What is the smallest object NASA has orbited?

I read that once OSIRIS-REx arrives at it in October 2018, the asteroid Bennu will have this distinction. Is Ceres currently the smallest - with Dawn orbiting it - or is there a smaller body that a NASA spacecraft has orbited, now or in the past?

And speaking of past, is there a list of some kind showing the different places around which NASA has put a vehicle into orbit?

Submitted August 31, 2017 at 04:14PM by mrguykloss http://ift.tt/2vNfv23