Today On Galileo - March 30, 1998
Encounter activities conclude this evening, just after 6:00 pm, Pacific Time. Shortly thereafter, the spacecraft begins processing and transmission to Earth pictures and science information acquired and stored on Galileo's onboard tape recorder during the last few days. The first items on the processing and transmission schedule are the pictures of Io's north and south poles taken on Saturday. Early in the morning, flight team members transmit to the spacecraft the set of computer commands that will control most of its activity until the next encounter period in late May. Today's flight path takes the spacecraft past the closest approach point to the last Galilean satellite for this orbit, Callisto, at 8:20 pm and a distance of 205,000 kilometers (128,000 miles).
The final observation of Europa for this encounter is performed this morning by the Near Infrared Mapping Spectrometer (NIMS). This global observation is the last in a set of three distant observations performed by NIMS this orbit. Io returns to the observing schedule today with a joint observation performed by the Ultraviolet Spectrometer and Extreme Ultraviolet Spectrometer as they gather information on Io's plasma torus. The plasma torus is the donut shaped cloud of neutral and ionized gases that is found along Io's orbit. It is believed to be sustained by all of the material that is ejected from Io by way of volcanic eruptions. This observation will allow scientists to keep tabs on and continue to map the activity levels within the torus.
Two observations of Jupiter are performed during today's science gathering. Both are performed in 'real-time', indicating that the data is almost immediately packaged and transmitted to Earth and not stored on the spacecraft's tape recorder for later processing. Both are performed by the NIMS instrument. The first looks at aurora near Jupiter's north pole while the second gathers more information on the makeup and temperatures of Jupiter's atmosphere.
A look at Callisto rounds out the remote sensing observation schedule for this encounter period. Performed jointly by the NIMS instrument and the Ultraviolet Spectrometer (UVS), the global observation will provide more information on the surface properties of this moon. A similar observation will be performed on the Callisto orbit in May 1999. The end of the encounter period also concludes the fields and particles instruments' survey of Jupiter's magnetic and electric field environment. This survey is planned to be repeated each and every encounter and will provide an orbit-to-orbit record of the activity levels within this environment.
Come back tomorrow for the return of This Week on Galileo as the Galileo spacecraft continues its exciting journey of discovery!