Mission Summary
ARTEMIS is a pair of recycled spacecraft that became the first to orbit the Earth-Moon Lagrange points. The two probes began as THEMIS B and THEMIS C, part of a five-satellite NASA mission launched in February 2007 to study magnetic substorms in Earth’s magnetosphere. With that work done, NASA redirected the two outermost satellites to the Moon and renamed them ARTEMIS P1 and P2.
Over roughly a year and a half of low-thrust maneuvering, the pair worked their way out to the Lagrange points, the gravitational balance points of the Earth-Moon system. ARTEMIS P1 entered orbit around the far-side L2 point on August 25, 2010, and P2 reached the near-side L1 point that October, the first time any spacecraft had circled an Earth-Moon libration point.
In mid-2011 both probes settled into orbit around the Moon itself, circling in opposite directions. From there they began returning the first three-dimensional measurements of the Moon’s weak magnetic field and its interaction with the solar wind, including the long plasma wake the Moon trails downwind of the Sun. The twin spacecraft continue to operate in lunar orbit.
Sources and notes can be found on the Sources page.
