This Week on Galileo

July 12-18, 1999

Galileo Plays Back Images from Jupiter Encounters

Galileo spends this week playing back images and other science data acquired during the spacecraft's passage through the heart of the Jupiter system earlier this month. The data are stored on Galileo's onboard tape recorder, from which it is read into the spacecraft computer, processed, packaged and transmitted to Earth. This week's playback schedule contains an observation by the Fields and Particles instruments, several by the Solid-State Imaging camera, one by the Photopolarimeter Radiometer, and one by the Near-Infrared Mapping Spectrometer.

The Fields and Particles instruments return the first half of a two hour observation that was recorded as the spacecraft flew through the Io torus. The observation contains measurements of plasma, and magnetic and electric fields within the torus. The torus is a region of intense plasma and radiation activity that is constantly replenished by the volcanic activity on Io and is a vital part of the Jovian magnetosphere. These recordings are to be repeated during each of the four Callisto encounters of the Perijove Reduction Campaign. As Galileo's perijove distance (or closest distance to Jupiter for a given orbit) is reduced from orbit to orbit, the observations will examine the Io torus at different distances from Jupiter. This encounter's observation, the second of four, spanned the region from 8.2 Jupiter Radii (586,000 kilometers, 364,000 miles) to 7.6 Jupiter radii (543,000 kilometers, 338,000 miles) within the torus. Galileo has not penetrated this deeply into the Io torus since the spacecraft's insertion into orbit around Jupiter in December of 1995.

The images taken by the Solid-State imaging camera capture the highest resolution views of Io obtained by Galileo to date. The first series of images contains a global view of Io at a resolution of 2.6 kilometers (1.6 miles) per picture element. The second set of images will form a regional map at a resolution of 1 to 1.5 kilometers (0.6-0.9 miles) per picture element, and a third series captures another region of Io at a resolution of 1.3 kilometers (0.8 miles) per picture element. These images have very high scientific value, as well as the ability to provide science planners with information that will be used in planning observations for the close encounters of Io that will occur in October and November of this year.

The Photopolarimeter Radiometer observation is one in a series of three taken during the last encounter. The observation is designed to characterize relatively large regions of Io's surface where temperatures are slightly higher than their surroundings. In addition, the observation will provide insight into how well different regions of the surface retain heat. The Near-Infrared Mapping Spectrometer also returns an observation of Io. It is designed to obtain high resolution spectral and spatial data describing Io's surface. The spectral data will allow scientists to identify different materials on Io's surface, while the spatial data will help them determine where these materials lie. This will be the highest resolution map of Io made to date by the Near-Infrared Mapping Spectrometer. These data are also very useful in identifying hot spots on Io's surface. Previous investigations of Io have revealed many new hotspots, and have captured variations in hot spot temperatures, corresponding to increasing and decreasing surface volcanic activity.

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

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Last updated: July 3, 1999

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