ARTEMIS goes to the Moon, Meets Lagrangian Points

I love Lagrangian points!

NASA has achieved another first for spaceflight... the first orbit around a Lagrangian point, or libration point. Unlike all other satellites, the ARTEMIS spacecraft is actually orbiting an area of empty space! These orbits aren't entirely stable, so they'll require a little maintenance.  Still, this is a cool thing.  Check out the unusual, kidney-like shape of the orbit.

Lagrangian points are a neat little trick of gravity.  There are five points in a two-body system (like the Sun-Earth system, or the Earth-Moon system) where you can place a third body of negligible mass and it can remain stationary relative to the other two.  The second Lagrangian point of the Sun-Earth system (not to be confused with the Earth-Moon system's L2, pictured above) is about 1.5 million kilometers away, and is the future home of the much anticipated James Webb Space Telescope, which will be launched in 2014.  And the fourth and fifth Lagrangian points on either side of Jupiter are home to a special class of asteroids known as Trojans.

Nice work, JPL.