Today, two different spacecraft at different ends of the solar system are closing in on major milestones. The first is the New Horizons spacecraft, destined for a flyby of Pluto in 2015. Tomorrow, it will pass the orbit of Uranus, the penultimate orbit to cross before it begins its observations of the distant dwarf planet. The New Horizons website has a position diagram of the spacecraft:
Generally, it’s position doesn’t change very quickly relative to the diagram (it took the spacecraft over 5 years to get to it’s present location and it’ll take more than 4 years before it makes its closest approach of Pluto).
The second spacecraft, which has arguably reached a more important milestone today, is the MESSENGER spacecraft which will be performing maneuvers for its final orbital insertion around Mercury within a few hours of this posting. On March 29, the spacecraft will begin taking the pictures that will make up it’s main mission, which is to survey the innermost planet from orbit in a similar manner to the Mars Reconnaissance Orbiter and the Lunar Reconnaissance Orbiter, which are in orbit around Mars and the Moon, respectively, ultimately giving us the first complete map (and a detailed one at that) of the surface of Mercury.