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
Space probe (first weather balloons deployed on another planet) at Venus before their rendezvous with Halley's Comet. This Japanese probe was the first non-US, non-Soviet interplanetary probe. A second Japanese probe, it made ultraviolet wavelength observations of the comet. The first space probe to penetrate a comet's coma and take close-up images of its nucleus. First solar wind sample return probe from sun-earth L1. First sample return probe from a comet tail. First probe to land on an asteroid. First sample return probe to launch from an asteroid. The Rosetta space probe flew by two asteroids and made a rendezvous and orbited