Results of a hubble space telescope search for natural satellites of dwarf planet 1 ceres

•A method for determining the size limitations of a satellite search is described.•No satellites of Ceres were detected within its Hill Sphere down to a diameter of 48m.•No satellite larger than 925m in diameter exists within five Ceres radii of its surface.•Satellite stability or capture around large main belt object may be different than for smaller object or Kuiper Belt objects. In order to prepare for the arrival of the Dawn spacecraft at Ceres, a search for satellites was undertaken by the Hubble Space Telescope (HST) to enhance the mission science return and to ensure spacecraft safety. Previous satellite searches from ground-based telescopes have detected no satellites within Ceres’ Hill sphere down to a size of 3km (Gehrels et al. 1987) and early HST investigations searched to a limit of 1–2km (Bieryla et al. 2011). The Wide Field Camera 3 (WFC3) on board the HST was used to image Ceres between 14 April–28 April 2014. These images cover approximately the inner third of Ceres’ Hill sphere, where the Hill sphere is the region surrounding Ceres where stable satellite orbits are possible. We performed a deep search for possible companions orbiting Ceres. No natural companions were located down to a diameter of 48m, over most of the Hill sphere to a distance of 205,000km (434 Ceres radii) from the surface of Ceres. It was impossible to search all the way to the surface of Ceres because of scattered light, but at a distance of 2865km (five Ceres radii), the search limit was determined to be 925m.