Today on Galileo
Tuesday, May 4, 1999
Once again, most of Galileo's attention is directed toward Jupiter as the spacecraft's Solid State Imaging camera and Utraviolet Spectrometer spend most of the day observing the giant planet. The activity is only briefly interrupted toward the end of the day to allow the Extreme Ultraviolet Spectrometer to perform a remote observation of the Io torus. On the flyby front, the spacecraft flies past Ganymede today at 3:18 am PDT [see note 1] at a distance of 636,000 kilometers (396,000 miles).
Throughout the day, the spacecraft's camera takes images of a variety of cloud features in Jupiter's atmosphere. These observations are designed to determine the dynamics of cloud motion in three dimensions, with high spatial and time resolution. Each feature is observed three to six times as it moves across Jupiter's sunlit hemisphere. Some of the features are also imaged after they have rotated into the night side of Jupiter, to look for lightning flashes which the scientists hope to correlate with clouds seen in the daylight images taken earlier in the same areas. The features covered by this observation campaign are equatorial waves, high speed jets, clouds in the north and south equatorial belts, and white ovals. In addition, the camera also makes an observation of Jupiter's aurora to measure its vertical structure at high resolution. The Ultraviolet Spectrometer takes advantage of these observation opportunities to also make measurements of these features.
In addition to the observations taken along with the spacecraft camera, the Ultraviolet Spectrometer also performs its own measurements of Jupiter. In one type of observation, the spectrometer measures hydrogen in Jupiter's dark atmosphere. Without sunlight, changes in hydrogen loss are caused by interaction with particles in Jupiter's magnetosphere and mixing of the upper atmosphere with lower cloud levels. In a second type of observation, taken on Jupiter's lit side, the spectrometer measures hydrocarbons in Jupiter's upper atmosphere. Finally, the spectrometer takes a look at aurora in Jupiter's atmosphere. These observations will allow scientists to further study the dynamics of Jupiter's upper atmosphere, and its interaction with Jupiter's magnetosphere.
Note 1. All times listed correspond to the Pacific Time zone (currently daylight time) and spacecraft event time. Radio signals indicating that an event has occurred on the spacecraft reach the Earth 33 to 50 minutes later, depending on the time of year. Currently, Pacific Daylight Time (PDT) is 7 hours behind Greenwich Meridian Time (GMT), and it takes radio signals 49 minutes to travel between the spacecraft and Earth.
For more information on the Galileo spacecraft and its mission to Jupiter, please visit the Galileo home page.
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