Ariane 5 + JUICE: a match made for the heavens

21.04.2023

We explain how the Ariane 5 rocket was optimized for the complex launch of JUICE, to give the Jupiter probe the best possible start for its incredible journey

After its perfect launch by Ariane 5, the European Space Agency (ESA) JUpiter ICy moons Explorer (JUICE) probe is now heading off on its fascinating quest – to study the solar system’s largest planet and investigate whether its “icy moons” could possibly sustain life.

JUICE is the last ESA science mission to set out with an Ariane 5. As for all launches, Ariane 5 was scrupulously optimized for its mission. While there were no major modifications, several aspects of the launch were particular and required some adaptions.

A single payload launch
Ariane 5 was designed primarily to launch two satellites together. With a single, relatively low-mass payload (approx. 6 tons), the thrust of the main stage Vulcain 2 engine had to be adapted at the end of its burn to reduce the launcher’s acceleration to remain within the rocket stage’s qualified envelope.

 A release in an escape orbit
To set the probe off on its interplanetary cruise, Ariane 5 had to accelerate JUICE to Earth-escape velocity (11 km/s). This meant calculating the best trade-off between the mass of propellant in the spacecraft and the maximum performance capacity of the rocket.

A daytime launch
The launch took place at exactly 9:14 am, local time at the Kourou spaceport in French Guiana, and therefore rocket and payload were exposed to direct sunlight.  This poses a substantial potential risk: solar radiation could damage JUICE’s 10 sensitive scientific instruments and also negatively alter the state of the propellants used by the HM7B upper stage engine. To avoid overheating, the launcher was put in “barbecue” mode – rolling continuously, so that no side was exposed to the sun for too long.

Following a to-the-second lift-off, the penultimate Ariane 5 rocket carried its precious passenger on a trajectory due east out over the Atlantic Ocean. After nearly half an hour together, the JUICE spacecraft separated smoothly from Ariane 5 to begin its eight-year voyage to the Jupiter system – and a thrilling new chapter in space exploration.