Juice redirected to Venus in world’s first flyby of Moon and Earth

The spacecraft’s closest approach to the Moon was at 23:15 CEST (21:15 UTC) on August 19, leading JOS to its closest approach to Earth more than 24 hours later at 23:56 CEST (21:56 UTC) on August 20.

As the JOCE probe flew just 6,840 kilometers above Southeast Asia and the Pacific Ocean, it took a series of images with its onboard surveillance cameras and collected scientific data with eight of its 10 instruments.

“The gravity assisted flight was flawless, everything went without a hitch, and we were very happy to see Joyce return so close to Earth,” said Ignacio Tanco, spacecraft operations manager for the mission.

The purpose of the flyby was to change Gus’s trajectory through space, using the gravity of first the Moon and then the Earth to change the spacecraft’s speed and direction.

The Moon flyby increased Goss’s velocity relative to the Sun by 0.9 km/s, which steered Goss toward Earth. The Earth flyby decreased Goss’s velocity relative to the Sun by 4.8 km/s, which steered Goss on a new path toward Venus. Overall, the Moon and Earth flybys caused Goss to deviate by 100 degrees from his pre-flyby path.

The high-risk flyby required highly accurate real-time navigation, but saved the mission about 100 to 150 kilograms (220 to 330 pounds) of fuel. In the month before the flyby, spacecraft operators gave GOSS a gentle nudge to put it on exactly the right approach path. They then tracked GOSS 24/7 from August 17 to 22.

Thanks to a flawless Ariane 5 launch in April 2023, Juice has a little extra fuel in its tanks to get closer to Jupiter’s moon Ganymede than originally planned. The successful flyby of the Moon and Earth has protected that extra science.

“Thanks to the very precise navigation carried out by ESA’s flight dynamics team, we were able to use only a small portion of the fuel allocated for this flight,” adds Ignacio. “This should increase the margins we have for difficult days, or to extend the scientific mission once we reach Jupiter.”

First scientific experiment in space

Although the primary goal was to change JUICE’s trajectory, the Moon flyby also provided an opportunity to test JUICE’s scientific instruments in space, with all ten instruments turned on during the Moon flyby, and eight more during the Earth flyby.

We expect to release images and spectra collected by some of Juice’s instruments in the coming weeks, as they are downloaded from the spacecraft and evaluated by instrument scientists. This includes high-resolution images of the Moon and Earth from Juice’s science camera. Janus.

“The timing and location of this double-flight allows us to study the behavior of Juice’s instruments comprehensively,” explains Claire Vallat, Juice’s operations scientist.

“This happens early in JUICE’s journey, allowing us to use the data to prepare the instruments for the Jupiter mission. Given our good knowledge of the physical properties of the Earth, Moon, and surrounding space environment, this is also the ideal location to understand how the instruments will respond to a real target.”

Next step: flower

In effect, this flyby of the Moon and Earth reduced JUICE’s energy, redirecting it toward an encounter with Venus in August 2025. This flyby of Venus will boost JUICE’s energy back toward Earth; the spacecraft will flyby our planet again in September 2026 and January 2029, gaining two more boosts before arriving at Jupiter in July 2031.

Delve deeper into the story of Gus’s flyby of the Moon and Earth with Rocket Science Blog.

He follows @ESA_Juice On X to get all the latest mission updates.

Enjoy the journey of flying over the Moon with a live broadcast from ESA, including a Q&A session with mission experts, on European Space Agency YouTube Channel.

About juice

ESA’s Jupiter Icy Moons Exploration Probe (JIMO) is humanity’s next bold mission to the outer Solar System. The probe will make detailed observations of the gas giant Jupiter and its three large ocean-bearing moons – Ganymede, Callisto and Europa. The ambitious mission will analyse these moons using a powerful suite of remote sensing, geophysical and in-situ instruments to discover more about these fascinating destinations as potential habitats for life, past or present.

JUICE will deeply observe Jupiter’s complex magnetic, radiation, and plasma environment and its interactions with the moons, studying the Jupiter system as a prototype for gas giant planetary systems throughout the universe.

The JOICE spacecraft was launched on an Ariane 5 rocket from Europe’s Kourou spaceport in April 2023. Its journey will take eight years, and include flybys of Earth and Venus before reaching Jupiter. The spacecraft will make 35 flybys of the three large moons as it orbits Jupiter, before changing its orbit to Ganymede.

Juice is a mission led by the European Space Agency with contributions from NASA, the Japan Aerospace Exploration Agency and the Israel Space Agency. It is the first major mission in ESA’s Cosmic Vision programme.

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