DOCUMENTATION FOR MIRSI COAD  (Version 1-12/03)

     
     PURPOSE
       Procedure in IRTF MIRSI reduction pipeline for reading MIRSI 
       FITS images, coadding them, and saving the results as a FITS file.  
       Some noise artifacts particular to MIRSI are removed.  The mean of  
       four observation times is saved in output header as 'MEANTIME'.


     CALLING SEQUENCE
       mirsi_coad, infile, outfile, path, ext=ext, help=help


     INPUTS
       infile - Name of MIRSI FITS file with four 320x240 images
                from chop/nod mode saved as extensions 0-3.
       outfile - Filename where results are saved.
       path - 2-element string vector with input and output paths


     OPTIONAL KEYWORD INPUTS: 
       ext - Set for extended objects 
       help - Set to print syntax


     OUTPUT
       320x240x2 image cube is saved to FITS file PDU.  First image
       in cube is (ext0-ext1)-(ext2-ext3).  Second image in cube is 
       (ext1-ext0)-(ext3-ext2).  Mean of observation times is saved 
       in header under MEANTIME keyword.


     REDUCTION PROCEDURE
       1. Create batch file with following information: 
                 infiles = ['file1.fits', 'file2.fits', ...]
                 outfiles = ['output1.fits', 'output2.fits', ...]
                 paths = ['/input_dir/', '/output_dir/']
       2. If reducing extended objects, set ext=1 in batch file, 
          otherwise set ext=0
       3. Put calling sequence in batch file: 
            n = # of infiles (should be the same as the # of outfiles)
            for i = 0, (n-1) do $ 
              mirsi_coad, infiles[i], paths, outfiles[i], ext=ext
       4. Execute batch file in IDL


     REQUIRED SUBROUTINES
       1. Astro Users Library
       2. CGMEDF.PRO
       3. FILEX.PRO
       4. GETIM.PRO
       5. SDEV.PRO