A convenient procedure for designing the direct
transfer trajectory from lunar L2 point (LL2) halo orbit to
a low lunar orbit (LLO) is presented in this paper. The tra-
jectory characteristics are analyzed to support the manned
lunar missions design aimed at lunar surface global access.
The concise procedure is established based on the circular
restricted three-body problem (CR3BP) model. An analyt-
ical algorithm is employed to estimate an initial maneuver
vector for approaching the Moon in its close vicinity. An it-
eration process is adopted to generate favorable trajectory
that satisfies the constraints at perilune. By introducing a
number of intermediate coordinate frames, an algorithm to
compute the arriving LLO inclination and right ascension
of ascending node (RAAN) is proposed. The orbital incli-
nation and RAAN in this paper are defined and established
in the J2000 frame rather than in the synodical frame. Nu-
merical results show that, regardless of value of out-of-plane
amplitude (Az) of the halo orbit, the overall maneuver cost
of the trajectory largely depends on departure position, and
it has two minima around 0.65 km/s. Further study shows
that the values of the arriving LLO inclination and RAAN
largely depend on the choices of the departure time and the
value of Az. The periodicity, due to the natural motion of the
Moon, is discovered to play a role in this time dependency.
It is concluded that the fuel optimal trajectory permits ac-
cess to almost any final lunar orbit, including a polar orbit,
by means of varying the departure time and Az value.

EB00000004461K

Available

• Analysis of direct transfer trajectories from LL2 halo orbits to LLOs