With its New Extension, Juno is Going to be Visiting Jupiter’s Moons

The Juno mission to Jupiter has been extended to September 2025 – or however long the spacecraft can keep operating around Jupiter.

While Juno has so far focused its attention on the giant planet alone, the mission extension will include observations of Jupiter’s rings and large moons, with targeted observations and close flybys planned of the moons Ganymede, Europa, and Io.

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

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

Juno has made discoveries about Jupiter’s interior structure, magnetic field, and magnetosphere, and has found its atmospheric dynamics to be far more complex than scientists previously thought. The camera on board, the JunoCam, has provided stunning views of the gas giant world. Space imaging enthusiasts are anticipating that JunoCam views of the Galilean moons should be nothing short of spectacular. Juno did take long-range images of the moon Ganymede in 2020.

Juno arrived at Jupiter in July of 2016, and originally, the projected end of the mission was February of 2018, because of how close the spacecraft was going to be to Jupiter and its radiation-laden environment. The harsh “working conditions” were expected to eventually make the spacecraft inoperable.

But the mission plan was changed when problems arose with the spacecraft’s main engine shortly after Juno’s arrival at Jupiter. Originally, the spacecraft was going to have a close-in 14-day orbit around the planet. But in late 2016, mission managers elected not to perform a final rocket burn for that orbit because of uncertainty of the engine’s reliability.

Instead, a revised plan put Juno in a 53-day orbit. This meant the entire mission operated at a slower scientific pace. However, Bolton said that slower pace has been a “saving grace,” Juno has been exposed to less severe radiation, allowing the mission to operate longer than originally planned.

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

NASA also extended the InSight mission at Mars for two more years, running through December 2022. InSight’s spacecraft and team deployed and operated its highly sensitive seismometer, measuring Marsquakes and collecting data on robust tectonic activity on the Red Planet, as well as enhancing our knowledge of the planet’s atmospheric dynamics, magnetic field, and interior structure.

An independent review panel recommended the two mission extensions to NASA.

“The Senior Review has validated that these two planetary science missions are likely to continue to bring new discoveries, and produce new questions about our solar system,” said Lori Glaze, director of the planetary science division at NASA Headquarters in Washington. “I thank the members of the Senior Review panel for their comprehensive analysis and thank the mission teams as well, who will now continue to provide exciting opportunities to refine our understanding of the dynamic science of Jupiter and Mars.”

NASA says that extended missions leverage the large investments in these missions, allowing continued science operations at a cost far lower than developing a new mission. “In some cases, the extensions allow missions to continue to acquire valuable long-duration datasets, while in other cases, they allow missions to visit new targets, with entirely new science goals,” NASA said in a press release.

Lead image caption: Citizen scientist Kevin M. Gill created this image using data from the spacecraft’s JunoCam imager. Credits: NASA/JPL-Caltech/Kevin Gill.