VARIOUS GROUND-BASED DETECTORS
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  Instrument Overview                                                         
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    This instrument name is used when a data set consists of                  
    observations taken, usually over a long period of time, by various        
    types of detectors attached to one or more ground-based                   
    telescopes.  The VARGBDET identifier is used when it is not               
    possible or not practical to identify even the generic type of            
    detector associated with the individual observations comprising           
    the data set.  The published references listed in the                     
    corresponding data set description may provide more information.