Grand LaGrange

The Artemis (Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun) mission is designed to study the Sun’s magnetosphere on opposite sides of the moon. The mission utilizes two of the five THEMIS spacecraft, which have completed their original mission. The five spacecraft were launched in 2007, and completed their research earlier in 2010. Their mission was to investigate the auroras in the Earth’s atmosphere and why they dramatically change from slowly shimmering waves of light to wildly shifting streaks of color. The data from the spacecraft will provide scientists with important details on how the planet’s magnetosphere works and the important Sun-Earth connection.

Now, two of these craft are headed toward the Moon and the two Lagrange points, EML-1 and EML-2.

As shown in the two diagrams below, EML-1 (L-1) lies between the Earth and the Moon (about 61,000 km above the Moon’s surface) and EML-2 (L-2) lies beyond the Moon at the same distance.

Artemis Orbit
Artemis Spacecraft P1
Earth Moon Lagrange Orbits

Image Credit: NASA / Goddard

Artemis Orbit Side
Artemis Spacecraft P1
Earth Moon Lagrange Orbits – Side View

Image Credit: NASA / Goddard

The first spacecraft (P-1) has migrated from Earth orbit to L-2 and entered a Lissajous orbit about L-2. These orbits (as seen in the diagrams above) are dynamically unstable, and require adjustments from on-board thrusters. The spacecraft will take from 14 to 15 days to complete a single loop. The plan is for the two spacecraft to spend about three months monitoring the influence of the magnetospheres of the Earth and the Moon on the solar wind. This will provide the first three-dimensional perspective of how energetic particle acceleration occurs near the Moon’s orbit as well as the space environment behind the Moon.

After this period, the spacecraft at L-2 will migrate to L-1 and join its sister. In late March of 2011, both spacecraft will maneuver into elliptical orbits around the Moon and continue to observe magnetospheric dynamics, solar wind and the space environment over the course of several years.

The research to be conducted by the Artemis program is important for several reasons. One is the pure research itself.

Second is the fact that both L-1 and L-2 are proposed as propellant and supply depots for the robotic and manned exploration of the Moon and the Solar System. Understanding the solar radiation environment at these locations will be important for manned operations and the health of the astronauts (see the related problems associated with Galactic Cosmic Rays (GCR) – The 800 Pound Gorilla).

For the importance of propellant depots, see the discussion in this post Post Augustine Commission – ULA Says “Fly Me to The Moon”, and the uses of propellant depots here The Augustine Commission – Final Report – Hits and Misses – Wrapped Up

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