ESA's Juice deep-space probe images Jupiter without even leaving home
ESA's Jupiter Icy Moons Explorer (Juice) deep-space probe showed its stuff recently when it captured an image of Jupiter and its four largest moons – even though the unmanned spacecraft won't launch for three years. The pictures were taken by mission engineers on the roof of Airbus Defence and Space's facility in Toulouse as part of a test of Juice's navigation camera (NavCam).
Scheduled to launch from ESA's Guiana Space Centre ELA-3 in June 2022 atop an Ariane 5 rocket, the Juice probe's mission involves a lot more than just popping off to Jupiter and then going into orbit around it. To save fuel and allow for a bigger payload, the spacecraft will reach Jupiter by means of a series of slingshot orbits that will see it fly by, Earth, Venus, Earth again, Mars, and Earth one last time before arrival at the Jovian system in October 2029.
Once on station, this whizzing about will only just be getting started as Juice ducks in and out of Jupiter's radiation belts, performing a series of flybys of the moons Europa, Ganymede, and Callisto before going into orbit around Ganymede in September 2032. It will remain there until it runs out of propellant, after which mission control will order it to make a controlled impact on the icy moon in February 2034.
Because of these elaborate maneuvers, a key bit of equipment aboard Juice is its NavCam. In conjunction with navigation data sent from Earth, the NavCam allows the onboard computer to determine the position and velocity of the spacecraft, so it can make the necessary corrections for a successful flyby.
According to ESA, this requires the NavCam to be specially hardened against radiation as well as being able to take accurate images of moons, planets, and stars. To achieve this end, engineers in June took an engineering prototype of the NavCam up on a roof as part of a series of evaluation tests, including onboard image processing. This saw the device take images of the Moon, stars, and Jupiter itself, catching unexpectedly clear pictures.
"Unsurprisingly, some 640 million km (398 million mi) away, the moons of Jupiter are seen only as a mere pixel or two, and Jupiter itself appears saturated in the long exposure images needed to capture both the moons and background stars, but these images are useful to fine-tune our image processing software that will run autonomously onboard the spacecraft," says Gregory Jonniaux, Vision-Based Navigation expert at Airbus Defence and Space. "It felt particularly meaningful to conduct our tests already on our destination."
A further test involved feeding NavCam simulated views of the larger Jovian moons to give engineers a better idea of what Juice will actually see during the mission and what sort of details it will be able to capture during the flybys. Later this year, the NavCam will be fitted with flight optics, which will be used for testing software as well as how well the camera works in the completed probe.