Do you know what…?
Can Earth’s gravity really steer a spacecraft to Jupiter?
On 28 September, the European Space Agency’s Jupiter Icy Moons Explorer, Juice, skimmed past Earth in a manoeuvre that turned our planet into a celestial steering wheel. The deflected the spacecraft’s by 20 degrees and increased its velocity by 3.5 km/s, while demanding remarkably little propellant. At closest approach, Juice passed 8,640 km above the Indian Ocean at 13:45 CEST. In the preceding four weeks, controllers needed just one tiny corrective nudge despite having set aside six opportunities. That precision matters: every kilogram of fuel conserved during the cruise can later support more ambitious operations around Jupiter and its ocean-bearing moons. In other words, mission planners are making Earth .
The encounter was not merely navigational. Earth also served as a familiar laboratory for calibration of Juice’s 10 scientific instruments, while the spacecraft crossed the magnetotail and measured magnetic fields and charged particles. Teams had to prioritise observations under tight operational constraints, particularly when Juice entered Earth’s shadow and relied on battery power. The spacecraft will return for another Earth flyby in January 2029 before heading towards Jupiter, which it is due to reach in 2031; once there, the mission plans 35 flybys of Ganymede, Europa and Callisto. The elegant trick behind this long journey is the slingshot effect: rather than carrying enough fuel to brute-force its way across the Solar System, Juice repeatedly borrows momentum from planets — a reminder that, in spaceflight, finesse can beat force.