MISR's Spectral (Color) Coverage
What are the colors seen by MISR?
In each of the nine MISR cameras, images will be obtained in four spectral
bands, i.e. in four different colors, one each for blue, green, red, and
near-infrared. The center wavelength of each of these bands is 446, 558, 672,
and 867 nanometers respectively.
Why are these particular color bands chosen?
The bands in the red and near-infrared (670 and 865 nm) provide vegetated
surface identification owing to their positioning on either side of the "red
edge" marking the transition between chlorophyll absorption and cellulose
reflectance. These two bands are also useful for marine aerosol studies since
water is nearly black at these wavelengths.
The green band at 555 nm is near the peak of the solar spectrum, and thus
will be given high weight in studies to estimate broadband reflecting properties
(albedos).
A wide range of spectral coverage is essential to using the wavelength
dependence of aerosol opacity to estimate the size distribution of the aerosol
particulates. Thus the blue channel at 443 nm provides nearly a twofold change
in particle size-to-wavelength ratio relative to the near-infrared channel at
865 nm.
The four bands also comprise an effective set for ocean color studies at low
ocean pigment concentrations.
Overall, the MISR wavelengths have been selected to avoid known ranges of
strong atmospheric gas absorption and solar Fraunhofer lines. These absorption
effects would complicate the retrieval of aerosol information, and make the
instrument more sensitive to changes in spectral response that might occur over
time during the life of the mission.
|
