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Abstract:
Within the preparation for the new release of the International Terrestrial Reference Frame – ITRF2020, the IGS ACs issued the results of the third reprocessing campaign – International GNSS Service (IGS) Repro3 based on the GNSS network solutions backwards starting from 1994. In total, nine IGS Analysis Centers (ACs) contributed to the IGS Repro3 initiative by providing their GNSS orbit. In this contribution, we analysed the GPS, GLONASS and Galileo orbit quality, based on the analysis of orbit misclosures, orbit differences, and Satellite Laser Ranging (SLR) residuals.
The standard deviation of SLR residuals of the best individual IGS Repro3 solutions equals 13, 14, 15, 17, 16, and 15 mm for Galileo-FOC, -FOCe, -IOV, GLONASS-K1B, -M, and -M+, respectively. The SLR validation of the individual AC solutions confirmed orbit modelling aspects, which are beneficial for the orbit products. For Galileo, the hybrid approach, which incorporates the analytical box-wing model and a limited set of estimated empirical parameters, significantly decreases fluctuations in SLR residuals, particularly for low Sun elevation angles (β) during orbit eclipses. Moreover, ESA, as the only AC, incorporates additional once-pre-revolution parameters in the along-track direction, which seems to be also beneficial, given the superb quality of their products. Moreover, none of the ACs mitigates the pattern of large negative SLR residuals for high β angles for the Galileo-IOV orbits. Finally, the consistency of the GLONASS orbit products delivered by individual ACs is higher than for the Galileo, despite using different approaches for handling non-gravitational forces.
