Trajectory analysis for interplanetary missions.

A brief outline of various methods for the computation of interplanetary trajectories is presented. One of these, the patched-conic method, used in the ESTEC Interplanetary Trajectory Program, is discussed in more detail and the various trajectory problems that arise during mission analysis are outlined and possible solutions given. The capabilities of the ESTEC program are also outlined and, by way of an example of its application, a trajectory study for a possible back-up Out-of-Ecliptic mission relying on an Ariane launch is briefly described.