A family of periodic orbits is proven to exist in the spatial lunar problem that are continuations of a family of consecutive collision orbits, perpendicular to the primary orbit plane. This family emanates from all but two energy values. The orbits are numerically explored. The global properties and geometry of the family is studied.
IntroductionWe consider the three-dimensional circular restricted three-body problem. This models the three-dimensional motion of a particle, P 0 , of zero mass in the Newtonian gravitational field generated by two particles, P 1 , P 2 of respective positive masses, m 1 , m 2 , in a mutual uniform circular motion. It is assumed that m 1 is much larger than m 2 . This problem is studied in a rotating coordinate system that rotates with the same constant frequency, ω of the circular motion of P 1 , P 2 , so that in this system P 1 and P 2 are fixed. Because m 1 is much larger than m 2 , we refer to P 1 as the Earth and P 2 as the Moon, for convenience.When P 0 moves about the larger particle, P 1 , the motion of P 0 can be completely understood if, for example, P 0 is restricted to the two-dimensional plane of motion of P 1 , P 2 . In this case, with m 2 = 0, assume that P 0 has precessing elliptic motion, of elliptic frequency ω * about P 1 , precessing with frequency ω. Then the Kolmogorov-Arnold-Moser(KAM) Theorem proves that this precessing motion persists if m 2 is sufficiently small and if ω and ω * are sufficiently noncommensurate. Otherwise, the motion is chaotic due to heteroclinic dynamics. That is, invariant KAM tori foliate the phase space. The motion of P 2 is proven to be stable [1]. When the initial elliptic motion of P 0 is not in the same plane as the P 0 , P 1 then under similar assumptions although KAM tori can be proven to exist, but stability cannot be guaranteed.A Family of Periodic Orbits in the Three-Dimensional Lunar Problem 2 In this paper we study the three-dimensional motion of P 0 about P 2 . This is referred to as the three-dimensional, or spatial, lunar problem. Relatively little is proven in general about the motion of P 0 unless the initial motion starts infinitely close to P 2 . The proof of existence of KAM tori in the three-dimensional lunar problem was obtained by M. Kummer under the assumption that the initial motion of P 0 lies infinitely near to P 2 [2]. ‡The main result of this paper is to prove the existence of a special family of periodic orbits about P 2 , nearly perpendicular to the primary orbit plane. More precisely, if we normalize m 1 = 1 − µ, m 2 = µ, then in the case of µ = 0 there exists a family of periodic orbits on the z−axis through P 2 , so perpendicular to the P 1 , P 2 plane, parameterized by their energy h. This family consists of consecutive collision orbits: Starting at collision at P 2 , they extend up the z−axis to a maximal distance d = d(h), then fall back to P 2 , and periodically repeat this oscillation, where d can have any positive value. We label these as φ * (t, h). These orbits have period T * (h). We prove that ...