Abstract
Satellite laser ranging (SLR) observations provide an independent validation of the global navigation satellite system (GNSS) orbits derived using microwave measurements. SLR residuals have also proven to be an important indicator of orbit radial accuracy. In this study, SLR validation is conducted for the precise orbits of eight Galileo satellites covering four to eight years (the current longest span), provided by multiple analysis centers (ACs) participating in the multi-GNSS experiment (MGEX). The purpose of this long-term analysis (the longest such study to date), is to provide a comprehensive evaluation of orbit product quality, its influencing factors, and the effect of perturbation model updates on precise orbit determination (POD) processing. A conventional ECOM solar radiation pressure (SRP) model was used for POD. The results showed distinct periodic variations with angular arguments in the SRP model, implying certain defects in the ECOM system. Updated SRP descriptions, such as ECOM2 or the Box-Wing model, led to significant improvements in SLR residuals for orbital products from multiple ACs. The standard deviation of these residuals decreased from 8–10 cm, before the SRP update, to about 3 cm afterward. The systematic bias of the residuals was also reduced by 2–4 cm and the apparent variability decreased significantly. In addition, the effects of gradual SRP model updates in the POD were evident in orbit comparisons. Orbital differences between ACs in the radial direction were reduced from the initial 10 cm to better than 3 cm, which is consistent with the results of SLR residual analysis. These results suggest SLR validation to be a powerful technique for evaluating the quality of POD strategies in GNSS orbits. Furthermore, this study has demonstrated that perturbation models, such as SRP, provide a better orbit modeling for the Galileo satellites.
Highlights
Satellite laser ranging (SLR) is a space geodetic technique that offers sub-centimeter single-shot precision for ground site-to-satellite distance measurements
∆u or γ.inDaytime observations accounted for ~25–40% of the total uals on local and time, as opposed to differences the accuracy of SLR observations during both daytime and nighttime measurements.In other words, the share of day and night observations was data, as mentioned previously. Roughly equal and such residual distributions could not be attributed to observation time. These results suggest that diurnal variations in the SLR residuals from Galileo satellite orbits are strongly correlated with the quality of solar radiation pressure (SRP) modeling
SLR observations were used to validate the accuracy of orbit products for Galileo satellites with the longest temporal spans currently provided by multi-GNSS experiment (MGEX) analysis centers
Summary
Satellite laser ranging (SLR) is a space geodetic technique that offers sub-centimeter single-shot precision for ground site-to-satellite distance measurements. Some studies have suggested the distribution characteristics of SLR residuals in observation local time could be related to perturbation modeling [17,18] These studies have demonstrated that SLR validation is an important technique for verifying the orbital accuracy of Galileo satellites, and a valuable tool for the improvement of dynamic GNSS POD modeling. This study utilizes long-term SLR observations, provided by the ILRS, to conduct SLR validation of Galileo orbital products produced as part of the multi-GNSS experiment (MGEX). The characteristics of these SLR validation results for multi-year orbits are analyzed and corroborated from multiple perspectives. Their significance for quality evaluation of POD modeling, SRP modeling, is assessed
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