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
Jupiter hydrogen composes up to 90% of Jupiter's atmosphere. The recorded temperature was more than 300 °C (>570 °F) and the windspeed measured more than 644 km/h (>400 mph) before the probes vapourised. NASA's "Juno" mission arrived at Jupiter on July 4, 2016, and is expected to complete 37 orbits over the next 20 months. The mission plan called for "Juno" to study the planet in detail from a polar orbit. On August 27, 2016, the spacecraft completed its first fly-by of Jupiter and sent back the first-ever images of Jupiter’s north pole. The next planned mission to the Jovian system