Nearest Planetary Object Approaches for Interstellar Probe's Journey Through the Inner and Outer Solar System

The trajectory of Interstellar Probe, yet to be determined, will take it through the asteroid belts consisting of hundreds of thousands of objects, and then through the Kuiper Belt domain of more distant objects consisting of several thousand known Centaurs, Transneptunian Objects, and Scattered Disk Objects. Near conjunctions with any of these objects could yield new science information on structure and composition. Although a targeted flyby of a dwarf planet, e.g. Haumea, may be planned as a planetary addition to IP's local interstellar mission, we are investigating whether one or more untargeted conjunctions might be found for smaller more numerous objects. We have been doing a preliminary survey of closest conjunctions encountered by sample spacecraft trajectories to the outer solar system, e.g. for New Horizons. A Jupiter gravity assist trajectory has been provided to us for IP. Daily position resolution is sufficient for sampling of nearest conjunctions. The International Astronomy Union's Minor Planet Center at the Smithsonian Astrophysical Observatory provides on-line listings of orbital elements for all known objects from asteroids to distant objects. For each daily point of a particular spacecraft trajectory we search for closest conjunctions to calculated positions at that day of each object in the MPC listings. This is done approximately from the MPC orbital elements with a two-body solution to Kepler's equation for bodies in orbit around the Sun. The Jet Propulsion Laboratory's Horizons data base provides more accurate trajectories for specific objects that can be compared to our results. Sample results for a non-IP spacecraft trajectory found multiple conjunctions within 0.01 AU for asteroidal bodies, e.g. Jupiter Trojans. Distant object conjunctions are rarer at distances greater than 0.1 AU as per a sample from the New Horizons trajectory. The new results to be presented will be from the IP JGA trajectory and any further updates. For statistical sampling with respect to the yet-unknown IP trajectory it is also of interest to compile nearest conjunctions for other spacecraft such as Voyager 1/2 and Pioneer 10/11.