Juno, the next spacecraft in Nasa‘s New Frontiers programme, is now poised for launch atop an Atlas 5 rocket at Cape Canaveral. Its destination is Jupiter and liftoff should occur during the three weeks that begin on Friday, the 5th, with arrival at the giant planet scheduled for the same date in 2016. The five year journey includes a return fly-by visit to the Earth to receive a “gravity assist” boost in October 2013.
The craft is due to enter an elongated orbit about Jupiter, taking 11 days to loop within 4,300 km of Jupiter’s equatorial cloud-tops at its low-point, or perijove, and a high-point, or apojove, some 2.7 million km further out, beyond the orbit of Callisto which is the farthest of Jupiter’s four main moons.
The orbit sweeps over the poles to provide our first clear views of those regions and their spectacular displays of aurorae. It also means that Juno avoids the worst of the Jovian radiation belts, though the craft’s sensitive electronics must still be shielded within a protective titanium vault. Powered by the first solar arrays to be deployed so far from the Sun, Juno’s prime aim it to study Jupiter’s origin and composition.
It should tell us how much water and ammonia exist in the atmosphere, how the latter varies and moves far below the visible clouds, and whether Jupiter has a rocky heart, perhaps even larger than the Earth. And how does its intense magnetic field shape its environment, including the aurorae and those lethal radiation belts?