Specifying Detectors

 Detectors are identified by their ``detector numbers''. These are integers varying from 1 to 62 and are described in paragraph C.4 of chapter II of the IRAS Catalogs and Atlases Explanatory Supplement (``Exp. Supp.'').

If the user is asked to select a group of detectors from a group of ``available'' detectors, a group expression may be given (see section ) in which each string in the group can be one of the following:

• An integer in the range 1 to 62 specifying an explicit detector number.
• One of the strings ``12um'', ``25um'', ``60um'' and ``100um''. These cause all available detectors from the specified wave band to be selected.
• A range of detectors, specified by two detector numbers separated by a colon (``:''). All available detectors whose cross scan positions are between those of the two detectors are selected. If the first detector number is omitted, no lower limit is imposed. If the second detector is omitted, no upper limit is imposed. Fig. II.C.6 and table II.C.3 in the Exp. Supp. list the positions of all 62 detectors.
• The string ``ALL''. This specifies that all available detectors should be selected.
• The string ``SMALL''. This specifies that all available small detectors (i.e. less than 4 arc-minutes cross-scan size) should be selected.
• The string ``LARGE''. This specifies that all available detectors should be selected, excluding the small detectors.
• The string ``NONE''. This specifies that no detectors should be selected, and may not be mixed with other options. A null parameter value is equivalent to ``NONE''.
• The string ``LIST''. This causes a list of available detectors to be displayed, but no detectors are selected. The user is re-prompted if this option is selected. This option may not be mixed with any other options.

All key words can be abbreviated and are case insensitive.

The selection of detectors is made from a list of available detectors. This is often all detectors for a given waveband. For instance the available detectors may be all those from the same band as the data supplied as input to the application. The help on the parameter concerned should say what detectors are available, and this list is displayed at run-time if the keyword LIST is supplied for the parameter.

The union of the specified detectors are used. Thus for instance, if all 62 detectors are available, and the group expression ``12$\mu$m,small'' is supplied, the returned set of detectors consists of all 12$\mu$m detectors together with all small detectors from all four bands, not just the small detectors from the 12$\mu$m band.