Europe's Jupiter probe, JUICE, made a “gravity assist” pass by the moon on Monday (August 19), taking several photos to commemorate the historic encounter.
JUICE, short for Jupiter Icy Moons Exploration, came within just 465 miles (750 kilometers) of the moon's surface on Monday evening for the first stage of an unprecedented gravity-assist double-header, with the second stage taking place on Tuesday evening as the spacecraft flies closer to Earth.
JUICE documented Monday's moon landing with images taken by two onboard security cameras, and the European Space Agency (ESA) shared them with the world in a live webcast, complete with commentary from JUICE team members, once the spacecraft landed on Earth. (The images aren't amazingly clear, but they weren't expected to be that clear; the security cameras were designed to check the deployment of the spacecraft's solar panels and science instruments, not to study celestial objects.)
Another photo of the Moon taken by JUICE on August 19, 2024. (Image credit: ESA)
JUICE is due to launch in April 2023 on a mission to explore Jupiter and three of its four large Galilean moons: Ganymede, Callisto, and Europa. All three moons are thought to have oceans of liquid water beneath their icy shells, and Europa's ocean may be in contact with a rocky ocean floor, which could lead to a variety of interesting chemical reactions. (The oceans on Ganymede and Callisto may be sandwiched between layers of ice.)
This week's Moon and Earth flybys are historic: No other mission has ever performed a double gravity assist, according to ESA. The two-part maneuver will set the spacecraft on a similar flyby of Venus in August 2025, sending JUICE hurtling toward the giant planet.
“In fact, this flyby is a braking maneuver, so we're not accelerating JUICE in the sense of increasing its speed relative to the Sun,” JUICE spacecraft operations manager Ignacio Tanco said during ESA's lunar flyby webcast.
“We find that by going Earth first, then Venus, we can save about half a year of cruise time and reach Jupiter around July 2031,” Tanko added. “This counterintuitive approach of braking first actually results in the shortest cruise phase.”
Tanko said the JUICE team would have had to use nearly all of the propellant in the spacecraft's tanks to achieve the same speed changes achieved by engine burns during this week's two flybys.
Tuesday's Earth flyby will bring JUICE to within just 4,250 miles (6,840 km) of the planet. If all goes as planned, closest approach will occur over the North Pacific Ocean at 5:57 p.m. EDT (21:57 p.m. GMT).
Amateur astronomers could theoretically be able to view the probe through a telescope during the encounter, as long as they were somewhere in or near Alaska or the North Pacific Ocean, according to members of the JUICE team.
Tuesday's flyby, however, will not feature a webcast of flyby photos: All of ESA's Pacific-area telemetry receiving stations are in the Southern Hemisphere, so the JUICE team will not be able to communicate with the spacecraft during the flyby, team members said Monday.
