Juno is a NASA New Frontiers mission currently orbiting the planet Jupiter. Juno was launched from Cape Canaveral Air Force Station on August 5, 2011 and arrived on July 4, 2016. The spacecraft is in a polar orbit to study Jupiter's composition, gravity field, magnetic field, and polar magnetosphere. Juno will also search for clues about how the planet formed, including whether it has a rocky core, the amount of water present within the deep atmosphere, mass distribution, and its deep winds, which can reach speeds of 618 kilometers per hour (384 mph). Juno will be the second spacecraft to orbit Jupiter, following the Galileo probe which orbited from 1995–2003.
The Juno spacecraft is powered by solar arrays, commonly used by satellites orbiting Earth and working in the inner Solar System, whereas radioisotope thermoelectric generators are commonly used for missions to the outer Solar System and beyond. For Juno, however, three solar array wings, the largest ever deployed on a planetary probe, will play an integral role in stabilizing the spacecraft and generating power. The spacecraft's name comes from Greco-Roman mythology. The god Jupiter drew a veil of clouds around himself to hide his mischief, but his wife, the goddess Juno, was able to peer through the clouds and see Jupiter's true nature.[9] The mission had previously been referred to by the backronym JUpiter Near-polar Orbiter in a list of NASA acronyms.
Juno completed a five-year cruise to Jupiter, arriving on July 4, 2016. The spacecraft will travel over a total distance of roughly 2.8 billion kilometers (18.7 AU; 1.74 billion miles). The spacecraft will orbit Jupiter 37 times over the course of 20 months.[12] Juno's trajectory used a gravity assist speed boost from Earth, accomplished through an Earth flyby two years (October 2013) after its August 5, 2011 launch.[13] In July 2016, the spacecraft will perform an orbit insertion burn to slow the spacecraft enough to allow capture. It will do two 53-day orbits before performing another burn on October 19 that will bring it into a 14-day polar orbit.
Once in the 14-day orbit, infrared and microwave instruments will begin to measure the thermal radiation emanating from deep within Jupiter's atmosphere. These observations will complement previous studies of its composition by assessing the abundance and distribution of water, and therefore oxygen. This data will provide insight into Jupiter's origins. Juno will also investigate the convection that drives general circulation patterns in Jupiter's atmosphere. Other instruments aboard Juno will gather data about its gravitational field and polar magnetosphere. The Juno mission is set to conclude in February 2018, after completing 37 orbits of Jupiter, when the probe will be de-orbited to burn up in Jupiter's outer atmosphere, so as to avoid any possibility of impact and biological contamination of one of its moons.
