Signal design and in-orbit performance of the new microwave satellite tracking system PRARE

The new two-way microwave satellite tracking system PRARE has been in continuous operation on-board ERS-2 since May 1, 1995. With the assistance of a network of mobile, autonomous PRARE ground stations, the PRARE space segment generates on a global basis two-way pseudonoise-coded range and carrier shifted Doppler measurements at the sub-dm resp. sub-mm/s level of accuracy. These data are primarily used by a number of international geoscience research groups to derive higher-level geodynamic products such as precise ERS-2 orbits, ground station coordinates and velocities, Earth gravity field parameters, or ionospheric quantities. The system's very high measurement accuracy is primarily based on an ensemble of fully coherent DLLs and PLLs inside the space segment controlled by a quartz-USO and an appropriately structured measurement signal. The paper describes the up-to-date status and performance of the PRARE system, whereby the main emphasis is laid on the signal design and the routine quality assessment efforts taken during data processing as well as on the proof of the adequacy of PRARE for the given tasks.