Today on Galileo
June 30, 1999
A few minutes prior to the flyby, the Solid-State Imaging camera makes two observations containing high resolution images of dark material found near a ringed feature. The observations are designed to allow scientists to study variations in the appearance of Callisto's surface in hopes of understanding the processes that modify the surface and the apparent deficit in the number of small craters.
Within minutes of the flyby, the Photopolarimeter Radiometer takes a high resolution look at a region near Callisto's equator. The observation is designed to measure the surface brightness temperatures which will provide information about the density and composition of surface materials.
The Near-Infrared Mapping Spectrometer performs the next three observations, two of which are performed in collaboration with the Utraviolet Spectrometer. As with yesterday's single observation, these are designed to obtain high resolution spectral and spatial measurements of different regions of Callisto's surface. The spectral data will allow scientists to identify different materials on the surface, while the spatial data will help them determine where these materials lie. During one of these recordings, the Dust Detector instrument will ride along with the Spectrometer's recording, collecting data on dust particles that are concentrated near Callisto and the other Galilean satellites. These particles may be generated as small fragments of ejecta when meteorites strike Callisto's surface, remaining in orbit about Callisto for some time.
The day's observing is wrapped up by three observations performed by the Ultraviolet Spectrometer. In two of them the spectrometer obtains measurements of Callisto's tenuous atmosphere. The observations are designed to allow scientists to study the potential long term variability of the atmosphere. In the third observation, the Ultraviolet Spectrometer obtains measurements of Callisto's surface with the objective of providing more information on what materials are found on the surface.
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 44 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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