A Concept for an Autonomous Space and Ground Segment Applied to the BIRD Satellite Mission

Abstract

In the framework on the BIRD satellite mission, a GPS-based system for the onboard generation of NORAD Twoline elements has been established. To that end, position data from a low-cost GPS receiver are applied to estimate the mean orbital elements and the ballistic coeffcient of the SGP4 analytical orbit model using an epoch state Kalman filter. The estimated SGP4 elements enhance the space segment autonomy, since they allow long-term orbit predictions aboard the spacecraft and the execution of autonomous scheduling functions, such as eclipse predictions and station contact forecasts. Furthermore, the SGP4 mean elements and the ballistic coefficient are applied to generate NORAD-compatible Twoline elements. An autonomous space and ground segment is achieved, since the onborad generated Twoline elements are transmitted to an experimental ground station for the computiation of the satellite contact times, thus avoiding a dedicated ground-based orbit interface.