***** File CMPRINFO.TXT                                                       
                                                                              
     This file describes the contents of the COMPRESS subdirectory of         
HAL_0023. The subdirectory contains the source code for the routine that      
compressed the LSPN digitized images.  It written in IBM FORTRAN to run on an 
IBM 3081. The algorithm used is called "previous pixel compression".  With the
10-bit digitization of Goddard's PDS microdensitometer, the algorithm was able
to compress the data by approximately a factor of 2.  A detailed description  
of the previous pixel algorithm can be found in the file COMPRESS.TXT located 
in this subdirectory.  Compressed LSPN images are to be found on HAL_0001     
through HAL_0018.