ESA’s JUICE Probe Set To Use First-Ever Double Gravity Assist for Launch to Jupiter

The European Space Agency's Jupiter Icy Moons Explorer (JUICE) is heading back to Earth after being launched for its space mission. This move is intentional, as the spacecraft will utilize the Moon and Earth to accelerate toward its final destination.

Goal of JUICE Mission

JUICE is an interplanetary spacecraft involved in the first large-class mission in ESA's Cosmic Vision 2015-2025 program. It is set to make detailed observations of Jupiter and its three large ocean-bearing moons - Europa, Callisto, and Ganymede - using remote sensing, geophysical, and in situ instruments.

Part of the probe's mission is to characterize the three moons as planetary objects and possible habitats. It will also aim to explore Jupiter's complex environments in-depth and study the wider Jupiter system as an archetype for gas giants across the Universe.

First-Ever Gravitational Slingshot

On November 17, JUICE conducted a 43-minute burn to get into position for its upcoming Earth-Moon flyby, the first double gravity assist of the two celestial bodies. It was also the explorer's largest maneuver so far.

According to ESA's ESOC mission control center Flight Dynamics Engineer Jula Schwartz, this maneuver used up almost 800 pounds (363 kilograms) of fuel. This is roughly 10% of the 8,047 pounds (3,650 kilograms) of fuel that JUICE launched.

To reach Jupiter's moons, the spacecraft needs to perform a series of gravity assists to save overall fuel. In this maneuver, JUICE will fly past the planets of the inner solar system and use their gravitational tide to slingshot itself toward its target.

This is just one of the two steps to put JUICE on the right trajectory for the double gravity assist, the first in the series to occur in August 2024. The first burn will do 95% of the work, whereas JUICE's velocity will change by almost 656 feet per second (200 meters per second). Since JUICE is one of the heaviest interplanetary spacecraft ever launched at 13,228 pounds (6,000 kilograms), it will take a lot of force and a lot of fuel to achieve this feat.

In the coming weeks, the JUICE's new orbit will be analyzed by ESA before the second burn is calibrated to fine-tune its trajectory for the double gravity assist. If everything goes well with both components of this maneuver, experts likely will not need to use the main engine again until the probe enters orbit around Jupiter in 2031. ESA will use JUICE's smaller thrusters for minor trajectory corrections between now and then, according to JUICE Spacecraft Operations Manager Ignacio Tanco.

The first burn will be particularly challenging since some parts could not be tested in advance. For instance, experts only had an estimate of how the liquid in the fuel tanks would move around as the probe accelerates. This must be known precisely because if the fuel behaves differently from how scientists expect it, it could cause JUICE to drift off course during the burn.