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
Galileo Probe data for further insights into the atmosphere, and one way to do this was to study the motion of the probe during the descent down. It was found that at 700 mbar of pressure the winds on Jupiter are prograde and increase to a speed of 170 m/s at 4000 mbars of pressure. Galileo Probe has cospar ID 1989-084E while the orbiter had id 1989-084B. Names for the spacecraft include "Galileo Probe" or "Jupiter Entry Probe" abbreviated JEP. The related COSPAR IDs of the Galileo mission: Galileo Probe The "Galileo" Probe was an atmospheric-entry probe carried by the main "Galileo"