Instruments for the JUICE Jovian Mission

The European Space Agency (ESA) announced the list of instruments selected for its JUICE mission to explore the Jovian system for three years starting in 2030 following a 2022 launch. (NASA is a junior partner on the mission.) The JUICE spacecraft will make two close flybys of the moon Europa, several flybys of Callisto, and then will settle into orbit around Ganymede for an extended study of that moon. During the tour of Europa and Callisto, the spacecraft will observe the cloud deck of Jupiter and investigate the magnetosphere surrounding the king of planets.

The JUICE mission will be a worthy successor to the Galileo mission of the 1980s and 1990s that similarly toured the Jovian system. To keep the cost of the mission around 1B Euro, the spacecraft will have only modest radiation hardening and will only briefly tiptoe into the higher radiation fields close to Jupiter. Hence, the spacecraft will make just two flybys of Europa where Galileo did a number of flybys. Unlike Galileo, the JUICE spacecraft will not come closer to Jupiter than the orbit of Europa and hence will not do close flybys of the moon Io. However, it will observe Io remotely to gauge its volcanic activity.

ESA’s mission will compliment NASA’s Juno mission that is en route to Jupiter. Juno will perform extremely close observations of Jupiter, skimming above the top of the atmosphere. During the close encounters, Juno will see just a tiny slice of the giant planet that lies directly beneath its orbit, but will see the entire area of each pole as it approaches and recedes from Jupiter. JUICE on the other hand will see the entire planet and be better able to study broad weather patterns, but only will see the poles obliquely. Also, Juno will ignore the moons, while JUICE makes the moons the primary focus.

ESA’s press release said very little about the instruments, literally giving just their names. (I suspect they were leaving the details to be given in the press releases from the individual nations funding the instruments.) Press releases from NASA and the Jet Propulsion Laboratory provided additional information on the instruments they are participating on. For the remainder of this post, I've organized the instruments by study area and pieced together the limited information from the three press releases and from the JUICE Assessment Study Report (the “Yellow Book”) that discussed general goals for types of instruments.

Remote sensing instruments to image and map composition:

• JANUS: Jovis, Amorum ac Natorum Undique Scrutator, camera system (Google translated the Latin as, “Thursday, love, and children everywhere Examiner,” which put a smile on my face.) No information was given whether the camera(s) will be narrow angle (telephoto), wide angle, or both. From the yellow book: A narrow angle camera could, “provide high resolution images of Jupiter and its moons. Global imaging from the high orbit [around Ganymede] and imaging of selected targets with resolution of few meters per pixel from the low altitude at Ganymede will make a breakthrough in our understanding of the geology of the icy satellite and history of its surface.”

• MAJIS: Moons and Jupiter Imaging Spectrometer. From the yellow book, the main goals for this type of instrument, “are to study the composition of the moons’ surfaces and the composition, dynamics, structure and morphology of the Jupiter atmosphere.”

• UVS: UV Imaging Spectrograph. From NASA’s press release: “The principal investigator is Randy Gladstone of Southwest Research Institute in San Antonio. This spectrometer will acquire images to explore the surfaces and atmospheres of Jupiter's icy moons and how they interact with the Jupiter environment. The instrument also will determine how Jupiter's upper atmosphere interacts with its lower atmosphere below, and the ionosphere and magnetosphere above. The instrument will provide images of the aurora on Jupiter and Ganymede.”

• SWI: Sub-millimetre Wave Instrument. From the JUICE yellow book: “The main objective of a submillimetre wave instrument is to investigate the structure, composition and dynamics of the middle atmosphere of Jupiter and exospheres of its moons, as well as thermophysical properties of the satellites surfaces.”

Three instruments will map the physical structure of the moons during close encounters and from Ganymede orbit:

• GALA: Ganymede Laser Altimeter. From the yellow book, “A Laser Altimeter (LA) will contribute to the characterisation of the icy moons. It will provide data about the topography, shape and tidal deformation of the icy surfaces. It will also be crucial for studies of the spacecraft orbit in the gravity field of a satellite by providing accurate range data.” 

• RIME: Radar for Icy Moons Exploration. From the NASA press release: “The principal investigator is Lorenzo Bruzzone of Universita degli Studi di Trento in Italy. The U.S. lead is Jeffrey Plaut of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. Under the lead of Bruzzone and the Italian Space Agency, JPL will provide the transmitter and receiver hardware for a radar sounder designed to penetrate the icy crust of Europa, Ganymede, and Callisto to a depth of about 5 miles (9 kilometers). This will allow scientists to see for the first time the underground structure of these tectonically complex and unique icy worlds.”

• 3GM: Gravity & Geophysics of Jupiter and Galilean Moons From the yellow book: This instrument will perform the “characterisation of internal structure and subsurface oceans at Ganymede and Callisto and possibly at Europa by tracking the spacecraft.”

Several instruments will study the magnetospheres of Jupiter and Ganymede and the particles trapped within them:

• J-MAG: Magnetometer for JUICE. From the yellow book: “The [magnetometer] instrument will characterize the permanent internal/intrinsic magnetic field of Ganymede; establish and characterize magnetic induction signatures in possible subsurface oceans at Ganymede, Europa and Callisto; investigate Ganymede’s mini-magnetosphere which is embedded within the Jovian magnetosphere; observe magnetic field signatures within the Jovian magnetosphere and aid in characterizing the dynamics within this magnetosphere.”

• PEP: Particle Environment Package. From the NASA press release: The principal investigator is Stas Barabash of the Swedish Institute of Space Physics. The U.S. lead is Pontus Brandt of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md. Under the lead of Barabash and the Swedish National Space Board, APL will provide instruments to this suite to measure the neutral material and plasma that are accelerated and heated to extreme levels in Jupiter's fierce and complex magnetic environment.

• RPWI: Radio & Plasma Wave Investigation. From the yellow book (and this is a mouthful of physics-speak): “RPWI consists of a set of sensors that measures the DC electric field (two E-field dipole sensors), the electric component of plasma waves (E-field sensors and use of the radar antenna), magnetic field component of electromagnetic waves (Search Coil Magnetometer), radio emissions (triad of radio antennae) as well as some detailed characteristics of the thermal plasma (Langmuir Probes) including electric conductivity. Most of the proposed measurements have never been carried out before around Jupiter and its moons.” 

A final instrument “does not include spacecraft hardware but will exploit VLBI – Very Large Base Interferometry – to conduct radio science.” I'm not sure what that means, but here is the instrument's name: 

• PRIDE: Planetary Radio Interferometer & Doppler Experiment

When more information becomes available, I’ll write additional posts on the instruments.