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Instrument: CZCS : Coastal Zone Color Scanner
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Description
The Coastal Zone Color Scanner Experiment (CZCS) onboard the Nimbus-7
spacecraft was designed to map chlorophyll concentration in water,
sediment distribution, gelbstoffe concentrations as a salinity
indicator, and temperature of coastal waters and ocean
currents. Reflected solar energy was measured in six channels to sense
color caused by absorption due to chlorophyll, sediments, and
gelbstoffe in coastal waters. The CZCS was a multi-channel scanning
radiometer which used a rotating plane mirror at a 45 degree angle to
the optic axis of a Cassegran telescope. The mirror scanned 360
degrees but only the 80 degrees of data centered on nadir were
collected for ocean color measurements. The instrument viewed deep
space and calibration sources during the remainder of the scan. The
incoming radiation was collected by the telescope and divided into two
streams by a dichroic beam splitter. One stream was transmitted to a
field stop that was also the entrance aperature of a small
polychromator. The radiance that entered the polychromator was
seperated and re-imaged in five wavelengths on five silicon detectors
in the focal plane of the polychromator. The other stream was directed
to a cooled mercury cadmium telluride detector in the thermal region
(10.5-12.5 micrometer). A radiative cooler was used to cool the
thermal detector. To avoid sun glint, the scanner mirror was tilted
about the sensor pitch axis on command so that the line of sight of
the sensor was moved in 2-deg increments up to 20 deg with respect to
the nadir. Spectral bands at 0.443 and 0.670 micrometers centered on
the most intense absorption bands of chlorophyll, while the band at
0.550 micrometers centered on the "hinge point," the wavelength of
minimum absorption. Ratios of measured energies in these channels were
shown to closely parallel surface chlorophyll concentrations. Data
from the scanning radiometer were processed, with algorithms developed
from the field experiment data, to produce maps of chlorophyll
absorption. The temperatures of coastal waters and ocean currents were
measured in a spectral band centered at 11.5 micrometers. Observations
were made also in two other spectral bands, 0.520 micrometers for
chlorophyll correlation and 0.750 micrometers for surface vegetation.
The scan width was 1556 km centered on nadir and the ground resolution
was 0.825 km at nadir. For a more detailed description, see Section 2
in "The Nimbus 7 Users' Guide" (TRF B30045), available from
NSSDC. Data are archived at SDSD. Since mid-1984, the instrument
experienced occasional start-up problems. It was finally turned off in
December 1986.

Online Resources
http://oceancolor.gsfc.nasa.gov/CZCS/
http://en.wikipedia.org/wiki/Coastal_Zone_Color_Scanner