Preprints IPM . M. In. Keldysh . 2013. No. 46. 21 s. The paper considers the issue of choosing the orbit of the Millimetron spacecraft a periodic trajectory in the vicinity of the L2 libration point of the Sun-Earth system .. Classification of periodic movements in the vicinity of collinear libration points. Implemented missions to libration points are considered. Flight trajectories of the spacecraft are considered in accordance with the given classification. Periodic solutions of the limited circular problem of three bodies, proposed as prototypes of the working orbit of the Millimetron spacecraft, are shown, their implementation in the full model of the forces acting on the spacecraft. Proposed as a working orbit of the spacecraft "Millimetron" to use a halo orbit with an exit from the ecliptic plane for 1 million km Presented calculated by the author halo-orbits with a large exit from the plane of the ecliptic, satisfying the ballistic requirements for the trajectory of the apparatus. These orbits in the full model of the forces operating on the spacecraft are quasi-periodic and require the execution of containment maneuvers with a period of 70-90 days.