SWS PIPELINE

From ERD to SPD

w × N
-------	=	sin(t + ß) + sin(t + ð)
D


  w: wavelength
  N: spectral order
  D: grating constant
  t: angle of incidence on the grating at current scanner setting
  ß: offset angle from used entrance aperture to optical axis
  ð: offset angle from used detector element to optical axis
• scanner position is measured by Linear Voltage Differential Transducer
• ß, ð, t-LVDT relationship is described by a 5th order polynomial function
• grating angle from get_grat_ang is used along with various cal-files to compute wavelengths
• if no unique wavelength can be assigned (order mix), wavelength is set zero
• all data with an unique order get a wavelength assigned, even if the data were not requested or are useless
• for non-SWS07 observations the FP data are not transferred to the AAR
• for AOT SWS01 observations the grating position is set to the value at the start, the wavelength to that at the middle of the reset interval
• for Fabry-Pérot measurements, once the grating wavelength is calculated the mechanical gap width from get_FP_gap is corrected using cal-file 18 to get the optical gap width and hence the wavelengths passing the FP

Cal-files:

• cal16a: Aperture offsets
• cal16b: Element offsets
• cal16c: Grating constants
• cal18:  Effective gap correction
• cal23:  Wavelength limits for bands
• cal24:  Wavelength limits for apertures

Help topic: IA derive spd

SWS TUTORIAL / PIPELINE / ERD to SPD : ... get_FP_gap < wave >> DAAR ...