A quarter of an hour before the launch of the Juice probe to Jupiter, the excitement was at its height and the eyes shone, riveted on the launch pad of Ariane 5, in Kourou (Guyana). At Toucan, the rooftop shared by journalists and scientists from the mission to observe the take-off of the rocket, it’s a cold shower about ten minutes before the scheduled launch, at 9:15 a.m. (local time). The rocket will remain on the ground this Thursday, April 13. In question ? “The weather gods,” laughs nervously Inès Belgacem, a post-doctoral researcher at the ESA (European Space Agency), who has been working on the mission for 7 years.

ESA’s flagship mission, Juice (Jupiter Icy Moons Explorer) is to explore Jupiter and its icy moons, in search of habitable environments. The voyage is planned to last eight years. This is the first time that space Europe will soar to a planet in the outer solar system, which begins after Mars.

“It’s infuriating, all the windows were green on the screens until the last moment, launches Claire Vallat, scientist at ESA, disappointed. Everything went absolutely perfect, and seven minutes before the launch, it’s all red… For me, Ariane was leaving now. Amidst the decomposed mines, the two colleagues discuss the weather: “It’s the rainy season,” says one. “Yes, but she should have started two weeks ago, she could have waited another two days,” quips the other.

If the “weather red” is not on for rain – which does not prevent the rockets from taking off – it is the risk of lightning that has prompted the operational teams to postpone the launch.

“It’s hard to digest,” says Claire Vallat. We still have launch windows: it could be tomorrow [Friday, editor’s note], Monday… and until April 25, but that has a price in terms of fuel. If the mission does not manage to leave before April 25, we will have to be patient until August. “It’s a pool game, the planets have to be in the right place at the right time. This launch has the particularity of not having a wide firing window, it is to the nearest second. So either she can leave at the moment T, or it’s over. »