Commercial Space Weather Data Pilot GNSS Processing and Product Evaluation

Under the National Oceanic and Atmospheric Administration (NOAA) space weather Commercial Weather Data Pilot (CWDP) program, a team from NOAA, UCAR, and several other partners is evaluating Global Navigation Satellite System (GNSS) space weather data products derived from observation data collected by small satellite constellations designed and operated by PlanetIQ and Spire Global. The pilot study included a 6 month data delivery phase with near real-time processing, reprocessing activities, and evaluation of higher level products.

COSMIC Data Analysis and Archive Center (CDAAC) system is utilized to generate electron density profile (EDPs), total electron content (TEC), and scintillation metrics. EDPs are generated using the approach utilized for other satellite missions (e.g. COSMIC-1 and -2). We derive absolute TEC tracks reaching from negative (minimum height of straight line 90 km) to positive elevations taking into account differential code bias and multipath calibrations. To monitor scintillation events, high rate carrier phase and signal-to-noise ratio observations (e.g. 50 Hz or 100 Hz) are downlinked under certain conditions. The high rate observations are used to derive scintillation amplitude and phase indices, and to geolocate ionospheric irregularity regions based on a back-propagation algorithm developed for COSMIC-2.

We present several study results. EDPs are evaluated by comparing to collocated COSMIC-2 EDPs for some cases to illustrate consistency, and via statistical summaries of the differences in obtained F2 peak layer critical frequency and height of peak electron density. We evaluate slant TEC distributions and compare to collocated COSMIC-2 TEC tracks where the time and observation geometry are similar. Spacecraft altitude differences, and resulting differences in the amount of TEC observed, are accounted for to the extent possible using the International Reference Ionosphere. We then estimate absolute TEC uncertainty from these comparisons using the approach applied previously for COSMIC-2 [1]. For scintillation we characterize amplitude and phase indices, and describe differences observed between high and low latitude scintillation events. We also report on progress applying the geolocation location algorithm to these data.

[1] Pedatella, N.M., Zakharenkova, I., Braun, J.J., Cherniak, I., Hunt, D., Schreiner, W.S., Straus, P.R., Valant-Weiss, B.L., Vanhove, T., Weiss, J. and Wu, Q., 2021. Processing and validation of FORMOSAT-7/COSMIC-2 GPS total electron content observations. Radio Science, 56(8). https://doi.org/10.1029/2021RS007267