  Luna 3 (or Lunik 3 in Russian sources) was the first spacecraft to perform a
flyby of the Moon. Launched in October 1959 on a translunar trajectory with
large semi-major axis and eccentricity, it collided with the Earth in late
March 1960. The short, 6-month dynamical lifetime has often been explained
through an increase in eccentricity due to the Lidov-Kozai effect. However, the
classical Lidov-Kozai solution is only valid in the limit of small semi-major
axis ratio, a condition that is satisfied only for solar (but not for lunar)
perturbations. We undertook a study of the dynamics of Luna 3 with the aim of
assessing the principal mechanisms affecting its evolution. We analyze the Luna
3 trajectory by generating accurate osculating solutions, and by comparing them
to integrations of singly- and doubly-averaged equations of motion in vectorial
form. Lunar close encounters, which cannot be reproduced in an averaging
approach, decisively affect the trajectory and break the doubly-averaged
dynamics. Solar perturbations induce oscillations of intermediate period that
affect the geometry of the close encounters and cause the singly-averaged and
osculating inclinations to change quadrants (the orbital plane ``flips''). We
find that the peculiar evolution of Luna 3 can only be explained by taking into
account lunar close encounters and intermediate-period terms; such terms are
averaged out in the Lidov-Kozai solution, which is not adequate to describe
translunar or cislunar trajectories. Understanding the limits of the
Lidov-Kozai solution is of particular significance for the motion of objects in
the Earth-Moon environment and of exoplanetary systems.
