Orbit design for hybrid ground-space targets

Abstract

For operationally responsive space missions, traditional orbit design problems are only for a single type of targets, i.e., only ground targets or only space targets. This paper studies the hybrid ground and space targets of interest by considering J2 perturbation. The ground-target visit problem needs the ground track of the designed orbit to pass through the ground target, and one ground target corresponds to one equality constraint. The space-target visit problem is viewed as the orbit flyby problem, and one space target corresponds to two equality constraints. According to the numbers of designed variables and equality constraints, there are two cases for the maximum number of hybrid targets: (1) two ground targets and two space targets; (2) four ground targets and one space target. For given orbital inclination and right ascension of ascending node, the other orbital elements of the designed orbit are obtained by numerical methods. Then, the problem is transformed into solving nonlinear equations only of two variables. Newton-Raphson iterations are adopted to solve the problem, and the initial guesses are obtained by the grid search method. Several numerical examples are presented to validate the proposed orbit design approach for hybrid ground-space targets.