Today on Galileo - April 3, 1997
Two satellite flybys are on today's schedule of activities for Galileo. Early in the afternoon, at a range of about 531,000 kilometers, the spacecraft will reach its closest point to Io for this orbit and, late this evening, it will encounter Europa at a range of just over 25,000 kilometers. The second set of commands for this encounter starts executing today and will finish executing on Sunday, bringing to an end the observing period.
The variety of observations scheduled today includes an image of Thebe designed to contribute to the construction of a global map. Io is observed through out the day, starting with remote Io torus observations performed by the UVS (Ultraviolet Spectrometer). These are followed by a complement of surface observations (including topography, chemistry and thermal) performed by the NIMS (Near Infrared Mapping Spectrometer), SSI (Solid State Imaging camera)and PPR (Photopolarimeter Radiometer) with a focus on the volcanoes Pele, Loki and Kanehekili. Jupiter's small red spot observations continue through out the day and are complemented by a north-south strip observation that not only will give context to the feature observations, but are also part of a tour-wide goal of mapping Jupiter from pole to pole. Yesterday's energy / hydrogen distribution observations are complemented by a brightside map. Finally, the NIMS and PPR will attempt to observe a hot spot near the latitude of the atmospheric probe's entry into Jupiter's atmosphere.
The geometry for this orbit is such that observations of Europa can be taken at a small solar phase angle, improving the interpretability of spectral observations. In addition, the high altitude makes it easier to coordinate observations between different instruments. NIMS observations will add to the goal of constructing a global map at regional resolution and will focus in on known regions like Tyre Macula and Flexus Linea (rings and lines). SSI will also observe these regions, perform a full disk observation and observations of cratered regions near the terminator (day and night dividing line) that will provide information about the shape of Io's surface. PPR performs a series of thermal and radiometry observations designed to map the surface thermal properties of Europa over all possible longitudes.
Finally, don't miss tomorrow's big encounter day.