Preliminaries

There are a few operations applied to all frames. First, history recording is switched on. It is recommended to leave this enabled, since it provides a record of the processing steps of your final spectra. Otherwise the pipeline becomes something of a black box. use the KAPPA command hislist to list the history records.
[_TURN_ON_HISTORY_]

The next step is to set the origin of the frame so that frame pixels retain the detector pixel indices. It then becomes possible to use a full-sized bad-pixel mask or a flat field on a subset of a detector's pixel grid.
[_SET_ORIGIN_]

For CGS4 data taken before 2000 August 13, the slit angle in the SANGLE header referred to the slit's physical position in the instrument, and after this date it referred to the slit's angle on the sky. For data taken before this date, the header value internal to ORAC-DR is set to coorespond to the on-sky angle.
[CGS4/_FIX_SANGLE_HEADER_]

For UIST data taken before 2002 December 2 and Michelle, raw data units are converted from ADU per second to the UKIRT standard of total ADU per exposure.
[UIST/_DATA_UNITS_TO_ADU_, MICHELLE/_DATA_UNITS_TO_ADU_]

For Michelle there is a validation check of the waveform used, comparing the waveform name given in the headers with other metadata, and recipes issue a warning if there is an inconsistency. For lowQ and MedN2 data taken before 2004 March 09, the gratings were installed the wrong way round in the cryostat, so these data are flipped along the dispersion axis at this stage in the data reduction.
[MICHELLE/_CHECK_WAVEFORM_, MICHELLE/_FLIP_FLIPPED_GRATING_FRAMES_]

A night log is created or appended in $ORAC_DATA_OUT for each frame processed. This tabulates the main parameters of the observation having first corrected defective or undefined headers.
[_NIGHT_LOG_, <instrument>/_FIX_EXTRA_HEADERS_ for MICHELLE, CGS4, and UIST]