Robert Hanbury

In fact, within three months Tizard accosted Hanbury and said he had an interesting research project in the Air Ministry for him.After an interview by R. A. Watson-Watt, Hanbury was offered a post at the Radio Research Board in Slough.
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It was to this research group that Hanbury was despatched to work on the secret project then known as R.D.F. (Radio location and Direction Finding) and later as Radar.He arrived at Orfordness in August 1936 and joined the small group then working on the development of receivers and antennae.

Tests on a wavelength of 13 metres were in progress with a transmitter generating 20-microsecond pulses at a peak power of 100 kilowatts.An array of dipoles produced a broad beam and Hanbury worked on the receiver and antennae using crossed dipoles and a goniometer to determine the angle of arrival of the reflected echo.
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E.G. Bowen was placed in charge of this development and Hanbury was transferred to his group in the autumn of 1937.
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Towards the end of 1938 Hanbury moved there to take charge of the installation and testing of the experimental equipment in aircraft.The details and hazards of this work have been described by Bowen (1987) and by Hanbury (119).
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Hanbury spent many hours testing and demonstrating the equipment in flight.
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In August 1939, only days before the outbreak of the war, Hanbury left Bawdsey Manor and Martlesham Heath to follow the first of the operational Blenheims to 25 Squadron at Northolt.His aim was to help the Squadron evolve their techniques for night-fighting with AI equipment.
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Hanbury spent most of his time at Northolt until the Fighter Interception Unit (FIU) was established at Tangmere early in 1940.Both at Tangmere and later at Ford, Hanbury was the senior of the small group of scientists helping with the training and introduction of the AI-equipped Blenheims for operational use as night fighters.During this period he also spent much time at various Coastal Command squadrons helping with the installation of ASV equipment and the training of RAF operators.
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Hanbury had long argued that success in a night battle would be achieved only when the fighter could be placed in the vicinity of the target under ground control, although he was not involved in the eventual success of such a system.[1]

Early in 1941, during a training flight at FIU, Hanbury suffered a serious incident when his oxygen supply failed at high altitude.He was unconscious when the aircraft landed and spent three months in hospital being treated for severe damage to his hearing.He was left with inferior hearing for the remainder of his life.He had previously burst an eardrum when testing AI equipment in May 1939.

Hanbury returned to TRE (now in Dorset) in June.By that time the primary interest in AI was the development of a system on centimetre wavelengths using the cavity magnetron (see Lovell, 1991) and since he could no longer fly at high altitude he decided to leave the air interception research group.He joined J.W.S. Pringle, a former member of Bowen's team at St Athan, who had started work on the Rebecca-Eureka beacons (119, Chapter 6).
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At the end of 1942 Hanbury went to America to collaborate with the US forces in the production and use of the Rebecca and Eureka beacons.It was his intention to return to England in 1943 but he was instructed to remain in the USA and join the Combined Research Group (CRG) at the Naval Research Laboratory in Washington.
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Although Hanbury contributed to the development of this technologically difficult system, it is evident from his own account (119) that he was unhappy to be so remote from the operations in Europe.

Before the UNBIFF could be tested under operational conditions the war ended and the British team was disbanded.Much of the work of the combined group on UNBIFF was later applied to civil aviation but Hanbury left Washington feeling that he had little to show for the two years there except for a number of technical reports.He returned to England in October 1945, two years after he had planned to return to the operational era of Rebecca and Eureka.

Post War 1945-49

When Hanbury returned to England he was still a scientific officer in MAP (Ministry of Aircraft Production).
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In the summer of 1947 Watson-Watt persuaded Hanbury to leave the scientific civil service and join him as one of three junior partners in his newly formed firm of research consultants.
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The problem was solved by P.M.S. Blackett, then Langworthy Professor of Physics at Manchester, who offered to support Hanbury for an ICI research fellowship.
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In October 1949 Hanbury joined Lovell's group at Jodrell as a candidate for the degree of PhD and his impact was instantaneous.
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When Hanbury arrived at Jodrell a number of researches were in progress, mainly on meteors and on radio astronomy.J.A.
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At a time when the nature of the localised radio sources was unexplained and many astronomers believed them to be a new type of radio star in the galaxy, Hanbury made a radio survey of the great loop in Cygnus with D. Walsh (18) and investigated the possibility that remnants of supernovae in the galaxy were the main contributors (16).
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During 1950 Hanbury joined in the discussions at Jodrell Bank about this problem.Techniques for using wavelengths below the metre wavebands did not then exist and the limits to angular size measurements were set by the difficulty of preserving phase stability along cable-connected aerials.If the radio sources were similar to the visible stars aerial separations of thousands of kilometres would be necessary to measure their angular size.There seemed no possibility of preserving the phase and amplitude over such distances.

Hanbury envisaged two separated individuals observing the noise-like signal from a source.If they saw similar signals a correlation would exist, but if they moved far enough apart the correlation would cease.Hanbury realised that the signal corresponded to the low-frequency fluctuations in the intensity of the source.Thus, the concept of the intensity interferometer emerged in which it was only necessary to compare the fluctuations in the intensity of a source as the separation of the receivers was increased until the correlation disappeared.This placed no limit on the separation of the receivers, since the comparison of the intensity of the fluctuations at the separate receivers could be made through cable, land line or radio link.

Hanbury stimulated two research students, R.C. Jennison and M.K. das Gupta, to develop an interferometer based on this idea.
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As Hanbury later remarked, he had spent two years 'building a steamroller to crack a nut' (119, p.108).However, there were soon to be developments of this concept that again changed his career.

The development of the phase-correlation interferometer

There were soon more straightforward developments of the phase-correlation system both at Jodrell Bank and elsewhere.An interferometer using the transit telescope with a smaller transportable array was used to determine the angular diameters of the 23 localised sources already delineated by Hanbury and Hazard (9).
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Hanbury, H.P.
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Several were found to have angular diameters of less than 3 seconds of arc and the important part this played in the discovery of quasars has been described by Hanbury (119) and by Lovell (1973).
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During these years of intense interest in the optical identification of radio sources, in 1961 Hanbury decided to gain some practical experience.
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The association of Hanbury and Twiss led to consequences not then foreseen.
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In their full mathematical treatment of the concept (14) Hanbury and Twiss concluded that although the idea could be used for measurements in the radio spectrum it could not be developed for the measurement of the angular diameter of stars in the optical spectrum because 'it breaks down due to the limitations imposed by photon noise'.
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It was against this background that discussion ensued about extending the radio intensity type of interferometer to the optical spectrum, notwithstanding the doubts already expressed by Hanbury and Twiss.
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In order to test this contentious issue, Hanbury and Twiss designed a laboratory experiment in 1955.
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In particular, two independent groups attempted to repeat the experiment and concluded that Hanbury and Twiss had misinterpreted their data and that if such a correlation existed, a major revision of fundamental concepts in quantum mechanics would be required (Ádám, Jánossy & Varga, 1955; Brannen & Ferguson, 1956).
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In their response (25) Hanbury and Twiss pointed out that although the experimental procedure in both cases was beyond reproach, their critics had missed the essential point that correlation could not be observed in a coincidence counte

Brown, Robert Hanbury, A.C., F.R.S., Professor Emeritus, University of Sydney; White Cottage, Penton Mewsey, Near Andover, Hampshire SP11 0RQ, England, Tel. 1264-77 2334.