Flight data analysis for the integrated navigation of ALFLEX (Automatic Landing Flight Experiment)

The National Space Development Agency of Japan (NASDA) and The National Aerospace Laboratory (NAL) have been studying the Japanese unmanned winged space vehicle named HOPE. In order to establish automatic landing technologies for the HOPE, the Automatic Landing Flight Experiment (ALFLEX) was carried out at Woomera airfield Australia, from July to August in 1996 and the ALFLEX vehicle was successfully landed to the runway automatically through all test flights. One of the main objects of the ALFLEX is to evaluate navigation methods, and for this reason, the ALFLEX vehicle has 4 navigation sensors, Inertial Measurement Unit (IMU), MLS receiver (MLSR), Differential GPS receiver (DGPSR) and Radio Altimeter (RA) and the data of these sensors are recorded during the flight. As for the onboard navigation system, two navigation methods are used for the ALFLEX, the IMU/DGPS integrated navigation is used during the hanging phase and the IMU/MLS/RA integrated navigation is used during the free flight phase. These onboard navigation systems were selected to reduce the risk of the experiment, and more advanced navigation systems which are investigated to apply to the HOPE were to be evaluated by the post processing. Therefore, we evaluated some integrated navigation methods using real flight data by the post processing. This paper outlines the ALFLEX experiment, the Guidance, Navigation and Control (GN&C) system of the ALFLEX and its navigation sensors first. Then this paper describes the system models, the measurement equations and the algorithms of the integrated navigation filters. Finally, this paper shows the flight data analysis results using the real flight data from the ALFLEX. The analysis consists of the calculation and the evaluation of the IMU inertial navigation and the integrated navigations such as the IMU/DGPS integrated navigation , the IMU/DGPS/RA integrated navigation and the IMU/MLS/RA integrated navigation.