***** File SOFTINFO.TXT                                                       
                                                                              
                                                                              
     The SOFTWARE directory contains software which is useful in accessing the
data on the CD-ROM.  Each set of software is described separately according to
function (image manipulation, ephemeris interpolation).  The source code is in
ASCII text files with fixed length records; the executables are binary files. 
The files VAXnnnnn.EXE can be transferred as fixed-length record files into a 
VAX environment for execution.                                                
                                                                              
  The Large-Scale Phenomena Discipline has supplied of its digital imagery in 
compressed form.  The file PREVPIX.TXT contains pseudo-code algorithms for    
compressing and decompressing these images.  In addition to the compressed    
data, subsampled and rescaled BROWSE images have also been provided.          
                                                                              
   The file PREVPIX.PRO is the original source code used to compress the      
images on the Comet Giacobini-Zinner Test Disc.  It is written in IDL, a      
vector-oriented interactive language for a variety of machines from Research  
Systems, Inc. of Denver, CO.  While IDL is not widely used, the file is       
included for completeness.                                                    
                                                                              
   The compression of the Comet Halley data was performed on an IBM 3081 at   
Goddard Space Flight Center a Fortran program written by John M. Bogert III.  
This program (PACKER.FOR) is included, and has an associated text file,       
COMPRESS.TXT, by way of description. The program (MIDGET.FOR) used to         
subsample the data is described in the file BROWSE.TXT.                       
                                                                              
     The files DECOMP.FOR and DECOMP.C are subroutines which implement the    
decompression algorithm described in the file DECOMP.TXT.  They are to be used
on the compressed LSPN images. The user will need to write a driver program to
perform the I/O and to pass the arrays to DECOMP in manageable size pieces.   
DECOMP.FOR has been tested on a VAX 11/750 under VMS version 5 and on a Sun   
3/60 under Unix.                                                              
                                                                              
     The program PCDECLSP.COM, associated source code and documentation are   
included to allow users with IBM-PC compatible computers to decompress the    
LSPN images.  The program was written to run under MS-DOS v3.x and is compiled
and linked using Turbo C v2.0 from Borland International.  It decompresses the
8-bit data (stored in .IMQ files) into the original 16-bit representation. The
data are read, decompressed using a slightly modified version of DECOMP.C and 
written out to a file.  The actual progress of decompression in percent is    
displayed on the screen as well as the actual size of the compressed file. The
output file is padded with NULLs to fill out the 2880 byte format of FITS. The
output image is a completely valid FITS byte stream.                          
                                                                              
     The following files contain the complete Fortran source code for the     
program OBSNTERP, used to interpolate between observations in the Comet Halley
ephemeris table.  (The documentation about the calculations can be found in   
the file EPHEM.TXT, while the actual table EPHEM.TAB and explanation about the
program (OBSNTERP.TXT) are located in a different subdirectory).  It has been 
tested under VAX/VMS Fortran (VMS version 5.x) and Microsoft Fortran v4.0.    
                                                                              
OBSNTERP.FOR                                                                  
ARGCH2.FOR                                                                    
INTERP.FOR                                                                    
JDATE.FOR                                                                     
                                                                              
                                                                              
     These files contain the complete C source code for the program OBSNTERP. 
They directly translate the Fortran code, and have been tested under VAX/VMS C
and TurboC v2.0 from Borland International. Note that the routine JDATE (from 
the file JDATE.FOR above) has been included in the INTERP.C module.           
                                                                              
OBSNTERP.C                                                                    
ARGCH.C                                                                       
INTERP.C                                                                      
                                                                              
                                                                              
     These files are the executable versions of OBSNTERP referred to in the   
file OBSNTERP.TXT in the EPHEM subdirectory.  PCNTERP.EXE runs on an IBM PC or
compatible under MS-DOS. VAXNTERP.EXE runs on VAXes under VMS version 5.      
                                                                              
PCNTERP.EXE                                                                   
VAXNTERP.EXE                                                                  
                                                                              

 Name                    Last modified      Size  Description
 Parent Directory                             -   
 browse/                 12-May-1990 21:52    -   
 compress/               12-May-1990 21:22    -   
 decomp/                 12-May-1990 21:53    -   
 interp/                 12-May-1990 21:53    -   
 softinfo.txt            30-Mar-1990 04:45  5.9K