Techniques for measuring radiance in sea and air.
Measurements of scattered sunlight often employ simple radiometers that are incapable of scanning azimuth phi and zenith angle theta. Instead, they measure integral moments of the radiance. Consider a set of N + 1 meters designed to measure moments Lambda(l) through Lambda(N+1). If each meter is judiciously designed, the Lambda(j) may be processed quite simply to deduce inherent properties of the scattering medium, namely, N moments of the volume scattering function. In the optimum design, each meter has an angular response that approximates a polynomial of degree N in cos theta. The theory of these meters is based on Boltzmann's equation of radiative transfer expressed in terms of spherical harmonics, a form in which this equation is particularly simple.
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