In yet another remarkable achievement, the National Aeronautics and Space Administration’s Juno spacecraft has successfully entered the orbit around Jupiter without being knocked down by the planet’s intense magnetic field and radiation. That the spacecraft, which had travelled 2.8 billion km since its launch on August 5, 2011, passed through a spot that was originally planned for, when it came closest to the planet, provides a measure of the level of success of the mission. Juno, with a diameter of 11.5 ft, is not the first spacecraft to enter into orbit around Jupiter. But unlike its predecessor, the Galileo spacecraft that explored the planet between 1995 and 2003, Juno will study Jupiter much more thoroughly given the array of nine scientific instruments that it carries on board. The most important difference between the two missions is Juno’s ability to see below the dense cloud cover of Jupiter; only a probe of Galileo entered the planet’s atmosphere. Getting as close as 5,000 km from the cloudtops and being able to see through the clouds will make it possible for Juno’s camera, Junocam, to take close-up photos of the poles and other points of interest. The main objectives of the mission are to understand the origin and evolution of Jupiter, to find out if the planet, like Earth, has a solid rocky core, to uncover the source of its intense magnetic field, to measure water and ammonia in deep atmosphere, and to observe the auroras.
Though the nine instruments will be turned on by the end of the week, the first full set of observations will not take place before the end of August when the spacecraft comes close to Jupiter on its first orbit; science experiments will begin in full earnest in mid-October when it gets into a 14-day orbit. Juno will orbit the planet from pole-to-pole, minimising the amount of radiation exposure, but the orbit will ultimately shift due to Jupiter’s intense gravitational field, making the spacecraft pass through more intense regions of radiation. Though shielded by a titanium vault, the radiation from Jupiter will slowly but surely compromise the instruments by the time it finishes its mission in February 2018. But before this happens, scientists expect to collect enough information to further our understanding of how the giant planet was formed some 4.5 billion years ago, and of the origins of the solar system. The amount of water it contains and the nature of its core will provide clues about where the planet formed early in the system’s life span. After orbiting the planet 37 times and returning invaluable scientific information, Juno will incinerate in Jupiter’s atmosphere in early 2018 as the Galileo spacecraft did.