ABSTRACT NEAR EARTH ASTEROID RENDEZVOUS (NEAR) ORBIT PHASE TRAJECTORY DESIGN

Trajectory design of the orbit phase of the Near Earth Asteroid Rendezvous (NEAR) mission involves procedures that depart significantly from those procedures used for previous missions. On previous missions, the trajectory design involved finding a flight path that satisfied a rigid set of spacecraft and mission design constraints. A precise spacecraft ephemeris was designed well in advance of arrival at the target body. For NEAR, the uncertainty in the dynamic environment does not permit a precise spacecraft ephemeris to be defined in advance of arrival at Eros. The principal cause of this uncertainty is limited knowledge of the gravity field and rotational state of Eros. As a result, the concept for NEAR trajectory design is to define a number of rules for satisfying spacecraft, mission and science constraints and then apply these rules to various assumptions for the model of Eros. We thus have a nominal, high and low mass model of Eros that may be used \ for testing the trajectory design strategy and thus bracket the ranges of parameter variations that would be expected to include the actual parameters of Eros. The final design is completed after arrival at Eros and determination of the gravity field and rotational state. I Before defining a targeting strategy, it is necessary to define spacecraft and mission constraint