of the NASA Advisory Committee and commissioner of the Presidential Commission on Air Safety and Security. He is a fellow of the Royal Institute of Navigation and the American Institute of Astronautics and Aeronautics.

Richard A. Riddell is a retired rear admiral, U.S. Navy, and is currently affiliated with General Dynamics. He held numerous positions of responsibility during his Navy career, culminating in directorships of the Special Programs Division and the Test and Evaluation and Technology Requirements Office of the CNO. He also served as director of the Strategic Submarine Division. As such, Admiral Riddell knows about naval needs in communications technology and applications of PTTI to communications and navigation. Admiral Riddell’s awards include the Legion of Merit with four Gold Stars, the Meritorious Service Medal with two Gold Stars, and the Navy Commendation Medal with three Gold Stars. He is a graduate of the U.S. Naval Academy.

Samuel R. Stein is a founder and president of Timing Solutions Corporation, a company that specializes in real-time applications and provides timing systems to the national laboratories, DOD systems such as GPS, and government prime contractors. He has developed ultra-high-precision time measurement, generation, and distribution systems and is an internationally recognized leader in time and frequency measurement methods and the ensembling of clocks. He previously held management positions at Ball Corporation (Efratom Division) and the National Bureau of Standards (now NIST).

Robert F.C. Vessot recently retired from his position as senior physicist at the Harvard-Smithsonian Center for Astrophysics, where he served as principal investigator of the Hydrogen Maser Laboratory from 1969 and now serves as a research associate. His research group built all the hydrogen masers used in NASA’s Deep Space Network and has supported radio astronomical Very Long Baseline Interferometry activities worldwide. He has worked on hydrogen masers since 1961 and did much to make the hydrogen maser the most stable oscillator available. Before joining Harvard-Smithsonian, he was manager of hydrogen maser research and development at Varian Associates/Hewlett-Packard (1960-1969). He was principal investigator for NASA’s Gravity Probe-A experiment, which confirmed Einstein’s predictions of the effects of relativistic gravitation on the rate of clocks at a precision of 70 parts per million. He currently works as a consultant for Kernco, a commercial provider of atomic frequency standards. In 1978, Dr. Vessot was awarded the NASA Medal for Exceptional Scientific Achievement. He received the IEEE Rabi Award in 1978 and the PTTI Distinguished Service Award in 2001.

John R. Vig is a research scientist and program manager at the U.S. Army’s Fort Monmouth. His work has focused primarily on frequency control devices, with a specialty in quartz crystal oscillators. He is a fellow of IEEE and has received that organization’s Cady Award. He is active in the IEEE Frequency Control Symposium, frequently serving in leadership roles, including chair of the Technical Program Committee for the 2002 international symposium. He has served as president of the IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society and is currently president of the IEEE Sensors Council.

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