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Measurements of the spectral optical depth were made during
ACE-1 (Nov.-Dec. 1995) using a Total Direct Diffuse Radiometer
(TDDR) mounted in a zenith port of the NCAR C-130. The TDDR is a
shadow-band radiometer with a hemispheric field of view and 7
channels (380, 412,500,675,862,1064, and 1640 nm). Each channel
has a bandpass of approximately 10 nm. As its name implies, the
TDDR measures the total, direct, and diffuse components of the
solar radiation field from which the optical depth is
obtained. The optical depth, as a function of wavelength, can
then be inverted to derive an estimate of the column aerosol
size distribution.
[Source: NOAA]
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