M.A. Andreu PRELIMINARY STUDY ON THE TRANSLUNAR HALO ORBITS OF THE REAL EARTH-MOON SYSTEM (5506K, Postscript) ABSTRACT. The computation of translunar Halo orbits of the real Earth-Moon system (REMS) has been an open problem for a long time, but now, it is possible to compute Halo orbits of the REMS in a systematic way. In this paper, we describe the method used for the numerical computation of Halo orbits for a time span longer than 41 years. Halo orbits of the REMS are computed from quasi-periodic Halo orbits of the Quasi-bicircular Problem (QBCP). The QBCP is a model for the dynamics of a spacecraft in the Earth-Moon-Sun system. It is a Hamiltonian system with three degrees of freedom and depending periodically on time. In this model, Earth, Moon and Sun are moving in a self-consistent motion close to bicircular. The computed Halo orbits of the REMS are compared with the family of Halo orbits of the QBCP. The results show that the QBCP is a good model to understand the main features of the Halo family of the REMS.