JUICE to Use Earth and Moon Gravity for Faster Journey to Jupiter
In mid-August, the JUICE spacecraft will utilize the gravitational pull of both the Moon and Earth to accelerate its journey to Jupiter.
The path to the gas giant Jupiter is long and complex. For the ESA’s JUICE (Jupiter Icy Moons Explorer) probe, this route includes three flybys of its home planet. The first of these is scheduled for August 19-20. During this period, JUICE will execute a pioneering dual gravity assist maneuver, utilizing the gravitational forces of both the Moon and Earth. This type of maneuver, often referred to as a swing-by, fly-by, or gravity assist, is unprecedented in space exploration.
Known within the ESA as a “LEGA” (Lunar-Earth Gravity Assist), this maneuver aims to alter both the direction and speed of the spacecraft. As a result, JUICE will decelerate and be redirected towards Venus. In August 2025, JUICE will gain momentum through another gravity assist at Venus, followed by two additional flybys of Earth in September 2026 and January 2029. Ultimately, JUICE is expected to reach Jupiter by July 2031. The probe was launched on April 14, 2023, aboard an Ariane 5 rocket from Kourou.
The logic behind JUICE decelerating to reach Jupiter faster might seem counterintuitive. One could have used the Earth flyby to boost JUICE towards Mars. However, this approach would have resulted in significant delays before the next planetary encounter, according to the European Space Agency. This initial deceleration maneuver acts as a shortcut through the inner solar system, part of a meticulously planned trajectory developed over the past 20 years.
Fuel Efficiency for Enhanced Science
The key aspect of the Moon-Earth flyby is its intentional proximity to the Moon, aimed at optimizing the gravitational assist from Earth. “We intentionally approach the Moon to enhance the gravitational assist from Earth,” said Arnaud Boutonnet, JUICE mission analyst, during a press conference on August 9. Typically, the Moon is considered a disturbance during Earth’s gravity assists. However, the LEGA maneuver leverages the Moon’s gravity to benefit JUICE instead of counteracting it. On August 19, JUICE will come within 700 kilometers of the Moon, and on August 20, it will be approximately 6,800 kilometers from Earth.
