An evaluation of Spire radio occultation data in assimilative ionospheric model GPSII and validation by ionosonde measurements

This paper presents the results of a comprehensive analysis of Spire Global, Inc.'s total electron content (TEC) observations using NorthWest Research Associate's (NWRA) assimilative ionospheric model GPSII. A week's worth of TEC data was collected from Spire's constellation of low-Earth orbiting micro-satellites carrying GNSS receivers and assimilated into GPSII. GPSII operation with the data was evaluated and the results were validated with observations from independent sources. Ground-based ionosondes were employed in diagnosing the accuracy of the derived models; NWRA studied the differences between the F2 peak parameters (f(0)F(2) and HmF2) derived from ionograms and those computed with GPSII. The analysis showed that Spire's TEC data was both compatible for ingestion into GPSII and that the assimilation of the data improved the comparison to ground-based ionosondes. On average f(0)F(2) was improved by 1.317 MHz and HmF2 was improved by 22.8 km with this data ingested into GPSII.