CODE’s five-system orbit and clock solution—the challenges of multi-GNSS data analysis

Abstract

This article describes the processing strategy and the validation results of CODE's MGEX (COM) orbit and satellite clock solution including the satellite systems GPS, GLONASS, Galileo, BeiDou, and QZSS. The validation with orbit misclosures and SLR residuals shows that the orbits of the new systems Galileo, BeiDou, and QZSS are affected by modelling deficiencies with impact on the orbit scale (e.g., antenna calibration, Earth albedo, transmitter antenna thrust). Another weakness is the attitude and solar radiation pressure (SRP) modelling of satellites moving in the orbit normal mode-which is not yet correctly considered in the COM solution. Due to these issues we consider the current state COM solution as preliminary. We, however, use the long time series of COM products for identifying the challenges and for the assessment of model improvements. The latter is demonstrated on the example of the solar radiation pressure (SRP) model, which has been replaced by a more generalized model. The SLR validation shows that the new SRP model significantly improves the orbit determination of Galileo and QZSS satellites at times when the satellite's attitude is maintained by yaw-steering. The impact of this orbit improvement is also visible in the estimated satellite clocks-demonstrating the potential use of the new

A New Online Service for the Validation of Multi-GNSS Orbits Using SLR

“…In parallel, the continuous 1-day orbits are fitted to the discrete satellite positions from the EPH file. The arc-fit strategy is consistent with the official CODE's MGEX solution processing [5] in an aim to correctly restore the orbit. Minor differences in orbit modeling are absorbed by estimating stochastic pulses in three orbital directions.…”

“…CODE solutions include satellites of the following systems: GPS, GLONASS-M, GLONASS-K, Galileo IOV, Galileo FOC, BeiDou-2 MEO, BeiDou-2 IGSO and QZSS. Besides CODE, there are five other ACs which deliver multi-GNSS orbit products in the framework of MGEX: Centre National d'Études Spatiales (CNES/CLS) [4], Helmholtz Centre Potsdam German Research Centre for Geosciences (GFZ) [5], Technische Universität München (TUM), Wuhan University (WU) [40] and Japan Aerospace Exploration Agency (JAXA) [41]. Products from all ACs can be included in the GOVUS service, which is one of the major plans for the future development.…”

Quality assessment of multi-GNSS orbits and clocks for real-time precise point positioning

“…As a reference product, the final CODE MGEX (Prange et al 2017) solution is employed. It provides both the orbits and clocks for GPS, GLONASS, Galileo and BeiDou excluding BeiDou GEO satellites, of which the latter are associated with a poor accuracy of their orbits .…”

Investigation on Reference Frames and Time Systems in Multi-GNSS

“…To study the accuracy of the broadcast orbits relative to the precise orbits provided by CODE [6] SP3 (Extended Standard Product 3 Orbit Format), the alignment of the reference systems adopted by broadcast orbits with respect to that provided by precise orbits is analyzed. The reference frames adopted by the several GNSSs in the broadcast ephemeris are different from each other, namely WGS84 (GPS), PZ-90.11 (GLONASS), GTRF (Galileo) and CGCS2000 (BeiDou), whereas the reference frame adopted by precise orbits is typically unique.…”