Selection of functional and operational requirements for the new 13-m DLR Ka-band ground station in Weilheim

Kurzfassung

Currently, there are several commercial satellite missions worldwide which provide high rate communication services at Ka-band frequencies (18-40 GHz) to various ground-based users. Moreover, commercial geostationary satellite missions slowly begin to use Ka-band frequencies for LEOP (Launch and Early Orbit Phase), TT&C (Telemetry, Tracking and Command) and payload data operations. One of such satellites is ViaSat-1, which is planned for the launch in 2011. At the same time, due to lack of millimeter wave and high data rate systems, future deep space and near-Earth missions are not in a position to downlink scientific data in a full capacity, which limits mission objectives and possible data return. High data return can only be implemented employing higher frequency bands, e.g. Ka-band. Putting in service higher frequencies allows several advantages. For example, Ka-band brings up to 600% link advantage over X-band. In this concern, the Ka-band antenna is an inevitable part of the modern ground station complex, which allows higher data throughput. Today ESA and NASA have already upgraded their Deep Space ground stations to provide Ka-band capability. There are several projects and potential missions which will require Ka-band support in Europe: H2SAT, EDRS, future L2 (Lagrange) and lunar programs, to name a few. These will include IOT (In-Orbit Testing), TT&C services and potentially LEOP. Having this in mind, GSOC has already started the development of a new full-motion 13-m Ka-band ground station, which will simultaneously enable the missions support and research of a new frequency band, including the design of a high data rate modems, rain attenuation models and Fade Mitigation Techniques. Due to the small wavelength (10-15 mm) of Ka-band signal, the requirements for such ground stations (for front- and back end) in terms of pointing accuracy, acceleration and velocity limits, Doppler shift compensation and the requirements to the specific hardware are very challenging compared to traditional S/X/Ku-band ground stations. This paper describes the most critical requirements partially based on CCSDS recommendations and the needs of future national and European space missions. The following problems have been addressed: frequency selection; pointing accuracy; angular velocity and acceleration, Doppler shift compensation, rain fade mitigation and link budget.