Add the keyword POLANGLE to VL-image FITS headers

	sxdelpar, primary_header, 'BLANK'

	; read the calibration curve to convert pmp raw voltages (dacpol) into effective polarization angles

	dacpol_cal = cal_pack.vl_channel.dacpol_cal

	if header.pol_id ne 5 then begin

		if fix(header.hdr_vers) le 4 then begin

			case header.pol_id of

				0: dacpol = header.dac1pol1

				1: dacpol = header.dac1pol1

				2: dacpol = header.dac1pol2

				3: dacpol = header.dac1pol3

				4: dacpol = header.dac1pol4

			endcase

		endif

		if fix(header.hdr_vers) ge 5 then begin

			dacpol = header.dac1pol1

		endif

		k = where(dacpol_cal.dacpol eq dacpol)

		angle = dacpol_cal.angle[k]

		angle = float(angle[0])

		fxaddpar, primary_header, 'POLANGLE', angle, '[deg] Polarization angle', after = 'POL_ID'

	endif

	; append wcs keywords

	wcs = metis_wcs(header, cal_pack, ref_detector = ref_detector)