Precise Orbit and Clock Products of Galileo, BDS and QZSS from MGEX Since 2018: Comparison and PPP Validation

In recent years, the development of new constellations including Galileo, BeiDou Navigation Satellite System (BDS) and Quasi-Zenith Satellite System (QZSS) have undergone dramatic changes. Since January 2018, about 30 satellites of the new constellations have been launched and most of the new satellites have been included in the precise orbit and clock products provided by the Multi Global Navigation Satellite System (Multi-GNSS) Experiment (MGEX). Meanwhile, critical issues including antenna parameters, yaw-attitude models and solar radiation pressure models have been continuously refined for these new constellations and updated into precise MGEX orbit determination and precise clock estimation solutions. In this context, MGEX products since 2018 are herein assessed by orbit and clock comparisons among individual analysis centers (ACs), satellite laser ranging (SLR) validation and precise point positioning (PPP) solutions. Orbit comparisons showed 3D agreements of 3-5 cm for Galileo, 8-9 cm for BDS-2 inclined geosynchronous orbit (IGSO), 12-18 cm for BDS-2 medium earth orbit (MEO) satellites, 24 cm for BDS-3 MEO and 11-16 cm for QZSS IGSO satellites. SLR validations demonstrated an orbit accuracy of about 3-4 cm for Galileo and BDS-2 MEO, 5-6 cm for BDS-2 IGSO, 4-6 cm for BDS-3 MEO and 5-10 cm for QZSS IGSO satellites. Clock products from different ACs generally had a consistency of 0.1-0.3 ns for Galileo, 0.2-0.5 ns for BDS IGSO/MEO and 0.2-0.4 ns for QZSS satellites. The positioning errors of kinematic PPP in Galileo-only mode were about 17-19 mm in the north, 13-16 mm in the east and 74-81 mm in the up direction, respectively. As for BDS-only PPP, positioning accuracies of about 14, 14 and 49 mm could be achieved in kinematic mode with products from Wuhan University applied.