*****  File FITSINFO.TXT                                                      
                                                                              
                                                                              
                        FITS Format Information                               
                                                                              
                                                                              
    All data was submitted to the International Halley Watch Lead Center on   
magnetic tape, written in standard FITS format.  There are three primary      
references to basic FITS (Wells et al, 1981) and its extensions (Greisen and  
Harten, 1981, Harten et al, 1988).  Although commonly viewed as a magnetic    
tape format, the actual FITS specifications can be interpreted to describe a  
general byte stream.  As such, FITS files may be written on any storage       
medium, including CD-ROM.  Note that there is no inherent record structure    
called for in the FITS agreements, only a blocking structure for block        
oriented media such as magnetic tape.                                         
                                                                              
    The basic FITS agreements call for only a few required keywords (SIMPLE,  
BITPIX, NAXIS, and END must be present; EXTEND may appear; NAXIS1, ..., NAXISn
appear as defined by the value of NAXIS).  We have also followed recommended  
conventions for the representation of values of keywords (dates in the format 
'dd/mm/yy', SI units used where possible, etc.).  The IHW has defined an      
additional set of mandatory keywords for all submissions to the Lead Center.  
These are presented in the table below:                                       
                                                                              
    OBJECT   - Name of the object in the data file, a text string.            
    FILE-NUM - Unique 6-digit number of the file submitted to the             
               Lead Center. The first digit identifies the network,           
               the other digits are assigned by the individual                
               disciplines, but must uniquely identify the file.              
    DATE-OBS - UT Date of mid-observation, in the format 'dd/mm/yy'.          
    TIME-OBS - UT Time of mid-observation, as fractional day.                 
    DATE-REL - IHW internal release date for data, a date string.             
    DISCIPLN - Name of the network submitting the file, a text                
               string.                                                        
    LONG-OBS - Longitude of the submitting observatory, in the                
               format 'ddd/mm/ss', in degrees from 0 to 360,                  
               increasing in the eastward sense.                              
    LAT--OBS - Latitude of the submitting observatory, in the format          
               'sdd/mm/ss'.                                                   
    SYSTEM   - An 8-digit coded character string identifying the              
               discipline, observatory and instrument which supplied          
               the data. The first character identifies the network           
               (1 = Astrometry, 2 = IR Studies, 3 = Large Scale               
               Phenomena, 4 = Near Nucleus Studies, 5 = Photometry &          
               Polarimetry, 6 = Radio Studies, 7 = Spectroscopy &             
               Spectrophotometry, and 8 = Amateur Observation), the           
               next three identify the observatory (by IAU code               
               number, where one is assigned, 500 otherwise). The             
               next four digits either identify the telescope/in-             
               strument combination (if there is an IAU number for            
               the observatory) or the country and observatory (if no         
               IAU number). See the file OBSCODES.TXT for a listing           
               of the system codes used for P/Giacobini-Zinner.               
    OBSERVER - Name of the observer(s) who took the data, a text              
               string. The notation "ET AL." indicates that there             
               were more than two observers, and the names of the             
               additional observers are given in a COMMENT later in           
               the header, with the subkeyword "ADD. OBS."                    
    SUBMITTR - Name of the person submitting the data to the Lead             
               Center, a text string.                                         
    SPEC-EVT - A logical value indicating that the observation is             
               a special event.  Either T or F.                               
    DAT-FORM - A character string defining the form of the data,              
               e.g., 'ASCII', 'NODATA'.                                       
                                                                              
                                                                              
    The individual disciplines have written appendices which describe the     
keywords used in addition to the mandatory ones.  Refer to the text files in  
the subdirectory APPENDIX below this one for more details on those keywords.  
                                                                              
    A more complete listing of keywords used, including their definitions,    
can also be found on the P/Halley Mixed data CD-ROM discs.                    
                                                                              
                                                                              
                                REFERENCES                                    
                                                                              
Greisen, E. W. and Harten, R. H.: 1981, Astron. Astrophys. Suppl. Ser.        
  44, 371.                                                                    
Harten, R. H., Grosbol, P., Greisen, E. W. and Wells, D. C.: 1988,            
  Astron. Astrophys. Suppl. Ser. 73, 365.                                     
Wells, D. C., Greisen, E. W. and Harten, R. H.: 1981, Astron. Astrophys.      
  Suppl. Ser. 44, 363.