THEMIS

THEMIS (Time History of Events and Macroscale Interactions during Substorms) is a NASA mission consisting of five identical satellites studying the Earth's magnetic field. It was launched in 2007 and in 2010 when the primary mission was complete, two of the satellites were repurposed. Instruments:

• EFI - Electronic Field Instruments.
• FGM - Fluxgate magnetometer.
• SCM - Search-coil magnetometer.
• ESA - Electrostatic Analyzer.
• SST - Solid State Telescope.

The name ARTEMIS (Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun) was given to a mission repurposing two of the satellites, to study the Moon's effect on the Earth's magnetic field. It placed the two in Moon-Earth Lagrangian points, then later in lunar orbit. This mission is now called THEMIS-ARTEMIS because NASA chose to use the name Artemis for its program of manned missions to the Moon, the Artemis program.

Note that THEMIS is also the name of an instrument on the Mars Odyssey mission.