Ganymede is bigger than the planet mercury, and is the only moon in the solar system that boasts its own magnetosphere.
According to NASA, Juno’s fly-past of Ganymede will be the closest a spacecraft has ever come to the solar system’s largest natural satellite since the agency’s Galileo spacecraft made its approach in 2000
The trip is expected to yield new insights into the composition of Ganymede, as well as its ionosphere, magnetosphere, and icy shell, and produce striking new images of the moon.
Juno’s instruments will begin collecting scientific data about three hours before the spacecraft’s closest approach, NASA said.
“Juno carries a suite of sensitive instruments capable of seeing Ganymede in ways never before possible,” said Juno principal investigator Scott Bolton of the Southwest Research Institute in San Antonio.
“By flying so close, we will bring the exploration of Ganymede into the 21st century, both complementing future missions with our unique sensors and helping prepare for the next generation of missions to the Jovian system – NASA’s Europa Clipper and ESA’s [European Space Agency’s] JUpiter ICy moons Explorer [JUICE] mission.”
NASA said Juno will utilise its Ultraviolet Spectrograph (UVS) and Jovian Infrared Auroral Mapper (JIRAM) instruments, while its Microwave Radiometer’s (MWR) will peer into Ganymede’s water-ice crust, to gain a deeper understanding of the icy crust’s composition and its temperature.
“Ganymede’s ice shell has some light and dark regions, suggesting that some areas may be pure ice while other areas contain dirty ice,” said Bolton.
“MWR will provide the first in-depth investigation of how the composition and structure of the ice varies with depth, leading to a better understanding of how the ice shell forms and the ongoing processes that resurface the ice over time.”
The results will complement those from ESA’s forthcoming JUICE mission, NASA said, which will look at the ice using radar at different wavelengths when it becomes the first spacecraft to orbit a moon other than Earth’s moon in 2032.
Radio signals sent up by Juno will be picked up by two antennas based at the Deep Space Network’s Canberra-based facility.
Within the coming days, NASA is expected to release the images captured by Juno of Ganymede.
Due to the speed of the fly-by, Juno will be able to capture just five images, as the icy moon moves into and out of JunoCam’s viewpoint within the space of just 25 minutes.
“Things usually happen pretty quick in the world of fly-bys, and we have two back-to-back next week. So literally every second counts,” said Juno mission manager Matt Johnson of JPL.
“On Monday, we are going to race past Ganymede at almost 12 miles per second (19 kilometres per second). Less than 24 hours later we’re performing our 33rd science pass of Jupiter – screaming low over the cloud tops, at about 36 miles per second (58 kilometres per second).
“It is going to be a wild ride.”
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