IMU-DM Integrated Navigation and Terminal Reentry Guidance for Accurate Guided Reentry Flight

High-accuracy reentry guidance has become increasingly important for reentry capsule spacecraft. For example, in an advanced concept study of the Japanese manned reentry capsule, an attempt has been made to land the capsule on the Japanese mainland. For this purpose, the targeted reentry guidance accuracy is to within 1 km at the point of parachute deployment. To meet this high requirement, we have been developing accurate real-time prediction guidance using numerical integration for reentry spacecraft. This guidance method is an explicit guidance law using real-time numerical integration to predict the accurate range during reentry flight, which already includes IMU-GPS integrated navigation, on-orbit alignment by star tracker and measured wind information utilization for range prediction. However, reentry guidance error analyses we did using those guidance methods showed that we need to made more effort to meet the targeted reentry guidance accuracy of 1 km, particularly given the considerable residual alignment error of inertial navigation and unpredictable upper-level wind variation. Accordingly we added the IMUDM (Drag Measurement) integrated navigation and improved terminal reentry guidance to the accurate real-time prediction guidance using numerical integration for reentry spacecraft. This paper outlines the real-time prediction guidance using numerical integration (REPNI Guidance), describes the methods and performances of IMU-DM integrated navigation and improved terminal reentry guidance and shows guidance accuracy using those methods by guidance error analyses and Monte Carlo simulations.