Magnetosphere of Jupiter By 1973 the magnetic moment was known within a factor of two, whereas the tilt was correctly estimated at about 10°. The modulation of Jupiter's DAM by Io (the so-called Io-DAM) was discovered in 1964, and allowed Jupiter's rotation period to be precisely determined. The definitive discovery of the Jovian magnetic field occurred in December 1973, when the Pioneer 10 spacecraft flew near the planet. As of 2009 a total of eight spacecraft have flown around Jupiter and all have contributed to the present knowledge of the Jovian magnetosphere. The first space probe to reach Jupiter was Pioneer 10 in
Exploration of Jupiter is also searching for clues about how Jupiter formed, including whether the planet has a rocky core, the amount of water present within the deep atmosphere, and how the mass is distributed within the planet. "Juno" also studies Jupiter's deep winds, which can reach speeds of 600 km/h. ESA's Jupiter Icy Moon Explorer (JUICE) has been selected as part of ESA's Cosmic Vision science program. It is expected to launch in 2022 and, after a series of flybys in the inner Solar System, arrive in 2030. In 2012, the European Space Agency's selected the "JUpiter ICy moon Explorer" (JUICE) as