Ballistic capture into distant retrograde orbits around Phobos: an approach to entering orbit around Phobos without a critical maneuver near the moon

This paper discusses an approach for designing missions to Phobos that do not require a critical maneuver in proximity of the moon. A low-energy transfer is designed that utilizes the aspherical mass distribution of Phobos to capture a spacecraft into a distant retrograde orbit (DRO) for the mission duration. The process for generating stable DROs in the Mars-Phobos system is discussed along with the method for generating and surveying a set of ballistic capture trajectories (BCTs) for DROs with altitudes between 0.5 and 14 km above Phobos. Statistical analysis of the BCT set reveals options for designing a mission to the desired DRO. This approach can be used in any three-body system when a significant perturbation is present, such as Phobos' aspherical co-rotating gravity field.