Leonardo for Juice in search of Jupiter

The Leonardo Group has given an important technological contribution to the JUICE (JUpiter ICy moons Explorer) mission thanks to the funding and coordination of the Italian Space Agency (Agenzia Spaziale Italiana, ASI) and the scientific supervision of the Italian National Institute for Astrophysics (Istituto Nazionale di Astrofisica, INAF).

In collaboration with the INAF, Leonardo has built the “JANUS” (Jovis, Amorum ac Natorum Undique Scrutator) high resolution camera at the Campi Bisenzio plant near Florence. Its purpose is to monitor Jupiter’s atmosphere and to study its three icy moons - Europa, Ganymede and Callisto - in-depth, in search of environments deemed capable of supporting forms of life. JANUS is the only high resolution camera of the JUICE mission, capable of observing a tennis ball from 1 km away.


One distinctive element of JANUS is its wheel with 13 filters of different colours. Each filter will allow JANUS’ eye to detect different concentrations of chemical elements: for example, red for methane and yellow for sodium. 
To keep the JANUS optics motionless, thereby guaranteeing high-quality images despite the stresses of the launch and sudden temperature changes, the mechanical and thermal design of JANUS was developed to restrict deformations with values below one-tenth of the thickness of a hair, making JANUS practically non-deformable. 
Leonardo is industrial head of the entire instrument, with the contribution of subsystems from DLR of Berlin, CSIC-IAA of Granada and CEI-Open University of Milton Keynes.

JANUS by the numbers


telescope filters

7.5 m

spatial resolution over Ganymede at 500 km from its surface

10 km

spatial resolution for Jupiter’s atmosphere

In Campi Bisenzio, near Florence, Leonardo has built the hyperspectral optical head for “MAJIS” (Moons and Jupiter Imaging Spectrometer), an instrument under French management built with a bilateral agreement between ASI and CNES. Its purpose is to observe and characterise clouds, ice and minerals on the surfaces of the three moons. It is a sort of flying laboratory the size of a bedside table for performing chemical-physical analyses from a few thousand km away. 

Consisting of two instruments in one that as a whole cover the range from visible to mid-infrared, MAJIS is equivalent to having 1,016 cameras, each of which captures the image in a single colour. By properly combining these images, it is possible to identify the minerals making up the surface of solid bodies and the gases in their atmospheres, and to measure their density, temperature, movements and so on.



In order to be able to observe in infrared, MAJIS is cooled down to -180°C by a special pair of radiators that “capture” the cold of deep space without any energy consumption. To do this, it was necessary to thermally insulate the instrument from the rest of the much warmer probe. For example, “feet” (bipods) are used to raise MAJIS. As thin as they are, these “feet” have been built and tested to sustain a force equivalent to the weight of a bus! With thermal insulation like this, it would be possible to keep an icicle inside an oven turned on for years without making it melt.

MAJIS was optically designed as a sort of “kaleidoscope”, in which light follows a complicated zig-zag path consisting of 28 lenses and mirrors. This idea arose from the need to reduce the space between the light’s entrance and the focal point so that the high performance required could be achieved, but with the low volume established by the mission.

MAJIS by the numbers

= 1.016

cameras each for each colour


lenses and mirrors


for thermal insulation cooling

JUICE’s photovoltaic panels were created at Leonardo’s Nerviano plant, near Milan. They are the largest ever built for an interplanetary mission, having an 85 sq.m surface and a total of approximately 24,000 cells to supply the electric power necessary at a distance of over 750 million km from the sun.



If they were to orbit the earth, these panels would be able to supply an entire block of flats. On Jupiter, instead, they will produce about 900 Watts, the energy used by a household appliance. This is because the intensity of the sunlight around Jupiter’s orbits is only a twenty-fifth of that received on earth.

PVA panels by the numbers

85 m2

of extension


solar cells per panel

10 km

from the sun


times less sunlight than on earth

+110°C/ -230°C

the temperatures the panels shall have to sustain

In Italy, Thales Alenia Space (a joint venture between Thales 67% and Leonardo 33%) is responsible for the development, building and testing of RIME (Radar Sounder for Icy Moons Exploration), one of the 10 most important instruments on board the JUICE probe. This instrument is essential to the success of the mission, thanks to its ability to detect the internal structure of layers of ice. RIME operates at a 9 MHz frequency and uses a 16-metre antenna built by Space Tech GmbH on behalf of Airbus Defence and Space.  The Radar Sounder is able to penetrate up to 9 km below the icy surface with a vertical resolution of up to 30 metres, making it able to explore the internal structure of Ganymede, Callisto and Europa. The University of Trento, responsible for the scientific aspects, is the interface with the ESA. Development was funded by the ASI under a contract with Thales Alenia Space, which designed and built the instrument with several units supplied by NASA/JPL.

In addition to RIME, Thales Alenia Space has built the KaT (Ka Translator), a fundamental part of the 3GM (Gravity & Geophysics of Jupiter and Galilean Moons) instrument, together with the Sapienza University of Rome.

Thales Alenia Space has also developed key equipment for the JUICE probe platform: the Deep Space Transponder - DST, the High Gain Antenna – HGA, and the High Attitude Accelerometer – HAA.

Telespazio (a joint venture between Leonardo 67% and Thales 33%) is taking part in the implementation of the JUICE mission, through its subsidiary Telespazio Germany, by providing engineering and operations support to ESA’s European Space Operations Centre (ESOC). Specifically, Telespazio engineers have contributed to the preparation of the space vehicle by being tasked with simulation activities and astrodynamics services. Moreover, Telespazio Germany has developed the operations simulator used by the mission’s Flight Control Team in the launch preparation phase.,


Cover photo: Exploring Jupiter and Ganymede artist’s impression - © ESA

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