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Multi-Constellation, Multi-Frequency Simulation of Ionospheric Scintillation along Radio Occultation Raypaths and Potential Impacts on Tropospheric Retrievals
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  • Charles Carrano,
  • Keith Groves,
  • William McNeil,
  • E. Robert Kursinski
Charles Carrano
Boston College

Corresponding Author:[email protected]

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Keith Groves
Boston College, Institute for Scientific Research
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William McNeil
Boston College, Institute for Scientific Research
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E. Robert Kursinski
PlanetiQ
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Abstract

In recent years, the need for improved global terrestrial and space weather specification and forecast has driven the development of new commercial satellite constellations to monitor radio occultations (RO) using Global Navigation Satellite System (GNSS) signals. These signals interact with irregularities in the ionosphere, causing radio wave scintillation that is known to degrade the performance of communication and navigation systems, and may also degrade the accuracy of RO tropospheric and stratospheric retrievals. This January, PlanetiQ will launch the first two of its planned 20 microsatellites commercial constellation (to be complete by 2022), focused on weather and space weather forecasting and climate. With this constellation, PlanetiQ intends to provide over 80 million global observations per day. The focus of this paper concerns a simulation study we conducted to assess possible impacts on tracking and tropospheric retreivals due to ionospheric scintillation. We constructed a 3D, time-dependent model for the strength, orientation, and spectral characteristics of the irregularities. Our methodology generates representative realizations of irregularity structure (space weather) rather than average conditions (climatology). We integrated through the model along each RO ray-path to determine the strength and location of an equivalent phase screen, which we used to generate realizations of intensity and phase scintillation at the receiver. The phase screen calculation is a generalization of our previous algorithm (Carrano et al., Radio Sci., 2011) which now admits propagation and scanning at arbitrary angles to the magnetic field. There were approximately 50,000 RO events between the 20 PlanetiQ microsatellites and the satellites of the GPS, GLONASS, Galileo, and BeiDou GNSS constellations each day. We simulated scintillation for each carrier frequency transmitted by each GNSS satellite for a total of 39 days. We discuss potential impacts of scintillation on satellite tracking and the accuracy of tropospheric retrievals as a function of season and solar activity. We compare the scintillation index (S4) along each RO raypath with a vertical propagation path through the same irregularities. These are compared with observations from the CORISS instrument onboard the C/NOFS satellite and ground based observations from the SCINDA network.