Bad pixels

The recipes apply a predetermined bad-pixel mask with the aim of removing the bulk of `hot' and `cold' pixels. This flags approximately 0.4% of UIST and ISAAC pixels, 0.1% of IRIS2 pixels, and 5% of Michelle's pixels.
[_MASK_BAD_PIXELS_]

Some of the instruments (UIST, CGS4) array tests are run, typically at the start of each night. As a part of these array tests a new bad-pixel-mask is generated on-the-fly, using the predetermined one as a basis. For UIST the new bad-pixel-mask is generated from a long-exposure dark observation, typically 100s. Any pixel that is 5-$\sigma$ higher than the 3-$\sigma$ clipped mean or 1000-$\sigma$ lower than the 3-$\sigma$ clipped mean is flagged as bad. For CGS4 any pixel higher than 1700 or lower than 15 for a dark whose exposure time is longer than 80 seconds, or higher than 1500 and lower than -100 for a dark whose exposure time is 80 seconds or shorter, is flagged as bad.