Juno: Close Encounters With Ganymede (Astronomy)

Also on board are two important Italian instruments created thanks to the contribution of the Italian Space Agency, INAF and Sapienza University of Rome. Alessandro Mura (Inaf): “Jiram’s data will finally be able to reveal how the surface of Ganymede interacts with the external environment, and will be invaluable for planning future observations such as those of the Juice mission currently scheduled for launch next year”

It will be a very close flyby what the NASA probe Juno , in orbit around Jupiter since 2016, will do today with Ganymede , one of its many moons. On board the probe there are numerous scientific instruments, including two with Italian participation with the support of the Italian Space Agency ( ASI ): the Jiram instrument , made in Italy by Leonardo and led by the National Institute of Astrophysics (Inaf); and the radioscience instrument KaT ( Ka-band Translator ), created by Thales Alenia Space and led by the La Sapienza University of Rome.

Juno was launched in August 2011 and is currently studying Jupiter’s magnetic field and atmosphere in an orbit that passes over its poles. The probe has collected an important amount of information to date, so much so that NASA, at the beginning of this year, extended the mission until 2025 .

Jiram ( Jovian Infrared Auroral Mapper , dedicated to Angioletta Coradini, an INAF astronomer who died in 2011 and former Principal Investigator of Jiram) is a near infrared camera (2-5 microns) capable of collecting both images and spectrograms, while the KaT allows the measurement of Jupiter’s gravity through the Doppler effect of a microwave signal.

This extension will make Juno “an explorer” of the entire Jovian system – the planet, its rings and moons – with multiple close passages, called flybys , planned for the three of Jupiter’s most intriguing Galilean moons: Ganymede, Europa and Io . Satellite encounters begin today with a low-altitude flyby – about 1,000 kilometers from the surface – of Ganymede during Juno’s 34th orbit around the giant planet. Among other things, these steps will serve to reduce the orbital period of the probe from about 53 days to 43 days.

Of all the objects in the Solar System, Ganymede is certainly one of the most interesting. It is the largest object without an atmosphere, the largest of all known satellites of the planets, the one with the lowest moment of inertia, and the only one known to possess an intrinsic magnetic field, which in turn is immersed in the most large magnetic field of Jupiter.

“Italy and the Italian Space Agency are once again at the forefront in the exploration of our solar system”, adds Giuseppe Sindoni , ASI project manager for Jiram: “Such accurate measurements and such high spatial resolution will help us to reveal the mysteries of Jupiter and its satellites ».

Alessandro Mura , head of Jiram for Inaf, notes that “Jiram data will finally be able to reveal how the surface of Ganymede interacts with the external environment, and will be invaluable for planning future observations such as those of the Juice mission currently scheduled for launch in the next year”. Finally, in two months, Juno will again observe Ganymede from a greater distance, and Jiram, thanks to its ability to acquire high resolution images, will have an additional observation window to complete those started today.

Juno will study these characteristics using his tools. The plasma instruments will investigate how charged particles of the Jovian environment circulate and precipitate around the moon, creating a kind of peculiar auroras. The magnetometer will make us understand how the magnetic fields of Ganymede and Jupiter “communicate” with each other. The radiometer will investigate the properties beneath the surface of Ganymede. Finally, the cameras, including the Italian infrared imaging spectrometer Jiram, will provide us with very high resolution images and spectra (up to a few hundred meters) of the moon’s surface.

Featured image: An image of Ganymede taken in 2019 by the Jiram instrument aboard Juno showing the north pole area and part of the illuminated face of the Jovian moon. The grid indicating the position of the parallels and meridians of the celestial body has been artificially superimposed on it. The thickest line indicates the zero meridian, the others are plotted every 30 ° of longitude. The parallels, on the other hand, have a spacing of 10 °. Credits: Nasa / Jpl / Jiram team


Provided by INAF

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