(UC Berkeley: Berkeley, CA) -- On Sunday, July 17, the moon acquired two new companions in less than a month. That’s when the second and third of two probes built by the University of California, Berkeley, and part of NASA’s five-satellite Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission will drop into a permanent lunar orbit after a meandering, two-year journey from its original orbit around Earth.

The first of the two probes settled into a stable orbit around the moon’s equator on June 27, 2011. The two spacecraft that comprise the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) mission will immediately begin the first observations ever conducted by a pair of satellites of the lunar surface, its magnetic field, and the surrounding magnetic environment.

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