EVALUATION OF THE APPROACHING TRAJECTORIES FOR LANDING ON THE ASTEROID 216 KLEOPATRA

Resumo

The goal of this work is to evaluate some orbital trajectories seeking the approaching for
landing on surface of the asteroid 216 Kleopatra. This asteroid, discovered by Johann Palisa in 1880,
has a very irregular shape with approximate dimensions of 217 x 94 x 81 km. Due to its shape, the
gravitational field around the asteroid cannot be considered central. Thus, a spacecraft approaching the
asteroid is subject to orbital perturbations, which can hinder the vehicle to describe the nominal
trajectory. In maneuvers for approach and landing, the trajectory deviations may result in very high
approach velocities, making impossible the soft landing on the surface of the asteroid. In addition, the
rotation of the asteroid is another difficulty for missions aimed at the soft landing. Due to the irregular
shape of the asteroid the relative distance between the surface and the spacecraft varies significantly
depending on the orbital plane adopted for the trajectory. In this work, the intention is to evaluate,
through numerical simulations, orbits of a spacecraft around the asteroid Kleopatra more appropriate
to get closer to the asteroid in order to minimize the relative velocity between the surface and the
spacecraft. For this, was used a polyhedral model of the asteroid's volume, based on radar
measurements from the Arecibo Observatory, to model the non-central gravitational field generated by
the heterogeneous mass distribution of the asteroid. Using the model of the gravitational field and the
simulation environment Spacecraft Trajectory Simulator (STRS), several approach paths were
simulated and compared in order to assist the choice of trajectories, considering the minimum value
for the velocity with respect to the surface at the point of the trajectory with minimum altitude.