The mission JUICE (Jupiter ICy moons Explorer) of the European Space Agency (ESA), launched in April 2023 and headed towards Jupiter’s icy moons, has successfully performed the first maneuver double gravity slingshot and the first overflight (fly by) combined of the Earth and the Moon in history. This orbital maneuver, called ALLOY (Lunar Earth Gravity Assist), was an extremely complex but crucial moment for the mission in order to reach the Jovian system in 2030 and explore its three icy moons Ganymede, Europa and Callisto. The maneuvers all took place between Monday 19th and Tuesday 20th August 2024 and consisted of a first fly-by (low flight) of the Moon followed by a second flyby of the Earth. Fly-bys exploit the gravitational pull provided by the two celestial bodies to further accelerate the probe, using a minimal fraction of the on-board fuel. The JIUCE probe will perform a fly-by of Venus in 2025.
The first overflight of the Moon has increased the speed of JUICE by 0.9 km/s relative to the Sun, guiding JUICE toward Earth. The second flyover of the Earth has instead reduced the speed of JUICE by 4.8 km/s relative to the Sun, putting the probe on a new trajectory that will allow a new fly-by, this time of Venus, in 2025. Overall, the double gravity slingshot diverted JUICE by a 100° angle compared to its pre-approach trajectory. This extremely complex and risky orbital maneuver is succeeded impeccably and allowed the probe to save as much as 100-150 kg of fuela huge amount for a space probe.
The first fly-by of the Moon
The first fly-by of the JUICE probe was the one with our natural satellite, the Moonwhich took place on the Italian evening of August 19thThe orbital maneuver took place practically in the dark, since the probe entered the lunar shadow at 10:38 pm Italian time, losing all radio contact with Earth and remaining there until 11:09 pm. At 11:07 pm the probe turned on its on-board cameras to immortalize the moment of maximum approach on the lunar soil, which occurred at 11.15pmwhen the probe was approximately 750 km from the selenic surface.
The mission has released two from the photo taken by the probe on the social network X. The first photo (above) was taken by the second monitoring camera (JMC2) of the probe to 11.15pm Italian, that is, at the time of maximum approachThe photo, 1024×1024 pixels, shows both the lunar surface and the antenna RHYMES (Radar for Icy Moons Exploration) from 16 meters. There second photo (below) was instead taken 10 minutes later the fly-by, at 11.25pm Italian time, from the first monitoring camera (JMC1). The image shows the Moon in a more grandiose way, in particular the color variations of the lunar surface, which is only possible if we have a large-scale overview of the lunar surface.
The flyby provided the gravitational pull needed for the probe to accelerate and place itself into an orbit that then allowed it to perform the second fly-by, this time of the Earth’s surface.
The second fly-by of the Earth
The probe’s second flyby took place on the Italian evening of August 20, when the probe, coming from the Moon, took advantage of the gravitational push provided by our planet to enter its final orbit that will take it to the Jupiter system in 2030. During the flyby the probe also tested its instruments, collecting data with 8 of the 10 on board.
The probe’s closest approach to Earth occurred at 23:56 Italian time, when the probe passed just 6840 km from the Earth’s surface, over south-eastern Asia and the Pacific Ocean. The image above was taken by the probe with the first monitoring camera (JMC1) at 23:48, about 10 minutes before the closest approach. The image shows our beautiful planet, in particular the immense Pacific Ocean and the terminator (line that separates the illuminated hemisphere from the dark one), and the probe’s antennas.
This successful flyby of Earth redirected JUICE’s path through space to place the spacecraft into an orbit that will carry it forward to another flyby, this time of Venus, scheduled for August 2025.
The objective of the JUICE mission
The probe JUICE (Jupiter ICy moons Explorer) of the European Space Agency (ESA) was launched at April 2023 with the aim of explore the Jupiter system and in particular his three frozen moons Ganymede, Europa and Callisto. These moons are very interesting from the point of view astrobiologicalsince there are clear indications that they hide vast underground oceans of salt water beneath the icy crust, thus categorizing them as some of the most promising places in the Solar System to look for extraterrestrial life.
JUICE will arrive in the Jovian system in 2030 and for 4 years it will perform well 35 close flybys of the moons, until they settled into orbit around Ganymede in 2034. During the mission, JUICE will study the Jupiter’s magnetosphere and its three natural satellites using well 10 different scientific instruments. In fact, it will be the most advanced and cutting-edge scientific laboratory ever sent to the outer solar system.
