Sixty-seven orbits of Jupiter. Two close-ups of its moon Europa—where astrobiologists think microbial life may exist—21 flybys of far-out Callisto, and nine months in orbit around the biggest moon in the solar system, Ganymede.
The European Space Agency’s billion-dollar JUpiter ICy moons Explorer will be an exciting mission of firsts. As well as being the first time a European spacecraft has ever visited Jupiter, JUICE is destined to become the first spacecraft to orbit a moon other than Earth’s when it arrives at Ganymede for a nine month mission finale.
Here’s everything you need to know about JUICE at Jupiter:
What is JUICE?
JUICE is a mission that the European Space Agency (ESA) has been working on since 2014, but whose origins date back a decade before that. It’s actually delayed by 11 months. It was originally supposed to launched in 2022 and arrive at Jupiter in October 2029.
“The development of the spacecraft took longer than than expected and the pandemic also had an impact,” said Andrea Accomazzo, Head of the Solar and Planetary Missions Division at ESA, who’s been intensively preparing for JUICE since 2019.
How much does JUICE cost?
It’s about €1.6 billion ($1.7 billion), but how ESA missions are funded is very different to how NASA missions are paid for. “We’re talking about €1 billion from ESA, but for a mission like this typically the scientific instruments are provided by national institutions,” said Accomazzo.
There are 10 instruments on the spacecraft, from a camera called JANUS and a spectrometer to reveal the moons’ chemistry to the all-important J-MAG magnetometer that will measure the magnetic fields of Jupiter and its moons. In total they cost about €600 million. In total the mission costs about the same at ESA’s BepiCololmbo and Rosetta missions.
JUICE’s incredible journey to Ganymede
It’s going to take many years for the solar-powered JUICE to reach its destination, using multiple gravity assists to speed-up, save propellant and set JUICE on course for its arrival at Jupiter in July 2031. “It will take us eight years to get to Jupiter because we need to gain energy,” said Accomazzo. “Our launcher can put us on an orbit that goes around the Sun, but that’s not enough to reach Jupiter directly so we will gain a lot of energy by doing planetary gravity assist manoeuvres—three times with Earth and once with Venus.”
The manoeuvres borrow from the orbital energy of each planet, transferring it to the spacecraft. In fact, the initial gravity assist flyby in August 2024 will be of both the Earth and the Moon—the first time such a double manoeuvre has ever been tried.
Here’s the timeline of what engineers have in plan for the spacecraft:
April 5–25, 2023: launch from Europe’s Spaceport in Kourou.
August 2024: first gravity assist flyby of Earth and the Moon.
August 2025: gravity assist flyby of Venus.
September 2026: second gravity assist flyby of Earth.
January 2029: third gravity assist flyby of Earth.
January 2031: science mission begins with first images of Jupiter.
July 2031: arrives in the Jovian system.
June 2032: first of 21 flybys of Callisto (2032-2034).
July 2032: two flybys of Europa.
December 2034: orbital insertion at Ganymede (after 12 flybys).
Late 2035: mission ends with JUICE plunging into Ganymede.
What will JUICE do?
When JUICE reaches its destination in 2031 it will become the first European spacecraft to visit Jupiter. It will then spend three and a half years studying the icy satellites of Ganymede, Europa and Callisto, but also conduct 67 orbits of Jupiter.
“The first element of the mission is a three-year tour of the moons, during which we will tilt the spacecraft’s orbit around Jupiter,” said Accomazzo. “We will insert the spacecraft into orbit around the equator of Jupiter then tilt it away from the equator by using the moons as gravity slingshots.” That will also mean JUICE gets to image Jupiter’s polar regions.
During its two flybys of Europa, JUICE will search for pockets of liquid water under Europa’s icy surface—which is suspected to hide a liquid ocean— and hunt for previously seen plumes of water vapor. At Callisto, during 21 flybys JUICE will study its cratered surface, look for evidence of a subsurface ocean and change the angle of its orbit around Jupiter to help it get into orbit of Ganymede.
“The goal of the mission is to study places around Jupiter with the possibility for life—because we think there is liquid water inside Europa, Callisto and Ganymede,” said Olivier Witasse, Planetary Scientist on the JUICE mission. “So the orbit is so we can make flybys of those three moons.”
Why will JUICE orbit Ganymede?
The crux of the mission is its orbit of Ganymede, which it’s scheduled to begin doing in December 2034. If its succeeds it will become the first spacecraft to orbit a moon other than Earth’s Moon. “Ganymede is our main target for this mission and we will orbit it for nine months,” said Witasse. “It’s a series of of three different orbits—elliptical, then high altitude circular orbit at 5000 kilometers to do the global mapping, and then the lower altitude at 500 kilometers to take precise measurements of the moon.”
Ganymede: the solar system’s largest moon
Bigger than Mercury and Pluto, Ganymede fascinates planetary astronomers. It may resemble our moon in appearance, but it possesses several unique features. For one, it is covered by a crust made of ice, but experts believe that beneath this icy surface lies an ocean approximately 65 miles deep. “There is a lot of liquid water underneath the surface, maybe six times more than on Earth and much more than on Europa,” said Witasse.
What’s more, Ganymede has its own magnetic field, indicating the presence of a liquid metallic component surrounding an iron core. That means it could be similar to Earth in some ways. “Ganymede is like a mini-planet,” said Witasse. “There are only three bodies that possess an internal magnetic field—Earth, Mercury and Ganymede.”
Will JUICE just study Jupiter’s moons?
JUICE will also study the environment around Jupiter. “We’re going to be spending a lot of time in Jupiter’s magnetosphere and we’re going to be coming up out of the equatorial plane, so JUICE will see the environment in a view that hasn’t been seen much before,” said Professor Michele Dougherty, lead scientist on the magnetometer onboard JUICE and a planetary scientist at Imperial College London. “We’ve got instruments that will look at the atmosphere of Jupiter and its aurora, so in some ways JUICE will cover a broader spectrum of science—it’s not just for scientists interested in moons, but also for those interested in the Jupiter system itself.”
How will the JUICE mission end?
In late 2035 the mission will come to an end when the spacecraft is purposely crashed into the Ganymede to be destroyed, largely to prevent it accidentally crashing into—and contamininting—Europa, where astrobiologists believe some kind of life may exist.
Any extension of the mission seems unlikely, though not impossible. “In the radiation environment we know that the solar panels will not work as they did at the beginning of the mission, but we’ll see how the spacecraft and the instruments behave,” said Witasse. “If there is still some fuel, and if the spacecraft is still maintainable, then we’ll continue the mission for as long as we can.”
Enter NASA’s Europa Clipper
JUICE won’t be the only spacecraft at Jupiter when it arrives. A year prior to JUICE’s arrival, NASA’s Europa Clipper mission will arrive and flyby Europa 32 times—one reason why JUICE is only going to undertake two flybys of that particular icy moon. Europa Clipper will launch between October 10-30, 2024 and has a slightly shorter journey to the Jovian system, scheduled to arrive in April 2030.
With JUICE joining Europa Clipper in the Jovian system, Jupiter and its tantalizing icy moons finally look set to be unveiled in the early 2030s.