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3. Qualifiers

Some instruments supported by ardlib allow the specification of one or more qualifiers. The use of qualifiers allows the user to influence the calculation performed by ardlib for the corresponding instrument. To illustrate this point, consider the mkinstmap program. It produces a 2-d image, called an instrument map, that represents the product of the detector QE with the mirror effective area, both which vary spatially. For example, 

    mkinstmap mirror="HRMA" detsubsys="ACIS-I3"
will generate an instrument map for the mirror-detector combination HRMA and ACIS-I3. Sometimes it is useful to generate an image of detector QE alone (showing any spatial non-uniformities). Rather than adding the logic to mkinstmap to handle such special cases, the user may attach the "area=1" qualifier to the mirror specification to cause ardlib to return a mirror effective area of 1.0 for that mirror, e.g., 
    mkinstmap mirror="HRMA;area=1" detsubsys="ACIS-I3"
It is important to note that the use of this qualifier is totally transparent to mkinstmap itself.

All instruments support the "help" qualifier. This qualifier prints out a list of qualifiers supported by the instrument. For instance, 

    mkinstmap mirror="HRMA;help" detsubsys="ACIS-I3"
results in the message: 
    ARDLIB: Valid options for subsystem "HRMA" include:
    ARDLIB:      SHELL=value     Valid values are: 1,3,4,6
    ARDLIB:     BITMAP=value     e.g., 1111 ==> all 4 shells
    ARDLIB:      AREA[=value]    (No value implies AREA=1)
Hence, to produce an instrument map for, say HRMA mirror shell 3, one may use 
    mkinstmap mirror="HRMA;shell=3" detsubsys="ACIS-I3"
It is important to understand that the only thing that mkinstmap knows about "HRMA;shell=3" is that it represents a mirror and has an effective area associated with it. Ardlib handles the rest.

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