Scheduling Scenarios for VLBI Observations of Satellites

In this paper, a methodology for automatic scheduling of Very Long Baseline Interferometry (VLBI) observations of satellites is presented and first scheduling approaches are investigated. For this investigation the orbit of a geostationary satellite has been chosen, but, the methodology has also been successfully applied to an orbit of a Global Navigation Satellite Systems satellite. A scheduling procedure based on covariance optimization is developed and observations are simulated. In contrast to other simulation studies for a dedicated VLBI satellite mission, we are performing a scheduling process where observations of quasars and satellites are considered being equally important. Thus, the satellites are consistently included into a VLBI experiment. To validate the individual schedules, simplistic daily constant orbit shifts are estimated and analyzed. In this way, the necessary time between two subsequent satellite observations and the geometry of the observing network are investigated. Taking into account all circumstances, large global networks are the best option for estimating orbit shifts. Such a configuration leads to a large number of observations and a good observing geometry for the orbit. For a geostationary satellite, it is sufficient to carry out only one observation per hour or even longer. However, the presented results are only valid for the estimation of orbit shifts. Various improvements of these initial investigations are imaginable, e.g., considering orbit parameters within the scheduling process or estimating realistic orbit parameters.