This Week on Galileo - November 24 - December 7, 1997
For the next two weeks, Galileo continues to read, process and transmit science information that is stored on the spacecraft's reel-to-reel tape recorder. This data was collected during seven consecutive days in early November as the spacecraft flew through the Jupiter system and close to Jupiter's moon Europa.
This Wednesday, Nov. 26, the spacecraft passes through apojove, or the farthest distance from Jupiter, for this orbit. Upon passing through apojove, the spacecraft starts heading back toward the gas giant and another encounter. This next encounter is scheduled to occur in mid-December and is the first of the Galileo Europa Mission, the follow-on mission to Galileo's primary mission. Galileo's primary mission officially comes to an end on December 7, 1997.
Processing and transmission of science data is interrupted this Wednesday, Nov. 26 as spacecraft navigators make minor corrections to the spacecraft's orbital path. These corrections are planned three times in an orbit but are not always required. One of these opportunities is typically close to the orbit's apojove. The processing of science data is also interrupted a week later, Dec. 3 to perform regular maintenance on the spacecraft's propulsion system.
The science information that is planned for processing and transmission to Earth within the next couple of weeks is a very good example of the tremendous variety of information that Galileo has been able to acquire.
The Solid-State Imaging (SSI) team returns several observations taken with the camera that will help refine what is known of the shape of Jupiter's minor moons. Three of these observations contain Thebe, three others contain Metis, one contains Adrastea and one more contains Amalthea. The SSI team also returns two images of Jupiter's rings.
Observations of Jupiter are returned by the Near Infrared Mapping Spectrometer (NIMS) team, the Ultraviolet Spectrometer (UVS) team, the Photopolarimeter Radiometer (PPR) team, and again by the SSI team. The NIMS observations focus on the characterization of a features of Jupiter's atmosphere known as brown barges and the construction of thermal maps. The UVS observations will be used to study auroral phenomena and the distribution of hydrogen (which can be tied to energy) in Jupiter's atmosphere. The PPR team returns a series of observations designed to construct a global map of a horizontal strip of Jupiter's atmosphere. The map is constructed from four different observations. Finally, the SSI team returns observations designed to look for traces of lightning in Jupiter's atmosphere and a series of observations that should enable the construction of a time-lapse history of aurora near Jupiter's north pole.
SSI, NIMS and PPR also return science information from observations of the volcanic moon Io. The NIMS observations are part of a series repeated almost every orbit. This series is designed to keep track of any changes in the characteristics of Io's surface. The PPR team returns an observation that catches Io's full disk. The SSI team catches Io while it's eclipsed from the Sun by Jupiter, thus making it easier to detect and observe thermal hot spots and volcanic plumes. SSI also returns images of six different volcanic regions while they were on Io's bright limb. These regions were imaged while on the limb in hopes of detecting a plume which would be clearly seen against the black sky of deep space. The regions returned this week include Cullann, Volund, Marduk, Pillan, Kanehikili and Loki.
During the second of these two weeks, the spacecraft will re-transmit some science information that had been previously sent to Earth. Since there may have been transmission problems the first time around, this second opportunity allows the science teams to fill in the gaps. During this second opportunity, the information must be re-processed and re-packaged for transmission. This allows the transmission schedule to be modified to re-play portions of observations that have been identified as particularly interesting or to simply add additional data from a particular observation. On the transmission schedule are observations of Callisto, more maps of Jupiter's atmosphere and observations of Jupiter's brown barges and aurora. Finally, the schedule contains several observations taken during the spacecraft's close flyby of the moon Europa including high-time resolution magnetosphere information gathered by the fields and particles instruments.