Basic pipeline

The basic pipeline shall operate on single pointings or ``well-defined'' observing sequences taken during a single night to produce instrument signature-free images and to derive object catalogues from them. The object catalogues will be used to provide the first pass astrometric and photometric calibration.

The two-dimensional image data products at this stage will be instrumental signature-corrected: single frames; lossless interleaved super frames; stacked dither (super)frames; tiled contiguous mosaics, combining four pointings with any of previous options; and confidence maps for all pipeline output products.

The catalogue data products will be lists of detected images with an agreed set of parameters summarising useful astronomical information and providing the necessary DQC information.

In more detail the requirements are:

• instrumental signature removal - bias, non-linearity, dark, flat, fringe
• sky background tracking and removal during stacking - possible need to also remove other 2D background variations from imperfect multi-quadrant operation of detectors
• define and produce a strategy for dealing with image retention from preceding exposures
• combine frames if part of an observed dither sequence or tile pattern
• consistent internal calibration to put observations on an approximately uniform system
• basic catalogue generation including astrometric, photometric, shape and DQC information
• final? astrometric calibration from the catalogue with an appropriate and agreed World Coordinate System (WCS) in all FITS headers
• basic photometric calibration from catalogue using suitable pre-selected standard areas covering entire field-of-view to monitor and control systematics
• each frame and catalogue supplied with provisional calibration information and overall morphological classification embedded in FITS files
• propagation of error arrays and use of confidence maps
• realistic errors on selected derived parameters
• nightly extinction measurements in relevant passbands (also possibly JCMT information on water vapour content since can alter apparent extinction/ effective bandpass more than airmass)
• pipeline software version control - version used recorded in FITS header