The Dynamica Behind the Genesis Mission & "Deep Impact"

Dr. Martin Lo, Navigation & Flight Mechanics, Jet Propulsion Lab/Caltech

The goal of the Genesis Mission is to collect solar wind samples in a halo orbit about the Sun-Earth L1 Lagrange point for two years and return them to Earth. This is the first robotic sample return mission and also the first mission to be designed using dynamical systems theory. In order to provide a return trajectory on the day-side, it was necessary to exploit the heteroclinic connection between the regions around L1 and L2. This approach provided an optimal solution which requires a single deterministic manuever of 5 m/s for the entire mission after launch.

Another way to look at the Genesis trajectory is that it is an Earth impact trajectory. However, since halo orbits are so unstable, it would seem that the Genesis trajectory is completely artificial. But exactly the opposite is true! The remarkable fact is that this behavior is quite generic throughout the Solar System. The unstable Lagrange points, L1, L2, and L3 play a significant role in the morphology and transport of material within the Solar System from the Asteroid Belt to the Kuiper Belt, from the zodical dust rings to Saturn's rings, from comet orbits to the Genesis orbit. In particular, the invariant manifold complex of the Lagrange points of the planets intersect one another in configuration space, forming an invisible gravitational network of dynamical channels connecting the entire Solar System.

A timely application is the Near Earth Object (comets and asteroids) Impact problem. In order for these objects to come near Earth, they must pass by L1 or L2 which act as gate keepers. The Jupiter comets clearly illustrate this phenomenon. Indeed, the celebrated Shoemaker-Levy-9 comet impact followed this route to its spectacular demise.