The orbiter has made 56 flybys of Jupiter and documented close encounters with three of the gas giant’s four largest moons. NASA’s Juno spacecraft will make its closest flyby to Jupiter’s moon Io in 20 years on Tuesday, December 30. The pass, about 930 miles (1,500 kilometers) from the surface of the most volcanic world in our solar system, is expected to allow Juno’s instruments to produce a wealth of data.

“By combining data from this flyby with our previous observations, the Juno science team is examining how Io’s volcanoes are changing,” said Juno principal investigator Scott Bolton of the Southwest Research Institute in San Antonio, Texas. “We look at how often they erupt, how bright and hot they are, how the shape of the lava flow changes, and how Io’s activity is related to the flow of charged particles in Jupiter’s magnetosphere.”

Io’s second super flyby is scheduled for February 3, 2024, and Juno will once again come within about 930 miles (1,500 kilometers) of the surface.

The spacecraft observed Io’s volcanic activity from 11,000 kilometers to 62,100 miles (100,000 kilometers) away and provided the first images of the moon’s north and south poles. The spacecraft also made flybys of Jupiter’s icy moons Ganymede and Europa.

“Through flybys in December and February, Juno will investigate the source of Io’s massive volcanic activity, whether there is a magma ocean beneath its crust, and the significance of Jupiter’s tidal forces mercilessly squeezing this tortured moon,” Bolton said.

Now in the third year of its expanded mission to explore Jupiter’s origins, the solar-powered spacecraft will also explore the gas giant’s ring system, which is home to some of its inner moons.

imagine this

All three cameras on Juno will be active during Io’s flyby. Jovian Infrared Auroral Mapper ( JIRAM (which takes images in the infrared range) will collect signatures of heat emitted from the volcanoes and calderas that cover the lunar surface. The mission’s Stellar Reference Unit (a navigation star camera that also provides valuable science data) will capture the highest-resolution image of the surface to date. And the JunoCam camera will capture color images in visible light.

JunoCam was incorporated into the spacecraft for public participation and is designed to operate on up to eight flybys of Jupiter. The upcoming Io flyby will be Juno’s 57th orbit around Jupiter, where the spacecraft and cameras endure one of the harshest radiation environments in the Solar System.

“The cumulative effect of all this radiation is starting to show up on JunoCam over the last few orbits,” said Ed Hurst, Juno project manager at NASA’s Jet Propulsion Laboratory in Southern California. “Images from the last flight show a reduction in the dynamic range of the thermal imager and the introduction of ‘stripe’ noise. Our engineering team is working on solutions to reduce radiation damage and maintain the thermal imager.”

More Io please

After months of study and evaluation, the Juno team adjusted the spacecraft’s planned future orbit to add seven new flybys of Io (18 in total) to the expanded mission plan. After passing near Io on February 3, the spacecraft will pass by Io on all other orbits, with each orbit gradually moving further away: the first will be about 10,250 miles (16,500 kilometers) above Io, and the last will be about 71,450 miles (115,000 kilometers) above Io. kilometer).

The gravitational pull that Io exerts on Juno during its flyby on December 30 will shorten the spacecraft’s orbit around Jupiter from 38 days to 35 days. Juno’s orbit will decline 33 days after the February 3 flyby.

From now on, Juno’s new orbit will cause Jupiter to block the Sun from the spacecraft for about five minutes, during a period called perigee when the orbiter is closest to the planet. Although the solar-powered spacecraft will encounter darkness for the first time since its flight in October 2013, the period will be brief enough that it will not affect its overall performance. The spacecraft will encounter similar solar eclipses during each flyby of Jupiter from now until the end of its extended mission, which ends in late 2025, except for the Feb. 3 period.

Starting in April 2024, the spacecraft will conduct a series of eclipse experiments that use the Juno Gravitational Science experiment to study Jupiter’s upper atmosphere, providing important information about the planet’s shape and internal structure.