Science operations support for the orbit change on the Interstellar Boundary Explorer (IBEX) mission

For the Interstellar Boundary Explorer (IBEX), a mission with one Earth-orbiting spacecraft with its spin axis pointing toward the Sun, an orbit change became necessary for the longevity of the mission. IBEX detects energetic particles that reveal global properties of the interstellar boundaries that separate our heliosphere from the local interstellar medium. The IBEX orbit is highly elliptical, and its original low perigee of only ~1.5 Re (radius of the Earth) exposed the spacecraft to a higher than desired level of radiation. A new orbit was chosen that raises perigee to greater than 7 Re (out of the radiation belts) and is in a 3 to 1 resonance with the Moon´s orbit around the Earth, which minimizes gravitational chaos. Due to fundamental changes, including adding a re-pointing maneuver mid-orbit and splitting data-taking time periods into multiple “orbit arcs”, the work needed to adapt ground systems and software was non-trivial, and many lessons were learned. The maneuver was successfully carried out in June, 2011.