Over the last decade the three body problem has emerged as the standard model for defining reference trajectories in space. It is now essentially feasible to patch together segments of trajectories defined by different sets of three bodies and construct a reasonably feasible trajectory in space. The actual trajectories may be constructed by solutions to either the circular restricted or the elliptic restricted three body problems (RTBP). For example, the stable manifolds of a three body cluster help in transferring the spacecraft into the Halo orbit and the unstable manifolds help in escaping from the Halo orbit. A combination of the stable and unstable manifolds could be utilized to transfer the spacecraft from the Sun-Earth system to the Sun-Jupiter system or another such system under the framework of the circular restricted TBP. A similar application is feasible with the elliptic restricted TBP. Further significant reductions in the fuel requirements can be achieved by adopting optimal elliptic restricted TBP trajectories including ballistic trajectories, which could be synthesized by methods outlined in this monograph, thus making hem suitable for mission planning. When spacecraft moving along these trajectories are used to relay telecommunications, or to monitor near Earth objects that are a threat to life on Earth and relay information about them back to Earth, their attitude must not only be continually assessed and the stability assured. However, because of the presence of gravity gradient torques, one must necessarily assess the attitude stability of these satellites along prescribed orbits, particularly if they are required to either point to the Sun or the Earth. The satellites may also be required to assess the state of the attitude of a celestial body such as a near Earth object, while simultaneously tracking its orbit.
