22 September 2010: Dawn is now just 23 million km away from 4 Vesta

This is an update to this post and all the previous ones, showing the distance between Dawn and 4 Vesta, as well as another probe (Rosetta) and the asteroid 21 Lutetia at a distance of 900,000 km for comparison, as that was the distance at which we obtained this photograph:

So here they are to scale (except for the probe), and with 4 Vesta's current position at 23 million km compared to the previous distance at 28 million km near the beginning of September, shown in grey.

Arrival is now in 297 days, but since Dawn uses an ion engine this arrival will just involve the tiniest bit of energy used for orbital insertion, and long before that the probe will be nearby and will have almost matched orbits with Vesta. The chief engineer updates Dawn's progress at the end of each month so we'll see if he has anything to say on the subject (from when we'll be able to see 4 Vesta from Dawn) this time. I emailed them on it a few weeks ago on that as well.