16924

This program would observe two low-inclination Scattered Disk Objects (SDOs) with five total orbits to measure their color and astrometry. These SDOs comma 2020 KS11 and 2020 KV11 comma are both potential future targets for observation by NASA.s New Horizons spacecraft. Their colors would be measured with WFC3-UVIS and two filters (F606W and F814W) to both compare their colors to other past New Horizons comma targets and to provide some of the first measurements of the colors of low-inclination SDOs. Low-inclination SDOs are relatively rare in the scattered disk population comma and previous ground-based color investigations were only able to measure colors for an even smaller fraction of those. The proposed observations would measure the colors of fainter and smaller SDOs than are possible to measure from the ground comma helping to understand this curious population. The proposed observations are critical to be performed in Cycle 29 comma as additional HST astrometry is required to improve their orbits sufficiently to allow New Horizons them comma and the sooner that astrometry is available comma the sooner that the New Horizons project can plan those observations. The proposed observations would improve the orbit of 2020 KS11 more than is possible with ground-based telescopes before it would be observed by New Horizons in 2024 comma and would provide as much improvement in the orbit of 2020 KV11 as eight semesters of ground-based data. These targets were not previously proposed to be observed in Cycle 29 comma as the Cycle 28 observations of them were required first to know that they were good targets for New Horizons comma and to know what quantity of additional HST astrometry would be required.