Today on Galileo - December 14-15, 1996
On Saturday at 4 p.m. PST, the spacecraft will begin executing the set of commands that will control its encounter activities through the end of Tuesday. With the start of the encounter, the fields and particles instruments resume their survey of the magnetospheric environment. With each pass through the Jovian system, the fields and particles instruments sample a different portion of this environment.
From Saturday night into Sunday morning, the UVS instrument completes its final remote observation of the Io torus for this orbit. The majority of these observations were completed in final days of the of the inbound cruise activities. Later in the day, UVS performs an observation of the bright side of Jupiter's atmosphere at a "fixed local time" for one Jupiter rotation. (This observation is said to have a "fixed local time" because the instrument pointing is kept relatively constant as Jupiter rotates through the instrument view. By doing this, the angle between the instrument view direction and the Sun is constant. Try to imagine being floating in space and being able to look at the Earth such that it is always 5 p.m. in the places you are looking at. This would be caused by the Sun being more or less in the same place in the sky for all of these places. If you could do this, you would be performing a "fixed local time" observation.) This observation is designed to provide a global map of Jupiter's energy at ultraviolet wavelengths as it rotates through this constant local time.
Finally on Sunday night, the spacecraft will perform the final orbit trim maneuver prior to its close flyby of Europa. This maneuver allows the navigators to fine tune the spacecraft's path so that it flys as close as possible along the path that was used to design the science observations.