Optimization of observing sequence based on nominal trajectories of symmetric observing configuration

Abstract

This paper presents the crucial method for obtaining our team’s results in the 8th Global Trajectory Optimization Competition (GTOC8). Because the positions and velocities of spacecraft cannot be completely determined by one observation on one radio source, the branch and bound method for sequence optimization of multi-asteroid exploration cannot be directly applied here. To overcome this difficulty, an optimization method for searching the observing sequence based on nominal low-thrust trajectories of the symmetric observing configuration is proposed. With the symmetric observing configuration, the normal vector of the triangle plane formed by the three spacecraft rotates in the ecliptic plane periodically and approximately points to the radio sources which are close to the ecliptic plane. All possible observing opportunities are selected and ranked according to the nominal trajectories designed by the symmetric observing configuration. First, the branch and bound method is employed to find the optimal sequence of the radio source with thrice observations. Second, this method is also used to find the optimal sequence of the left radio sources. The nominal trajectories are then corrected for accurate observations. The performance index of our result is 128,286,317.0 km which ranks the second place in GTOC8.