Upper limits on the size of satellites of Asteroid (4) Vesta from 2007 Hubble Space Telescope observations

► Vestan satellite upper limit is 22 ± 4 m, ∼10 times smaller than previous searches. ► Volunteer searchers found almost all objects brighter than 22.5 ± 0.4 magnitude. ► With albedo at 700 nm of 0.47 (Vesta's), this magnitude corresponds to a radius of 22 ± 4 m. ► The region searched does not extend to the altitude of the Dawn mission's spacecraft. ► There remains scientific reason to search for satellites with the Dawn spacecraft.