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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 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 lines
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
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
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
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
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)