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Biographical / Historical
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Department of Special Collections and University Archives
Title: Ronald Bracewell papers
Bracewell, Ronald N. (Ronald Newbold)
Identifier/Call Number: SC0896
71.25 Linear Feet
Date (inclusive): 1958-2007
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[identification of item], Ronald Bracewell Papers (SC0896). Dept. of Special Collections and University Archives, Stanford
University Libraries, Stanford, Calif.
Biographical / Historical
Ronald Newbold Bracewell (July 22, 1921 – August 12, 2007) was the Lewis M. Terman Professor of Electrical Engineering, Emeritus
of the Space, Telecommunications and Radioscience Laboratory at Stanford University.
He was born in Sydney, Australia, in 1921, and educated at Sydney Boys High School. He graduated from the University of Sydney
in 1941 with the B.Sc. degree in mathematics and physics, later receiving the degrees of B.E. (1943), and M.E. (1948) with
first class honours, and while working in the Engineering Department became the President of the Oxometrical Society. During
World War II he designed and developed microwave radar equipment in the Radiophysics Laboratory of the Commonwealth Scientific
and Industrial Research Organisation, Sydney under the direction of Joseph L. Pawsey and Edward G. Bowen and from 1946 to
1949 was a research student at Sidney Sussex College, Cambridge, engaged in ionospheric research in the Cavendish Laboratory,
where he received his Ph.D. degree in physics under J. A. Ratcliffe.
From October 1949 to September 1954 Dr. Bracewell was a Senior Research Officer at the Radiophysics Laboratory of the CSIRO,
Sydney, concerned with very long wave propagation and radio astronomy. He then lectured in radio astronomy at the Astronomy
Department of the University of California, Berkeley from September 1954 to June 1955 at the invitation of Otto Struve, and
at Stanford University during the summer of 1955, and joined the Electrical Engineering faculty at Stanford in December 1955.
In 1974 he was appointed the first Lewis M. Terman Professor and Fellow in Electrical Engineering (1974–1979). Though he retired
in 1979, he continued to be active until his death.
Professor Bracewell was a Fellow of the Royal Astronomical Society (1950), Fellow and life member of the Institute of Electrical
and Electronic Engineers (1961), Fellow of the American Association for the Advancement of Science (1989), and was a Fellow
with other significant societies and organisations.
For experimental contributions to the study of the ionosphere by means of very low frequency waves, Dr. Bracewell received
the Duddell Premium of the Institution of Electrical Engineers, London in 1952. In 1992 he was elected to foreign associate
membership of the Institute of Medicine of the U.S. National Academy of Sciences (1992), the first Australian to achieve that
distinction, for fundamental contributions to medical imaging. He was one of Sydney University's three honourees when alumni
awards were instituted in 1992, with a citation for brain scanning, and was the 1994 recipient of the Institute of Electrical
and Electronic Engineers' Heinrich Hertz medal for pioneering work in antenna aperture synthesis and image reconstruction
as applied to radio astronomy and to computer-assisted tomography. In 1998 Dr. Bracewell was named Officer of the Order of
Australia (AO) for service to science in the fields of radio astronomy and image reconstruction.
At CSIRO Radiophysics Laboratory, work that in 1942-1945 was classified appeared in a dozen reports. Activities included design,
construction, and demonstration of voice-modulation equipment for a 10 cm magnetron (July 1943), a microwave triode oscillator
at 25 cm using cylindrical cavity resonators, equipment designed for microwave radar in field use (wavemeter, echo box, thermistor
power meter, etc.) and microwave measurement technique. Experience with numerical computation of fields in cavities led, after
the war, to a Master of Engineering degree (1948) and the definitive publication on step discontinuities in radial transmission
While at the Cavendish Laboratory, Cambridge (1946–1950) Bracewell worked on observation and theory of upper atmospheric ionisation,
contributing to experimental technique (1948), explaining solar effects (1949), and distinguishing two layers below the E-layer
(1952), work recognised by the Duddell Premium.
At Stanford Professor Bracewell constructed a microwave spectroheliograph (1961), a large and complex radio telescope which
produced daily temperature maps of the sun reliably for eleven years, the duration of a solar cycle. The first radio telescope
to give output automatically in printed form, and therefore capable of worldwide dissemination by teleprinter, its daily solar
weather maps received acknowledgement from NASA for support of the first manned landing on the moon.
Many fundamental papers on restoration (1954–1962), interferometry (1958–1974) and reconstruction (1956–1961) appeared along
with instrumental and observational papers. By 1961 the radio-interferometer calibration techniques developed for the spectroheliograph
first allowed an antenna system, with 52" fan beam, to equal the angular resolution of the human eye in one observation. With
this beam the components of Cygnus A, spaced 100", were put directly in evidence without the need for repeated observations
with variable spacing aperture synthesis interferometry.
The nucleus of the extragalactic source Centaurus A was resolved into two separate components whose right ascensions were
accurately determined with a 2.3-minute fan beam at 9.1 cm. Knowing that Centaurus A was composite, Bracewell used the 6.7-minute
beam of the Parkes Observatory 64 m radiotelescope at 10 cm to determine the separate declinations of the components and in
so doing was the first to observe strong polarisation in an extragalactic source (1962), a discovery of fundamental significance
for the structure and role of astrophysical magnetic fields. Subsequent observations made at Parkes by other observers with
a 14-minute and wider beams at 21 cm and longer wavelengths, though not resolving the components, were compatible with the
λ2 dependence expected from Faraday rotation if magnetic fields were the polarising agent.
A second major radiotelescope (1971) employing advanced concepts to achieve an angular resolution of 18 seconds of arc was
designed and built at Stanford and applied to both solar and galactic studies. The calibration techniques for this leading-edge
resolution passed into general use in radio interferometry via the medium of alumni.
Upon the discovery of the cosmic background radiation: a remarkable observational limit of 1.7 millikelvins, with considerable
theoretical significance for cosmology, was set on the anisotropy in collaboration with Ph. D. student E.K. Conklin (1967),
and was not improved on for many years; the correct theory of a relativistic observer in a blackbody enclosure (1968) was
given in the first of several papers by various authors obtaining the same result; the absolute motion of the Sun at 308 km/s
through the cosmic background radiation was measured by Conklin in 1969, some years before independent confirmation.
With the advent of the space age, Bracewell became interested in celestial mechanics, made observations of the radio emission
from Sputnik 1, and supplied the press with accurate charts predicting the path of Soviet satellites, which were perfectly
visible, if you knew when and where to look. Following the puzzling performance of Explorer I in orbit, he published the first
explanation (1958-9) of the observed spin instability of satellites, in terms of the Poinsot motion of a non-rigid body with
internal friction. He recorded the signals from Sputniks I, II and III and discussed them in terms of the satellite spin,
antenna polarisation, and propagation effects of the ionised medium, especially Faraday effect.
Later (1978, 1979) he invented a spinning, nulling, two-element infrared interferometer suitable for space-shuttle launching
into an orbit near Jupiter, with milliarcsecond resolution, that could lead to the discovery of planets around stars other
than the sun. This concept was elaborated in 1995 by Angel and Woolf, whose space-station version with four-element double
nulling became the Terrestrial Planet Finder (TPF), NASA's candidate for imaging planetary configurations of other stars (Scientific
American, April 1996).
Imaging in astronomy led to participation in development of computer assisted x-ray tomography, where commercial scanners
reconstruct tomographic images using the algorithm developed by Bracewell for radioastronomical reconstruction from fan-beam
scans. This corpus of work has been recognized by the Institute of Medicine, an award by the University of Sydney, and the
Heinrich Hertz medal. Service on the founding editorial board of the Journal for Computer-Assisted Tomography, to which he
also contributed publications, and on the scientific advisory boards of medical instrumentation companies maintained Bracewell's
interest in medical imaging, which became an important part of his regular graduate lectures on imaging, and forms an important
part of his 1995 text on imaging.
Experience with the optics, mechanics and control of radiotelescopes led to involvement with solar thermophotovoltaic energy
at the time of the energy crisis, including the fabrication of low-cost solid and perforated paraboloidal reflectors by hydraulic
Bracewell is also known for being the first to propose the use of autonomous interstellar space probes for of communication
between alien civilisations as an alternative to radio transmission dialogs. This hypothetical concept has been dubbed the
Bracewell probe after its inventor.
As a consequence of relating images to Fourier analysis, in 1983 he discovered a new factorisation of the discrete Fourier
transform matrix leading to a fast algorithm for spectral analysis. This method, which has advantages over the fast Fourier
algorithm, especially for images, is treated in The Hartley Transform (1986), in U.S. Patent 4,646,256 (1987, now in the public
domain), and in over 200 technical papers by various authors that were stimulated by the discovery. Analogue methods of creating
a Hartley transform plane first with light and later with microwaves were demonstrated in the laboratory and permitted the
determination of electromagnetic phase by the use of square-law detectors. A new elementary signal representation, the Chirplet
transform, was discovered (1991) that complements the Gabor elementary signal representations used in dynamic spectral analysis
(with the property of meeting the bandwidth-duration minimum associated with the uncertainty principle). This advance opened
a new field of adaptive dynamic spectra with wide application in information analysis.
Professor Bracewell was interested in conveying an appreciation of the role of science in society to the public, in mitigating
the effects of scientific illiteracy on public decision making through contact with alumni groups, and in liberal undergraduate
education within the framework of the Astronomy Course Program and the Western Culture program in Values, Technology, Science
and Society, in both of which he taught for some years. He gave the 1996 Bunyan Lecture on The Destiny of Man.
Among colleagues at Stanford, Bracewell also was known for his insatiable appetite for knowledge in general, whether it was
regarding local flora or foreign languages. The Stanford Alumni Association often called on Bracewell to lecture on topics
related to space, Renaissance technology and scientific illiteracy; through the alumni association, Bracewell published a
book titled The Galactic Club: Intelligent Life in Outer Space.
In 2005, the Stanford Historical Society debuted a 300-page book by Bracewell that catalogs the more than 350 species of trees
on campus, titled
Trees of Stanford and Environs. Over the years, Bracewell led many tree tours around campus and, in the late 1970s, taught an undergraduate seminar titled
I Dig Trees.
Bracewell was also a designer and builder of sundials. He built one on the South side of the Terman Engineering Building.
He built one at the home of his son, Mark Bracewell. He built another on the deck of professor John Linvill's house.
As his seminar "I Dig Trees" indicated, Dr. Bracewell was known for having a tremendously keen, intelligent sense of wry,
science-infused humor. One of his treasured family photos showed him sitting on the ground, legs akimbo, with a beer bottle
in front of him that he had neatly balanced on one of its bottom edges—his proof that even that thin edge had 3 balance points.
Professor Bracewell was survived by his wife, a son, Mark, a daughter, Wendy, and two grandchildren.
The Archives at The National Radio Astronomy Observatory is the repository for Ronald N. Bracewell's papers on radio astronomy:
Subjects and Indexing Terms
Bracewell, Ronald N. (Ronald Newbold)