Bad data masks (ARD)

  A number of the ESP application allows image regions to be defined as being of poor quality by two basic methods; by use of an NDF whose data component values are set bad (either explicitly or by use of the quality component and the badbits flag -- see SUN/33) or by interpreting bad-region commands contained within an ordinary text file (an ASCII Region Definition file -- ARD file -- see SUN/183)

An NDF, with the appropriate pixels set to the bad value, can be produced interactively using the KAPPA applications ARDGEN and ARDMASK (SUN/95).

The capabilities of the ARD option (which uses little disk and could form part of a `database' of data masking information) are described below.

As things stand, with images generated using a known CCD, the bad or hot pixels, rows or columns might be defined by ARDGEN so that they are always set to bad and excluded from all subsequent processing. The information required is often supplied by the observatory operating the CCD and can placed in a text file using any text editor.