Characterization and Mitigation of Interference between GNSS Radio Occultation and Reflectometry Signals for Low Altitude Occultations

Ian Collett, Y. Jade Morton, and Brian Breitsch

Abstract:	This research investigates the mutual interference between a GNSS signal refracted through the atmosphere and the same signal reflected from the surface below. For low altitude occultations, the path length difference between the direct and reflected signal is small enough that the reflected signal can be present as multipath when tracking the direct signal. This poses a problem when making remote sensing measurements using GNSS-RO or GNSS-R techniques. Here, this issue is addressed in context to GNSS data collected by an antenna dish on the summit of Haleakala on the Hawaiian island of Maui. GPS L1, L2, and L5 signals are tracked and the signal intensity is calculated in post processing. First, a definition is proposed for the multipath presence transition elevation, a threshold below which the reflected signal can be present as multipath on the direct signal. This threshold is calculated for the GPS signals collected in the mountaintop geometry. Next, the first steps are taken to mitigate the mutual interference between the direct and reflected signals. A frequency-domain filtering approach and a time-domain smoothing approach are both applied to the signal intensity in an effort to separate the multipath contribution and the direct signal contribution.
Published in:	Proceedings of the 31st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2018) September 24 - 28, 2018 Hyatt Regency Miami Miami, Florida
Pages:	2848 - 2858
Cite this article:	Collett, Ian, Morton, Y. Jade, Breitsch, Brian, "Characterization and Mitigation of Interference between GNSS Radio Occultation and Reflectometry Signals for Low Altitude Occultations," Proceedings of the 31st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2018), Miami, Florida, September 2018, pp. 2848-2858. https://doi.org/10.33012/2018.15861
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