Crater Mapping in the Pluto-Charon System: Considerations, Approach, and Progress

Abstract:

NASA's New Horizons mission successfully made its closest approach to Pluto on July 14, 2015, at 11:49A.M. UTC. The flyby nature of the mission, distance to the system, and multiple planetary bodies to observe with a diverse instrument set required a complex imaging campaign marked by numerous trade-offs; these lead to a more complicated crater population mapping than a basic orbital mission. The Pluto and Charon imaging campaigns were full-disk or mosaics of the full disk until ≈3.5 hrs before closest approach when the pixel scale was 0.9 km/px. After this, several LORRI-specific imaging campaigns were conducted of the partial disk and later the full crescent, while additional strips were ride-alongs with other instruments. These should supply partial coverage at up to 70–80 m/px for Pluto and 160 m/px for Charon. The LORRI coverage at ≈0.4 km/px does not cover the entire encounter hemisphere, but the MVIC instrument provided comparable full-disk coverage (0.5 km/px) and partial disk at 0.3 km/px. The best images of the non-encounter hemispheres of Pluto and Charon are ≈21 km/px (taken midnight July 10-11). As with any single flyby mission, we are constrained by the best pixel scales and incidence angles at which images were taken during the flyby. While most high-resolution imaging by quantity has been done over areas of variable solar incidence as the spacecraft passed by Pluto and Charon, these cover a relatively small fraction of the bodies and most coverage has been at near-noon sun which makes crater identification difficult. Numerous team members are independently using a variety of crater mapping tools and image products, which will be reconciled and merged to make a more robust final database. We will present our consensus crater database to-date of both plutonian and charonian impact craters as well as correlations with preliminary geologic units. We will also discuss how the crater population compares with predictions and modeled Kuiper Belt Object size-frequency distributions.