Wednesday, September 3, 2025 at 9:23:19 AM IST
On Sunday, August 31, 2025, the European Space Agency’s (ESA) Jupiter Icy Moons Explorer (JUICE) spacecraft successfully completed a critical gravity-assist flyby of Venus. This maneuver, which had its closest approach at 05:28 UTC (1:28 a.m. EST), marks the second of four planned planetary slingshots designed to propel the heavy interplanetary probe on its long journey to the Jupiter system. Without the use of any onboard propellant, the close pass by Venus provided a significant velocity boost of 5.1 km/s, bending JUICE’s trajectory and setting it on its course for the outer solar system.
The flyby was a crucial step for the mission, which launched from French Guiana in April 2023. Unlike a direct path to Jupiter, which would require an impractical amount of fuel, JUICE’s flight plan involves a series of gravity assists. Its first, and a world-first, was a double flyby of the Earth and Moon in August 2024, which redirected its path. The Venus flyby in August 2025 was designed to further raise the spacecraft’s aphelion, the farthest point of its orbit from the Sun, in preparation for its next and final two gravity assists. These will be flybys of Earth in September 2026 and January 2029, which will provide the final pushes needed for JUICE to escape the Sun’s gravitational pull and make its final approach to Jupiter.
The Venus flyby was not without its challenges. Being so close to the Sun, the spacecraft had to endure an intense solar flux of around 3000 W/m². To protect its sensitive instruments and electronics from the extreme heat, the spacecraft’s main high-gain antenna was deliberately pointed toward the Sun, acting as a thermal shield. This critical self-preservation measure meant that none of the scientific instruments were active during the flyby, and as a result, no images or scientific observations of Venus were captured. This was a necessary trade-off to ensure the long-term health of the spacecraft and its instruments for their ultimate mission at Jupiter.
Just weeks before the flyby, mission teams at ESA’s European Space Operations Centre (ESOC) had to work for nearly 20 hours straight to resolve a communication anomaly that had temporarily severed contact with the spacecraft. The issue, caused by a subtle timing bug in the software that controls the signal amplifier, was resolved through a series of “blind commands” sent from Earth, a challenging task given the immense distance and the 22-minute communication lag. The successful restoration of contact was a major relief and a testament to the team’s calm and methodical approach, ensuring that JUICE was in perfect health and ready for its crucial Venus encounter.
The JUICE mission is the first large-class mission of ESA’s Cosmic Vision 2015-2025 program. Its main objective is to explore Jupiter and three of its largest icy moons—Ganymede, Callisto, and Europa—which are believed to harbor vast subsurface oceans and are considered to be some of the best places in the solar system to search for life beyond Earth. After its long cruise phase, JUICE is scheduled to arrive at Jupiter in July 2031. It will then spend at least 3.5 years conducting a detailed tour of the Jovian system, performing 35 flybys of its moons, with a particular focus on Ganymede, the only moon in the solar system with its own magnetic field. The mission will culminate in December 2034 with JUICE becoming the first spacecraft to enter orbit around a moon of another planet, orbiting Ganymede for a period of about a year before the conclusion of its mission.
