Ronald N. Bracewell

Ronald Newbold Bracewell (1921 – ) is the Lewis M. Terman Professor of Electrical Engineering, Emeritus of the Space, Telecommunications and Radioscience Laboratory at Stanford University.

Ronald Newbold Bracewell 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 honors. During World War II he designed and developed microwave radar equipment in the Radiophysics Laboratory of the Commonwealth Scientific and Industrial Research Organization, Sydney under the direction of J.L. Pawsey and E.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. His present position is L.M. Terman Professor of Electrical Engineering Emeritus.

Professor Bracewell is 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 is a Fellow with other significant societies and organizations.

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 honorees 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.

His book reviews have been commissioned by American Journal of Physics, Applied Optics, IEEE Transactions on Information Theory, Journal of the Optical Society of America, Physics Today, Queen's Quarterly, Science, Scientific American, Spectrum, The Observatory, The Russian Review, and The Times Higher Education Supplement.

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 (1954).

While at the Cavendish Laboratory, Cambridge (1946-1950) Bracewell worked on observation and theory of upper atmospheric ionization, contributing to experimental technique (1948), explaining solar effects (1949), and distinguishing two layers below the E-layer (1952), work recognized 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 acknowledgment 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 (one arcminute). With this beam the components of Cygnus A, spaced 100", were put directly in evidence without the need for variable spacing 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 polarization 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 <math>\lambda^2<math> dependence expected from Faraday rotation if magnetic fields were the polarizing 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 polarization, and propagation effects of the ionized 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 inflation.

Government advisory duties have included membership of panels advisory to the National Science Foundation (past chair of astronomy advisory panel and member of panel on large radiotelescopes), Naval Research Laboratory (committee advisory to the Naval Research Station, Sugar Grove), Office of Naval Research (astronomy panel), National Academy of Sciences (panel on astronomical facilities), National Radio Astronomy Observatory, Jet Propulsion Laboratory Advisory Group on Radio Experiments in Space, and Advanced Research Projects Agency (chair of Arecibo Evaluation Panel). Subsequently he advised the President of Cornell University as chair of the National Astronomy and Ionospheric Center Advisory Board.

Professor Bracewell was a consulting editor to the McGraw-Hill series of textbooks in electrical engineering for many years and has served on the editorial advisory boards of Planetary and Space Science, Publications of the Astronomical Society of the Pacific, Cosmic Search, Journal of Computer Assisted Tomography, and Journal of Visual Communication and Image Representation, and from 1961 to 1968 was on the board of Reviews of Astronomy and Astrophysics, a periodical that he helped to found. He is on the editorial board of the International Journal of Imaging Systems and Technology.

Professor Bracewell was a member of the Stanford University Senate (1970-72, 1978-80), of the Committee on Committees (1970-72), Director of the Radioscience Laboratory 1970-1975, as well as other significant memberships in Standford University.

In 1974 he was appointed the first Lewis M. Terman Professor and Fellow in Electrical Engineering (1974-1979) and in 1980 received the Outstanding Service Award of the Electrical Engineering Department. He was the Tektronix Distinguished Visitor, (summer 1981).

He was the Christensen fellow at St. Catherine's College, Oxford, associated with the Astrophysics Department (autumn 1987), and senior visiting fellow at the Institute of Astronomy and fellow commoner at Churchill College, Cambridge (autumn 1988). He was a founding board member of the Sidney Sussex Foundation.

He spent the Summer quarter of 1975, Winter and Spring quarters of 1979-80, and Spring quarter of 1981-82 at Stanford in Florence teaching general astronomy, statics, dynamics, fluid dynamics, semiconductor physics and Renaissance mechanics and lecturing at the Arcetri Observatory.

A current series of papers on aspects of solar physics, especially the sunspot cycle and the solar interior, was stimulated by the discovery in South Australia of thousands of laminated sediments that embody a rich record of astronomical cyclicity in Precambrian times. Other current geophysical interests include solar influence on the ocean surface temperature and magnetic precursors of earthquakes.

As a consequence of relating images to Fourier analysis, in 1983 he discovered a new factorization 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, the chirplet, was discovered (1991) that complements the Gabor elementary signals used in dynamic spectral analysis (with the property of meeting the bandwidth-duration minimum associated with the uncertainty principle). This advance will open a new field of adaptive dynamic spectra with wide application in information analysis.

Professor Bracewell is 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.

Publications

Probably incomplete.

• Bracewell, R.N. and Pawsey, J.L., Radio Astronomy (Oxford, 1955) (also translated into Russian and reprinted in China)

• Bracewell, Ronald N., ed., Paris Symposium on Radio Astronomy, IAU Symposium no. 9 and URSI Symposium no. 1, held 30 July - 6 August 1958 (Stanford Univ. Press, Stanford, CA, 1959) (also translated into Russian)

• Professor Bracewell translated Radio Astronomy, by J.L. Steinberg and J. Lequeux, (McGraw-Hill, 1963) from French

• Bracewell, R.N., The Fourier Transform and Its Applications (McGraw-Hill, 1965, 2nd ed. 1978, revised 1986) (also translated into Japanese and Polish)

• Bracewell, R.N., Trees on the Stanford Campus (Stanford: Samizdat, 1973)

• Bracewell, R.N., The Galactic Club: Intelligent Life in Outer Space (Portable Stanford: Alumni Association, 1974) (also translated into Dutch, Japanese, and Italian)

• Bracewell, R.N., The Hartley Transform (Oxford University Press, 1986) (also translated into German and Russian)

• Bracewell, R.N., Two-Dimensional Imaging (Prentice-Hall, 1995)

• Bracewell, R.N., Fourier Analysis and Imaging (Plenum, 2004)

• Bracewell, R.N., Trees of Stanford and Environs (Stanford Historical Society, 2005)

Chapter contributions

Bracewell has contributed chapters to:

• Textbook of Radar Microwave Transmission and Cavity Resonator Theory, ed. E.G. Bowen, 1946
• Advances in Astronautical Sciences Satellite Rotation, ed. H. Jacobs, 1959
• The Radio Noise Spectrum Correcting Noise Maps for Beamwidth, ed. D.H. Menzel, 1960
• Modern Physics for the Engineer Radio Astronomy, ed. L. Ridenour and W. Nierenberg, 1960
• Statistical methods in Radio Wave Propagation Antenna Tolerance Theory, ed. W.C. Hoffman, 1960
• Advances in Geophysics Satellite Studies of the Ionization in Space by Radio, ed. H.E. Landsberg, 1961 (O.K. Garriott and R.N. Bracewell)
• Handbuch der Physik Radio Astronomy Techniques, ed. S. Flugge, 1962
• Encyclopedia of Electronics Extra-terrestrial Radio Noise, ed. C. Susskind, 1962
• Stars and Galaxies Radio Broadcasts from the Depths of Space, ed. T.L Page, 1962
• Radio Waves and Circuits Aerials and Data Processing, ed. S. Silver, 1963
• Light and Life in the Universe Life in the Galaxy, ed. S.T. Butler and H. Messel, 1964
• Encyclopaedia Britannica Telescope, Radio, 1967
• Vistas in Science The Microwave Sky, ed. David L. Arm, 1968
• Man in Inner and Outer Space The Sun (Five Chapters), ed. H. Messel and S.T. Butler, 1968
• Image Reconstruction from Projections: Implementation and Applications Image Reconstruction in Radio Astronomy, ed. G. Hermann, 1979
• Annual Review of Astronomy and Astrophysics Computer Image Processing, ed. G. Burbidge et al., 1979
• Energy for Survival How It All Began, Man the Lazy Animal, and Energy from Sunlight, ed. H. Messel, 1979
• Life in the Universe Manifestations of Advanced Civilizations, ed. J. Billingham, 1981
• Extraterrestrials: Where Are They? Preemption of the Galaxy by the First Advanced Civilization, ed. M.H. Hart and B. Zuckerman, 1982, 1995
• Transformations in Optical Signal Processing Fourier Inversion of Deficient Data, ed. W.T. Rhodes, J.R. Fienup and B.E.A. Saleh, 1984
• The Early Years of Radio Astronomy Early Work on Imaging Theory in Radio Astronomy, ed. W.T. Sullivan, III, 1984
• Indirect Imaging Inversion of Nonplanar Visibilities, ed. J.A. Roberts, 1984
• Fourier Techniques and Applications The Life of Joseph Fourier and Fourier Techniques and Applications, ed. J.F. Price, 1985
• Yearbook of Science and Technology Wavelets, 1996
• Encyclopedia of Applied Physics Fourier and Other Mathematical Transforms 1997
• Cornelius Lanczos—Collected Published Papers with Commentaries The Fast Fourier Transform andSmoothing Data by Analysis and by Eye ed. W.R. Davis et al., 1999