JUICE (spacecraft)

JUICE—an acronym for Jupiter Icy Moons Explorer—is a European Space Agency (ESA) interplanetary mission designed to study Jupiter and its three largest icy moons: Ganymede, Callisto, and Europa. Launched in April 2023, JUICE represents one of ESA’s most ambitious endeavours in planetary science, aiming to explore the conditions that might support life in the outer Solar System. The mission is part of ESA’s Cosmic Vision 2015–2025 programme and marks Europe’s first dedicated mission to the Jovian system.

Background and Objectives

The concept for JUICE originated in the late 2000s as part of a joint ESA–NASA initiative known as the Europa Jupiter System Mission (EJSM). When NASA later focused on its own mission, Europa Clipper, ESA proceeded independently with JUICE. The spacecraft was formally approved in 2012 as ESA’s first large-class mission under Cosmic Vision.
The primary objective of JUICE is to investigate the habitability potential of icy worlds in the Jovian system. It seeks to determine whether subsurface oceans exist beneath the icy crusts of Ganymede, Europa, and Callisto, and to understand their geological activity, chemical composition, and magnetic environments. The mission also aims to study Jupiter’s atmosphere, magnetosphere, and its complex interaction with its moons.

Design and Construction

JUICE was constructed by Airbus Defence and Space at its Toulouse facility, with contributions from numerous European research institutions. The spacecraft design emphasises endurance, power efficiency, and radiation protection to survive Jupiter’s harsh environment.
Key physical and technical features include:

• Launch Mass: Approximately 6,000 kg.
• Power Source: 85 m² solar arrays producing around 850 watts at Jupiter’s distance from the Sun.
• Structure: Aluminium and composite body with reinforced shielding against radiation.
• Propulsion: Bi-propellant main engine with multiple smaller thrusters for attitude and trajectory control.
• Communication: High-gain antenna (2.5 m diameter) for deep-space data transmission via ESA’s deep-space network.

Due to the low sunlight intensity at Jupiter’s orbit, JUICE’s solar arrays are the largest ever deployed on an ESA interplanetary spacecraft, enabling reliable operation far from the Sun.

Scientific Instruments

JUICE carries a suite of ten sophisticated scientific instruments, developed by international collaborations across Europe, Japan, and the United States. These instruments are designed to conduct remote sensing, geophysical measurements, and in-situ analyses:

1. JANUS (Optical Camera): High-resolution imaging of Jupiter and its moons’ surfaces.
2. MAJIS (Moons and Jupiter Imaging Spectrometer): Analyses surface and atmospheric composition using visible and infrared wavelengths.
3. UVS (Ultraviolet Spectrograph): Studies auroras, atmospheric gases, and surface–space interactions.
4. SWI (Sub-millimetre Wave Instrument): Measures temperature and dynamics in Jupiter’s stratosphere.
5. GALA (Ganymede Laser Altimeter): Maps topography and ice layer structure using laser pulses.
6. RIME (Radar for Icy Moons Exploration): Penetrates up to 9 km beneath icy crusts to detect subsurface oceans.
7. J-MAG (Magnetometer): Examines the magnetic fields of Jupiter and Ganymede.
8. PEP (Particle Environment Package): Analyses plasma and energetic particle populations.
9. RPWI (Radio and Plasma Wave Instrument): Studies electric and magnetic fields in the magnetosphere.
10. 3GM (Gravity & Geophysics of Jupiter and Galilean Moons): Uses radio science to measure gravity fields and atmospheric properties.

Together, these instruments will allow JUICE to conduct the most comprehensive study ever performed of Jupiter’s moons, integrating atmospheric, surface, and interior data.

Launch and Trajectory

JUICE was launched on 14 April 2023 aboard an Ariane 5 rocket from Europe’s Spaceport in Kourou, French Guiana. Due to the vast distance between Earth and Jupiter, the spacecraft is following a complex gravity-assist trajectory to gain the necessary speed while conserving fuel.
Its interplanetary route includes multiple flybys:

• Earth–Moon system (August 2024) – the first-ever combined Earth–Moon gravity assist.
• Venus (2025) – to gain additional acceleration.
• Earth flybys (2026 and 2029) – for final trajectory adjustments toward Jupiter.

JUICE is expected to arrive at Jupiter in July 2031, marking the start of its detailed scientific phase.

Mission Phases

The mission is divided into several operational phases:

1. Cruise Phase (2023–2031): Includes planetary flybys, instrument calibration, and system checks.
2. Jupiter System Tour (2031–2034): Extensive study of Jupiter, its magnetosphere, and multiple moon flybys.
3. Ganymede Orbital Phase (2034–2035): JUICE will become the first spacecraft ever to orbit a moon other than Earth’s, conducting detailed analysis of Ganymede’s magnetic field, internal structure, and potential ocean.
4. End of Mission: JUICE is expected to impact Ganymede in a controlled descent after exhausting its fuel supply.

Scientific Goals

The key scientific objectives of JUICE can be grouped under three main themes:

• Exploration of Habitability: Assessing whether the subsurface oceans of Ganymede, Europa, and Callisto possess conditions suitable for life, including water, energy sources, and essential chemical ingredients.
• Characterisation of Ganymede: Investigating Ganymede’s magnetic field, geology, ice shell, and core composition to understand how large icy moons evolve.
• Study of Jupiter’s System: Examining Jupiter’s atmosphere, weather systems, magnetic environment, and interactions with its moons to gain insight into gas giant dynamics.

The combination of radar, magnetometry, and imaging instruments will help determine the thickness of ice shells, the salinity of subsurface oceans, and the potential for geological or thermal activity beneath the surface.

Collaboration and International Participation

While JUICE is an ESA-led mission, it involves contributions from several international partners. NASA provides hardware and technical support for certain instruments, such as the ultraviolet spectrograph, while the Japan Aerospace Exploration Agency (JAXA) and Italian Space Agency (ASI) contribute to instrumentation and communications systems.
This collaborative framework underscores the mission’s global scientific importance, combining expertise and resources from multiple space agencies to advance the study of icy moons and planetary habitability.

Challenges and Engineering Achievements

Operating near Jupiter presents unique challenges: extreme radiation, low solar energy, and vast communication delays. Engineers designed JUICE with robust radiation shielding, redundant systems, and autonomous operational capabilities. The spacecraft also employs a highly stable thermal control system to manage the temperature variations between inner and outer Solar System environments.
Communications with Earth will have a signal delay of approximately 45 minutes, requiring JUICE to perform many tasks autonomously.

Expected Outcomes and Legacy

By the end of its mission, JUICE is expected to transform scientific understanding of the Jovian system and icy moon habitability. It will provide:

• High-resolution mapping of moon surfaces and subsurface oceans.
• Detailed insights into Ganymede’s intrinsic magnetic field and internal structure.
• Comprehensive data on Jupiter’s atmosphere, magnetosphere, and radiation belts.
• Comparative studies of the three major icy moons to reveal the diversity of ocean worlds.