Today on Galileo - May 5, 1997
The day's activities start with the completion of the UVS (Ultraviolet Spectrometer) observations of the Ganymede neutral torus. Later, a couple observations of Callisto are performed. The first, again by the UVS instrument, observes Callisto at solar phase angles not visible from Earth. The second, by the NIMS (Near Infrared Mapping Spectrometer) instrument, is a global observation that will be used to further investigate Callisto's mineralogy and determine the distribution of the different materials on Callisto's surface. Most of the day, however, is spent with the UVS performing remote Io torus observations. Remember that these observations are used to determine the temperature of electrons and characterize the distribution of energy in the Io torus.
Early in the day, the spacecraft turns in order to improve the viewing geometry for remote sensing observations of Io. Without the turn, these observations would be carried out with the instruments looking back through the spacecraft booms (magnetometer and RTGs). Since the booms are mounted on the spinning side of the spacecraft, a boom would pass through the instrument view fields about once every 7 seconds. The turn moves the booms out of the way and eliminates the risk of observations being lost due to boom blockage. The spacecraft stays in this special orientation through Wednesday afternoon.
At the end of the day, the flight team will transmit the second set of commands for the encounter period to the spacecraft. This set will begin to execute late Tuesday.