ESA’s JUICE To Perform ‘Double World First’ Lunar-Earth Flyby – How Can You See It?

The European Space Agency’s (ESA) Jupiter Icy Moons Explorer (JUICE) will return to Earth on 19-20 August. Flight controllers will manoeuvre the JUICE spacecraft to pass by the Moon before heading towards Jupiter. This unique manoeuvre called ‘double world first’ will help JUICE take a shortcut to Jupiter by using Venus’ gravitational pull.

During the flyby, as a treat for skywatchers and astrophotographers, the JUICE spacecraft might be visible in the night sky.

JUICE’s Gravity Assist

On Monday, 19 August, at 21:16 UTC (coinciding with the day named after the Moon in Greek and Roman tradition), the JUICE spacecraft will first fly by the Moon. This will provide an additional boost to enhance the subsequent Earth flyby, which will occur on Tuesday, 20 August, at 21:55 UTC. During this Earth encounter, the spacecraft will be directed towards Venus for a gravity assist in the coming year.

In simpler terms, JUICE will use Earth’s gravity to adjust its speed and path as it continues its journey towards Jupiter.

What Makes Juice’s ‘Double World First’ That Unique?

According to Guiseppe Sarri, the former ESA Project Manager for the JUICE mission, this event marks the first time in history that a spacecraft will execute a double Moon-Earth gravity assist — an unprecedented but risky achievement.

“This manoeuvre will allow to save a lot of propellant, but it is a bit more risky than a simple one-planet gravity assist,” he explains. “Because the two flybys are so close, there will be no time to measure the trajectory and correct for possible errors after the Moon flyby and before the Earth flyby. It has to be right from the beginning.”

Why JUICE’s Earth And Venus Flybys Matter Before Jupiter?

The flybys or gravity assists, help increase the spacecraft’s speed to escape the Sun’s gravity and reach Jupiter. Just like a spacecraft needs enough speed to leave Earth, it also needs much more speed to break free from the Sun’s pull to reach the outer planets. Without these flybys, the spacecraft would need much more fuel, making it impossible to launch.

“Multiple flybys require a lot of mission analysis calculation, trajectory determination and correction to make the flying profile right. Any mistake will translate into additional corrections, depleting the available propellant on board. In the worst case, one could crash on the planet or be lost in space, but with the experience accumulated in all these years by the operation teams, this event is unlikely,” resumes Sarri.

JUICE’s Earth-Moon flyby Scientific Goals

As Giuseppe Sarri mentioned, no particular science will be performed during the flybys. However, it will allow scientists to check the instrument’s performance further. 

“A full week of testing was done in early July, and everything is working as expected,” assured Sarri.

One goal is to use the instruments similarly to how they will be used at Jupiter. A special task is to use the RIME antenna, a 16-meter-long antenna meant to study ice on Jupiter’s moons. It will send a signal for the first time and receive a reflection from a real planetary surface, specifically the Moon, from about 700 km away.

Where Will JUICE Be Visible From Earth?

ESA reports that the JUICE spacecraft might be seen from Earth during its flyby if you have clear skies and are in the right location.

JUICE will make its closest approach to Earth at 23:57 CEST on 20 August (01:57 UTC on 21 August). It will travel over Southeast Asia and the Pacific Ocean, so people in that region may have a chance to spot it in the night sky.

ESA’s mission analysis has created a map of the Earth flyby, allowing you to see the planned path and key details of the spacecraft’s approach. Also, look for trajectory data here. However, you’ll need powerful binoculars or a telescope to view Juice’s impressive flyby.

However, an easier way to follow along will be to monitor the ESA’s blog or X account, where the agency plans to post photos taken by JUICE’s two monitoring cameras during the flyby on Monday night and early Tuesday morning.

The photos will also be shared publicly on social media and the Rocket Science blog as soon as they arrive on Earth.

Background: JUICE Mission

ESA’s Juice launched on an Ariane 5 rocket from Europe’s Spaceport in French Guiana at 14:14 CEST on 14 April. Ariane 5 launched this bold mission to explore the hidden secrets of the icy moons orbiting Jupiter.

This ambitious mission aims to study the moons using advanced remote sensing, geophysical, and in situ instruments to learn more about these intriguing places as possible habitats for past or present life. JUICE is set to monitor Jupiter’s complex magnetic, radiation, and plasma environment and how it interacts with the moons. Additionally, it will examine the Jupiter system as a model for gas giant systems throughout the Universe.