Bless 'em, but to me this mission is a waste of money.
Instead of using chemical propellants that necessitate several years of EXPENSIVE mission control support thru 2010, they coulda used DS1's ion drive (solar power is readily available with smaller, lighter panels on an inner solar system mission vs. DS1's asteroid quest) with a small chem stage for hi-thrust insertion into Mercury orbit. DS1 also proved out better solar cell technology and more importantly, AutoNav, a system that eliminated most of ground control labor. NASA still prefers 1960 style mission design.

-philw (cost is still not important to NASA)