Wednesday, July 14, 2010
The first interesting image Rosetta sent of the asteroid 21 Lutetia from a distance of 900,000 km is worth taking a look at again, as just one year from now Dawn is going to arrive at 4 Vesta, a much much more massive asteroid than 21 Lutetia. A bit over 100 times more massive, in fact, and a diameter of 540 km instead of 100 km for 21 Lutetia. Also, due to the fact that Dawn is using an ion engine to approach the asteroid and thus will be making a very finely tuned and long-term approach, it will be within observable range probably even a few months before arrival.
The image of 21 Lutetia at 900,000 km away looked like this:
and if we were to superimpose 4 Vesta next to the asteroid it would look something like this.
However, Dawn is 49 times farther away than Rosetta was when it took that image. It seems likely though that Dawn should be able to obtain images of 4 Vesta of a resolution similar to the one taken by Rosetta of 21 Lutetia at 900,000 some two or perhaps even three months before arrival, and considering how good the Dawn team is at PR I'm sure they will mention this a month or two beforehand if this is what Dawn will be able to do.