Today on Galileo - June 22, 1997
The eighth science encounter of Galileo's orbital tour starts today. For the next eight days, activity on the spacecraft will again focus on acquiring data from the Jupiter system. The primary satellite target for this encounter is Callisto and closest approach occurs on Wednesday morning. This will be only the second close flyby of Callisto. The first flyby took place during the third orbit of the orbital tour. The encounter period also includes a non-targeted flyby of Ganymede on Thursday. The spacecraft instructions that begin to execute today will run through Thursday afternoon.
As is typical with the first day of the encounter period, the observation schedule is very light. The fields and particles instruments continue to collect data from their survey of the Jupiter magnetosphere. This will continue through the encounter into the cruise period. Deep in the middle of the second fields and particles "mini-tour", instruments have been continuously sampling the magnetosphere since the previous encounter, Ganymede - Orbit 8. The only other observation performed today is by the UVS (Ultraviolet Spectrometer) instrument which looks at the so-called Callisto neutral torus. Scientists believe that a moon forms a neutral (i.e. non-electrically charged) torus when neutral (no electrical charge) particles are stripped off the satellite and then remain in the same orbit as the satellite, forming a doughnut-shaped distribution.