This may give you an answer Cole, but I'm sure you have something diabolical to reply. Do it quick becasue the astroid is heading twards your outhouse.
In a nutshell, I think the Hubble is for great distances in light years, anything close would be in and out of the lens pretty fast, or maybe too close for its focal distances at all. It may be able to see it approching, but when its between earth and the moon, would pass out of the lens real fast. Hubble can probably not move its lens that fast to follow it. If you remember the hubble repair was becasue the lens did not allow for great distances and needed to be corrected. I'm guessing that now limits things close up, which was not the intention of the Hubble. I think you probably understand you could not use a long lens on a camera to do a portrait with.