Prior to processing any OmegaCAM data, the frames need to be matched in terms of setup and in terms of dependencies. The Organization, Classification, and Association (OCA) of frames (raw calibrations and science, as well as pipeline processed products) occurs at several places within the VLT Data Flow.
Based on information available in the headers, raw frames are matched to the files (i.e. product frames) that they require in order to be processed, and in terms of association rules based on the keywords:
For example, matching rules could be as follows:
2. Basic and Static Calibrations
Static calibrations are only needed for processing standard stars and science frames. To do this, the OmegaCAM data reduction scheme requires:
Raw frames generated by the bias, bias readnoise, detector gain and linearity, dark, and shutter test templates can be reduced by the pipeline without the need for any other calibration products.
3. Dependent Calibrations
The dome flat recipe (omega_mdome) requires, apart from the raw dome-flat frames, a master bias and a hot pixel map. The recipe output will be a master dome flat and a hot pixel map.
The twilight flat recipe (omega_mflat) requires, apart from the raw sky-flat frames, a master bias, a hot pixel map, a master dome flat, and a cold pixel map. The recipe output will be a master twilight flat, a master flat (a combination of the master dome and twilight flats), and a bad pixel map (a combination of the hot and cold pixel maps).
The standard star recipe (omega_standard_star) requires, apart from the raw standard star frame, a master bias, a master flat, and a master bad pixel map. The recipe output will be a fully reduced standard star field, a standard star field mask, a zeropoint fits table, and a photometric fits table.
4. Association Cascade
The calibration cascade is can be represented as: