The first pass of the Galileo spacecraft through the Jovian system this summer resulted in the highest resolution images of Europa ever obtained, at approximately 1.6 km/pixel. Some overlap exists between the high resolution (2 km/pixel) Voyager coverage and the new Galileo images, and this overlap region has been studied in detail to provide qualitative and quantitative measures of the effect of photometric geometry on the appearance of topographic and albedo features. It is apparent that previous feature classification schemes need to be reconsidered, as features can be seen to change categories based solely on photometric geometry. For example, numerous albedo-dark bands seen by Voyager are observed by Galileo to be bright lineaments or topographic ridges. The overlapping Voyager and Galileo images are also being carefully reprojected, ratioed, and compared to search for changes which may have taken place in the 17 years between the images, and provide an upper limit on the size of such changes which could occurred undetected. So far, we have found no observable geologic activity. We are also in the process of convolving the Galileo images to reduce their resolution and make it comparable to the Voyager images, so as to eliminate apparent changes due solely to resolution differences. While the change in pixel scale from the 2 km/pixel Voyager images to the 1.6 km/pixel Galileo images is not that large, the improved detector performance of the Galileo CCD has resulted in an increase in apparent resolution of close to a factor of two. We are also reprocessing and calibrating the Voyager high-resolution 4-color Europa data, which covers an area adjacent to the newly-obtained Galileo 6-color image. We plan to use the Voyager short-wavelength (UV) color data to expand the longer-wavelength Galileo color coverage.
AAS/Division for Planetary Sciences Meeting Abstracts #28
- Pub Date:
- September 1996