Ronald N. Bracewell, an astronomer and engineer who used radio telescopes to make early images of the sun's surface and in work that also led to advances in medical imaging, died Aug. 12 at his home in Stanford. He was 86.
The cause was a heart attack, his family said.
With his colleagues at Stanford University in the 1950s, Mr. Bracewell designed a specialized radio telescope, called a spectroheliograph, to receive and evaluate microwaves emitted by the sun.
The device was actually a series of linked dish antennas on Stanford's campus that scanned the sun by day and the broader sky by night. In the 1960s, Mr. Bracewell used the telescope to draw daily contour maps of the sun's surface temperatures and to make images of the shape and surface temperatures of stars and other heavenly matter. The maps helped to predict the solar storms that regularly disrupt radio communications on Earth.
Later, in the 1970s, the techniques and a formula devised by Mr. Bracewell were applied by other scientists in developing X-ray imaging of tumors, called tomography, and other forms of medical imaging that scan electromagnetic and radio waves. Mr. Bracewell advised researchers at Stanford and other institutions, but did not conduct laboratory research in the field.
Von R. Eshleman, a professor emeritus of electrical engineering at Stanford, said that the principles developed by Mr. Bracewell in radio astronomy were directly applicable to tomography, and that “the mathematics he worked out turned out to be common to both fields.”
In the 1980s, Mr. Bracewell, who was Australian, combined his expertise in astronomy with geology and examined unusually dark layers deposited in Australia's red sandstones that he and others theorized must be connected to the sun's activity. The researchers proposed that the regularity of the layers suggested that sunspots had affected temperatures on Earth, leading to periods of melting permafrost in Australia some 680 million years ago.
Mr. Bracewell also posed tantalizing questions about the chances of discovering other intelligent life in the universe. Early in his career, he wrote in the journal Nature about the possibility of “superior galactic communities” and the most practical means of contacting them. In 1960, he suggested the best way might be to send satellites to check for radio signals around 1,000 planets as distant as 100 light-years away, and he periodically revisited the subject.
With J.L. Pawsey, Mr. Bracewell prepared a standard textbook, “Radio Astronomy” (1955), and explained what was then providing “a new window on the universe,” Eshleman said.
A later textbook, “The Fourier Transform and Its Applications” (1965), covers a mathematical concept that is a core subject in engineering. The book, intended for graduate students, is still widely used and remains “a fundamental text on the subject of signals, systems and communications, and is a continuing achievement,” said Umran S. Inan, a professor of electrical engineering and director of Stanford's Space, Telecommunications and Radioscience Laboratory.
Mr. Bracewell joined Stanford in 1955 and became a professor emeritus of electrical engineering there in 1991. He became a U.S. citizen in the 1990s.
Mr. Bracewell is survived by his wife of 54 years, Helen.
He is also survived by a son, Mark, of San Jose; a daughter, Wendy, of London and Sheffield, England; a brother, Mark, of Melbourne, Australia; and two grandchildren.
Mr. Bracewell's interest in life and matter in its manifold forms was rooted on Earth. In 2005, he produced a scholarly survey of some of his campus' flora, in “Trees of Stanford and Environs.”
“I have a strong feeling,” he said in an interview at the time, “that if people try to become acquainted with their trees, it would enhance their life.”