Kinematic Determination Of GNSS Orbits Including Clock Modeling

Abstract

Modern orbital products from the International GNSS Service (IGS) analysis centers are based on dynamic orbit models including a variety of perturbation forces. It is well-known that the errors caused by modeling deficiencies are propagating into further products like satellite clock corrections, station coordinates, Earth rotation parameters (ERP) and troposphere zenith delays, producing artifacts in the time series at the draconitic period of about 352 days for data from the Global Positioning System (GPS). In contrast to the orbit determination strategy used by the IGS analysis centers, we propose a purely kinematic estimation of the satellite position. The high correlation between the radial component of the orbit and the satellite clock error is resolved by modeling the behavior of the latest generation of clocks available on board Galileo and GPS Block IIF satellites. Using a linear polynomial as deterministic mode and applying epoch-to-epoch constraints to stochastic satellite clock corrections, consistent kinematic orbits with an RMS below 3.3 cm for Galileo satellites equipped with Passive Hydrogen Maser (PHM) clocks are found. When the kinematic orbits are compared to dynamic orbits produced by the European Space Operations Centre (ESOC), systematic signals are visible, with effects strongly correlated with the solar β angle. The kinematic orbit results are also confirmed by Satellite Laser Ranging, showing a reduction of the standard deviation of the residuals of up to 47% compared to dynamic orbits.