This Week on Galileo - November 17-23, 1997
This week Galileo continues to transmit science pictures, maps and other information from its encounter with the Jupiter system and the moon Europa earlier this month. This is the second of five weeks available for returning this data to Earth before it is recorded over with new science data during Galileo's next encounter. The process of reading science data from the tape recorder and packaging the data for transmission to Earth is known as playback and is interrupted only once this week. The interruption occurs on Friday when the spacecraft performs a turn. The turn is required to keep the radio antenna pointing toward the Earth. These turns are performed regularly to keep up with the Earth as it drifts in the sky relative to the spacecraft.
This week's processing and transmission schedule will return data from observations taken primarily during the spacecraft's close flyby of the moon Europa. The single exception is an additional observation of the moon Io.
The week starts with the return of data from an observation performed by the Solid State Imaging (SSI) camera. Playback of this observation was initiated late last week and spills over into this week. The observation contains information about a region of Europa near the terminator (or line separating the dayside from the nightside). The region contains terrain with colored spots or blotches (mottled) and the Mannann'an crater. Also in the observed region are wedge-shaped bands and a prominent example of a feature known as a "triple band". These band features are believed to be indicators of where Europa's surface has cracked and split apart. The Near Infrared Mapping Spectrometer (NIMS) returns a similar observation of Europa's surface. The NIMS observation contains a region of straight and curved triple bands. Later in the week the SSI team returns another high-resolution observation of Europa's surface. This observation was designed to catch an unexplored region containing a curious dark spot. The observation was performed under lighting conditions that should make it possible for scientists to get a good idea of the morphology or shape of this region.
A large portion of the week is spent returning data from a 2 hour and 40 minute fields and particles instruments observation. This observation contains high time-resolution data recorded from these instruments as the spacecraft flew past Europa and then through Jupiter's magnetic equator. The fields and particles instruments are designed to provide data on the structure and dynamics of the magnetic and electric fields around Jupiter and any particles that may be present. The complement of instruments includes the Dust Detector, Energetic Particles Detector, Heavy Ion Counter, Magnetometer, Plasma Subsystem and Plasma Wave Subsystem.
SSI returns an observation this week that's unlike the others. It is an Io observation designed to obtain data on how intensely light is reflected from the fiery moon's surface. This "photometric" information is useful in identifying what types of different materials can be found on Io's surface.