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@ARTICLE{Bohn:838135,
      author       = {Bohn, Birger and Lohse, Insa},
      title        = {{C}alibration and evaluation of {CCD} spectroradiometers
                      for ground-based and airborne measurements of spectral
                      actinic flux densities},
      journal      = {Atmospheric measurement techniques},
      volume       = {10},
      number       = {9},
      issn         = {1867-8548},
      address      = {Katlenburg-Lindau},
      publisher    = {Copernicus},
      reportid     = {FZJ-2017-06839},
      pages        = {3151 - 3174},
      year         = {2017},
      abstract     = {The properties and performance of charge-coupled device
                      (CCD) array spectroradiometers for the measurement of
                      atmospheric spectral actinic flux densities (280–650 nm)
                      and photolysis frequencies were investigated. These
                      instruments are widely used in atmospheric research and are
                      suitable for aircraft applications because of high time
                      resolutions and high sensitivities in the UV range. The
                      laboratory characterization included instrument-specific
                      properties like the wavelength accuracy, dark signal, dark
                      noise and signal-to-noise ratio (SNR). Spectral
                      sensitivities were derived from measurements with spectral
                      irradiance standards. The calibration procedure is described
                      in detail, and a straightforward method to minimize the
                      influence of stray light on spectral sensitivities is
                      introduced. From instrument dark noise, minimum detection
                      limits
                       ≈  1  ×  1010 cm−2 s−1 nm−1
                      were derived for spectral actinic flux densities at
                      wavelengths around 300 nm (1 s integration time). As a
                      prerequisite for the determination of stray light under
                      field conditions, atmospheric cutoff wavelengths were
                      defined using radiative transfer calculations as a function
                      of the solar zenith angle (SZA) and total ozone column
                      (TOC). The recommended analysis of field data relies on
                      these cutoff wavelengths and is also described in detail
                      taking data from a research flight on HALO (High Altitude
                      and Long Range Research Aircraft) as an example. An
                      evaluation of field data was performed by ground-based
                      comparisons with a double-monochromator-based, highly
                      sensitive reference spectroradiometer. Spectral actinic flux
                      densities were compared as well as photolysis frequencies
                      j(NO2) and j(O1D), representing UV-A and UV-B ranges,
                      respectively. The spectra expectedly revealed increased
                      daytime levels of stray-light-induced signals and noise
                      below atmospheric cutoff wavelengths. The influence of
                      instrument noise and stray-light-induced noise was found to
                      be insignificant for j(NO2) and rather limited for j(O1D),
                      resulting in estimated detection limits of
                      5  ×  10−7 and 1  ×  10−7 s−1,
                      respectively, derived from nighttime measurements on the
                      ground (0.3 s integration time, 10 s averages). For
                      j(O1D) the detection limit could be further reduced by
                      setting spectral actinic flux densities to zero below
                      atmospheric cutoff wavelengths. The accuracies of photolysis
                      frequencies were determined from linear regressions with
                      data from the double-monochromator reference instrument. The
                      agreement was typically within $±5 \%.$ Because
                      optical-receiver aspects are not specific for the CCD
                      spectroradiometers, they were widely excluded in this work
                      and will be treated in a separate paper, in particular with
                      regard to airborne applications.},
      cin          = {IEK-8},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-8-20101013},
      pnm          = {243 - Tropospheric trace substances and their
                      transformation processes (POF3-243)},
      pid          = {G:(DE-HGF)POF3-243},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000409039900002},
      doi          = {10.5194/amt-10-3151-2017},
      url          = {https://juser.fz-juelich.de/record/838135},
}