Workshop 2018
Lars Prange - An empirical SRP model for the orbit normal attitude mode - October 29, 2018 • 416 Views
The Center for Orbit Determination in Europe (CODE) is contributing to the IGS MGEX (Multi-GNSS Extension) since its start in 2012 with an orbit and clock solution. This CODE MGEX (COM) solution currently considers the satellite systems GPS, GLONASS, Galileo, BeiDou, and QZSS. Because of its experimental character, the COM solution is subject to frequent changes and improvements. One of the severest handicaps of the COM solution so far was the poor modelling of solar radiation pressure (SRP) of the BeiDou and QZS-1 spacecrafts at times, when they are oriented according to the orbit normal (ON) attitude. Based on theoretical considerations and on simulations we designed an empirical SRP model particularly well suited for the ON-mode and verified it with MGEX data. The new model is able to significantly improve the estimated orbits and clock corrections of QZS-1. Results from an external SLR orbit validation indicate that the orbit accuracy obtained with our model is comparable to that achievable with a ray-tracing model. The benefits of our new SRP model are not so pronounced for BeiDou spacecrafts - in particular not for BeiDou IGSOs in connection with long orbit arcs. We addressed this issue by developing a modified version of the model retaining a minimum number of SRP parameters supported by empirical parameters. Both versions of the new model have been activated in the operational COM solution in Summer 2018. Apart from a general overview of the current status of the COM solution, the impact of the aforementioned model change on the COMs QZS-1 and BeiDou orbits is discussed in more detail.

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