Summary
ESA says Juice’s 28 September 2026 Earth flyby bent its path by 20° and increased its velocity by 3.5 km/s. The encounter also gave the mission teams an opportunity to test and calibrate science instruments in space.
ESA’s Jupiter Icy Moons Explorer (Juice) used Earth’s gravity on 28 September 2026 to reshape its route to Jupiter. The European Space Agency says the flyby deflected the spacecraft’s path by 20° and increased its velocity by 3.5 km/s, using little of the propellant reserved for the encounter.
Juice passed 8,640 km above the Indian Ocean at its closest approach, at 13:45 CEST (11:45 UTC). Its onboard monitoring cameras took images of Earth and the Moon during the encounter.
How the flyby changed Juice’s course
A gravity assist uses a planet’s gravity to bend a spacecraft’s path. Because the planet is moving around the Sun, the encounter can also change the spacecraft’s motion in its orbit around the Sun, helping alter its course without relying on a large engine burn.
The approach required precise navigation. ESA says that in the four weeks before the flyby, operators made one small trajectory correction out of six opportunities set aside for the task. The spacecraft had been tracked especially closely since 17 August, with that close tracking due to continue until 10 October.
The flyby also left more of the reserved propellant available for Juice’s work at Jupiter, according to Angela Dietz, the mission’s spacecraft operations manager. There, the spacecraft is intended to make detailed observations of Jupiter and its large moons Ganymede, Callisto and Europa.
A chance to test the science instruments
Changing course was the main objective, but the flyby also gave the teams an opportunity to operate Juice’s science instruments in space and prepare them for observations at Jupiter. ESA says teams from its spacecraft and science operations centres worked with the external instrument teams to plan activities across the mission’s 10 science instruments.
During several days in Earth’s magnetotail—the region of the magnetic field that stretches away from the Sun—Juice could measure magnetic fields and charged particles. ESA says those observations can be compared with measurements by the European-Chinese Smile mission near Earth’s poles, linking activity farther down the magnetotail with conditions closer to Earth.
Instrument operations had to be prioritised around spacecraft resources and conditions, including a period when Juice was in Earth’s shadow and relying on battery power. ESA said images and spectra from some instruments, including high-resolution images of Earth and the Moon from the JANUS science camera, were expected to be published after reaching Earth and being evaluated by the instrument teams.
The flyby is part of Juice’s eight-year cruise to Jupiter. ESA says the spacecraft is due to return to Earth for a final flyby in January 2029, then continue towards Jupiter, where it is expected to make 35 flybys of the three large moons before changing orbit to Ganymede.