History
Low energy transfers to the Moon were first demonstrated in 1991 by the Japanese spacecraft Hiten, which was designed to swing by the moon but not to enter orbit. The Hagoromo subsatellite was released by Hiten on its first swing-by and successfully entered lunar orbit, but suffered a communications failure.
Edward Belbruno and James Miller of the Jet Propulsion Laboratory had heard of the failure, and helped to salvage the mission by developing a ballistic capture trajectory that would enable the main Hiten probe to itself enter lunar orbit. The trajectory they developed for Hiten used Weak Stability Boundary Theory and required only a small perturbation to the elliptical swing-by orbit, sufficiently small to be achievable by the spacecraft's thrusters. This course would result in the probe being captured into lunar orbit using zero delta-v, but required five months instead of the usual three days for a Hohmann transfer.
Read more about this topic: Low Energy Transfer
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