The high resolution ASCII dataset directory is sub-divided into orbit range
sub-directories in order to reduce the number of files in a single 
directory. Each directory contains all files submitted to PDS which contained
data records within the 100 orbit range beginning with the the orbit name
used as the directory name (i.e. directory ORB3601 contains all orbits
between 3601 and 3700). Files which did not contain any data (zero records) 
have not been included on this volume. Not all orbits have been submitted to
PDS with data.

High resolution data files are described in the file DATASET.TXT.