In 2010, after THEMIS successfully completed its prime mission, two of the five spacecraft were sent on a new path: into orbit around the Moon to begin the first systematic measurements of conditions in the magnetotail — the distant tail of Earth’s magnetic environment. (The three remaining THEMIS probes continue to orbit Earth, sending back valuable information to help scientists further understand substorms.)

The new mission, known as the Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun, or THEMIS-ARTEMIS, took its name from the Greek goddess of the Moon.