MYRON KAYTON, PhD, is President of Kayton Engineering Company, with forty years of experience designing avionic, navigation, communication, and process systems. He has served as TRW's Chief Engineer for Spacelab avionics, Head of System Engineering for Space Shuttle avionics, and Project Engineer for the electronics of the Inertial Upper Stage. During the Apollo project, he was Deputy Manager for Lunar Module Guidance and Control at NASA's Johnson Space Center and is a former section head at Litton's Guidance and Control Division, where he designed some of the earliest multisensor navigation systems. Dr. Kayton is a Fellow of the Institute of Electrical and Electronics Engineers and an elected member of the corporate board of directors. An instrument-rated pilot, he also holds an FAA Project Raincheck certificate in air traffic control. WALTER R. FRIED, MS, is a navigation systems consultant who is widely known in the field of navigation. In his long career in aerospace electronics, he has worked on most types of navigation systems, as well as on air traffic management, airborne radar, antennas, and communication systems. He was instrumental in developing a new FM-CW Doppler navigation radar for helicopters that is still in widespread use. Mr. Fried was Chief Scientist for Subsystems of the F-111 Avionics System and Technical Director of the JTIDS Relative Navigation System. He served on the FAA-commissioned Blue-Ribbon RTCA Task Force on the "Global Navigation Satellite System Transition and Implementation Strategy" and on several other GPS-related RTCA Committees. A Fellow of the IEEE, he is a coauthor of the book Airborne Radar.