Transfers to lunar libration point orbits

In this paper, two-impulse transfers from low Earth orbit (LEO) to libration point orbits (LPOs) near the Moon are investigated. The transfer orbit is separated into two portions: trans-lunar and manifold segments. Based on locations of apogees of transfers, transfer orbits are classified into short and long transfers. For short transfers with duration shorter than 50 days, trans-lunar segments are analyzed preliminarily in the two-body model. Using the optimal manifold injection points of the preliminary analysis as initial guesses, short transfers are constructed and compared in the Earth-Moon circular restricted three-body problem. Since undesirable short transfers with large fuel cost are excluded by the preliminary analysis, our results are more selective than previous researches. Using lunar flyby transfers from LEO to low Moon orbits as initial guesses, long transfers are designed and discussed in the Sun-Earth-Moon restricted four-body problem. Since lunar flyby is necessary for Pareto-efficient solutions, our design method of long transfers is more targeted and efficient compared with the previous optimization of low-energy transfers. Finally, the obtained short and long transfers are extended to the ephemeris model.