This paper deals with the orbital synthesis for the "Nozomi" spacecraft, which was launched in July 1998. The spacecraft trajectory was tactically designed to extract the gravity assist from the Sun, Earth and the Moon so as to be boosted up even beyond escape energy. This orbital maneuvers well demonstrated how this scheme works well. However, an incident occurred when the spacecraft was about to leave the Earth on 20 December 1998 owing to the pressurization problem of the reaction control system aboard. The correction capability was greatly lost and the original scenario was on the verge of collapse. Within two Weeks from then, the trajectory correction had to be performed if the Mars was targeted even though the fuel was not enough. An alternative flight was designed within the shortest available period and the correction was canceled and the spacecraft was directed to return to the Earth first. The altered flight utilizes double Earth swingbys to change its ellipse apsis direction completely to the opposite side so that the Mars Insertion delta-V can be drastically reduced. The paper describes how the orbital synthesis is devised. Trajectory correction strategy is also given for the "Nozomi" to fly back to the Earth in 2002. The contents, in part, were already reported in the IAF congress in Amsterdam in 1999.
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