Gregory J. Whiffen

Simple control laws for continuous-thrust escape or capture and their use in optimisation

Interplanetary missions which use low-thrust, high specific impulse propulsion can further capitalise on the capabilities of the propulsion system by using it to effect escape from the launch body or capture at a target body.

Earth Orbit Raise Design for the Artemis Mission

ARTEMIS is a mission to send two spacecraft from Earth orbit to libration orbits around the Moon Lagrange points and then into lunar orbit. Lunar flybys were used early in the mission to send the spacecraft into low-energy lunar transfers which were designed to arrive in the libration orbits for minimal ΔV . ARTEMIS began by raising the Earth orbits of each spacecraft to achieve the planned lunar flybys. Spacecraft configuration and operation constraints made the Earth orbit raise phase of the mission a significant mission design challenge by itself. This paper describes the process used to find trajectories that achieved mission goals and the resulting series of Earth orbits that culminated in successful lunar flybys.

Dawn Navigation and Mission Design at Dwarf Planet Ceres

Dawn, one of NASA’s Discovery Program missions, was launched on September 27, 2007, to explore two residents of the main asteroid belt in order to yield insights into important science questions about the formation and evolution of the solar system [1]. Its main objective is to acquire data from orbit around two complementary bodies, Vesta and Ceres, the two most massive objects in the main belt. From July of 2011 to September of 2012, the Dawn spacecraft orbited Vesta and returned much valuable science data, collected during the six planned mapping orbits at the protoplanet. Figure 1 depicts the Dawn’s interplanetary trajectory and timeline.