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
STS-61-F STS-61-F STS-61-F was a United States Space Shuttle mission planned to launch on 15 May 1986 using "Challenger". It was cancelled after "Challenger" was destroyed earlier that year. The main objective of STS-61-F was to deploy the "Ulysses" solar probe, which would travel to Jupiter and use it as a gravitational slingshot in order to be placed into polar orbit around the Sun. This mission would have marked the first use of the Centaur-G liquid-fueled payload booster, which would also be used on the subsequent mission to send the Galileo probe in orbit around Jupiter. Due to the use of