Author(s): DaveBowman2001 EarthMoon toutatis

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The THEMIS mission began in February 2007 as a constellation of five NASA satellites (A to E) to study energy releases from the Earth's magnetosphere. As of 2023, three of the satellites orbit the Earth within the magnetosphere, while two have been moved into orbit around the Moon since 2010. Those two (B and C) were renamed ARTEMIS after their arrival on the Moon. All satellites are still active


  • There are a total of five THEMIS satellites, three in Earth orbit and two in lunar orbit (see Table below)
  • The ARTEMIS satellites has no connection to NASA's Artemis Program, which aims to return humans to the Moon in the 2020s

A THEMIS satellite in high Earth orbit

Time History of Events and Macroscale Interactions during Substorms (THEMIS)
Mission Start Orbiting
THEMIS-A (Explorer 85) 2007-Feb-18Earth
THEMIS-B (ARTEMIS-P1/Explorer 86) Moon
THEMIS-C (ARTEMIS-P2/Explorer 87)
THEMIS-D (Explorer 88) Earth
THEMIS-E (Explorer 89)

A THEMIS satellite (renamed ARTEMIS) in high lunar orbit

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