ESA's Juice spacecraft has had close-ups with the Moon and Earth and is on its way to Venus, having snapped images with its monitoring cameras and collected scientific data as it passed.

The ultimate destination of the spacecraft is Jupiter, but to save fuel, the probe is using the gravity of the Earth, Moon, and Venus to send it on its way. The European Space Agency (ESA) reckons the slingshots will save the mission up to 150 kg of fuel, even if it likely cost controllers some chewed fingernails as the probe made its lunar-Earth flyby.

The closest approach to the Moon, which increased Juice's speed relative to the Sun by 0.9 km/s, occurred at 2115 UTC on August 19, and the nearest approach to the Earth, which decreased the probe's speed by 4.8 km/s, occurred at 2156 UTC on August 20, ESA said.

"The gravity assist flyby was flawless, everything went without a hitch, and we were thrilled to see Juice coming back so close to Earth," said Ignacio Tanco, the mission's Spacecraft Operations Manager.

It did indeed come close to Earth, passing 6,840 km above Southeast Asia and the Pacific Ocean, to be precise. Eight of the probe's instruments collected data during the Earth flyby. Ten were running during the Moon flyby. One was the spacecraft's scientific camera, JANUS - an abbreviation of the Latin phrase "Jovis, Amorum ac Natorum Undique Scrutator" (Comprehensive exploration of Jupiter, and his loves and descendants) - collected data which will be downloaded in the coming weeks.

Stars of the show, however, were Juice's cameras designed to monitor the deployment of the probe's appendages. These were pressed into service to capture images from the flyby and, after some light processing, produced some impressive results. In one set, the spacecraft is clearly visible, with the Moon in the background. Another shows the Earth.

So precise was the flyby that controllers only required a small fraction of the propellant reserved for course corrections. Coupled with a flawless Ariane 5 launch in April 2023, Juice has a little extra, er, juice in the tank for when it reaches its final destination.

"This will add to the margins we keep for a rainy day, or to extend the science mission once we get to Jupiter," Tanco said.

While using gravity to adjust trajectories and save fuel is not new, hats must be doffed to the ESA Flight Dynamics team for the calculations behind an inherently risky maneuver. Hopefully, there will be time for some celebrations and perhaps some beverages at ESA's Darmstadt control center before the next rendezvous with Venus in August 2025. ®

https://www.theregister.com//2024/08/21/esa_juice_gravity_assist/