On autonomous imagery of phobos and Deimos using flyby camera on board planet-B spacecraft

ISAS (Institute of Space and Astronautical Science) is currently planning to launch PLANET-B spacecraft toward Mars in 1996, which is injected onto 300 km by 10 rm (Martian Radii) elliptical orbit in September of 1997. Major purpose of PLANET-B mission is, first of all, plasma physics observation around the Mars. As PLANET-B spacecraft is supposed to carry optical imaging instrument MIC(Mars Imaging Camera), close-up imagery of Martian satellites, Phobos and Deimos is also planned. However, high resolution imagery of Martian satellites inevitably requires quite a closest approach with those small objects and its resolution is almost governed by the navigation accuracy on which camera orientation sequence is to be based. This paper presents a preliminary analysis of overcoming this difficulty by making use of autonomous, real-time and on-board navigator whose information source is optical image of those satellites. The results obtained here show that radio metric navigation solution in combination with Martian satellites ephemeris will not help in orientating camera direction correctly and out of practical use, but that autonomous navigation aid is quite efficient and satisfactory to take close-up pictures of those satellites with simplified Kalman filter on board. This filter is a kind of automated target tracker rather than a navigator. Here are presented new schemes that can provide navigation properties in real time such as ballistic parameters as well as phase angle on B-plane. A special attention is focused on how camera elevation angle is programmed in case of spin stabilized spacecraft like PLANET-B. And a new idea to it that is irrelevant to B-plane properties is given.