Juice launches toward Jupiter with instrument checks still ahead

ESA’s Juice spacecraft launched from French Guiana on an Ariane 5 on April 14, beginning its journey to Jupiter’s icy moons. The agency confirmed liftoff at 14:14 CEST, a signal from the spacecraft at 15:04 and deployment of its solar arrays at 15:33.

Photograph: ESA’s ESTEC premises in Noordwijk, 5 October 2014, not the Juice launch. Hnapel / Wikimedia Commons, CC BY-SA 4.0. Source-provided resized image; responsive crops.

Those enormous wings have a modest electrical target. ESA’s spacecraft specifications describe 85 square metres of solar panels designed to supply roughly 850 watts far from the Sun. Their cross-shaped layout lets them fold inside the launcher before opening in space.

Opening them was a launch-day milestone. ESA’s prelaunch operations schedule explicitly made its success announcement conditional on solar-array deployment. It also set out two and a half weeks of antenna and boom deployments, and an intensive three-month instrument-commissioning programme.

The reason for extending the hardware goes beyond making room. Sensors mounted on booms are kept away from the spacecraft’s body to limit magnetic interference. The design includes a 10.6-metre magnetometer boom and a 16-metre radar antenna. Getting those structures into position is part of making the measurements scientifically useful.

Juice is intended to make 35 flybys of Ganymede, Callisto and Europa before moving into orbit around Ganymede. The mission will investigate these worlds as potential habitats.