The European Space Agency’s Jupiter Icy Moons Explorer will skim 8,640 kilometers above Earth on September 28, 2026, using the planet’s gravity to alter its speed and trajectory en route to Jupiter while keeping its 10 scientific instruments active to gather planetary data.
Spacecraft do not simply coast into the outer solar system on a straight trajectory. Doing so would demand an enormous rocket and an unthinkable reservoir of fuel, both to pick up the necessary velocity for the journey and to brake hard enough upon arrival to avoid flying past Jupiter entirely. Instead, flight controllers at the European Space Operations Centre in Darmstadt, Germany, devised an intricate orbital ballet using planetary gravity assists.
The Jupiter Icy Moons Explorer—known as Juice—launched on April 14, 2023, from Europe’s Spaceport in French Guiana aboard an Ariane 5 rocket. It carries nearly 3,000 kilograms of chemical propellant for its eight-year transit. To preserve that fuel, the mission relies on a sequence of flybys around Earth, the Moon, and Venus to reshape its path for free.
Trajectory Adjustments and the September 28 Earth Flyby Mechanics
Sunday’s encounter marks the spacecraft’s third Earth flyby. The closest approach occurs at 13:45 CEST (11:45 UTC) on September 28, 2026, passing over the Indian Ocean at an altitude of 8,640 kilometers. The maneuver deflects Juice’s trajectory by approximately 20 degrees and increases its velocity relative to the Sun by roughly 3.5 km/s.
Ahead of the pass, the flight dynamics team established a guidance campaign starting August 17 with six designated time slots for trajectory correction maneuvers. Angela Dietz, Juice Spacecraft Operations Manager, noted that a maneuver at minus four weeks proved of relatively small size, but extremely effective
in placing the spacecraft precisely where needed.
The timing creates an operational challenge. From the evening of September 27 through the early morning hours of September 28, Juice travels through Earth’s shadow, forcing the probe to operate entirely on battery power. Operators prioritized essential instrument observations to protect the power reserves.
Milestones From the Lunar-Earth Double Pass and Venus Slingshot
The journey to this point included major operational hurdles. In August 2024, Juice executed the first-ever lunar-Earth double flyby.
Science teams activated instruments during the 2024 pass. A subsequent Venus flyby bent its orbit and gave it a little extra speed.
Scientific Data Collection and Instrument Calibration During the Pass
Between September 23 and October 3, all 10 onboard science instruments remain active to study Earth and the Moon.
“This is great news for science, because it means we will be able to turn Juice in all different directions to point its science instruments at different parts of Earth and the moon.”
Claire Vallat, Juice Project Scientist
Researchers use the window to calibrate analysis tools ahead of the Jupiter arrival.
Following this week’s assist, Juice requires one final Earth flyby in January 2029 to lock onto its optimal flight corridor. The probe is scheduled to enter orbit around Jupiter in July 2031, shifting in 2034 to orbit Ganymede, its ultimate destination among the Jovian ice moons.
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