Abstract. The Global Positioning System (GPS) has become a stealth utility. GPS serves one billion users with diverse applications for not just navigation, but also communications, finance, power systems, agriculture, etc. The world-wide dependency on GPS has far exceeded original expectations. In this talk, I present my research on protecting GPS by promoting interoperability with other satellite systems and by mitigating interference and jamming.

The US GPS and Russian Glonass constellations are being joined by the European Galileo and Chinese Compass systems. Moreover, all of these satellite navigation systems plan to have multiple new signals transmitting in multiple new frequency bands. The signals are exposed to interference from existing aeronautical systems and jamming from personal privacy devices. If the four systems are implemented, we will have 120 satellites and over 300 signals in space for global navigation by 2030.

Thus far, two test satellites of the Galileo system and one medium-earth-orbit satellite from the Compass system have been launched. Unfortunately, when the new satellites were put into orbit, their signal specifications were unpublished. In this talk, I will present my approach to decoding the spread spectrum codes and deriving the underlying code generators for the open civil signals based on observations alone. My decoding work has built a foundation for research on multi-constellation interoperability and redundancy. I will then answer the question, “how many navigation satellites are too many?”

I will also present my recent work on mitigating positioning errors, such as pulsed interference from existing radio systems. I will show with flight test data that my time-frequency hybrid blanking algorithm outperforms existing methods.

Bio. Grace Xingxin Gao is a research associate in the Department of Aeronautics and Astronautics at Stanford University. She received her B.S. degree in Mechanical Engineering in 2001 and her M.S. degree in Electrical Engineering in 2003, both at Tsinghua University, China. She obtained her Ph.D. degree in Electrical Engineering at Stanford University in 2008. She currently leads 3 projects, radio frequency interference mitigation, multi-constellation Global Navigation Satellite System (GNSS), and GNSS monitoring, all sponsored by Federal Aviation Administration. She has won a number of awards, including RTCA William E. Jackson Award, Institute of Navigation (ION) Early Achievement Award, 50 GNSS Leaders to Watch by GPS World Magazine, and multiple best presentation awards at ION GNSS conferences. In 2012, Grace has been elected and serves as Institute of Navigation Council member and co-chair of the Technical Committee on Air Navigation.