CYGNSS based ionospheric electron content estimation: An analysis
NASA's Cyclone Global Navigation Satellite System (CYGNSS) will detect variations in GNSS signals reflected from ocean surfaces for estimation of surface wind speeds, planned for launch in 2016. The CYGNSS data product, a Delay Doppler Map (DDM) will contain atmospheric propagation errors. In this work, we present a mathematical model to characterize the ionospheric and tropospheric effects. The measurement model represents pseudoranges from the direct and the reflected signals as a sum of path lengths, atmospheric refraction effects, and noise. From the model we can address two different ionospheric problems: one in which the ionospheric electron content is a potential secondary science product, and alternatively, one in which the ionosphere is a nuisance parameter. For these two objectives, respectively, we present an estimation of relative electron content using GNSS reflectometry, and simulation of typical ionospheric delay errors that will remain in the DDM. Distinct configurations for the geometric term are shown in order to analyze the accuracy of the estimated ionospheric delay. To account for adequate buffer in delay for open loop tracking, we perform simulations for typical ionospheric delay error from CYGNSS against three main factors: satellite elevation angle, latitude, and local time.