ESA GNC Conference Papers Repository
The Phobos-Grunt Project: Ballistics, Navigation, and Flight Control
The Phobos-Grunt mission is planned to 2011 in Russia with the purpose to deliver to the Earth the rock samples of the Marss satellite Phobos. Besides there is a task to deliver the Chinese SC on the Mars orbit. The high requirements to the accuracy of the orbit determination both the SC and the Phobos under influence of various disturbance factors, errors of maneuver executions lead to concern with problems of ballistics, navigation, and flight control of the SC in the PhobosGrunt mission. The article discusses various mission aspects beginning with an insertion into the EarthMars transfer trajectory, the strategy of corrections, and the accuracy of the insertion of the SC into Martian orbit. The first mission task is planned to separate the Chinese satellite YH-1 in the proper way. During the orbital maneuvering stages in the vicinities of Mars and Phobos, a scheme of sequential operations is realized that provides after motions on several various orbits (the observation orbit, the quasi-synchronous orbit) the insertion of the SC with the prescribed accuracy into a point 40-80 km above the Phobos surface over the theoretical landing area. It is noted that a new adaptable numerical theory of the Phobos motion and theoretical researchers in the frame of three body problem have been needed to meet all requirements about relative motion the SC and Phobos 3 km with respect to position and 1 m/sec with respect to velocity. Taking into account all constraints by radio visions from tracking stations on the Earth, by solar antenna illuminations and so on, there were done calculations of landing windows. There is fulfilled the sequence of operations for a controlled landing and there are considered methods for solving the problems of navigation and control during a self-contained landing. Then there is considered the liftoff from Phobos, insertion into the parking orbit, and the MarsEarth transfer to enter the Earth atmosphere under angle ~ 40°. The landing is implemented on the Russian polygon sized 30 km, the prediction error of the particular landing point being at most 3 km.