An illustration showing the trajectory of ESA’s Juice spacecraft during its lunar-Earth gravity assist, featuring a high-resolution ENA image of the million-degree hot plasma halo encircling Earth captured by NASA’s JENI instrument. The white rings denote equatorial distance of 4 and 6 Earth radii. The inset showcases measurements taken by the NASA’s JENI and JoEE instruments during their passage through the radiation belts, revealing a highly structured energetic ion and electron environment. Credit: ESA/NASA/Johns Hopkins APL/Josh Diaz
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From Aug. 19–20, ESA's (European Space Agency's) Juice (Jupiter Icy Moons Explorer) mission made history with a daring lunar-Earth flyby and double gravity assist maneuver, a spaceflight first. As the spacecraft zipped past our moon and home planet, Juice's instruments came online for a dry run of what they'll do when they reach Jupiter. During that time, two of NASA's onboard instruments added another first to the list: capturing the sharpest-ever image of Earth's radiation belts—swaths of charged particles trapped in Earth's magnetic shield, or magnetosphere.

The Jovian Energetic Neutrals and Ions (JENI) instrument, built and managed by the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, on behalf of NASA, took the image as Juice soared away from Earth. What it captured is invisible to the human eye.

Unlike traditional cameras that rely on light, JENI uses special sensors to capture energetic neutral atoms emitted by charged particles interacting with the extended atmospheric hydrogen gas surrounding Earth. The JENI instrument is the newest generation of this type of camera, building on the success of a similar instrument on NASA's Cassini mission that revealed the magnetospheres of Saturn and Jupiter.

"As soon as we saw the crisp, new images, high fives went around the room," said Matina Gkioulidou, deputy lead of JENI at APL. "It was clear we had captured the vast ring of hot plasma encircling Earth in unprecedented detail, an achievement that has sparked excitement for what is to come at Jupiter."

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