Interstellar Object Encounter Trade Space Exploration

2017 and 2019 saw the discovery of the first two interstellar objects (ISO) in the solar system, 1I 'Oumuamua and 2I Borisov, but left scientists with more questions than answers as to the objects' origins. To fully resolve these open questions, scientists need a closer look at an interstellar object via a dedicated spacecraft and close approach. However, ISOs pose unique engineering challenges for close encounters because of their extremely high relative velocity, unfavorable approach geometry, and limited alert time; ISOs often are only discovered a few months before a spacecraft would need to launch to encounter it. Typical encounters with small bodies have occurred at relative velocities on the order of 10 km/s or less with approach phase below 90 deg (at least half-lit). Except for the Halley Armada in the 80s, the most extreme flybys have been of comet Borrelly at a relative velocity of 16.6 km/s (but only a phase angle of 65 deg) and Annefrank at a phase angle of 150 deg (but a relative velocity of only 7.2 km/s). Furthermore, planetary missions generally target bodies whose ephemerides are well constrained because of many years of Earth based observations. On the other hand, ISOs typically have relative velocities of 30–90 km/s, phase angles biased towards over 90 deg, and larger position uncertainties because of shorter ground-based observational arcs, and thus represent much more difficult targets. Our team has been designing the flight system architectures and technologies necessary to enable future reconnaissance of an interstellar object by flyby, potentially including an impactor. This endeavor seeks to catalyze planetary exploration and its intersection with exoplanet science. We establish encounter guidance, navigation, and control requirements within the trade space of trajectories to a synthetic ISO population. Flight system constraints, Earth departure capabilities, and ability for a mission team to quickly respond to an inbound target limit the accessible space for a future mission. This trade space analysis reveals enabling mission architectures, and provides recommendations for supporting investment to enable an ISO mission in the next decade.