Analysis of Galileo Clock Products of MGEX-ACs

Compared with the positioning and timing results of each analysis center (AC), international GNSS service (IGS) combined products benefit in stability, reliability, completeness, and robustness. IGS initiated the multi-GNSS experiment (MGEX) to promote the engineering and science applications of multi-GNSS since 2011. Within MGEX, currently there are seven ACs provide satellite orbit and clock products of multi-GNSS, and the timing is right to start investigating combined products of multi-GNSS. At the IGS workshop 2018, a proposal has been made to combine the satellite orbit and clock products for multi-GNSS. In this paper, analysis of Galileo clock products of the MGEX-ACs has been performed from the view of clock combination. Galileo orbit and clock products of three ACs (COD, GFZ and CNES/CLS) in the first week of 2019 are analyzed. Results show that, day boundary discontinuities of COD clocks is within 1ns and same level can be found for CNES/CLS, while that of GFZ is a little large. Consistency between COD and GFZ is better than that of COD and CNES/CLS, and narrow-lane uncalibrated phase delay absorbed by clocks should be considered when combining the CNES/CLS clocks. Inter-category clock consistency can be found between Galileo in-orbit validation (IOV) and full operational capability (FOC) satellites. Pronounced bump in the clock Allan deviation is visible from the stability analysis result of MGEX AC Galileo clock products. It is because orbit errors are mapped to the apparent clock, and the harmonics should be considered in the modeling of Galileo satellite clock to account for the residual orbit errors.