World’s first lunar-Earth flyby gave Juice spacecraft the gravity boost it needed

In a stellar display of celestial navigation, ESA’s Juice spacecraft has expertly navigated a tricky and world-first lunar-Earth gravitational flyby, setting its course for the depths of the outer Solar System.

This mission is a critical step towards unraveling the secrets of Jupiter and its intriguing moons, and in the grand scheme of things, expanding our knowledge about possible life-friendly habitats beyond our blue planet.

Precision ballet of celestial bodies

Being in the right place and at the right time is an art — and this is exactly what the European Space Agency’s Jupiter Icy Moons Explorer (Juice) demonstrated this week with a perfect lunar-Earth flyby.

With this maneuver, Juice didn’t just prove stellar navigation is possible, but that it’s a sublime blend of science and artistry.

On August 19, 2024, it danced dangerously close to the Moon, followed by a rendezvous with Earth just over a day later, in the first-ever lunar-Earth flyby for a gravity assist on its way to Jupiter.

Why? To maneuver itself towards Venus using the gravitational pull of these celestial bodies. As you can imagine, this wasn’t easy. It needed extremely accurate, real-time navigation to keep Juice on its intended path.

Juice executed a perfect flyby

Ignacio Tanco, the mission’s Spacecraft Operations Manager, could hardly contain his excitement. “The gravity assist flyby was flawless, everything went without a hitch, and we were thrilled to see Juice coming back so close to Earth.” he said.

The main goal of this flyby was to adjust Juice’s pace and direction. Simple enough, right? Not really. It involved some intricate calculations.

The Moon’s gravity increased Juice’s speed by 2,000 mph, guiding it towards Earth. Then, it was Earth’s turn to decrease the spacecraft’s speed by 10,700 mph, effectively rerouting it towards Venus.

The result? A deflection by an angle of 100° from its original route – all without guzzling up too much fuel.

Saving fuel for a long journey ahead

This deft maneuver not only conserved between 100 to 150 kg (220 to 330 lbs) of fuel for the Juice spacecraft but also ensured a bit of extra propellant remained in its tanks.

“Thanks to very precise navigation by ESA’s Flight Dynamics team, we managed to use only a tiny fraction of the propellant reserved for this flyby,” added Ignacio.

This additional fuel not only provides a buffer for unforeseen circumstances but could also come in handy, allowing the spacecraft to get even closer to Jupiter’s largest moon, Ganymede, than originally planned.

The proximity to Ganymede presents a unique opportunity for detailed observations and data collection.

“This will add to the margins we keep for a rainy day, or to extend the science mission once we get to Jupiter,” Ignacio added.

Calibrating scientific instruments

While the primary objective of the flyby was to alter Juice’s trajectory to optimize its mission path, it also offered a priceless chance to thoroughly test the spacecraft’s advanced scientific instruments in the harsh environment of space.

This testing phase is crucial, as it helps ensure that all systems are functioning correctly and can withstand the challenges of the mission, ultimately contributing to the success of future explorations of the Jovian system.

Claire Vallat, Juice Operations Scientist, underscored the significance of this testing phase, saying, “The timing and location of this double flyby allow us to thoroughly study the behavior of Juice’s instruments.”

Juice continues voyage to Jupiter after flyby

Juice’s journey is far from done. After its launch in April 2023, and now with what could be called a “secondary launch” this week after returning to Earth, the spacecraft is now journeying towards Venus, with another flyby slated for August 2025.

This rendezvous with Venus will further adjust Juice’s trajectory, setting it on a course back to Earth for two more flybys.

Once Juice reaches Jupiter, the real work begins. It will scrutinize the gas giant and its three large ocean-bearing moons — Ganymede, Callisto, and Europa — seen as potential habitats for life.

Juice’s endeavor is a significant stride in humankind’s exploration of the outer Solar System. Each move, each observation, moves us closer to answering the deeper questions about our place in the cosmos.

As Juice continues on its path, it will bring us face to face with discoveries that could change our understanding of the universe forever.

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