Juice spacecraft is zooming by Earth and the moon today on its way to Jupiter

A team over at the European Space Agency (ESA) are on a mission to Jupiter with their spacecraft ‘Juice’.

Juice will pass by Earth at 5:57 p.m. ET on August 20. The European Space Agency will provide animated tracking of the spacecraft, accessible here.

For enthusiasts in Southeast Asia equipped with binoculars or telescopes, there may be a unique opportunity to observe Juice as it traverses the sky directly overhead.

Yet, curious minds have been scratching their heads wondering why it’s taking so long? Shouldn’t we be there by now?

And why is Juice returning back home and flying past Earth again today after launching on April 14, 2023… over 16 months ago?

As per the flight dynamics experts at ESA’s Mission Control, it’s a tad more convoluted than hopping on a straight flight from New York to London.

Juice flies by Earth en route to Jupiter

This marks a significant milestone in space exploration — a double world first. We are witnessing the inaugural lunar-Earth flyby and the first-ever double gravity assist maneuver.

This daring feat will adjust Juice’s speed and trajectory as it navigates through space; however, precision is critical. Even the slightest miscalculation could divert Juice from its intended path, jeopardizing the mission’s success.

Following Juice’s launch in April 2023, this flyby represents the initial step in the spacecraft’s intricate journey through the Solar System, ultimately aiming for Jupiter.

During the flyby, Earth’s gravitational influence will alter Juice’s course, effectively ‘braking’ it and setting the stage for a subsequent flyby of Venus in August 2025.

This pivotal moment will initiate a series of energy boosts, as Juice harnesses momentum from Venus and then twice from Earth — analogous to consuming three consecutive espressos in the realm of space exploration.

How does this complex maneuvering contribute to our understanding of celestial bodies, and what implications does it hold for future missions?

Why can’t Juice travel straight to Jupiter?

When Juice launched from Earth, the spacecraft was travelling at a speed of about 30 km/s, just like our planet does around the Sun.

Simply put, it’s already got quite a bit of ‘orbital energy’. But, if we decide to take a straight flight path from Earth to Jupiter, it would require a big rocket and a lot of fuel.

Then, we’d need even more fuel to slow down and enter Jupiter‘s orbit, rather than zipping past it.

Did you know that astronomical distances between planets aren’t fixed? For instance, the shortest distance between Earth and Jupiter (when both are on the same side of the Sun) is close to 600 million kilometers. But as they move in their separate orbits, this distance changes constantly.

So, engineers have to calculate the launch time based on where Jupiter will be when the spacecraft arrives. It’s a bit like passing a baton in a relay race, where both the giver and the receiver are in motion.

To stay in Jupiter‘s orbit and study the gas giant up-close, a spacecraft needs to decelerate. This slowdown maneuver requires a lot of fuel. So, what do we do when we want to save up on fuel? We take the most suitable route.

Juice, Jupiter, and rockets

The ESA’s Juice weighs just over 6000 kg, it’s one of the heaviest interplanetary probes ever launched, packed with a suite of scientific instruments to study Jupiter.

So, a massive rocket like Ariane 5 is needed to launch it, but even that isn’t enough to send Juice straight to Jupiter in a couple of years.

To further optimize the journey, flights to outer planets use gravity-assist maneuvers, essentially using the gravity of one celestial body to get a boost in speed. Think of it as using a trampoline to perform an impressive jump that you couldn’t do otherwise.

Juice stealing orbital energy

Here’s some Physics 101. To get into orbit around another planet, you need to match its orbital energy. So, Juice, the spacecraft, needs to increase its orbital energy to reach Jupiter. And how does it do that? By stealing it from Earth, Venus, and Mars!

Once Juice reaches Jupiter in July 2031, the real challenge begins. To get a closer look at the Jovian moons, Juice will perform an extraordinary 35 flybys of the Galilean moons – Europa, Ganymede, and Callisto. But all that space acrobatics requires precision. A wrong move and you could be lost in space!

The most crucial maneuver will be slowing Juice down by about 1 km/s just 13 hours after a Ganymede gravity assist, before it enters the Jupiter system.

This maneuver is a delicate dance of speed, angle, timing, direction, and the size of the maneuver. Blow any of these, and Juice can find itself off track, forcing it to expend fuel to correct its course.

Final countdown to exploration

As we inch closer to Juice’s arrival at Jupiter, excitement builds within the scientific community. This mission not only aims to unveil the mysteries of the gas giant but also seeks to understand the intriguing dynamics of its moons, particularly the potential habitability of Europa.

The intricate algorithms and models designed by the ESA ensure that every maneuver is executed with pinpoint accuracy, paving the way for discoveries that could shape our understanding of the solar system and beyond.

Each successful phase of this journey brings us nearer to unraveling the enigmatic secrets that Jupiter holds.

So, are we ready to find out what secrets lie beneath the frozen oceans of Ganymede, Callisto or Europa? Through the marvel of flight dynamics, by trading energy with the Universe, we will find out… in time.

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