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from https://www.theverge.com/2023/4/17/23686138/juice-launch-jupiter-moon-esa-ariane-5-rocket

JUICE spacecraft launched to investigate the habitability of Jupiter’s
icy moons
/ The Jupiter Icy Moons Explorer mission will visit three of Jupiter’s largest moons — Europa, Ganymede, and Callisto — to investigate whether they could be potentially habitable.
By GEORGINA TORBET

Apr 17, 2023, 6:30 AM PDT|1 Comment / 1 New
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JUICE launch to explore Jupiter’s moons
Photo by JODY AMIET/AFP via Getty Images

The European Space Agency (ESA) successfully launched its JUICE
spacecraft to study Jupiter’s icy moons on Friday, April 14th. The
Jupiter Icy Moons Explorer mission will visit three of Jupiter’s largest moons — Europa, Ganymede, and Callisto — to investigate whether they
could be potentially habitable, a question that has been igniting debate
among astronomers since the first evidence of subsurface oceans on these
moons was seen by the Galileo mission in the 1990s.

JUICE launched at 8:14AM ET from Europe’s Spaceport in French Guiana, carried by an Ariane 5 rocket. The launch had been delayed from its
original launch date of April 13th due to weather conditions, but the
skies today were clear for liftoff.

The spacecraft separated from the rocket shortly after liftoff, making
signal contact with Earth at 9:04AM. It then deployed its large solar
arrays, which unfurled to their full size of 27 meters across, with full deployment confirmed at 9:33AM. With that, the spacecraft begins its
eight-year journey to the Jupiter system.

The mission is to investigate whether Jupiter’s moons could be
potentially habitable

The launch had to occur within a tiny window of just one second in order
to work with the spacecraft’s complex trajectory. The spacecraft will
begin its journey around the orbit of Earth, making a flyby of Earth and
the Moon in August 2024. This will be the first time that a spacecraft
will perform a maneuver called a Lunar-Earth gravity assist (LEGA),
which involves flying first past the Moon and then past Earth just a day
and a half later. This will give the spacecraft a boost, but it requires launching at an exact time.

“We have to launch on the second in order to have the right trajectory towards the first orbit around the Sun that will allow us to come back
to Earth,” ESA payload system engineer Alessandro Atzei explained in a prelaunch briefing.

The spacecraft will continue by circling toward the inner solar system,
making a flyby of Venus in 2025 before traveling back out to Earth’s
orbit for two more flybys in 2026 and 2029. Then, it will be able to
power out toward Jupiter, arriving at the Jupiter system in 2031.

This will be the first time that a spacecraft will perform a maneuver
called a Lunar-Earth gravity assist

This journey is designed to conserve as much fuel as possible, as the spacecraft will need its fuel reserves to perform maneuvers at Jupiter.
Once JUICE arrives at Jupiter, it will perform a total of 35 flybys of
Europa, Ganymede, and Callisto, the three icy moons.

At this point, the spacecraft will be so far from the Sun that its huge
solar panels, which are 85 square meters in area, will produce just a
few hundred watts of power, or about enough to run a microwave. Its
instruments have to be designed to operate while using power very
sparingly as well as dealing with the harsh radiation environment of
Jupiter.

The 10 instruments on board include remote sensing instruments like a
camera and spectrograph for observing targets that are far away as well
as in situ instruments like a magnetometer and radio and plasma wave
instrument for measuring the immediate environment around the
spacecraft. A further experiment on board, called the Planetary Radio Interferometry and Doppler Experiment, or PRIDE, will test whether it is possible to use radio telescopes on Earth to determine the spacecraft’s precise position.

The probe will arrive at the Jupiter system in 2031

These instruments will be used to investigate Jupiter’s moons, with a particular focus on Ganymede. Ganymede is unusual in that it is the
largest moon in the solar system and the only moon known to produce its
own magnetic field. That magnetic field sits within the powerful
magnetic field of Jupiter, and the two interact producing strong auroras
around the moon. Ganymede’s surface is also of interest as it varies in
age, with both smooth younger terrain and areas of much older pockmarked terrain, which can help scientists understand how the Jupiter system
evolved over billions of years.

The most intriguing feature of Ganymede, though, is that, like Europa
and Callisto, it is thought to have a liquid water ocean beneath a crust
of ice several miles thick. Evidence for this comes from the Galileo
mission, which found perturbations of Jupiter’s magnetic field near
Europa that suggested a subsurface ocean, plumes of water bursting
through the surface detected by Hubble, and the detection of water vapor
in Europa’s atmosphere made using ground-based telescopes.

Given the necessity of liquid water for almost all forms of life, that
has made these moons some of the best locations in the solar system to
search for potentially habitable environments. The JUICE spacecraft will
not look for evidence of life directly but will look for indications
that the moons could potentially host life by looking for biosignatures
such as the presence of biologically essential elements like carbon and
oxygen.

To assess whether these environments really are habitable, scientists
need to look at the bigger picture of the Jupiter system as a whole. “To understand this question of habitability we need to explore the Jupiter
system globally — so to study Jupiter, its atmosphere, its weather, its strong rotating magnetic field, the volcanic moon Io, the other moons in
the system, and how all these bodies are connected to each other,” JUICE project scientist Olivier Witasse explained in the science briefing. “So Jupiter is really a miniaturized solar system.”

“To understand this question of habitability we need to explore the
Jupiter system globally”

Studying this system can help us learn about the entire solar system as
well as investigate whether these distant worlds could potentially host
life. “Today, we have sent a suite of ground-breaking science
instruments on a journey to Jupiter’s moons that will give us an
exquisite close-up view that would have been unimaginable to previous generations,” said Carole Mundell, ESA’s director of science, in a statement.

“The treasure trove of data that ESA Juice will provide will enable the science community worldwide to dig in and uncover the mysteries of the
jovian system, explore the nature and habitability of oceans on other
worlds and answer questions yet unasked by future generations of
scientists.”


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