Low-energy transfers to long-term capture in the Earth-Moon system

In this paper, low-energy transfers of asteroids to long-term capture (LTC) in the Earth-Moon system (EMS) based on the concept of short-term capture (STC) are constructed and analyzed. Stable LTC orbits distributed in three regions are investigated via the finite-time Lyapunov exponent. Then, five types of low-energy transfers to different target LTC orbits are constructed and discussed. Two kinds of design strategies of low-energy transfers starting from STC orbits and LTC orbits are proposed, respectively. Numerical results indicate that fuel costs of low-energy transfers to stable LTC orbits in the EMS are less than 50 m/s; fuel costs of low-energy transfers to unstable libration point orbits are less than 5 m/s. Taking asteroid 2006 RH¹²⁰ as an example, a low-energy transfer is constructed in the ephemeris model. The design methods of low-energy transfers we proposed in this paper can be applied to the asteroid redirect missions.