Juice Spacecraft Gains Speed in Earth Flyby

By Laura Kensington Philadelphia, PA · INDIAN OCEAN —

Published Updated 3 min read

The Juice spacecraft completed an Earth gravity assist on September 28, 2026, increasing its velocity by 3.5 km/s. This maneuver saved up to 150 kg of propellant while allowing engineers to calibrate science instruments.

INDIAN OCEAN — The European Space Agency's Jupiter Icy Moons Explorer (Juice) completed a gravity assist flyby of Earth on September 28, 2026. The maneuver increased the spacecraft's velocity by 3.5 km/s and deflected its trajectory by an angle of 20 degrees relative to its previous path.

Juice reached its closest point to Earth at 13:45 CEST (11:45 UTC) on that date, passing 8,640 km above the Indian Ocean. This altitude is closer than the orbit of geostationary satellites, which sit at 35,786 km. The 2026 Earth flyby saved 100–150 kg of propellant compared to a direct trajectory to Jupiter, representing a quantifiable efficiency gain for the mission.

The flyby provided an opportunity to test and calibrate the spacecraft's science instruments using Earth and the Moon as targets. This was the third instrument calibration opportunity during the mission, following a 2024 lunar-Earth gravity assist and 2025 observations of Comet 3I/ATLAS. "Juice's journey to Jupiter provides only a few opportunities to calibrate and validate the instruments under well-understood environmental conditions," explains Juice project scientist Claire Vallat, who led the effort.

"Given the limited time available and operational constraints, instrument activities sometimes have to be prioritized, for example when Juice was in Earth's shadow this morning, and relying on battery power alone. During this flyby, calibration activities were prioritized based on their relevance to preparing the instruments for their work at Jupiter, while also considering whether an opportunity is unique or can be scheduled later in the journey." The spacecraft spent several days traveling through Earth's magnetotail, measuring magnetic fields and electrically charged particles. The European-Chinese Smile mission simultaneously observed northern lights and measured magnetic fields and particles closer to Earth.

Why It Matters

The 2026 Earth flyby of Juice was the third gravity assist maneuver in the mission's eight-year journey, following a lunar-Earth flyby in August 2024 and a Venus flyby in August 2025. Juice is scheduled to return for a third and final Earth flyby in January 2029. The 2029 flyby will place Juice on the final trajectory to reach Jupiter in 2031.

The mission is scheduled to carry out 35 flybys of Jupiter's moons Ganymede, Callisto, and Europa. Juice launched on an Ariane 5 rocket from Europe's Spaceport in Kourou in April 2023.

Timeline

Juice reached its closest point to Earth at 13:45 CEST (11:45 UTC) on September 28, 2026. The spacecraft captured images of Earth and the Moon using its onboard monitoring cameras during the flyby.

Video footage from the flyby includes views from Juice monitoring camera 2 (JMC2) showing Earth as a thin crescent, and JMC1 showing the entire disc of Earth with Africa visible. An image taken by Juice monitoring camera 1 (JMC1) at 13:56 CEST shows Earth as the spacecraft moved away from closest approach.

What's New

Later reporting indicates that the European Space Agency’s Jupiter Icy Moons Explorer (Juice) performed a lunar-Earth gravity assist in August 2024, which was the first ever of its kind. The 2024 lunar-Earth gravity assist flyby of Juice was the first of its kind, involving a dual Moon-Earth maneuver that deflected the spacecraft by 100° and saved 100–150 kg of fuel, setting a precedent for complex multi-body gravitational assists. Additional details confirm that Juice’s 2026 Earth flyby was part of a planned sequence of three Earth gravity assists, with the final one scheduled for January 2029 to set the spacecraft on a trajectory toward Jupiter.

The 2026 Earth flyby marked the second time that Juice used Earth’s gravity to adjust its trajectory, following a similar maneuver in January 2024 as part of a lunar-Earth gravity assist. Juice’s closest approach was at 13:45 CEST (11:45 UTC) on 28 September. As Juice flew just 8640 km above the Indian Ocean, it snapped a series of images with its onboard monitoring cameras. In January 2029, Juice will meet Earth one last time, coming back for a third flyby of our home planet to put it onto the final track to meet Jupiter in 2031.

fact_check Facts

The European Space Agency's Jupiter Icy Moons Explorer (Juice) completed a gravity assist flyby of Earth on September 28, 2026.
The flyby deflected the spacecraft's trajectory by an angle of 20 degrees relative to its previous path.
Juice reached its closest point to Earth at 13:45 CEST (11:45 UTC) on September 28, 2026.
At closest approach, the spacecraft passed 8,640 km above the Indian Ocean.
Angela Dietz, Spacecraft Operations Manager
"The flyby required ultra-precise navigation in real time. Thanks to our very careful planning, we used only a small amount of the propellant reserved for this flyby," says Angela Dietz, Juice's Spacecraft Operations Manager. "This gives us more to use at Jupiter to carry out observations of the planet's icy moons."
The spacecraft captured images of Earth and the Moon using its onboard monitoring cameras during the flyby.
An image taken by Juice monitoring camera 1 (JMC1) at 13:56 CEST shows Earth as the spacecraft moved away from closest approach.
Video footage from the flyby includes views from Juice monitoring camera 2 (JMC2) showing Earth as a thin crescent, and JMC1 showing the entire disc of Earth with Africa visible.
The flyby provided an opportunity to test and calibrate the spacecraft's science instruments using Earth and the Moon as targets.
Claire Vallat, Project Scientist
"Juice's journey to Jupiter provides only a few opportunities to calibrate and validate the instruments under well-understood environmental conditions," explains Juice project scientist Claire Vallat, who led the effort. "Given the limited time available and operational constraints, instrument activities sometimes have to be prioritized, for example when Juice was in Earth's shadow this morning, and relying on battery power alone. During this flyby, calibration activities were prioritized based on their relevance to preparing the instruments for their work at Jupiter, while also considering whether an opportunity is unique or can be scheduled later in the journey."
The spacecraft spent several days traveling through Earth's magnetotail, measuring magnetic fields and electrically charged particles.

menu_bookBackground & Sources

Context and data our newsroom added to the originating report, with the primary source for each item shown below it.

The monitoring cameras provide 1024 x 1024 pixel snapshots that can be processed in color.
This was the third instrument calibration opportunity during the mission, following a 2024 lunar-Earth gravity assist and 2025 observations of Comet 3I/ATLAS.
The European-Chinese Smile mission simultaneously observed northern lights and measured magnetic fields and particles closer to Earth.
Juice is scheduled to return for a third and final Earth flyby in January 2029.
The 2029 flyby will place Juice on the final trajectory to reach Jupiter in 2031.
Juice launched on an Ariane 5 rocket from Europe's Spaceport in Kourou in April 2023.
The mission is scheduled to carry out 35 flybys of Jupiter's moons Ganymede, Callisto, and Europa.
Juice’s 2026 Earth flyby was part of a planned sequence of three Earth gravity assists, with the final one scheduled for January 2029 to set the spacecraft on a trajectory toward Jupiter.
Source: esa.int
The European Space Agency’s Jupiter Icy Moons Explorer (Juice) performed a lunar-Earth gravity assist in August 2024, which was the first ever of its kind.
A study titled "Solar Energetic Particle Events Detected in the Housekeeping Data of the European Space Agency's Spacecraft Flotilla in the Solar System" was published in 2023 in Space Weather.
Source: doi.org
Juice’s closest approach to Earth during the 2026 flyby occurred at an altitude of 8,640 km above the Indian Ocean, which is significantly closer than the orbit of geostationary satellites (35,786 km).
The 2026 Earth flyby marked the second time that Juice used Earth’s gravity to adjust its trajectory, following a similar maneuver in January 2024 as part of a lunar-Earth gravity assist.
The 2024 lunar-Earth gravity assist flyby of Juice was the first of its kind, involving a dual Moon-Earth maneuver that deflected the spacecraft by 100° and saved 100–150 kg of fuel, setting a precedent for complex multi-body gravitational assists.
Source: esa.int
The 2026 Earth flyby saved 100–150 kg of propellant compared to a direct trajectory to Jupiter, a quantifiable efficiency gain that underscores the strategic importance of gravity assists in deep-space missions.
During the 2026 flyby, Juice conducted calibration activities for its scientific instruments, prioritizing those relevant to its mission at Jupiter, while also considering the uniqueness of the opportunity.

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