ARTEMIS-P1 Becomes First Spacecraft to Orbit Earth-Moon L1 Point

In August 2010, NASA’s ARTEMIS-P1 spacecraft became the first mission to navigate to and enter orbit around the Earth-Moon L1 Lagrange point. The spacecraft originally launched in 2007 as part of the THEMIS mission, which consisted of five probes studying Earth’s magnetosphere. Two of these spacecraft were later repurposed for the ARTEMIS mission, short for Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun. Using carefully planned low-energy transfer trajectories, ARTEMIS-P1 gradually moved from Earth orbit toward the Earth-Moon system and entered a Lissajous orbit around the L1 point. The Earth-Moon L1 point lies between Earth and the Moon where gravitational forces and orbital motion allow spacecraft to maintain position with relatively low fuel use. After arriving in August 2010, ARTEMIS-P1 performed stationkeeping maneuvers to remain in a looping Lissajous orbit around L1. Together with its companion spacecraft ARTEMIS-P2, the mission later demonstrated operations at both the Earth-Moon L1 and L2 Lagrange points. These were the first spacecraft to conduct sustained stationkeeping around both locations within the Earth-Moon system. From these vantage points, the ARTEMIS spacecraft studied the interaction between the solar wind, Earth’s magnetotail, and the Moon. The probes measured plasma flows, magnetic reconnection events, and particle acceleration processes in the region. After completing Lagrange point operations, both spacecraft transitioned into lunar orbits in 2011, continuing investigations of the lunar environment and solar wind interactions.