Orbit determination of GIOVE-A using SLR tracking data

The first European navigation test bed satellite GIOVE-A was launched on 28 December 2005. SLR observations of GIOVE-A, collected from the ILRS tracking network, are available since 21 May 2006. SLR data are primarily needed for the validation of the microwave-based orbit. As no microwave tracking data are available until now, the orbit determination based on SLR data is of high interest. We present GIOVE-A orbit determination results based on SLR-only data. In addition, the contribution of SLR data to the microwave-based orbit determination is demonstrated. For the SLR-based orbit determination of GIOVE-A SLR data of the first GIOVE-A SLR tracking campaign were used. Orbits with different arc lengths were determined, as well as orbit predictions. Orbit overlaps were derived to assess the orbit quality. SLRbased orbits of 9-days arc length were determined with an accuracy of about 10 cm in radial orbit component, and about 0.5 m and 1 m in along-track and out-of-plane components. The microwave-based GIOVE-A orbits as well as the first Galileo orbits in the In Orbit Validation (IOV) phase will rely on microwave tracking data of a very limited number of stations. Therefore, SLR would give an important contribution to the orbit determination through a combined analysis of microwave and SLR data. The possible improvement of the orbit accuracy including SLR observations is demonstrated on the basis of an a priori variance-covariance analysis. For this purpose SLR range measurements and simulated microwave data of GIOVE-A are used.