OBJECT                        = EBINSTRUMENT                                  
EARTH_BASE_ID                 = "ECAS"                                        
INSTRUMENT_ID                 = "2CP"                                         
/* Instrument Information:                                                    
 OBJECT                       = INSTINFO                                      
  INSTRUMENT_NAME             = "2 CHANNEL PHOTOMETER"                        
  INSTRUMENT_TYPE             = PHOTOMETER                                    
  INSTRUMENT_DESC             = "                                             
The following instrument description is extracted from Tedesco et al.         
1982: This two-channel computer-controlled photometer is an adaptation        
of one of the instruments originally built for the 1977 stellar               
occultation by Uranus (Hubbard and Zellner 1980).  Light entering this        
photometer strikes a rotating segmented mirror that alternately               
directs star and sky light to a focal plane diaphragm.  The throw of          
this mirror is 3.2 mm.  Hence, as normally used on the 61-inch and            
90-inch telescopes of the University of Arizona Observatories, skies          
are taken about 32 arcseconds away from (generally north of) the              
program object.  Star-sky dwell time ratios of 1:1, 3:1, or 9:1 over a        
4 second cycle, are selectable by the observer.  Following the                
diaphragm is a manually controlled, 2.5 mag neutral density filter            
used to observe objects brighter than about visual magnitude 8 at the         
61-inch telescope.  The beam next encounters a dichroic mirror that           
reflects wavelengths less than about 0.52 um through a filter slide           
onto a blue sensitive photomultiplier tube and transmits longer wave-         
lengths through a second filter slide onto a red sensitive photo-             
multiplier tube.                                                              
Pulse counting electronics and Fabry imaging are employed in both             
photometric channels.  The blue photomultiplier is an uncooled EMI            
9789QB (bialkali photocathode) with quantum efficiency near 20% at            
0.38 um.  The dark current varies from 1 to 50 counts per second              
depending on ambient temperature.  The red channel can accommodate            
either a thermoelectrically cooled RCA C31034-05 (GaAs photocathode)          
or a dry-ice cooled Varian VPM 159A.12D (InGaAsP photocathode).  The          
RCA tube has an effective quantum efficiency of about 22% at 0.55 um,         
about 14% at 0.86 um, and is essentially insensitive beyond 0.9 um.           
Dark counts are generally between 1 and 25 per second.  The Varian            
detector, which must always be kept at a temperature of less than -20         
degrees centigrade, is maintained at dry ice temperature even between         
observing runs.  Its effective quantum efficiency is about 18% at 0.40        
um, about 6% at 1.0 um, and about 0.5% at 1.1 um.                             
The response functions of the eight filters used in ECAS as well as           
that of the dichroic beam splitter are given in the ECASFLTR dataset          
distributed through PDS.                                                      
"                                                                             
 END_OBJECT                   = INSTINFO                                      
/* Instrument Reference:                                                      
 OBJECT                       = INSTREFINFO                                   
  REFERENCE_KEY_ID            = "TEDESCOETAL82"                               
/* Citation Reference                                                         
  OBJECT                      = REFERENCE                                     
   DOCUMENT_TOPIC_TYPE         = "INSTRUMENT DESCRIPTION"                     
   JOURNAL_NAME                = "ASTRONOMICAL JOURNAL"                       
   PUBLICATION_DATE            = 1982-11-01                                   
   REFERENCE_DESC              = "Tedesco, E. F., D. J. Tholen, and B.        
Zellner 1982.  The Eight-Color Asteroid Survey:  Standard Stars.              
Astron. J. vol. 87, no. 11, 1585-1592, 1982."                                 
/* Author Reference:                                                          
   OBJECT                     = REFAUTHORS                                    
    AUTHOR_FULL_NAME          = "Edward F. Tedesco"                           
   END_OBJECT                 = REFAUTHORS                                    
   OBJECT                     = REFAUTHORS                                    
    AUTHOR_FULL_NAME          = "David J. Tholen"                             
   END_OBJECT                 = REFAUTHORS                                    
   OBJECT                     = REFAUTHORS                                    
    AUTHOR_FULL_NAME          = "Benjamin Zellner"                            
   END_OBJECT                 = REFAUTHORS                                    
  END_OBJECT                  = REFERENCE                                     
 END_OBJECT                   = INSTREFINFO                                   
END_OBJECT                    = EBINSTRUMENT                                  
END