Hayabusa Descent Navigation based on Accurate Landmark Tracking Scheme

Abstract

The spacecraft Hayabusa performed the descent flights to the target asteroid ltokawa in November of 2005. The surface of ltokawa has a lot of boulders and there are few flat areas where the spacecraft can touch down safely. With the reaction wheels lost prior to the touchdown events, it was very difficult to control translational motion accurately, since the guidance accuracy of several millimeters per second was requested. To accurately determine the spacecraft position, a landmark tracking scheme with the help of the ground operation was introduced and developed in the Hayabusa mission. The Hayahusa project team developed new tools that combined human assist with the computer aided terminal display. The proposed landmark tracking scheme did contribute to the successful precise navigation to the specified area on the surface. This paper presents a descent navigation method with the landmark tracking used for the Hayahusa mission, including the developed ground operation tools.