Plate Nº 91 · recorded October 10, 2026
Space & AstronomyReported finding
ESA's Juice Spacecraft Swings Past Earth on 28 September
ESA's Juice spacecraft returns to Earth on 28 September for its third gravity assist, using our planet's pull to change speed and direction en route to Jupiter.
By Nathan Brooks2 min read477 words
In brief
- Juice flies past Earth on 28 September for its third gravity assist.
- ESA flight controllers guide the spacecraft close to Earth to alter its speed and direction.
- The spacecraft's final destination is Jupiter and its icy moons.
- The manoeuvre trades planetary momentum for spacecraft velocity without heavy fuel use.
On 28 September, the European Space Agency's Jupiter Icy Moons Explorer — Juice — will fly past Earth for the third time, using our planet's gravity to change its speed and direction on the long journey to Jupiter.
Flight controllers at ESA will guide the spacecraft close to the home planet it left behind, letting Earth's gravitational pull do work that no onboard engine could realistically perform. The manoeuvre is a gravity assist: a carefully aimed planetary flyby that trades a sliver of a planet's orbital momentum for a significant change in a spacecraft's velocity.
Why does a Jupiter probe keep coming back to Earth?
Jupiter sits far from our planet, and reaching it demands more energy than current rockets can hand to a spacecraft in a single launch. Mission designers solve the problem by routing probes on extended tours of the inner Solar System, stealing momentum from the planets they pass.
When Juice sweeps past Earth on 28 September, the planet's gravity will tug on the spacecraft and alter both how fast it travels and the direction it points. The spacecraft gains energy; the planet, vastly more massive, loses an amount so tiny it is unmeasurable. Controllers must aim the flyby with precision, because the geometry of the pass determines the new trajectory.
This is the third such Earth encounter on Juice's itinerary, a pattern typical of missions headed to the outer Solar System. Each assist reshapes the orbit so that the spacecraft arrives at its next waypoint — and ultimately at Jupiter — with the velocity it needs, all without burning large reserves of propellant.
What happens during the flyby?
Flight controllers guide the craft in from deep space, tracking its position and trimming its course so that it passes Earth at the right distance and angle. The closer and better-aimed the pass, the more the trajectory changes.
Gravity assists are routine but demanding operations. Controllers monitor the spacecraft continuously, and the outcome of the encounter sets up the next leg of the voyage. A successful pass on 28 September keeps Juice on track toward its destination: Jupiter and its icy moons.
What is Juice going to Jupiter for?
The mission's full name states its target: the Jupiter Icy Moons Explorer. Jupiter hosts a family of large, frozen moons, and Juice is designed to study them. ESA launched the spacecraft to investigate these distant worlds, which planetary scientists consider among the most intriguing bodies in the Solar System.
Before any science at Jupiter begins, however, Juice must get there. The 28 September Earth flyby is one of the remaining steps in that journey — a brief homecoming in which the planet itself acts as part of the propulsion system.
After the pass, the spacecraft will continue along its revised path, carrying ESA's ambitions toward the largest planet in our neighbourhood.
via cosmos.esa.int (Original)