Arc recipe

The recipe name is isaacp lw_arc. It is very similar to the SW equivalent, see Sec. . The slit curvature and the wavelength calibration are computed in the same way. The main difference lies in the way the frames are classified.

• The frames are classified by instrument setting.
• For each setting, there should be an even number of frames. In some cases, there will be one pair of frames (an arc with the grating at a single order) and in other cases, there will be two pairs of frames (arcs with the grating in the first and then third order).
• In each pair, there should be a dark (a frame with the lamp off) and a frame with the arc lamp on. The lamp frame is dark corrected and then reduced, and a table containing the results is written to disk.

The procedure produces two output files: a FITS table, which contains the fit to the slit curvature and the linear dispersion relation; and a PAF file, which contains the same information as the FITS file as well as additional quality control information.

With the -c option, the recipe will produce the spectrum corrected for slit curvature.