JUICE (Jupiter Icy Moon Explorer): A European mission to explore the emergence of habitable worlds around gas giants

JUICE - JUpiter ICy moons Explorer - is the first large mission in the ESA Cosmic Vision 2015-2025 programme. The mission was selected in May 2012, and entered in implementation phase “D” in March 2019. Due to launch in May 2022 and to arrive at Jupiter in October 2029, it will spend at least three ½ years making detailed observations of Jupiter and three of its largest moons, Ganymede, Callisto and Europa.  The status of the project and the main milestones in 2020-2021 are presented.

Science Objectives

The focus of JUICE is to characterise the conditions that might have led to the emergence of habitable environments among the Jovian icy satellites, with special emphasis on the three worlds, Ganymede, Europa, and Callisto, likely hosting internal oceans. Ganymede, the largest moon in the Solar System, is identified as a high-priority target because it provides a unique and natural laboratory for analysis of the nature, evolution and potential habitability of icy worlds and waterworlds in general, but also because of the role it plays within the system of Galilean satellites, and its special magnetic and plasma interactions with the surrounding Jovian environment. The mission also focuses on characterising the diversity of coupling processes and exchanges in the Jupiter system that are responsible for the changes in surface and space environments at Ganymede, Europa and Callisto, from short-term to geological time scales. Focused studies of Jupiter’s atmosphere and magnetosphere, and their interaction with the Galilean satellites will further enhance our understanding of the evolution and dynamics of the Jovian system. The overarching theme for JUICE is the emergence of habitable worlds around gas giants. At Ganymede, the mission will characterize the ocean layer, provide topographical, geological and compositional mapping of the surface, study the physical properties of the icy crust, characterize the internal mass distribution, investigate the exosphere, study the intrinsic magnetic field and its interactions with the Jovian magnetosphere. At Europa, the focus will be on the surface composition, understanding the formation of surface features and subsurface sounding of the icy crust over recently active regions. Callisto will be explored as a witness of the early solar system, trying to elucidate the mystery of its internal structure. JUICE will also perform a multidisciplinary investigation of the Jupiter system as an archetype for gas giants. The Jovian atmosphere will be studied from the cloud top to the thermosphere. Concerning Jupiter’s magnetosphere, investigations of the three dimensional properties of the magnetodisc and of the coupling processes within the magnetosphere, ionosphere and thermosphere will be carried out. JUICE will study the moons’ interactions with the magnetosphere, gravitational coupling and long-term tidal evolution of the Galilean satellites.

The payload

The JUICE payload consists of 10 state-of-the-art instruments plus one experiment that uses the spacecraft telecommunication system with ground-based instruments. This payload is capable of addressing all of the mission's science goals, from in situ measurements of the plasma environment, to remote observations of the surface and interior of the three icy moons, Ganymede, Europa and Callisto, and of Jupiter’s atmosphere. A remote sensing package includes imaging (JANUS) and spectral-imaging capabilities from the ultraviolet to the sub-millimetre wavelengths (MAJIS, UVS, SWI). A geophysical package consists of a laser altimeter (GALA) and a radar sounder (RIME) for exploring the surface and subsurface of the moons, and a radio science experiment (3GM) to probe the atmospheres of Jupiter and its satellites and to perform measurements of the gravity fields. An in situ package comprises a powerful suite to study plasma and neutral gas environments (PEP) with remote sensing capabilities of energetic neutrals, a magnetometer (J-MAG) and a radio and plasma wave instrument (RPWI), including electric fields sensors and a Langmuir probe. An experiment (PRIDE) using ground-based Very Long Baseline Interferometry (VLBI) will support precise determination of the spacecraft state vector with the focus at improving the ephemeris of the Jovian system.

The mission profile

The mission is due to launch from Kourou with an Ariane 5 ECA. The baseline launch is 20 May 2022, with two backup launch slots in September 2022 and August 2023. The baseline interplanetary transfer sequence relies on gravity assist with Venus, the Earth and Mars. The Jupiter orbit insertion will be performed in October 2029. A Ganymede swing-by is performed just before the capture manoeuvre. The tour of the Jupiter system, as currently designed, starts with a series of three Ganymede swing-bys. The spacecraft is transferred to Callisto to initiate the Europa science phase, one year after the Jupiter insertion. This phase is composed of two fly-bys, separated by 15 days, with closest approach at 400 km altitude. The next phase is a 200-day period characterized by an excursion at moderate inclinations, in order to investigate regions of the Jupiter environment away from the equatorial plane. A series of resonant transfers with Callisto raise the inclination with respect to Jupiter’s equator to a maximum value of about 28 deg. The spacecraft is then transferred from Callisto to Ganymede with a series of Callisto and Ganymede flybys, followed by a gravitational capture with the moon. The orbital phase around Ganymede is split into a first elliptical subphase, a circular orbit at 5000 km altitude followed by another elliptical sub phase, and then a circular phase at 500 km altitude. The duration of the Ganymede phase is about nine months, the end of mission being planned in September 2033. The spacecraft will eventually impact the surface.

The key project milestones in 2020-2021

•  February 2020: First instrument delivered
•  May 2020: Interface test between the spacecraft engineering model and the mission operations centre
•  Second quarter of 2020: Instrument deliveries and integration
•  January 2021: Start of the environmental tests
•  First half of 2021: Spacecraft tests
•  November 2021: Flight acceptance review