speak at professional conferences. Two such addresses that were subsequently published were at the invitation of the Division of Radiophysics (34, 35). His final major presentation was at the 25th General Assembly of the International Astronomical Union held in Sydney in July 2003;40 it was titled ‘The early developments of Australian radio astronomy’.

Harry as a person – at work and at home

As we have seen, Harry was very thorough in every task that he undertook and was analytically precise. He would invariably follow the subject through with extreme attention to detail, often to the frustration of those working around him. Of course, this was to stand him in good stead when the need arose. Harry was a person of the highest integrity, had professional competence of a high order in many different fields of engineering and science, and made outstanding contributions to science through engineering. Harry was never the ‘centre of attention’ at staff parties, preferring to discuss engineering in the corner of the room with colleagues. He had very little time for ‘small talk’.

Harry’s son Adam related some of his father’s strengths and weaknesses in a eulogy at Harry’s funeral (paraphrased):

In retirement Harry continued, and indeed expanded his professional associations, performed consulting work and yet still had the energy to deliver a keynote address to the International Astronomical Union at Darling harbour earlier in 2003 ... So what characterized the man behind these impressive achievements? Harry was notable for his ability to focus, his unswerving attention to detail, his patience, curiosity, professionalism and stamina. He was fully absorbed by his work, as can happen when a passion dovetails with a career and natural talent. He wasn’t a religious man – his philosophy was defined more by what he didn’t believe in. He was well read and maintained a keen interest and indeed opinions on a broad range of current affairs. The study at home was Harry’s world, often emerging for meals and returning not long after ... In 1955 Harry had married Margo who was the eldest in a large Catholic family. Without her support and dedication in caring for Harry and the two children Adam and Kate, there is no doubt that his career would have suffered. Margo’s death in 1992 hit him very hard. To his credit, after a year or so, he picked himself up again and his intellectual appetite sustained him, whether it was contributing to historical books and papers, helping with obituaries, or researching the family tree in considerable detail ... Harry was a true gentleman. He was also a private man. He was independent, but loyal to his professional network and to those close to him.

Awards, honours and fellowships

  • Order of the British Empire – Officer (Civil), for services to science (1972).
  • Fellow, Australian Academy of Science (1976).
  • Fellow, Australian Academy of Technological Sciences and Engineering (1979).
  • Fellow, Institution of Engineers Australia (1980).
  • Australian Medal of the Guild of Air Pilots and Air Navigators (1982).
  • Centenary Medal for service to Australian society and to the science of radiophysics (2003).

About this memoir

This memoir was originally published in Historical Records of Australian Science, vol.16, no.2, 2005. It was written by:

  • Bruce MacA. Thomas, Formerly Chief Research Scientist, CSIRO Australia Telescope National Facility, Sydney, Australia. (Corresponding author)
  • Brian J. Robinson, Formerly Research Fellow, CSIRO Australia Telescope National Facility, Sydney, Australia.

Numbers in brackets refer to the bibliography.

Acknowledgments

The assistance and contributions of the following are gratefully acknowledged: Adam and Kate Minnett, Dr Bevan Jones (regarding Interscan [Australia]), Roger Madsen (for loan of his grandfather’s documentation) and reviewers for their helpful comments on the draft.

Notes and references

  1. Information provided by Adam and Kate Minnett, including: ‘The Eulogy of Harry Minnett’, by Adam Minnett, 24 December 2003. We have also drawn on unpublished information prepared by Harry Minnett and others on his career: (a) Minnett, H.C., ‘Notes on engineering work’, 11 February 1976; (b) addendum to (a): Wild, J.P., ‘H.C. Minnett: description of scientific and engineering work’, 21 January 1975; (c) Minnett, H.C., ‘Curriculum Vitae’, including a list of publications, April 1997.
  2. Evans, W.F., History of the Radiophysics Advisory Board, 1939–1945 (Melbourne: CSIRO, 1970), especially Annexure 15.
  3. White, F.W.G., ‘John Percival Vissing Madsen, 1879–1969’, Records of the Australian Academy of Science, 2 (pt. 1) (1970), 51–65.
  4. Minnett, H.C., and Robertson, Sir Rutherford, ‘Frederick William George White, 1905–1994’, Historical Records of Australian Science, 11 (pt. 2) (1996), 239–258.
  5. Wright, J.F.H., Measurement in Australia, 1938–1988: A History of Australia’s National Standards Laboratory (Lindfield, NSW: CSIRO Division of Applied Physics, 1988), pp. 118–120. See also pp. 94–95 relating to the support of the National Standards Laboratory for the reflector measurement programme for the Parkes radio telescope upgrade project.
  6. Personal files relating to H.C. Minnett, CSIRO Division of Radiophysics, Marsfield (archived information).
  7. Evans, History of the Radiophysics Advisory Board (op. cit. note 2); MacLeod, R. (Ed.), ‘The Boffins of Botany Bay: Radar at the University of Sydney, 1939–45’, special thematic section of Historical Records of Australian Science, 12 (pt. 4) (1999), 411–493.
  8. Quotation transcribed by B.J. Robinson from an unidentified source.
  9. Evans, History of the Radiophysics Advisory Board, Annexure 15.
  10. Information about Harry’s war-time work in the Laboratory has been drawn from the following sources in addition to the works already cited in notes 2 and 7 above: (a) technical reports written by Harry (some in collaboration with colleagues) now in the library of the Radiophysics Laboratory, Marsfield; (b) unpublished letters written by Harry to E. Simmonds, historian of the Radar Air Defence Branch of RAAF Association, NSW Division, ‘Birth of Light-Weight Air Warning (LW/AW) Array’ (7 March 1994) and ‘Involvement of Radiophysics Laboratory staff in establishing Air-Warning Stations’ (12 July 1994).
  11. See note 6.
  12. Bird, T.S., ‘Going strong after 50 Years: Antenna R and D at the CSIRO Division of Radiophysics’, IEEE Antennas and Propagation Magazine, 35 (April 1993), 39–48. See also Robertson, P., Beyond Southern Skies: Radio Astronomy and the Parkes Telescope (Cambridge: Cambridge University Press, 1992), and Sullivan, W.T., III (Ed.), The Early Years of Radio Astronomy (Cambridge: Cambridge University Press, 1984), especially the section relating to Australia, pp. 83–190.
  13. Minnett, H.C. and Yabsley, D.E., ‘Methods of distance measurement for the navigation of long-range aircraft’, Radiophysics Laboratory Report No. RPL83, August 1953.
  14. See the biographical memoirs of White and Bowen, jointly authored by Harry (items 32 and 36 in his bibliography).
  15. Goddard, D.E. and Milne, D.K. (Eds), Parkes: Thirty Years of Radio Astronomy (Melbourne: CSIRO Publishing, 1994).
  16. Discussion between B.J. Robinson and B.Y. Mills, 2004.
  17. Minnett, H.C., ‘Notes on engineering work’, 11 February 1976. See also Wallis, Barnes et al., ‘Improvement in telescope mounting’. British Patent Application No. 29248/1955 (Full specification, 11 January 1957).
  18. Minnett, H.C., ‘Feasibility of servo-drive and control system for a large altazimuth-mounted radio telescope’, Design Study Report, Appendix C, Freeman Fox and Partners, London, December 1957.
  19. Goddard and Milne, Parkes: Thirty Years of Radio Astronomy (op. cit. note 15).
  20. Minnett, H.C., ‘CSIRO Division of Radiophysics progress reports on studies under NASA Research Grant NsG-240-62, 1962–65’: (a) Progress Report No. 1, Division Report RPR141, April 1962. (b) Progress Report No. 2, Division Report RPR148, August 1963. (c) Progress Report No. 3, Division Report RPR151, March 1964. (d) Progress Report No. 4, Division Report RPR158, November 1964. (e) Progress Report No. 5, Division Report RPR162, March 1965.
  21. Yabsley, D.E., ‘Improvement of the Parkes 64-m radio telescope surface efficiency to provide useful performance at 1.35 cm wavelength’, IREECON Convention Digest, (1977), 203–205.
  22. Yabsley, D.E., Puttock, M.J. and Loughry, K.J., ‘A millimetre-wavelength surface for the centre of the Parkes radio telescope’, IREECON Convention Digest, (1977), 96–99.
  23. Thomas, B.MacA., Schafer, J.T., Sinclair, M.W., Kesteven, M.J. and Hall, P.J., ‘The Parkes radio telescope modified for rapid receiver changes’, IEEE Antennas and Propagation Magazine, 39 (no. 2) (April 1997), 54–63.
  24. Kesteven, M.J., ‘Microwave holography for antenna metrology’, Journal of Electrical and Electronic Engineering Australia, 14 (1994), 85–97.
  25. Minnett, H.C., hand-written notes giving a preliminary analysis of the focal-region fields of a paraboloidal antenna (14 December 1963; 1 January 1964).
  26. Thomas, B.MacA., ‘The early stages of hybrid-mode horn development in CSIRO’, Division of Radiophysics Internal Report No. RPP3002, April 1986.
  27. Minnett, H.C., ‘CSIRO Division of Radiophysics progress reports on studies under NASA Research Grant NsG-240-62, 1962–65’: Progress Report No. 5, Division Report RPR162, March 1965.
  28. Thomas, B.MacA., ‘A review of the early development of circular-aperture hybrid-mode corrugated horns’, IEEE Transactions on Antennas and Propagation, AP–34, No. 7 (July 1986), 930–935.
  29. Minnett, H.C., ‘Anglo-Australian 150-inch optical telescope-preliminary investigations of drive and control system’, Report to AAT Joint Policy Committee, CSIRO Division of Radiophysics Report, 26 January 1968.
  30. Bird, ‘Going strong after 50 Years’ (op. cit. note 12); also IREECON International Convention Digest (Australia) for 1975, 1977, 1979 and 1981.
  31. Patents applied for relating to developments for the Interscan Microwave Landing System: (a) Wild, J.P. and Minnett, H.C., ‘Monitoring scanning radio beams’, Australian Patent Application PC0756/75, 28 February 1975; (b) Minnett, H.C. and Cooper, B.F.C., ‘Modulation of scanning radio beams’, Australian Patent Application PC1919/75, June 1975.
  32. Minnett, H.C., ‘Radio astronomy and the Parkes 64 metre telescope’, in: CSIRO Executive Seminar on Astronomy held at Culgoora and Parkes, 11–12 December 1980, Section 6. See also special issue: ‘The Australia Telescope’, Journal of Electrical and Electronics Engineering Australia, 12 (no. 2) (June 1992).
  33. Minnett, H.C., ‘Analysis of a new very-high-frequency omni range (VOR) antenna’, Interscan Australia Pty Ltd report, September 1983.
  34. Minnett, H.C., ‘Handbook for CVOR antenna’ for Department of Aviation, Interscan International Ltd Report, 1984, 1, pp. 1–36 (29 figs) and, 2, pp. 1–23 (9 figs).
  35. Minnett, H.C., ‘Design and construction of a ground-reflection antenna range at “Fleurs”, Badgery’s Creek’, Interscan Australia Pty Ltd Report, 1984.
  36. Minnett, H.C., ‘Priorities for Australian telecommunications research: a report to Government by the Australian Telecommunications and Electronics Research Board’, April 1987 (limited circulation).
  37. Lovell, A. C. B., ‘Joseph Lade Pawsey, 1908–1962’, Biographical Memoirs of Fellows of the Royal Society, 10 (1964), 232–234.
  38. Letters to E. Simmonds, op. cit. (note 10). See also Minnett, H.C., review of R. Hanbury-Brown, Boffin: A Personal Story of the Early Days of Radar, Radio Astronomy and Quantum Optics (1991), in Historical Records of Australian Science, 9 (pt. 2) (1992), 192–194.
  39. MacLeod, ‘The Boffins of Botany Bay’ (op. cit. note 7).
  40. Minnett, H.C., ‘Fifty years in radio science and its applications’, programme of the 25th General Assembly of the International Astronomical Union, Sydney, July 2003 (IAU Commission 41: Inter-Union Commission for the History of Astronomy, Scientific Meeting No. 2: ‘The early development of Australian radio astronomy’). No abstract or paper provided.

Bibliography

  1. Minnett, H.C., ‘Aerial duplexing’, chapter IX, pp. 294–320, and ‘Frequency converters’, chapter XII, pp. 389–411, in A Text-Book of Radar: A Collective Work by the Staff of the Radiophysics Laboratory, CSIRO, Sydney, Australia, First edition (Sydney: Angus & Robertson, 1947), Second edition (Cambridge: Cambridge University Press, 1954).
  2. Piddington, J.H. and Minnett, H.C., ‘Microwave thermal radiation from the Moon’, Australian Journal of Scientific Research A, 2 (No. 1, March 1949), 63–71.
  3. Piddington, J.H. and Minnett, H.C., ‘Solar radiation of wavelength 1.25 centimetres’, Australian Journal of Scientific Research A, 2 (No. 4, December 1949), 539–549.
  4. Minnett, H.C. and Labrum, N.R., ‘Solar radiation at a wavelength of 3.18 centimetres’, Australian Journal of Scientific Research A, 3 (No. 1, March 1950), 60–71.
  5. Piddington, J.H. and Minnett, H.C., ‘Solar radio-frequency emission from localised regions at very high temperatures’, Australian Journal of Scientific Research A, 4 (No. 2, June 1951), 131–157.
  6. Piddington, J.H. and Minnett, H.C., ‘Observations of Galactic radiation at frequencies of 1210 Mc/s and 3000 Mc/s’, Australian Journal of Scientific Research A, 4 (No. 4, December 1951), 459–475.
  7. Piddington, J.H. and Minnett, H.C., ‘Radio-frequency radiation from the constellation of Cygnus’, Australian Journal of Scientific Research A, 5 (No. 1, March 1952), 17–31.
  8. Minnett, H.C.,‘Diagrammatic representation of the pass and stop regions for wave propagation in a magneto-ionic medium’ in J.L. Pawsey and R.N. Bracewell, Radio Astronomy (Oxford: Oxford University Press, 1955), chapter 3, pp. 85–90.
  9. Bowen, E.G. and Minnett, H.C., ‘The Australian 210-ft radio telescope’, Journal of the British Institution of Radio Engineers, 23 (No. 1, January 1962), 49–54.
  10. Minnett, H.C., ‘The Australian 210-ft radio telescope – features of the new instrument’, Sky and Telescope, 24 (No. 4, October 1962), 184–189.
  11. Bowen, E.G. and Minnett, H.C., ‘The Australian 210-ft radio telescope’, Proceedings of the Institution of Radio Engineers Australia, 24 (No. 2, February 1963), 98–105.
  12. Minnett, H.C., ‘Le radiotelescope de Parkes’, Journal des Telecommunications, Union Internationale des Telecommunications, 30 (No. 12, December 1963), 383–387.
  13. Broten, N.W., Cooper, B.F.C., Gardner, F.F., Minnett, H.C., Price, R.M., Tonking, F.G. and Yabsley, D.E., ‘Some observations at 6 cm wavelength with the Australian 210-ft radio telescope’, Australian Journal of Physics, 18 (No. 1, February 1965), 85–90.
  14. Minnett, H.C., ‘Performance study of the 210-ft radio telescope at Parkes’, Conference on Design and Construction of Large Steerable Aerials, London, Inst. Elect. Eng. Conference Publication No. 21, June 1966, pp. 257–261.
  15. Minnett, H.C. and Thomas, B.MacA., ‘Synthesis of improved feeds for large circular paraboloids’, Conference on Design and Construction of Large Steerable Aerials, London, Inst. Elect. Eng. Conference Publication No. 21, June 1966, pp. 262–266.
  16. Minnett, H.C. and Thomas, B.MacA., ‘A method of synthesizing radiation patterns with axial symmetry’, IEEE Transactions on Antennas and Propagation, 14 (No. 5, September 1966), 654–656.
  17. Minnett, H.C. and Yabsley, D.E., ‘Performance of the Parkes 210-ft paraboloid at wavelengths from 6 to 75 cm’, Proceedings of the Institution of Radio and Electronics Engineers Australia, 27 (No. 11, November 1966), 304–312.
  18. Puttock, M.J. and Minnett, H.C., ‘Instrument for rapid measurement of the surface deformations of a 210-ft radio telescope’, Proceedings of the Institution of Electrical Engineers, 113 (No. 11, November 1966), 1723–1730.
  19. Minnett, H.C., ‘Radio, structural and electrical performance of the Parkes radio telescope’, Abstracts of Technical Papers at the National Radio and Electronic Engineering Convention, Sydney, May 1967, First edition, April 1967, p. 108.
  20. Minnett, H.C. and Thomas, B.MacA., ‘Fields in the image space of symmetrical focusing reflectors’, Proceedings of the Institution of Electrical Engineers, 115 (No. 10, October 1968), 1410–1430.
  21. Thomas, B.MacA., Minnett, H.C. and Vu, T.B., ‘Fields in the focal region of a spherical reflector’, IEEE Transactions on Antennas and Propagation, AP–17 (No. 2, March 1969), 229–232.
  22. Minnett, H.C., Yabsley, D.E. and Puttock, M.J., ‘Structural performance of the Parkes 210-ft paraboloid’, in J. Mar and H. Liebowitz (Eds), Structures Technology for Large Radio and Radar Telescope Systems (Cambridge, MA: MIT Press, 1969), pp. 135–149.
  23. Phillips, C.J.E., and Minnett, H.C., ‘Radiation of circular apertures with structural shadows’, Proceedings of the Institution of Electrical Engineers, 118 (September 1971), 1214.
  24. Minnett, H.C., ‘Progress on the 150-inch Anglo-Australian Telescope’, Proceedings of the Astronomical Society of Australia, 2 (No. 1, July 1971), 2–6 (invited paper). ‘Addendum’, 2 (No. 3, October 1972), 161–162.
  25. Minnett, H.C., ‘How engineering is affecting astronomy’. Invited paper presented at Section 5, Engineering: 44th ANZAAS Congress, Sydney, August 1972, pp. 1–12.
  26. Minnett, H.C. and Thomas, B.MacA., ‘Propagation and radiation behaviour of corrugated feeds’, Proceedings of the Institution of Electrical Engineers, 119 (No. 9, September 1972), 1280. (Letter to Editor on paper by Clarricoats and Saha.)
  27. Minnett, H.C. and O’Keeffe, H.B., ‘Interscan – a new microwave Approach and Landing Guidance System for International Civil Aviation’, Journal of the Asia Electronics Union, 7 (No. 2, Serial No. 24, 1974), 15–20.
  28. Minnett, H.C. ‘The Interscan system’, IREE International Electronic Convention 1975, Convention Digest, August 1975, pp. 238–240.
  29. Minnett, H.C. and Thomas, B.Mac.A., ‘Symmetric reflectors with zero depolarisation’, Electronics Letters, 12 (No. 11, May 1976), 291–293.
  30. Minnett, H.C. and Boyd, G.H., ‘Interscan – a new microwave Approach and Landing Guidance System’, Navigation (Journal of the Australian Institute of Navigation), 5 (No. 2, December 1977), 583–594.
  31. Thomas, B.MacA. and Minnett, H.C., ‘Modes of propagation in cylindrical waveguides with anisotropic walls’, Proceedings of the Institution of Electrical Engineers, 125 (No. 10, October 1978), 929–932.
  32. Brown, R. Hanbury, Minnett, H.C. and White, F.W.G., ‘Edward George Bowen, 1911–1991’, Historical Records of Australian Science, 9 (No. 2, 1992), 151–166.
  33. Minnett, H.C., ‘Early history of Australian radar’, Letter to the Editor, Electronics Australia, 56 (No. 2, February 1994), 4–5.
  34. Minnett, H.C., ‘Eulogy to Dr E.G. Bowen’, in D.E. Goddard and D.K. Milne (Eds), Parkes: Thirty Years of Radio Astronomy (Melbourne: CSIRO Publishing, 1994), pp. 4–6.
  35. Minnett, H.C., ‘The construction of the Parkes 210-ft radio telescope’, in D.E. Goddard and D.K. Milne (Eds), Parkes: Thirty Years of Radio Astronomy (Melbourne: CSIRO Publishing, 1994), pp. 12–18.
  36. Minnett, H.C. and Robertson, Sir Rutherford, ‘Frederick William George White, 1905–1994’, Historical Records of Australian Science, 11 (No. 2, 1996), 239–258.
  37. Melrose, D.B. and Minnett, H.C., ‘Jack Hobart Piddington, 1910–1997’, Historical Records of Australian Science, 12 (No. 2, 1998), 229–246.
  38. Minnett, H.C., ‘The Radiophysics Laboratory at the University of Sydney’, Historical Records of Australian Science, 12 (No. 4, 1999), 419–427.
  39. Minnett, H.C., ‘Radar and the bombing of Darwin’, Historical Records of Australian Science, 12 (No. 4, 1999), 429–455.
  40. Minnett, H.C., ‘Light-weight air warning radar’, Historical Records of Australian Science, 12 (No. 4, 1999), 457–467.

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