Juice spacecraft gears up for first Earth-moon gravity boost


The European Space Agency (ESA)’s Juice mission is heading to Jupiter, but it isn’t traveling all that way in a straight line. Instead, like most solar system missions, the spacecraft makes use of the gravity of other planets to give it a push on its way.

But Juice will be making an unusual maneuver next year, carrying out the first gravity assist flyby around both Earth and the moon. This week, the spacecraft made its longest maneuver yet to get into position ahead of the first of its kind flyby in 2024.

Artist’s impression of ESA’s Jupiter Icy Moons Explorer (JUICE) approaching Earth. ESA/Lightcurve Films/R. Andres

On November 17, the Juice spacecraft burned 10% of its fuel on a 43-minute-long maneuver, adjusting its trajectory so that it is in place for an encounter with Earth and the moon next year. The spacecraft will perform a second part of this maneuver which will bring it back towards Earth in August, first passing by the moon and then passing by Earth.

By using the gravity of both of these bodies, the gravity assist will be even more effective. Spacecraft often use Earth flybys to get a boost, but this is the first time a spacecraft will use the moon as well.

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“It was the first part of a two-part maneuver to put Juice on the correct trajectory for next summer’s encounter with Earth and the Moon. This first burn did 95% of the work, changing Juice’s velocity by almost 200 m/s,” said Julia Schwartz, Flight Dynamics Engineer at ESA’s ESOC mission control center, in a statement.

“Juice is one of the heaviest interplanetary spacecraft ever launched, with a total mass of around 6000 kg, so it took a lot of force and a lot of fuel to achieve this. In a few weeks, once we’ve analyzed Juice’s new orbit, we will carry out the second, much smaller part of the maneuver. Splitting the maneuver into two parts allows us to use the second firing of the engine to iron out any inaccuracies of the first.”

Firing the spacecraft’s main engine uses up a lot of fuel, so the hope is that after the second part of the maneuver, Juice won’t need to fire its main engine again until it has to slow down and enter the orbit of Jupiter. Smaller adjustments along the way will be made with its smaller thrusters, which are a more efficient use of precious fuel.

After performing the Earth-moon flyby, the spacecraft’s path includes several other flybys of Earth and Venus, gradually increasing its energy to send it away from the sun’s gravity and toward Jupiter.

Juice is scheduled to arrive at Jupiter in 2031, and you can follow along with its journey on the Where is Juice now? webpage.

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