2007 Tycho Brahe Award

Presented to: Dr. Yoaz Bar-Sever

Citation: For outstanding contributions to the art of GPS satellite orbits and signal modeling for high-accuracy spaceborne navigation and science applications.

Dr. Yoaz Bar-Sever is a principal engineer at NASA's Jet Propulsion Laboratory, where he currently is the program manager of the NASA Global Differential GPS (GDGPS) System. For nearly 20 years he has been involved in GPS technology development and its scientific applications. His key contributions cover the areas of GPS orbit and signal modeling for precision terrestrial and spaceborne GPS navigation. During this time he has written more than 50 journal papers and conference articles and played a leadership role in various activities of the International GNSS Service. He is also a long-time member of The Institute of Navigation for which he has repeatedly served as session chair.

The pioneering and innovative research of Dr. Bar-Sever in the area of precision GPS orbit and signal modeling has enabled cm level ephemeris products with numerous benefits for science and navigation. His significant contributions to the art include: identifying and solving the yaw attitude problem of GPS satellites during eclipse season; developing and refining an empirical approach to derive solar radiation forces for GPS satellites in orbit; pioneering the estimation of antenna phase center offset of the GPS satellites in orbit, showing large discrepancies with the official pre-launch-calibrated values; improving the state of the art in atmospheric sensing with GPS and GPS orbit determination accuracy by introducing the atmospheric gradient model to GPS data processing; leading the transformation of the GDGPS from a proofof- concept prototype in 2000 to a fully operational system; and, demonstrating signal in space for the new TDRSS Augmentation Service for Satellites (TASS), extending GDGPS services to space to enable precise real time navigation in Earth orbit. Dr. Bar-Sever is currently leading the effort at NASA to enhance and operationalize the TASS system.

Dr. Bar-Sever received a Ph.D. in Applied Mathematics from the Technion - Israel Institute of Technology, and a Master in Electrical Engineering from the University of Southern California.