Elachi has served in a variety of research and management positions at JPL since 1971. Most recently, he has been director for space and Earth science programs since 1994. Other positions he has held include manager for radar development and leader of the radar remote sensing team. He will begin the post May 1.

Baltimore said he believes Elachi "knows JPL better than anyone and will be best able to lead the Laboratory in the coming years."

"Charles has an extraordinary record of accomplishment in his 30 years at JPL. He is an alumnus of Caltech and so knows the school well. He is an expert in remote sensing, and in recognition of his work he was one of the youngest members ever elected to the National Academy of Engineering. He has long been a leader of planetary exploration at JPL and is widely respected at the Laboratory. I look forward to having a close working relationship with him," Baltimore said.

"Charles Elachi brings formidable talents to his new job, both as a scientist and a leader," said NASA Administrator Dan Goldin. "In addition to already being responsible for many of JPL's missions in solar system exploration, Earth sciences and astrophysics, he has led efforts to create road maps of our exploration strategies decades into the future. He is both an effective administrator and a visionary."

Elachi said he is honored to be entrusted with the leadership of JPL. "For the last 40 years JPL has enjoyed a tradition of excellence as a NASA center and division of Caltech, and I intend to continue that tradition. My commitment is to continue the tradition of excellence and boldness in exploring our solar system, understanding the origin of galaxies and applying that knowledge to better understand the changes on our own planet," Elachi said.

Elachi was born April 18, 1947, in Lebanon. He received a bachelor's degree in physics from the University of Grenoble, France, and a diploma in engineering from the Polytechnic Institute, Grenoble, both in 1968, and a master's degree and doctorate in electrical sciences from Caltech in 1969 and 1971, respectively. He also earned a master's in business administration from USC in 1978 and a master's in geology from UCLA in 1983.

He is perhaps best known for his role in the development of a series of imaging radar systems for the Space Shuttle that allowed scientists to see through clouds that blanket Earth. It even penetrates the top layer of soil in arid regions, revealing hints of what lies below the surface.

Elachi served as principal investigator on numerous NASA research and development studies and flight projects. He is currently team leader of the Cassini Titan radar experiment and a co-investigator on the Rosetta comet nucleus sounder experiment. He is the author of more than 200 publications on space and planetary exploration, Earth observation from space, active microwave remote sensing, wave propagation and scattering, electromagnetic theory, lasers and integrated optics, and he holds several patents in those fields. In addition, he has authored three textbooks on remote sensing. He has taught "The Physics of Remote Sensing" at Caltech since 1982.

In 1988, the Los Angeles Times selected him as one of "Southern California's rising stars who will make a difference in L.A." In 1989, Asteroid 1982 SU was renamed 4116 Elachi in recognition of his contribution to planetary exploration.

Elachi has participated in a number of archaeological expeditions in the Egyptian Desert, the Arabian Peninsula, and the Western Chinese Desert in search of old trading routes and buried cities using satellite data. Some of these expeditions have been featured in National Geographic magazine.

He is married to Valerie Gifford Elachi and has two daughters, Joanna, 25, and Lauren, 15. He lives in Altadena.

He replaces Dr. Edward C. Stone, who will return to full- time teaching and research at Caltech where he has taught since 1967. The David Morrisroe Professor of Physics, Stone has been widely regarded as an energetic and thoughtful leader at JPL.

Stone was project scientist for the Voyager mission, a project that launched twin spacecraft in 1977 and sent them on a 12-year tour of the outer solar system, flying past the giant planets Jupiter, Saturn, Uranus and Neptune.

Named JPL director in January 1991, Stone has led the laboratory during a decade in which it took on management of dozens of missions exploring the solar system, Earth sciences and astrophysics. Highlights of his decade leading JPL include Galileo's five-year orbital mission to Jupiter, the launches of Cassini to Saturn, Mars Global Surveyor and a new generation of Earth sciences satellites such as TOPEX/Poseidon and SeaWinds, and the spectacularly successful Mars Pathfinder landing in 1997. Stone's last day at the helm at JPL will be April 30.

Baltimore praised Stone for leading JPL with great distinction during the past 10 years. "Many seminal discoveries about the solar system have been made during his tenure and a much deeper appreciation of the earth's dynamic cycles has emerged from missions flown by JPL under his leadership. Ed is a person of high integrity, unflagging energy and deep commitment to the Laboratory and its goals. It has been a great pleasure for me to work with him as JPL director and I look forward to having him back on the Caltech campus full time."

Goldin also has high praise for Stone and his accomplishments. "Over the past decade, Ed Stone led JPL from managing a handful of large projects to overseeing dozens of new, smaller exploration missions. A great deal of what we know about the solar system has been a result, directly or indirectly, of Ed's work. It has been my honor to work with Ed Stone in revolutionizing the way JPL does business, because JPL is the most important organization in the field of astrophysics and planetary science."