Today on Galileo - February 19, 1997
Jupiter continues to be the one of the main focuses of the science activities. More importantly we see scheduled the first observations of the selected feature of Jupiter's atmosphere. Recall that these selected features are important enough for all four remote sensing instruments to coordinate their observations of them. The feature selected for this orbit is know as a White Oval. These ovals are easily seen from Earth and, like the Great Red Spot, some are very long lived - so long that some of them have been given names: BC, FA, DE (not very interesting names, but nevertheless names). These ovals are typically found to roll around in the boundary regions between two opposing zonal jet streams. One of the more interesting questions about these ovals is: How can they last for so long? What provides them with the energy they need to keep going? The coordinated observations of these features should provide some of the answers to these questions. The data gathered by the remote sensing instruments will provide information on cloud particles distributions, thermal characteristics as well as images and maps at different visible and near infra red wavelengths, thus providing a full characterization of these features. In support of these observations, two Jupiter North-South strip observations are also performed today. Recall that these observations are designed to provide data on the global characteristics of Jupiter's atmosphere in the same time period that the selected feature observations are taken.
Other Jupiter observations performed today are a single Hot Spot observation performed by NIMS (Near Infrared Mapping Spectrometer). This is the only Hot Spot observation of this orbit. Hot Spots were the featured track during Galileo's previous encounter period. The last of the Jupiter aurora observations is performed today, and, to compliment the dark side observation taken yesterday, a "fixed local time" map is also performed today. This observation is said to have a "fixed local time" when the angle between the instrument view direction and the Sun is constant - like if you were floating in space and were able to look at the Earth such that it was always 5 p.m. in the places you were looking at.
The second main focus for today's observing activity is Io. The last remote Io torus observations are performed today, but new observations of Io while eclipsed by Jupiter and observations designed to monitor Io's volcanic activity take their place. Finally a single observation of the minor moon Thebe is performed by SSI (Galileo's imaging camera).
Tune in tomorrow for the big day of flybys: Io, Europa and Jupiter.