Institute of Navigation GNSS 2008 16-19 September 2008, Savannah, GA Evaluation of Deep Signal Fading Effects Due to Ionospheric Scintillation on GPS Aviation Receivers Jiwon Seo, Todd Walter, Tsung-Yu Chiou, Juan Blanch, and Per Enge Stanford University BIOGRAPHY Jiwon Seo is a Ph.D. candidate in Aeronautics and Astronautics at Stanford University. He received his B.S. in Aerospace Engineering from KAIST (Korea Advanced Institute of Science and Technology) and received M.S. degrees in Aeronautics and Astronautics, Electrical Engineering from Stanford. He was a recipient of Samsung Lee Kun Hee Graduate Fellowship for five years. His current research focuses on aircraft navigation using GPS and WAAS under severe ionospheric scintillation of the equatorial region. Todd Walter is a Senior Research Engineer in the Department of Aeronautics and Astronautics at Stanford University. Dr. Walter received his Ph.D. in 1993 from Stanford and works on developing WAAS integrity algorithms and analyzing the follow on systems to WAAS. He is a fellow of the ION. Tsung-Yu Chiou is a Ph.D. candidate in the Aeronautics and Astronautics Department at Stanford University. He received his B.S. in Aerospace Engineering in 1998 from Tamkang University, Taiwan and his M.S. from Stanford in 2002. His research currently focuses on the performance analysis and validation of Doppler-aided GPS carrier-tracking loops. He is also looking into the solutions to the problem of GPS/WAAS performance degradation caused by ionospheric scintillation. Juan Blanch graduated from Ecole Polytechnique, France in 1999. He holds an M.S. in Aeronautics and Astronautics (2000), an M.S. in Electrical Engineering (2003) and a Ph.D. in Aeronautics and Astronautics (2003) from Stanford University. He received the 2004 Bradford W. Parkinson Award for Graduate Student Excellence in GNSS for his doctoral dissertation. He is currently a Research Associate in the Stanford GPS laboratory, where he works on the design of integrity algorithms for the Wide Area Augmentation System. He is an active member of the WAAS Integrity Performance Panel and the GPS Evolutionary Architecture Study. His research interests include: high integrity estimation of ionospheric delays for GNSS, Receiver Autonomous Integrity Monitoring algorithms, and next generation SBAS algorithms. Per Enge is a Professor of Aeronautics and Astronautics at Stanford University, where he is the Kleiner-Perkins, Mayfield, Sequoia Capital Professor in the School of Engineering. He is also the Director of the GPS Research Laboratory, which works with the Federal Aviation Administration, U.S. Navy and U.S. Air Force to pioneer systems that augment the Global Positioning System (GPS). Prof. Enge has received the Kepler, Thurlow and Burka Awards from the Institute of Navigation for his work. He is a Member of the National Academy of Engineering (NAE), a Fellow of the ION, and a Fellow of the IEEE. ABSTRACT Deep and frequent GPS signal fading due to strong ionospheric scintillation is major concern for aircraft navigation in the equatorial region during solar maximum periods. Deep signal fading can break a receiver’s carrier tracking lock on a satellite channel and the satellite cannot be used for position solution until a receiver reacquires the lost channel. Frequent signal fading also causes frequent reset of the carrier smoothing filter of aviation receivers. Aviation receivers reduce code noise by as much as a factor of 10 by using carrier smoothing, but frequent loss of lock reduces the effective smoothing time and significantly increases the effect of code noise. This paper analyzes navigation availability during a strong scintillation period based on real scintillation data from the previous solar maximum. Both effects from satellite loss due to deep fading and shortened carrier