It performs a null debiassing, bad-pixel masking, dark subtraction, flat-field creation, flat-field division, integer shifts of origin to register, and mosaicking. See the “Notes” for further information.

This recipe aims to keep pace with the pipeline’s incoming data, and is intended for faint sources and for moderately crowded fields.

• A World Co-ordinate System (WCS) using the AIPS convention is created in the headers should no WCS already exist.

• For IRCAM, old headers are reordered and structured with headings before groups of related keywords. The comments have units added or appear in a standard format. Four deprecated headers are removed. FITS-violating headers are corrected. Spurious instrument names are changed to IRCAM3.

• The bad-pixel mask applied is $ORAC_DATA_CAL/bpm.

• Each dark-subtracted frame has thresholds applied beyond which pixels are flagged as bad. The lower limit is 5 standard deviations below the mode, but constrained to the range $-$100 to 1. The upper limit is 1000 above the saturation limit for the detector in the mode used.

• The flat field is created by combining normalised object frames using the clipped median at each pixel.

• Registration is performed using the telescope offsets transformed to pixels.

• There is no resampling, merely integer shifts of origin.

• The recipe makes the mosaics by applying offsets in intensity to give the most consistent result amongst the overlapping regions. The mosaic is not trimmed to the dimensions of a single frame, thus the noise will be greater in the peripheral areas having received less exposure time. The mosaic is not normalised by its exposure time (that being the exposure time of a single frame).

• For each cycle of jittered frames, the recipe creates a mosaic, which is then added into a master mosaic of improving signal to noise. The exposure time is also summed and stored in the mosaic’s corresponding header. Likewise the end airmass header and end UT headers are updated to match that of the last-observed frame contributing to the mosaic.

• Intermediate frames are deleted except for the flat-fielded (_ff suffix) frames.

• The integrated mosaic in $<$m$>$$<$date$>$_$<$group_number$>$_mos, where $<$m$>$ is the instrument’s group prefix.

• A mosaic for each cycle of jittered frames in
  $<$m$>$$<$date$>$_$<$group_number$>$_mos$<$cycle_number$>$, where $<$cycle_number$>$
  counts from 0.

• The individual flat-fielded frames in $<$i$>$$<$date$>$_$<$obs_number$>$_ff, where $<$i$>$ is the frame prefix. The naming format is slightly different for some non-UKIRT instruments.

• The created flat fields in flat_$<$filter$>$_$<$group_number$>$ for the first or only cycle, and flat_$<$filter$>$_$<$group_number$>$_c$<$cycle_number$>$ for subsequent cycles.

NUMBER = INTEGER

USEVAR = LOGICAL

• The processing engines are from the Starlink packages: Ccdpack, Kappa, Figaro.

• Uses the Starlink NDF format.

• History is recorded within the data files.

• The title of the data is propagated through intermediate files to the mosaic.

• Error propagation is controlled by the USEVAR parameter.