lrowaccal

This program applies dark, flat-field, radiometric, and temperature corrections for each framelet based on the band's filter number. There is also an optional mask to replace special pixels in the calibrated image. In order to output in I/F units, the cube must have spice data.

Corrections are applied in the following order: Dark, Flat-field, Radiometric, Special pixel mask, and Temperature.

Dark Correction:

If the DarkFile parameter is set, the given file(s) will be used for calibration. If DarkFile is set to "Default" or not set at all, the dark files will be looked up based on the time and temperature in the WAC being calibrated. The parameter,MiddleTemperatureFpa, is used for temperature and StartTime for time. This program, lrowaccal, will attempt to find the 2 dark files with closest time/temperature and interpolate/extrapolate from them. The method for finding dark files is as follows:

• Create filename template based on WAC image offset and type (UV, BW, etc). Example: WAC_UV_Offset68_*C_*T_Dark.????.cub
• Look in $lro/calibration/wac_darks for matching files.
• Sort files on two factors:
  1. abs(dark temp - WAC temp)
  2. abs(dark time - WAC time)
• Example:
  WAC Temp = 23.33 and WAC Time = 314264519.932493
  
  WAC_UV_Offset68_-10C_319412928T_Dark.0005.cub
  WAC_UV_Offset68_-15C_319412928T_Dark.0005.cub
  WAC_UV_Offset68_-20C_311632116T_Dark.0005.cub
  WAC_UV_Offset68_-20C_319412928T_Dark.0005.cub
  WAC_UV_Offset68_-25C_319412928T_Dark.0005.cub
  WAC_UV_Offset68_-30C_311632116T_Dark.0005.cub
  
  becomes
  
  WAC_UV_Offset68_-25C_319412928T_Dark.0005.cub
  WAC_UV_Offset68_-20C_311632116T_Dark.0005.cub
  WAC_UV_Offset68_-20C_319412928T_Dark.0005.cub
  WAC_UV_Offset68_-30C_311632116T_Dark.0005.cub
  WAC_UV_Offset68_-15C_319412928T_Dark.0005.cub
  WAC_UV_Offset68_-10C_319412928T_Dark.0005.cub
  
• Take the 2 closest temperatures (-25C and -20C in the example).
• Select the closest time for each temperature.
  Example result:
  
  WAC_UV_Offset68_-25C_319412928T_Dark.0005.cub
  WAC_UV_Offset68_-20C_311632116T_Dark.0005.cub
  
• If only one temperature is available, the 2 times that are closest to the WAC time will be chosen. This will allow WACs to always be calibrated against something, instead of just failing.
  Example result:
  
  WAC_UV_Offset68_-20C_311632116T_Dark.0005.cub
  WAC_UV_Offset68_-20C_319412928T_Dark.0005.cub
  

Once the dark files are found, the correction is applied:

        output[pixel] -= (dark1[pixel] - dark2[pixel])/(dark1Temp - dark2Temp)*(frameTemp-dark2Temp) + dark2[pixel]
      

        dark1, dark2 = dark file cubes
        dark1Temp, dark2Temp = temperature of dark1 file and dark2 file
        frameTemp = (WAC EndTemperatureFpa - WAC BeginTemperatureFpa)/WAC NumFramelets * frame + WAC BeginTemperatureFpa
      

Flat-field Correction:

        output[pixel] /= flatfield[pixel]
      

Radiometric Correction:

      output[pixel] /= WAC ExposureDuration
      if radiometricType == iof
        output[pixel] *= solarDistance2 / iofResponsivity[band]
      else
        output[pixel] /= radianceResponsivity[band]
      

        solarDistance is distance from the Moon to the Sun
      

Special Pixel Mask:

      for each framelet in the output cube
        if specialPixelMask[pixel] is special
          outputFramelet[pixel] = specialPixelMask[pixel]
      

Temperature Correction:

        for each framlet in the output cube
          if output[pixel] is special- leave it alone
          else preform the correction
        

                inputPixel
            --------------------
             a*(frameTemp) + b

             Where: 
               'a' and 'b' are band dependent constants, read in from a file.
             AND
               frameTemp = (WAC EndTemperatureFpa - WAC BeginTemperatureFpa)/WAC NumFramelets * frame + WAC BeginTemperatureFpa