NASA Gives Two Probes in Space New Orders: To the Moon
An artist's concept of the ARTEMIS spacecraft in orbit around the Moon.
Credit: NASA

Two NASA spacecraft have begun a new mission, switching their focus from Earth's magnetic field to the moon.

This week, the twin unmanned probes began studying how the solar wind from the sun electrifies, alters and erodes the moon's surface. Their observations may return valuable information for future explorers and give planetary scientists a hint of what's happening on other worlds around the solar system, researchers said.

NASA calls the new mission Artemis, short for Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon?s Interaction with the Sun. Its two spacecraft are recycled from an early multi-probe mission to study the interactions between Earth's magnetic field and the solar wind. [Illustration of Artemis probes.]

"Artemis will provide a unique two-point view of the moon's under-explored space environment," Artemis? principal investigator Vassilis Angelopoulos of UCLA said in a statement. "These two spacecraft are headed for an incredible new adventure."

From Earth to the moon

NASA first launched the two spacecraft, along with three others, in 2007 as part of a mission called Themis (Time History of Events and Macroscale Interactions during Substorms).

The five Themis probes orbited Earth, helping scientists determine how storms in our planet's magnetic field lead to Earth's colorful auroras ? also known as the northern and southern lights.

Themis completed its primary mission in 2008. The Themis team then proposed that the two outermost spacecraft use their extra fuel to propel themselves into lunar orbits ? making it the first two-satellite mission to the moon.

The first Artemis probe settled into a temporary Lagrange point orbit on the far side of the moon on Aug. 25 of this year. The second entered a Lagrange point last week, on Oct. 22.

Lagrange points are places where the gravity of Earth and the moon balance, creating a sort of gravitational parking lot for spacecraft.

After six months at the Lagrange points, the two Artemis probes will move closer to the moon. The spacecraft will be approximately 62 miles (100 km) from the lunar surface at first, but will eventually move closer.

Understanding the solar wind

Artemis will measure solar wind turbulence on scales never sampled by previous missions, researchers said. Solar wind is a stream of charged particles emitted from the upper atmosphere of the sun.

The two spacecraft will look to see how the solar wind affects the moon, a rocky world that has no substantial magnetic field to protect it. By contrast, Earth's magnetic field shields it to a large extent.

Over the next several years, Artemis will also help scientists understand how the Earth's magnetosphere is shaped by the strong solar wind at the distance of the moon, researchers said.

"Artemis is going to give us a fundamental new understanding of the solar wind," said David Sibeck, Artemis project scientist at NASA's Goddard Space Flight Center in Maryland.

Artemis will work in tandem with current missions ? such as NASA's Lunar Reconnaissance Orbiter, Ladee (Lunar Atmosphere and Dust Environment Explorer) and Grail (Gravity Recovery and Interior Laboratory), as well as China's Chang'e 2 probe ? to prepare the ground for increased robotic exploration of the moon, researchers said.

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