SUN-PERTURBED EARTH-TO-MOON TRANSFERS WITH BALLISTIC CAPTURE

A method is described for constructing a new type of low energy transf er trajectory from the Earth to the moon leading to ballistic capture. This is accomplished by utilizing the nonlinear Earth-moon-sun pertur bations on a point mass in three dimensions. The interaction of the gr avitational fields of the bodies defines transition regions in the pos ition-velocity space where the dynamic effects on the point mass tend to balance. These are termed week stability boundaries. The transfer i s obtained by the use of trajectories connecting the weak stability bo undaries. It uses approximately 18% less DELTAV than the Hohmann trans fer to insert a spacecraft into a circular orbit about the moon. The u se of this transfer has recently been demonstrated by Japan's Hiten sp acecraft, which arrived at the moon on October 2, 1991. Application of the transfer method is also made to the Lunar Observer Mission.