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Len Tyler, who studied the planets using radio waves, has died at 82

Over a four-decade career that began after he earned his PhD at Stanford, Tyler worked on key explorations of the solar system.
Portrait of Professor G. Leonard Tyler
George Leonard Tyler, 1940-2023

G. Leonard “Len” Tyler, an electrical engineer and leader of numerous studies of the planets of the solar system, died March 16 in Port Townsend, Washington. The cause was late-stage Alzheimer’s disease. He was 82.

Tyler was an expert in radar astronomy – using controlled radio waves to gather information about the structures and atmospheres of neighboring planets and moons. The radio equipment was often carried aboard spacecraft like the Mars Global Surveyor, Pioneer, Viking, Galileo, Voyager, and New Horizons missions and the data was beamed back to Earth at the speed of light.

He was best known for pioneering and perfecting the science of radio occultation, where radio signals pass through planetary atmospheres and bounce off the harder surfaces below to map the underlying structures. In 1968, as a young research assistant, Tyler first appeared in a Stanford News report about his studies of the soil on the surface of the moon. In subsequent years, working through NASA’s Jet Propulsion Laboratory, Tyler would lead successful studies of Mars, the rings of Jupiter and Saturn, and the structure of Neptune, among other explorations of Earth’s solar siblings.

“He was the premier expert in radio science for several decades – the person NASA chose to lead radio exploration of the planets and moons,” said Howard Zebker, professor of electrical engineering and of geophysics, a one-time advisee and later colleague of Tyler’s at Stanford.

At the peak of his career, Tyler could often be found flying his Piper Comanche from Palo Alto to Pasadena, California, home of the Jet Propulsion Laboratory (JPL). He led numerous flagship scientific missions through JPL over a 40-year career that began soon after earning his PhD in electrical engineering at Stanford. Tyler retired to Port Townsend in 2006.

Former colleagues noted that Tyler would like to joke he had “visited every planet in the solar system” and “never met an asteroid that he didn’t like.” In fact, Asteroid 195405 has been permanently assigned his name in recognition of Tyler’s contributions to the study of Pluto and the Kuiper Belt.

Not every project was a resounding success, however. In 1993, Tyler was lead investigator on experimental equipment borne by the ill-fated, billion-dollar Mars Observer that inexplicably fell into radio silence three days before it was to enter Mars orbit. Tyler’s team had hoped to explore Mars’ gravitational field and atmosphere. “It’s gone. I think it’s gone. … It’s a very big loss,” a disappointed Tyler told Stanford News at the time.

Tyler published over 200 peer-reviewed scientific papers in his career and was promoted to research professor by 1974. In 1991, Tyler’s body of work was so highly regarded that he made the relatively rare leap from research professor to tenured professor of electrical engineering at the age of 50 – a promotion notable enough it was covered by Stanford News.

While justifiably proud of his research achievements, Tyler was similarly proud of his teaching and advising, from the undergraduate to the doctoral levels.

“I had the unique opportunity to have Len Tyler as an advisor and as a mentor. I can fairly say that I would not be where I am today without him. He always put his students first,” Zebker recalled of his friend. “I owe him a great deal of respect and gratitude and I can’t say enough about him.”

In 1989, he was elected an IEEE Fellow. Tyler received NASA Medals for Exceptional Scientific Achievement in 1977, 1981, and 1986, as well as the NASA Medal for Public Service in 1992.

George Leonard Tyler was born October 18, 1940, in Bartow, Florida. He earned his Bachelor of Science degree in 1963 from the Georgia Institute of Technology and his MS (’64) and PhD (’67) from Stanford. All degrees were in electrical engineering.

Tyler is survived by his second wife, Joanne Tyler, of Port Townsend, Washington, whom he married in 1977; two children from his first marriage, a daughter, Virginia Kimmel, and her husband, Larry, of St. Louis, Missouri; and a son, Matthew Tyler, and his wife, Karen Obermeyer, of Port Townsend; as well as a grandson, Davis Tyler.

A Stanford memorial is planned for summer; details are forthcoming.

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