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, f0F2, and the peak height of the F2 layer, HmF2) 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 f0F2 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 HmF2at 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 f0F2 are a factor of four smaller than corresponding errors for IRI, while GPSII HmF2 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.

The Ionospheric Exploration Based on TJU#01 Meteorological Microsatellite Mission: Initial Results

“…The results prove that the occultation data of commercial companies are comparable with most of the scientific missions, and have a positive impact on the weather forecast (Bowler, 2020). Furthermore, the electron density profiles retrieved from Spire ionospheric measurements as well as the assimilative ionospheric model have strong agreement with the ground-based digisonde observations (Forsythe et al, 2020;Kramer et al, 2021).…”

“…The results prove that the occultation data of commercial companies are comparable with most of the scientific missions, and have a positive impact on the weather forecast (Bowler, 2020). Furthermore, the electron density profiles retrieved from Spire ionospheric measurements as well as the assimilative ionospheric model have strong agreement with the ground-based digisonde observations (Forsythe et al, 2020;Kramer et al, 2021).Recently, a Chinese company called Tianjin Yunyao Aerospace Technology Co., Ltd. (YUNYAO) launched its first meteorological microsatellite, TJU#01, on 7 December 2021. It is a big success to send independent-built RO receiver into the space by commercial organization in China.…”

Study of Ionospheric Bending Angle and Scintillation Profiles Derived by GNSS Radio-Occultation with MetOp-A Satellite

“…Usually, GNSS RO measurements are validated against external data sources. Ionosonde stations and incoherent scatter radars, for instance, are commonly used as a reference to the validation [12][13][14][15][16][17][18][19][20][21][22] since they provide accurate observations of the electron density. In-situ measurements provided by external satellite missions are also extensively used to assess the RO measurements [23][24][25][26][27][28][29][30].…”