An Evaluation of Spire Radio Occultation Data in Assimilative Ionospheric Model GPSII and Validation by Ionosonde Measurements
Abstract
This paper presents a comprehensive analysis of results obtained using NWRA’s assimilative ionospheric model GPSII when it is driven by Spire Global, Inc.’s global navigation satellite system ‐ radio occultation (GNSS‐RO) measurements. Results of the assimilative model are validated using the database of Digisonde and Dynasonde ionograms. A week’s worth of dual‐frequency phase data was collected from Spire’s constellation of low‐Earth orbiting micro‐satellites carrying GNSS receivers and assimilated into GPSII. A validation study of GNSS‐RO measurements was performed in four geographical regions. GPSII operation with the data was evaluated and the results were validated against independent ionospheric measurements. Ground‐based ionosondes were employed in diagnosing the accuracy of the derived models; we studied the differences between the F2 peak parameters (the F2 layer critical frequency, , and the peak height of the F2 layer, ) derived from ionograms and those computed with GPSII. For the 1,491 validation events used in this study, the magnitude of the deviation of the GPSII‐predicted at an ionosonde location from the corresponding ionosonde‐observed value was found on average to be 0.608 MHz (with a median of 0.461 MHz) and the magnitude of the deviation of the GPSII‐predicted at an ionosonde location from the corresponding ionosonde‐observed value was found to be on average 22.9 km (with a median value of 18.0 km). Median GPSII validation errors for are a factor of four smaller than corresponding errors for IRI, while GPSII errors are a factors of two smaller than those for IRI. 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.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Apr 01, 2021
- Source ID
- 10.1029/2020rs007139
Entities
People
- Kelsey K. Kramer
- L. J. Nickisch
- Sergey V. Fridman
Organizations
- Defense Advanced Research Projects Agency
- Northwest Research Associates