Dynamics of Spacecraft and Small Planetary Bodies

ITA has been actively involved with ESA's Rosetta mission since its launch in March 2004. The main goal of this very ambitious mission is to study the comet 67P/Churyumov-Gerasimenko (67P/C-G) with which the Rosetta spacecraft will rendezvous in August 20 14. The spacecraft will then be placed in orbit about the nucleus and follow the comet to a close approach with the Sun in August 2015. A lander will also be dispatched to the nucleus and perform in-situ measurements. Comets are pristine objects presumed to hold important clues to the conditions in the early solar system. ITA is participating on a Rosetta Radio Science Investigation (RSI) team which will use Doppler tracking data to compute an accurate orbit of the spacecraft and study the gravity field of the comet nucleus from the perturbations it induces on the orbiting spacecaft. In this respect, the outgassing pressure of the coma on the spacecraft, as will be studied, is of great importance. The nature of the pressure forces on the probe are also of relevance to the stability of Rosetta's orbit about the nucleus, which has been studied at ITA. Dive maneuvers have been suggested for the orbiter in order to reduce the risks for the lander. Whether or not such dive orbits really are predictable, a s will be explored as part of this project, is somewhat uncertain and of importance to the evaluation of risk for Rosetta. A final report will be written which summarizes our research on the navigation and orbit stability of Rosetta. Our results will b e applied to a wide range of Rosetta scenarios in this report. Of importance is also the determination of the target comet's orbit. Models and techniques have been developed at ITA in order to improve the comet orbit. This work will be completed as part of the project, as well as related applications to the dynamics of asteroids.