Abstract
In order to establish automatic landing technologies for space planes, the Automatic Landing Flight Experiment (ALFLEX) was planned and 13 flights were carried out from July to August in 1996. As one of the research items of ALFLEX, we developed the pseudolite differential Global Positioning System (GPS) System for ALFLEX to acquire the differential GPS (DGPS) navigation technique for automatic landing. We chose a pseudolite method for the DGPS system of ALFLEX designed because the pseudolite method simplified the onboard system and improved the geometrical dilution of precision (GDOP) at landing. Although the pseudolite had these advantages, the method had some technical challenges and had many newly developed elements, and we encountered some difficulties during the development of the pseudolite DGPS System. However finally the pseudolite DGPS system worked well with good accuracy at the automatic flight experiment. This paper outlines the pseudolite DGPS System for ALFLEX and the results of its development. Then this paper presents the evaluation results of navigations; DGPS navigation, carrier smoothing DGPS navigation, IMU-DGPS-RA integrated navigation and IMU-DGPS integrated navigation. Finally this paper discusses the evaluation results of multipath effect on the pseudolite signal and the comparison of the GDOP between the pseudolite method and the datalink method.
