Resolution-calibration inputs at the L1/APS boundary

The L1 calibration set contains wavelength-calibrated arc products (warc_) and associated wavelength-solution products. Arc files provide arc-line widths/FWHM information, including the L1 fibre-table Resol field and the arm-specific WARCF_* provenance keywords. PyAPS’s aps_fwhm.py can fit spline FWHM profiles from the wave_* calibration route, and that implementation remains useful for diagnostics, fallbacks and configurations for which no preferred LSF product is available.

The production analysis baseline uses the solar-twilight lsf_* products through aps_lsf.py. The selected calibration source and fallback are recorded with each run.

The detailed calibration and propagation contract is given in W12. It explains why the on-sky calibration is preferred, its FITS and spline representation, and its propagation to MOS fibres, reconstructed IFU spaxels, bins and scientific engines.