Roamy here. I’m always fascinated by how some spacecraft really exceed their designed lifetime. Here’s two satellites that not only finished their original mission but had enough fuel left over to go do something else. Two of the THEMIS satellites studied Earth’s magnetic field for two years then were moved to study the Moon, especially the wake the Moon leaves in the solar wind. The two satellites were renamed ARTEMIS for Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun, which shows NASA can come up with an acronym for anything. They are currently at the L1 and L2 Earth-Moon Lagrangian points, which is where gravitational pulls between the Earth and Moon cancel each other out. The article says these are the first spacecraft for these orbits, though NASA has sent spacecraft to the Earth-Sun Lagrangian points before.
In April, they will elongate the orbits to get closer to the Moon and get even more data on what happens to the Moon’s surface when it passes through the Earth’s magnetic field. Their mission is currently planned through 2012. Pretty good for two satellites described as “dead spacecraft walking”.