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Anti-aristarchus writes:

Story at SciTechDaily:

On Monday, June 7, at 1:35 p.m. EDT (10:35 a.m. PDT), NASA's Juno spacecraft will come within 645 miles (1,038 kilometers) of the surface of Jupiter's largest moon, Ganymede. The flyby will be the closest a spacecraft has come to the solar system's largest natural satellite since NASA's Galileo spacecraft made its penultimate close approach back on May 20, 2000. Along with striking imagery, the solar-powered spacecraft's flyby will yield insights into the moon's composition, ionosphere, magnetosphere, and ice shell. Juno's measurements of the radiation environment near the moon will also benefit future missions to the Jovian system.

Ganymede is bigger than the planet Mercury and is the only moon in the solar system with its own magnetosphere – a bubble-shaped region of charged particles surrounding the celestial body.

"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."

[...] Signals from Juno's X-band and Ka-band radio wavelengths will be used to perform a radio occultation experiment to probe the moon's tenuous ionosphere (the outer layer of an atmosphere where gases are excited by solar radiation to form ions, which have an electrical charge).

"As Juno passes behind Ganymede, radio signals will pass through Ganymede's ionosphere, causing small changes in the frequency that should be picked up by two antennas at the Deep Space Network's Canberra complex in Australia," said Dustin Buccino, a signal analysis engineer for the Juno mission at JPL. "If we can measure this change, we might be able to understand the connection between Ganymede's ionosphere, its intrinsic magnetic field, and Jupiter's magnetosphere."

[...] Due to the speed of the flyby, the icy moon will – from JunoCam's viewpoint – go from being a point of light to a viewable disk then back to a point of light in about 25 minutes. So that's just enough time for five images.

"Things usually happen pretty quick in the world of flybys, 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 kilometers 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 kilometers per second). It is going to be a wild ride."

Juno's wild ride. She always was a goddess not to be messed with!

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