JANUS will study global, regional and local features and processes on the moons, as well as map the clouds of Jupiter. It will have a resolution up to 2.4 m per pixel on Ganymede and about 10 km per pixel at Jupiter.

The main aim of JANUS’s observations during the lunar-Earth flyby was to evaluate how well the instrument is performing, not to make scientific measurements. For this reason, JANUS took images with various camera settings and time intervals – a bit like if you’re going out to test a DSLR camera for the first time.

In some cases, researchers intentionally ‘blurred’ the images so that they can test out resolution recovery algorithms. In other cases, they partially saturated the image to study the effects induced on the unsaturated areas.

The name JANUS comes from the Latin phrase 'Jovis, Amorum ac Natorum Undique Scrutator', or roughly 'Scrutiniser of Jupiter, and all his loves and descendants'. Jupiter's four largest moons – the main focus of Juice’s mission – are named after protagonists in the 'love affairs' of Zeus, the equivalent of Jupiter in Greek mythology.

JANUS will transform our knowledge of Jupiter’s icy moons, by capturing them with a resolution and coverage 50 times greater than previous cameras sent to the Jovian system. The camera is equipped with an onboard computer that manages all instrument functions, processes commands, and sends data back to Earth.

In imaging our own Moon, with no atmosphere, JANUS could test out how it will function at Ganymede, Callisto and Europa. In contrast, Jupiter itself has a huge, turbulent atmosphere; JANUS’s images of Earth can better simulate imaging the different layers and components of Jupiter’s atmosphere.

For more information, see the original press release from the Italian National Institute for Astrophysics (INAF).

Note: These images are preliminary and have not been processed to use for science