This Week on Galileo

July 19-25, 1999

Galileo Playback Interrupted

Data playback is interrupted twice this week as Galileo travels through apojove, or the farthest point from Jupiter this orbit. After passing through apojove on Thursday, the spacecraft begins its journey back toward the Jupiter system, heading for another close flyby of Callisto in mid-August. The science information returned this week comes from observations made by the Near-Infrared Mapping Spectrometer, the Photopolarimeter Radiometer, the Solid-State Imaging camera, the Utraviolet Spectrometer, and the Fields and Particles instruments. The Fields and Particles instruments are comprised of the Dust Detector, Energetic Particle Detector, Heavy Ion Counter, Magnetometer, Plasma Detector, and Plasma Wave Instrument. Data processing and transmission to Earth is interrupted on Monday so the spacecraft can perform standard maintenance on its onboard tape recorder. Playback is paused again on Friday to perform a flight path correction.

Two observations are returned this week by the Near-Infrared Mapping Spectrometer. Both observations are designed to obtain high resolution spectral and spatial measurements of Io's surface. These measurements allow identification of the different materials on Io's surface and determination of where on the surface they lie. Several observations of this type were conducted during Galileo's most recent encounter earlier this month. When they're combined, they will form the highest resolution map of Io at infrared wavelengths made to date. Previous observations of this type have been very useful in discovering many new hotspots on Io.

The Photopolarimeter Radiometer returns one observation this week. The third in a series of three, the observation will provide information on the surface temperatures on Callisto. The data will be used to identify and characterize relatively large regions of the surface whose temperatures are slightly higher than the surrounding terrain. The measurements will also provide scientists with clues as to how well different regions of Callisto's surface retain heat.

The Solid-State Imaging camera returns three sets of images this week. The first set will yield stereo images of Io when combined with images expected to be taken later this year. Once combined, the resulting images will produce very high resolution stereo views of Io at resolutions of 1.4 kilometers (0.87) per picture element. The next image set is part of a campaign to monitor Io's plume activity in preparation for two close flybys of Io later this year. The observations will also allow scientists to compare Io's volcanic activity with measurements of the Io torus and near-Io environment made by the Fields and Particles instruments. The camera's final image set will provide data on a cloud of sodium that has been found in the vicinity of Io's orbit. The cloud has a neutral electrical charge, and the data will allow scientists to identify the source or sources of the cloud and improve the understanding of how sodium and other neutral materials are removed from Io.

In the latter part of the week, Galileo starts with a second pass through the data stored on the tape recorder. This second pass allows the replay of data lost in transmission to Earth, reprocessing of data using different parameters, or return of additional new data. This week's second pass schedule includes a Solid-State Imaging camera observation of dark material found near a ringed structure on Callisto, Ultraviolet Spectrometer measurements of Callisto's surface, and portions of the Fields and Particles instruments' high resolution recording of the Io torus.

For more information on the Galileo spacecraft and its mission to Jupiter, please visit the Galileo home page.

Return to Project Galileo Homepage

Comments and suggestions about this website may be directed to
gllbug@jplpio.jpl.nasa.gov
Last updated: July 3, 1999

NASA/JPL Logo