With its new expansion, Juno will visit the moons of Jupiter

The Juno mission to Jupiter has been extended until September 2025 – or as long as the spacecraft can continue to operate around Jupiter.

While Juno has so far focused its attention on the one giant planet, the mission expansion will include observations of Jupiter’s rings and large moons, with focused sightings and planned close-up overflights of the moons Ganymede, Europa and Io.

These will be the first close flights of these moons since the Galileo mission in 1995-2003.

“One of the exciting things about the mission [extension]Juno principal investigator Scott Bolton said, speaking in September 2020 at a meeting of NASA’s Outer Planets Advisory Group, “are we going to go visit the satellites and the rings.” He’s really becoming a full system explorer, not as focused as the main mission was, so he’s potentially nurturing a more diverse community because the satellite geologists, the people in the ring will all be getting data that I think is very interesting and unique.

Juno made discoveries about Jupiter’s inner structure, magnetic field, and magnetosphere, and found its atmospheric dynamics to be far more complex than scientists previously thought. The onboard camera, the JunoCam, provided a stunning view of the world of the gas giant. Fans of space imagery expect JunoCam views of the Galilean moons to be nothing short of spectacular. Juno took long-range images of the Ganymede moon in 2020.

Juno arrived in Jupiter in July 2016, and the mission’s originally scheduled end date was February 2018, due to the spacecraft’s proximity to Jupiter and its radiation-laden environment. The harsh “working conditions” were expected to end up rendering the spacecraft unusable.

But the mission plan was changed when issues arose with the spacecraft’s main engine soon after Juno arrived in Jupiter. Originally, the spacecraft would have a 14-day close orbit around the planet. But at the end of 2016, mission directors opted not to burn a final rocket for that orbit due to uncertainty over the reliability of the engine.

Instead, a revised plan put Juno in a 53-day orbit. This meant that the whole mission was operating at a slower scientific pace. However, Bolton said that a slower pace was a “saving grace,” Juno was exposed to less severe radiation, allowing the mission to run longer than originally intended.

“I think the lesson is that we were flexible, and that’s good in missions,” Bolton said in September. “So when you design a mission, try to be flexible because you don’t know which curve ball you’re going to get thrown at.”