Juice-Toka’s Lunar Flight: Everything You Need to Know

What is happening?

First it is a dual world. The first lunar-Earth flight and the first dual gravity assist maneuver. It will change the speed and direction of the Juice to alter its flow through space, but it’s a bold move; the slightest mistake could throw Juice off course and spell the end of the mission.

Following Juice’s launch in April 2023, this lunar-to-Earth flyby is the first step in the spacecraft’s waltz through the Solar System on its journey to Jupiter.

During the flyby, Earth will bend Juice’s trajectory through space, ‘braking’ it and redirecting it on course for a Venus flyby in August 2025. From that point, the power boost will begin, with Juice to be accelerated by Venus and then twice by Earth – the space exploration equivalent of drinking three espressos in a row.

Why should it happen?

Jupiter is on average ‘only’ 800 million km from Earth. Without a giant rocket, sending Juice directly to the giant planet would require an impossible 60,000 kg of propellant on board. And then Juice would have to carry a huge amount of extra propellant to slow itself down enough to go into orbit around Jupiter once it arrives, instead of just crawling straight into outer space.

So Juice is taking the scenic route, using the gravity of other planets to carefully adjust his trajectory through space and ensure he reaches Jupiter at the right speed and direction. This incredibly complex, constantly evolving path has been carefully planned by Juice’s dedicated mission analysis team over the past 20 years.

Somewhat counterintuitively, using lunar-Earth flight to slow Juice down at this point in his journey is actually more efficient than using flight to speed him up. If we had instead used this flyby to give Juice a push to Mars, we would have had to wait a long time for the next planetary flyby. This first ‘braking’ maneuver is a way to take a shortcut through the inner solar system.

Find out more about why Juice’s journey to Jupiter is so long and complex

How are we making it happen?

Mission operators have already adjusted Juice’s path to ensure that it arrives first at the Moon, then a day later at Earth, at exactly the right time, at the right speed and traveling in the right direction. They are certain of success, but this is a dangerous challenge that no other space mission has ever faced before.

As Juice Spaceship Operations Manager Ignacio Tanco says: “It’s like going through a very narrow corridor, very, very fast: pushing the accelerator to the max when the difference in the side of the road is only millimeters.”

The liquid will be extremely close to both the Moon and Earth, meaning that pinpoint accuracy in real time is required in all navigation maneuvers. From August 17-22, Juice will be in constant contact with ground stations around the world. Every second of the way, day and night, the operators will be carefully watching the data coming from the Juice, making every little adjustment necessary to keep the ship on course.

Bonus science!

As if steering Juice around two major space obstacles wasn’t enough, ESA will also activate the spacecraft’s ten science instruments as it passes by the Moon and Earth.

The lunar-to-Earth flyby provides a prime test environment for instrument teams to collect and analyze data from an actual surface in space for the first time. For some instruments, this is the only opportunity to make certain measurements during Juice’s entire eight-year journey to Jupiter. This will give scientists and engineers the chance to calibrate their instruments, smooth out any remaining problems, and who knows, they might even make some surprising scientific discoveries.

The lunar-to-Earth flight is particularly important for Juice’s Radar for the Exploration of the Icy Moon (RIME) instrument, as the RIME data is being disturbed by electronic noise inside the craft.

The August 19 flyby of the moon is one of the few chances before arriving at Jupiter for the RIME team to check how this noise is affecting the instrument’s performance. During closest approach to the Moon, RIME will have eight minutes to observe alone, with the other instruments either turned off or set to quiet mode. Based on these observations, the RIME team will work on an algorithm to correct the noise problem.

How can you follow?

A lucky few may even be able to see Juice fly overhead, with the spacecraft flying directly over Southeast Asia and the Pacific Ocean. Powerful binoculars or a telescope will give you the best chance to see the spacecraft. Trajectory data can be found here.

Meanwhile, Juice’s two on-board monitoring cameras will take pictures along the Moon-to-Earth flight, which we’ll share publicly via social media and our Rocket Science blog once they’re taken back to Earth.

Follow @ESA_Juice AND @esaoperations on X for the latest updates.