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  NASA's Juno reaches Jupiter July 4thJun 06, 2016 8:27 PM PDT | url
Added 1 new A* page:In less than a month, on the 4th of July, NASA's Juno ("JUpiter Near-polar Orbiter") probe will reach Jupiter; the plan is for it to orbit the gas giant in an elliptical polar orbit 37 times—through 2018—studying Jupiter's water content, core mass, gravitational and magnetic fields, atmosphere, aurorae, and the distortion of spacetime caused by its rotation (a relativistic effect also known as frame-dragging).
Taking a long curve in over the poles will allow Juno to avoid long-term exposure to Jupiter's intense radiation belts; the previous Jupiter probe, Galileo, orbited through the radiation belts, and suffered numerous faults as a consequence of the bombardment of radioactive particles during its eight years of orbit, including loss of photographic images (and complete loss of its camera for the final year of the mission), loss of data playback, radio frequency shifts, gyroscopic anomalies, and current leakages that could cause the spacecraft to reboot into safe mode. By avoiding the worst of the radiation belts, Juno will hopefully be free of such problems; it also has a 1-cm-thick titanium wall to act as a radiation shield.
All previous spacecraft to operate in the outer solar system have been powered by the decay of a radioactive material, but because of "the global shortage" of the isotope generally used, plutonium 238, "as well as advances made in solar cell technology over the past several decades," Juno is the first probe of the outer solar system ("the farthest solar-powered trip in the history of space exploration") to obtain its power entirely from solar panels—three rather large solar panels, because only about 4% of the sunlight that would reach it around Earth will reach it at Jupiter; its polar orbit will also allow it to maximize its time exposed to sunlight.
Juno launched in August, 2011, and its nearly five-year trip to Jupiter included, funnily enough, a fly-by of where it came from—Earth—about midway through, in October 2013, in order to get a boost in velocity from the pull of Earth's gravity as the planet circled the Sun: Juno's initial launch from Earth flung it into an orbit wider than Earth's around the Sun, but after a year and a month, a little thrust from its engine arced it back to meet us again a little over two of our own loops around the Sun later, and it swung by at just the right distance to get enough of a tug from our gravity to fling it even further out against the pull of the Sun's gravity than before, this time far enough to meet Jupiter coming around the Sun on its own very long orbit; this is all visible in an elegant NASA animation on YouTube.
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