PDS_VERSION_ID                     = PDS3                                     
  LABEL_REVISION_NOTE              = "NULL"                                   
                                                                              
OBJECT                             = INSTRUMENT_HOST                          
  INSTRUMENT_HOST_ID               = "IRAS"                                   
  OBJECT                           = INSTRUMENT_HOST_INFORMATION              
    INSTRUMENT_HOST_NAME           = "INFRARED ASTRONOMICAL SATELLITE"        
    INSTRUMENT_HOST_TYPE           = "SPACECRAFT"                             
    INSTRUMENT_HOST_DESC           = "                                        
                                                                              
        Instrument Host Overview                                              
        ========================                                              
        The Infrared Astronomical Satellite (IRAS) was a spacecraft with a    
        telescope mounted in a liquid helium cooled cryostat. The telescope   
        was a f/9.6 Ritchey-Chretien design with a 5.5 m focal length and a   
        0.57 m aperture. The mirrors were made of beryllium and cooled to     
        approximately 4 K.                                                    
                                                                              
        The focal plane assembly contained the survey detectors, visible star 
        sensors for position reconstruction, a Low Resolution Spectrometer    
        (LRS) and a Chopped Photometric Channel (CPC). The focal plane        
        assembly was located at the Cassegrain focus of the telescope and was 
        cooled to about 3 K.                                                  
                                                                              
        The survey array consisted of 62 rectangular infrared detectors       
        arranged in staggered rows such that any real point source crossing   
        the focal plane as the satellite scanned would be seen by at least two
        detectors in each wavelength band. Most of the detectors in each band 
        had standard size apertures (see table below), with one or two being  
        half-sized.                                                           
                                                                              
        The LRS was a slitless spectrometer sensitive from 7.5 to 23 microns  
        with a resolving power of about 20.                                   
                                                                              
        The CPC operated during some pointed observations. It mapped sources  
        simultaneously at 50 and 100 microns, and used a cold internal chopper
        for flux reference. However, the focal plane temperature was lower    
        than expected, which resulted in CPC detector anomalies that rendered 
        CPC data very difficult to use.                                       
                                                                              
        Instrument Summary                                                    
        ------------------                                                    
        In the table below, the center wavelengths are in microns. For the    
        survey array, the FOV is determined by the rather large detector mask 
        size and is roughly the native 'resolution' of the data in that band. 
        The resolution of the IRAS image data is not governed by the          
        resolution of the telescope, which was diffraction limited longwards  
        of 12 microns, but by the size of the detectors.                      
                                                                              
          ------------------------------------------------------------------  
                                                                              
                                    SURVEY ARRAY                              
                                                                              
            Center  # working    FOV     Bandpass  Detector Average 10-sigma  
          Wavelength detectors (arcmin)  (micron)  Material Sensitivity (Jy)  
                                                                              
             12         16    .75 x 4.5  8.5- 15    Si:As        0.7          
             25         13    .75 x 4.6  19 - 30    Si:Sb        0.65         
             60         15    1.5 x 4.7  40 - 80    Ge:Ga        0.85         
            100         13    3.0 x 5.0  83 -120    Ge:Ga        3.0          
                                                                              
          ------------------------------------------------------------------  
                                                                              
                                       CPC                                    
                                                                              
            Center  # working    FOV     Bandpass  Detector Average 10-sigma  
          Wavelength detectors (arcmin)  (micron)  Material Sensitivity (Jy)  
                                                                              
             50         1        1.2     41 - 63    Ge:Ga        7.0          
            100         1        1.2     84 -114    Ge:Ga        7.0          
                                                                              
          ------------------------------------------------------------------  
                                                                              
                                       LRS                                    
                                                                              
           Slit width    Wavelength Range    Detector   Resolving             
            (arcmin)         (micron)        Material     Power               
                                                                              
              5.0           8  - 13           Si:Ga      14-35                
              7.5           11 - 23           Si:As      14-35                
                                                                              
          ------------------------------------------------------------------" 
  END_OBJECT                       = INSTRUMENT_HOST_INFORMATION              
                                                                              
  OBJECT                           = INSTRUMENT_HOST_REFERENCE_INFO           
    REFERENCE_KEY_ID               = "NEUGEBAUERETAL1984"                     
  END_OBJECT                       = INSTRUMENT_HOST_REFERENCE_INFO           
                                                                              
  OBJECT                           = INSTRUMENT_HOST_REFERENCE_INFO           
    REFERENCE_KEY_ID               = "BEICHMANETAL1988"                       
  END_OBJECT                       = INSTRUMENT_HOST_REFERENCE_INFO           
                                                                              
END_OBJECT                         = INSTRUMENT_HOST                          
END