We received word this week that Steven J. Ostro, a pioneering radar astronomer at the Jet Propulsion Laboratory, died on December 15th after a two-year fight with cancer. He was 62.

Planetary radar astronomer Steven Ostro holds 3-D models of two of his most prized "catches": the near-Earth asteroid 4179 Toutatis (in his left hand) and dogbone-shaped 216 Kleopatra.

Jeanne Marie Ostro

The worldwide community of planetary scientists has grown tremendously since I started covering the solar-system beat in the mid-1970s, and a great many of them are friends. So too was Steve.

He and I crossed paths in the mid-1980s, not long after he joined JPL's planetary-radar group. Steve basically invented the technique of using powerful radar antennas to probe asteroids, beginning with a successful "ping" of the main-belt heavyweight 1 Ceres while a graduate student at MIT.

Steve realized radar's potential not only for determining the surface characteristics of small rocky bodies but also for pinpointing their line-of-sight distance and velocity with incredible accuracy. Guided by his skill at wringing absolutely every bit of information from a radar echo, both of these capabilities became powerful analytical tools in the effort to understand near-Earth asteroids and the threat they pose to Earth.

Over time Steve and radar scientists he trained racked up hundreds of successful asteroid "hits" with the NASA dish and the even larger Arecibo radio telescope in Puerto Rico. They're all tallied on the informative website that Steve maintained to chronicle his team's work.

One encounter I'll never forget took place in August 1989, when I headed west to cover Voyager 2's historic flyby of Neptune. As it happened, a small Earth-crossing asteroid designated 1989 PB had been discovered just a week beforehand, and Ostro intended to use NASA's giant tracking antenna in the Mojave Desert — a couple hours' drive from JPL — to try to record the interloper.

Steven Ostro atop NASA antenna

Steve Ostro poses atop the feedhorn for NASA's giant tracking antenna in California's Mojave Desert.

S&T: J. Kelly Beatty

"Want to join me?" he inquired. He didn't need to ask twice!

After driving in predawn darkness to reach the facility, I met him at the base of the gargantuan antenna. The gleaming-white dish is 210 feet (70 m) across, and it looks a lot bigger in person than it does in photos. Steve took the time to give me an insider's tour that culminated with climbing onto the towering feedhorn.

Once he'd completed his observing run, it became clear that the asteroid (later numbered and named 4769 Castalia) was a contact binary — a double-lobed body joined by a narrow waist of rubble.

I'll remember Steve as a study in contrasts. On one hand, there was a quiet intensity about him, even in friendly conversation, yet he had a powerfully persuasive style of lecturing that commanded your attention. And although he enjoyed having the fruits of his observations promulgated to a wide public audience, Steve notoriously guarded his findings until he felt the conclusions were rock-solid and beyond reproach.

"I feel extremely fortunate to be doing this work," he said in 2003, on the occasion of receiving a lifetime-achievement award from his planetary-scientist peers. "It's like a Star Trek fantasy — seeing a world that no one has ever seen before. That's what I've been able to do over and over."

Near-Earth asteroid 4769 Castalia

This computer reconstruction of the near-Earth asteroid 4769 Castalia utilized radar echoes obtained in 1989, when the object passed 3½ million miles from Earth. The two-lobed body is likely a "contact binary" that assembled from a gentle collision between two minor planets.

© 1994 American Association for the Advancement of Science.

My final contact with Steve came this past summer, when he graciously agreed to write a perspective for the 100th anniversary of the Tunguska impact over Siberia. "I'm so honored to be the lead comment!" he wrote to me after I'd posted it.

And I'm honored to have known you, Steve. You left us too soon, and you'll be sorely missed.

Learn more about his life and work by reading the remembrances posted by Charlene Anderson and Louis Friedman of the Planetary Society, and by the touching blog written by his brother, Stu Ostro. S&T contributing editor David Levy also profiled Steve in his Star Trails column for May 2005.


Image of Bill Murrell

Bill Murrell

December 19, 2008 at 4:39 pm

I met Steve several years ago also. He came at my invitation to speak about radar astronomy. I also went with him to Goldstone one day as he was imaging Mithra. As a layman I found it very interesting and he explained what was happening so that I could understand it.

The last time I spoke with him was about a year ago. A really nice guy and I will miss him.

Bill Murrell

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bob kelly

December 26, 2008 at 7:54 am

Steven's brother, Stu, has an appreciation of Steven and his work at http://www.weather.com/blog/weather
Scroll down to the December 16 entry.

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