extract orders (order table), modes OPT or AVG; if OPT, store weight map;
extract master flat in same way as science spectrum (OPT or AVG); if OPT, use weight map; normalize extracted flat by its median;
divide extracted science spectrum by extracted and normalized master flat;
resample science spectrum using line table(s);
merge the orders;
flux-calibrate the final spectrum if an appropriate master response curve is available .
The pipeline processing of science data starts with data preparation: the raw input frames are rotated and in the case of the red mosaic data, split for each detector.
The prescan and overscan regions are trimmed. The instrument's background light is corrected in two steps.
A master bias frame is subtracted.
The interorder background light is estimated by a minimum filter being applied in small boxes at the background positions defined in the background table.
The optimal extraction provides the object signal and its variance. The flat-field correction is performed in pixel-order space on the extracted data.
The signal is then resampled to constant wavelength bins. Finally the orders are merged into a single spectrum.
A flux-calibrated spectrum can be produced in addition to the extracted spectrum if a response curve is provided. Details about flux calibration and master response curves are given here.
The UVES pipeline run on science data by QC Garching to create the IDP used OPT extraction if the image slicer had not been used, and AVG extraction for image slicer data.
Flat fields were applied in pixel-order space. Flux-calibrated spectra were provided for all settings except for those with 520nm and 600nm central wavelength.
Find more information on IDP here ...
Find the phase3 spectral archive interface here.