20. January 2023
The JUICE spacecraft sets off for Europe's spaceport

From Eu­rope to Jupiter via Kourou

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JUICE – ESA's Jupiter mission
JUICE – ESA's Jupiter mis­sion
Image 1/7, Credit: ESA/ATG medialab (spacecraft); NASA/JPL/DLR (Jupiter, moons)

JUICE – ESA's Jupiter mission

The Eu­ro­pean Space Agen­cy (ESA) will ex­plore the largest plan­et in the So­lar Sys­tem, Jupiter, and its large icy moons (from left) Io, Ganymede, Eu­ropa and Cal­lis­to at close range for a pe­ri­od of four years start­ing in 2031 us­ing the Jupiter Icy Moons Ex­plor­er (JUICE) space­craft. The mis­sion is sched­uled to launch in April 2023.
The Galilean moons
The Galilean moons
Image 2/7, Credit: NASA/JPL/DLR

The Galilean moons

With a di­am­e­ter of ap­prox­i­mate­ly 140,000 kilo­me­tres, Jupiter is the largest plan­et in the So­lar Sys­tem. Against its hori­zon and the cloud vor­tex of the fa­mous 'Great Red Spot', the plan­et's four largest moons look small, but they are large: (from left) Cal­lis­to has a di­am­e­ter of 4821 kilo­me­tres and is the third largest moon in the So­lar Sys­tem. Its in­ner neigh­bour, Ganymede, at 5286 kilo­me­tres, is the largest moon in our plan­e­tary sys­tem. Eu­ropa, 3122 kilo­me­tres, and Io, 3666 kilo­me­tres, the in­ner­most of the four, are com­pa­ra­ble in size to Earth's Moon. The icy moons Eu­ropa, Ganymede and Cal­lis­to are the fo­cus of ESA's JUICE mis­sion.
The Ganymede Laser Altimeter
The Ganymede Laser Al­time­ter
Image 3/7, Credit: HENSOLDT Optronics

The Ganymede Laser Altimeter

The Ganymede Laser Al­time­ter (GALA) will mea­sure the tidal de­for­ma­tion of Ganymede's ice crust to pro­vide ev­i­dence for the ex­is­tence of a glob­al in­te­ri­or ocean. It will al­so pro­duce a map of the moon's to­pog­ra­phy. This will help re­searchers un­der­stand the pro­cess­es that shaped this icy moon’s sur­face. Mea­sure­ments tak­en at dif­fer­ent times dur­ing Ganymede's sev­en-day or­bit around Jupiter will be used to de­ter­mine the tidal de­for­ma­tion of the satel­lite's shape. GALA will al­so car­ry out mea­sure­ments of Eu­ropa and Cal­lis­to. This im­age shows the transceiv­er as­sem­bly. It con­tains a pow­er­ful laser that sends short laser puls­es to the moons' sur­faces sev­er­al times a sec­ond, and a re­ceiv­ing tele­scope that catch­es the re­flect­ed laser puls­es and for­wards them to the de­tec­tion elec­tron­ics. GALA was de­vel­oped un­der the lead­er­ship of DLR and con­struct­ed in col­lab­o­ra­tion with in­dus­tri­al part­ner HEN­SOL­DT Op­tron­ics GmbH (Oberkochen) and re­search in­sti­tu­tions from Ger­many, Japan, Switzer­land and Spain.
GALA central units
GALA cen­tral units
Image 4/7, Credit: DLR (CC BY-NC-ND 3.0)

GALA central units

Two cen­tral elec­tron­ic units were de­vel­oped for the Ganymede Laser Al­time­ter (GALA) on the JUICE space­craft and pri­mar­i­ly con­struct­ed at the DLR In­sti­tute of Plan­e­tary Re­search. The GALA Elec­tron­ic Unit (ELU) can be seen on the left and the GALA Laser Elec­tron­ic Unit (LEU) on the right. The ELU con­trols the en­tire in­stru­ment, pro­cess­es the raw sci­en­tif­ic da­ta and pro­vides var­i­ous sup­ply volt­ages. The Uni­ver­si­ty of Bern and the In­sti­tu­to de As­trofísi­ca de An­dalucía (Spain) con­tribut­ed com­po­nents for the ELU. The LEU as­sem­bly (right) con­trols the laser sys­tem and pro­vides the re­quired laser pump cur­rent of 200 am­peres. This unit was de­vel­oped and built by HEN­SOL­DT Op­tron­ics GmbH un­der a con­tract with the DLR In­sti­tute of Plan­e­tary Re­search, with fund­ing from the Ger­man Space Agen­cy at DLR.
The JANUS camera system
The JANUS cam­era sys­tem
Image 5/7, Credit: LDO

The JANUS camera system

JANUS is a cam­era sys­tem on JUICE. It will pho­to­graph the sur­faces of Jupiter's moons Ganymede and Eu­ropa in high res­o­lu­tion and thus pro­vide the ba­sis for map­ping the icy moons. The im­age da­ta will al­so be used to record and in­ter­pret the vis­i­ble ef­fects of the tidal ef­fects re­spon­si­ble for the sub­crustal oceans. Thir­teen spec­tral chan­nels in the vis­i­ble light and near in­frared spec­tral range al­low for the in­ves­ti­ga­tion of min­er­al­o­gy. Io and many of the small­er moons will al­so be ob­served from a dis­tance. JANUS was de­vel­oped in Italy, Ger­many, Spain and the UK; parts of the hard­ware were man­u­fac­tured at the DLR In­sti­tute of Plan­e­tary Re­search.
Preparations for the journey to Kourou
Prepa­ra­tions for the jour­ney to Kourou
Image 6/7, Credit: Airbus SAS 2022 JB Accariez-Masterfilms

Preparations for the journey to Kourou

ESA's prime con­trac­tor for the con­struc­tion of the JUICE space­craft is Air­bus De­fence and Space. This im­age shows the space­craft dur­ing so­lar ar­ray test­ing, on­ly a small part of which can be seen here. The mis­sion's tar­get, the gas plan­et Jupiter and its icy moons, is five times as far away from the Sun as Earth. On­ly one twen­ty-fifth as much of the Sun's en­er­gy reach­es it. As a re­sult, the space­craft's so­lar ar­rays must be large. With a to­tal of 85 square me­tres, JUICE's ar­rays gen­er­ate ap­prox­i­mate­ly 850 watts, used for the op­er­a­tion of the space­craft, com­mu­ni­ca­tions and the 10 sci­en­tif­ic in­stru­ments.
JUICE in the clean room
JUICE in the clean room
Image 7/7, Credit: © DLR. All rights reserved

JUICE in the clean room

The JUICE space­craft in the clean room at Air­bus De­fence and Space in Toulouse on 20 Jan­uary 2023 short­ly be­fore be­ing shipped to the Eu­ro­pean space­port in French Guiana. The so­lar ar­rays on the space­craft are not vis­i­ble here, as they will be in­stalled short­ly be­fore pack­ag­ing and de­liv­ery.
  • The Jupiter Icy Moons Explorer (JUICE) spacecraft is in Toulouse being prepared for transport to Europe's spaceport in Kourou. The spacecraft is scheduled for launch in April on an Ariane 5 launcher.
  • After arriving in the Jupiter system in July 2031, JUICE will study the planet and its icy moons from orbit, first around Jupiter and later around Ganymede.
  • DLR is providing the Ganymede Laser Altimeter (GALA) and significant contributions to the JANUS camera. The German Space Agency at DLR provides funding to a total of seven instruments on JUICE.
  • Focus: Jupiter, icy moons, exploration, search for life

"Trois, deux, un – et décollage!" This is how the last three seconds will be counted down in the control centre in Kourou, French Guiana, this April before one of the last Ariane 5 launch vehicles lifts off from Europe's Spaceport. The target of the European Space Agency's (ESA) largest planetary mission to date is Jupiter and its large icy moons Ganymede, Callisto and Europa. The Jupiter Icy Moons Explorer (JUICE) will study them up close from 2031 onwards. Under their icy crust, the moons could likely harbour oceans in which life could possibly exist. The Institute of Planetary Research at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) played a major role in the construction of two of the ten scientific instruments. The German Space Agency at DLR manages the German ESA contributions to JUICE on behalf of the German government and will provide approximately 100 million euros of funding across seven of the spacecraft’s instruments over the life of the mission.

By air to South America

JUICE must first be transported from Europe to South America. At present, the spacecraft, which has not yet been fuelled and weighs approximately 2400 kilograms empty, is located at the industrial prime contractor, Airbus Defence and Space, in Toulouse, southern France. There it was presented to the media on 20 January 2023 before being packed for transport to Kourou on an Antonov cargo aircraft. The transport across the Atlantic will take place in early February. In Kourou, the spacecraft will then be placed on the Ariane 5 ECA launcher and encased in a protective fairing. When fuelled, the JUICE spacecraft will weigh 6.1 tonnes. The launch window for the eight-year journey to Jupiter opens in April.

JUICE is the first L-class mission in ESA's Cosmic Vision programme, where the L stands for Large. The aim of this programme is to improve our understanding of the Solar System, including how the planets formed and under what conditions life can develop – Earth being our only current example. JUICE is a large project with its extensive scientific payload. Its target is Jupiter, the largest planet in the Solar System. It is five times as far away from the Sun as Earth, has a diameter of 140,000 kilometres – ten times as large and 318 times as massive as our home planet – and is orbited by a total of 79 moons. Of these, the four largest – Ganymede, Callisto, Io and Europa – are of enormous scientific interest. They are referred to as the Galilean moons after their discoverer, Galileo Galilei (1564-1641).

Three ice worlds and a volcanic hellscape

Io, the innermost of the four, is so violently deformed by the planet's tidal forces that magma is permanently formed in the rock mantle at temperatures of well over 1000 degrees Celsius. This molten rock is transported to the surface by enormous volcanoes. Sulphur-yellow Io is the most volcanically active body in the Solar System. From the innermost outwards, the three satellites Europa, Ganymede and Callisto follow. Ganymede, with a diameter of 5262 kilometres, is the largest moon in the Solar System; Europa and Io, with diameters of less than 4000 kilometres, are about as large as Earth's Moon; Callisto, with a diameter of 4821 kilometres, is the third largest moon in our planetary system.

It takes Europa twice as long as Io to orbit Jupiter; Ganymede four times as long. This means that these three moons repeatedly line up like a string of pearls. This creates resonance effects that, through interactions with the powerful gravitation and tidal forces emanating from Jupiter, generate heat in the interior of Europa and Ganymede. This causes enough heat to be present under their ice crusts, which are as cold as minus 160 degrees Celsius, which prevents water from freezing even at a distance of over 700 million kilometres from the Sun. This sustains deep layers of water, called subsurface oceans.

Oceans (and life?) under kilometre-thick ice crusts

In the case of Europa, it could be that the ocean under the ice crust, which is only a few kilometres thick, is more than 100 kilometres deep. This would mean that there is more water under the moon's surface than in all the oceans on Earth combined. There could also be an ocean below the surface of Callisto; as with Ganymede, magnetic field measurements have provided clear indications here. Both Ganymede and Callisto could have several layers of water, but located at greater depths.

Water is a basic prerequisite for the emergence and development of life as we know it. It is therefore conceivable that, hidden from the view of observations made from space, life has developed in the subsurface oceans of Jupiter's icy moons. JUICE will not be able to determine this, but it will be able to characterise the icy moons in more detail than NASA's Voyager (flyby 1979) and Galileo (orbiter, 1995-2003) missions, as well as confirm the presence of the oceans, how deep they are, how much water they contain and which mineral substances could be dissolved in the water.

The JANUS camera maps Ganymede and Europa

One of the JUICE instruments that will be used to answer these and other questions is the JANUS camera system. The main task of JANUS is to photographically record and map Ganymede and Europa It is also intended to record and interpret the visible effects of tidal forces on the surfaces, which are responsible for the subcrustal oceans. This includes tectonic phenomena such as fissures and ridges or spectral changes caused by the presence of different minerals produced as a result of cryovolcanism.

For this purpose, the camera system has 13 spectral channels in the visible light and near infrared spectral ranges in addition to a high spatial resolution. Io, and many of the smaller moons, will also be observed from a distance. JANUS was developed in Italy, Germany, Spain and the UK, and parts of the hardware were built at the DLR Institute of Planetary Research.

Tracking the oceans with lasers

The Ganymede Laser Altimeter (GALA) will measure the tidal deformation of Ganymede's ice crust to provide evidence for the existence of the global interior ocean. In addition, several million time-of-flight measurements will be used to produce a comprehensive map of the moon's regional and local topography, which will be assembled into a global elevation model of Ganymede. This will allow us to understand the processes that shaped the unique surface of this icy moon. The tidal deformation of the satellite's shape will also be determined using measurements taken at different times during Ganymede's seven-day orbit around Jupiter. From the strength of the deformation at the different orbital points, the existence of the inner ocean can be proven, and the mechanical properties of the overlying ice layer determined.

The altimeter will also be used to acquire measurements of Europa and Callisto. While researchers hope to find evidence of water just below Europa’s surface, in the case of Callisto it is likely to be found in deeper layers. GALA was developed under DLR's supervision, in collaboration with industrial partner HENSOLDT Optronics GmbH (Oberkochen) and research institutions from Germany, Japan, Switzerland and Spain. It will be the first time that such an instrument has been used in the outer Solar System.

Weather forecast for Jupiter and its moons

Another instrument from Germany on board JUICE is the Sub-millimetre Wave Instrument (SWI), which is the primary responsibility of the Max Planck Institute for Solar System Research in Göttingen. It will be used to examine the middle atmospheric layers of the gas giant Jupiter as well as the extremely thin atmospheres – or more correctly, 'exospheres' – and surfaces of the Galilean moons. The focus will be on determining the thermal structure, dynamics and composition of the various layers of Jupiter's atmosphere and how they interact, as well as Jupiter's internal structure.

ESA mission with strong German participation

JUICE is the largest and most comprehensive ESA mission to explore a planetary system within the Solar System. NASA and the Japanese Aerospace Exploration Agency (JAXA) have also contributed to the mission. ESA provides funding for the satellite platform, the Ariane 5 ECA launcher and the operation of the spacecraft. The funding for the scientific payloads for JUICE is largely provided by national space agencies and the participating institutes. In addition to the JANUS, SWI and GALA instruments, the German Space Agency at DLR is funding further German scientific contributions from the national space programme to the Particle Environment Package (PEP) particle spectrometer, the Jupiter Magnetometer (J-MAG), the Radar for Icy Moons Exploration (RIME) radar instrument and the 3GM instrument for radio sounding of Jupiter's atmosphere.

JUICE will reach Jupiter in July 2031 and complete a total of 35 flybys of the moons by November 2035. In September 2034, the spacecraft will be steered into an elliptical, later circular, orbit around Ganymede. JUICE will be the first mission to orbit the moon of another planet. By the time the mission ends in September 2035, JUICE will have orbited Ganymede approximately 1250 times. Should fuel still be available, further orbits will take place at an altitude of just 200 kilometres, enabling measurements of a quality that would set the standard for decades to come. At the end of the mission, the spacecraft will be deliberately steered to crash into the surface of Ganymede and be completely destroyed in the collision with the rock-hard ice. As the suspected ocean inside Ganymede is estimated to be 100 kilometres deep and night temperatures below minus 160 degrees Celsius, there is no danger of contamination of Ganymede’s ocean by terrestrial microbes that might have travelled along on JUICE as 'stowaways'.

Contact
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    Ger­man Aerospace Cen­ter (DLR)

    Cor­po­rate Com­mu­ni­ca­tions
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  • Martin Fleischmann
    Ger­man Aerospace Cen­ter (DLR)
    Ger­man Space Agen­cy at DLR
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  • Ulrich Köhler
    Ger­man Aerospace Cen­ter (DLR)
    In­sti­tute of Plan­e­tary Re­search
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    12489 Berlin
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  • Christian Chlebek
    Ger­man Aerospace Cen­ter (DLR)
    Ger­man Space Agen­cy at DLR
    Space Sci­ence
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