The ASTER Science Team has developed a new assessment method to improve the accuracy of scene cloud cover metadata values. The cloud cover values will begin to be updated at LP DAAC on January 12, 2010. Updates will continue for older data until modifications have been completed for the entire archive. This is anticipated to be finished by the end of January 2010. Daily updates will routinely continue for newly acquired imagery.
The new improved cloud cover values will be available for use in searching the LP DAAC ASTER product inventory. Generation of the updated scene cloud cover percentage takes place after scene collection, so there will always be a delay of several days until the more accurate value is available. Note that metadata in the hdf granules will not be changed, and will contain the values produced using the earlier cloud assessment approach.
Further information regarding the improved cloud masking algorithm has been authored by Hideyuki Tonooka, and is available online at http://tonolab.cis.ibaraki.ac.jp/ASTER/cloud/.
Please contact LP DAAC User Services for additional information or if you have questions.