***** File COMPINFO.TXT                                                       
                                                                              
     This directory contains compressed, full-resolution data of comet Halley 
obtained by the IHW Large-Scale Phenomena Discipline.  The chronological first
date of the image set is that of the directory name.                          
                                                                              
     The digital data associated with wide-field images would, if left        
uncompressed, fill between 35 and 40 compact discs.  With both project costs  
and user comfort in mind, it was decided to use a relatively straightforward  
data compression technique to reduce the number of discs 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%, reducing the number  
of CD-ROMs required to less than 20.                                          
                                                                              
     The compression was accomplished using the program called PACKER.FOR,    
given in the SOFTWARE subdirectory.  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.