ARTEMIS-P1 Begins Orbiting the Moon

NASA's ARTEMIS-P1 spacecraft began orbiting the Moon on June 28, 2011. Artemis-P1 had been orbiting the L1 Lagrange point of the Earth-Moon system since January. A Lagrange point is a point wherethere is perfect equilibrium between the Earth's, Moon's and the Sun's gravities.

On June 22, the spacecraft started using its thrusters to take it out of its orbit around the Lagrange point. On June 27, 10:04 AM EDT, flight engineers began directing ARTEMIS-P1 into orbit around the Moon. At this time, the craft was about 2,400 miles away from the Moon. It entered orbit around the Moon on June 28, at 12:30 PM EDT.

A second spacecraft, ARTEMIS-P2, which is orbiting the L1 Lagrange point, is scheduled to be moved into lunar orbit on July 17.

The ARTEMIS-P1 and ARTEMIS-P2 spacecraft began as satellites that were used in NASA's THEMIS mission, which began in 2009.  THEMIS was a group of five satellites studying substorms coming from the Earth's magnetosphere.  The Earth's auroras are caused by these substorms.

The outer two of the five satellites from the THEMIS mission were later renamed ARTEMIS-P1 and ARTEMIS-P 2 and were moved into orbit around the Moon's Lagrange points as part of a new mission to study the space environment around the Moon, including the solar wind.

ARTEMIS-P1 began orbiting the L2 Lagrange point on August 25, 2010.

A second spacecraft, ARTEMIS-P2, began orbiting the L1 Lagrange point on October 22, 2010.

The L2 Lagrange point is on the side of the Moon farthest from Earth, while the L1 Lagrange point is on the side of the Moon closest to Earth.

On January 9, 2011, ARTEMIS-P1 moved to the near side of the Moon and began to orbit the L1 Lagrange point, joining ARTEMIS-P2.

The two ARTEMIS spacecraft were the first spacecraft ever to be placed in orbit around the Moon's Lagrange points, in kidney-shaped orbits known as Lissajous orbits.

The full name of the ARTEMIS mission is Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun. Artemis was the name of an ancient Greek goddess who was associated with the Moon.

THEMIS stands for Time History of Events and Macroscale Interactions during Substorms. Themis was the name of a Titan in Greek mythology.