***** File COMPINFO.TXT                                                       
                                                                              
     This directory contains compressed, full-resolution data of comet        
Giacobini-Zinner obtained by the IHW Large-Scale Phenomena Discipline.        
                                                                              
With both project costs and user comfort in mind, it was decided to use a     
relatively straightforward data compression technique to reduce the amount of 
space required for the data. A previous pixel algorithm was chosen to         
accomplish this, with the result that the data have been compressed by almost 
50%.  When applied to both the P/G-Z and P/Halley imagery this will reduce the
number image CD-ROMs to less than 20.                                         
                                                                              
     The compression was accomplished using the program called PACKER.FOR,    
given in the FORTEAN subdirectory of the SOFTWARE directory.  The compression 
algorithm is briefly described in the file COMPRESS.TXT in the DOCUMENT       
subdirectory.                                                                 
                                                                              
     The file extensions for compressed data (.IMQ = image, .HDR = header,    
.LBL = label) follow the IHW filename conventions. To reconstruct the original
FITS byte stream, the .HDR and the .IMQ files for the appropriate observation 
must be concatenated.  The FITS headers have been modified using the FITS     
extensions to take account of the fact that the data have been compressed.