Topside ionospheric tomography exclusively based on LEO POD GPS carrier phases: Application to autonomous LEO DCB estimation

This article belongs to the Special Issue New Insights in GNSS Remote Sensing for Ionosphere Monitoring and Modeling.This paper presents a novel technique to estimate DCBs from GPS transmitters and receivers on-board Low Earth Orbit (LEO) satellites. The technique consists of obtaining the DCBs as residuals from the difference between the ionospheric combination of the code and the associated ionospheric delay. The ionospheric delay is computed with TOMION, a background-model-free ionospheric tomographic technique based on dual-frequency GPS carrier phase data only, and solved with a Kalman filter. Thus, DCBs are also estimated epoch-wise from the LEO Precise Orbit Determination (POD) GPS receiver as a secondary product. The results for GPS satellite DCBs, obtained exclusively from the three MetOp LEO POD GPS receivers over four consecutive weeks, are in full agreement (i.e., at the level of a few tenths of ns) with those reported independently with other techniques from hundreds of ground-based receivers exclusively, by JPL and CODE analysis centers.This research was funded by EUMETSAT in the context of the project Assessment of GRAS Ionospheric Measurements for IonosphericModel Assimilation (GIMA, number EUM/CO/21/4600002530/RN). The work has been performed coinciding with the execution of the PITHIA-NRF H2020 project (H2020-INFRAIA-2018-2020101007599).Peer reviewe