ANALYSES OF THE EQUATOR-S GPS MISSION DATA AT ALTITUDES ABOVE THE GPS- CONSTELLATION

摘要

On-board the HEO satellite Equator-S a GPS receiver was flown in order to investigate the dependence of the signal quality on the altitude in heights above the GPS constellation. Signal quality means here not only the electrical parameters but also the quality of the data. In this paper some of the most important received data is visualised and commented. The focus, however, lies besides of the results of the detailed electrical parameters analysis on the measurements. More specifically, the carrier-to-noise ratios are correlated the signal strength parameters and related to the spacecraft and antenna attitude and receiver measurements as pseudoranges and carrier phases are compared to orbit information of the DLR and the NASA. Although no navigation solution was possible because four satellites could not be seen simultaneously interesting results from the relative distances could be obtained. The satellite flew nearly in the equatorial plane with an perigee of 500 km and an apogee of 67000 km. Thus, also the Geostationary Orbit could be taken under investigation. The highest altitude where measurements could be obtained was 61000 km, which has not been reached by any other GPS-mission. Several measurements near the Geostationary Orbit have been made and also side lobes of the GPS-signal could be received "near" the GPS-constellation.