An.exact energy balance is conducted on a spherical thermal radiation detector. The thermal radiation heat transfer to the spherical detector is computed utilizing models of the surface optical properties that vary with surface temperature, wavelength and angle of incidence. Studies have been conducted to analyze the detector under the assumptions of gray, diffuse radiation and constant thermophysical properties. The previous studies have been helpful in developing the theory of operation of such detectors. However, the extreme accuracy required in the experiment necessitates an assessment of the effects of non-gray and non-diffuse radiation and surfaces on the detector behavior.

The effects of non-gray and non-diffuse radiation and surfaces on the detector behavior is assessed by non-dimensionaliz;ing the energy balance. Three correction factors are developed to describe the behavior of tl;le three components of radiant flux incident to the detector. The correction factors are developed to equal unity for a perfectly diffuse gray radiation and surfaces.

The realistic model of the surface optical properties for an aluminum detector consists of independent models of emittance, long wavelength absorptance; and solar absorptance. The emittance as a function of temperature was determined from the Davisson, and Weeks analytical expression. The long wavelength absorptance as a function of incident angle, wavelength, and temperature was determined by utilizing Fresnel’s equations in conjunction with the Drude-Zener theory to obtain the complex index of refraction. The solar absorptance as a function of incident angle was determined from the experimental results of M. G. Hoke.

The results of the analysis reveals that the earth radiation field is not diffuse. The polar ice caps were found to reflect incident solar radiant flux specularly to the spherical detector. The absorptance of the earth-'reflected solar component as a function of incident angle is important and responded to the specularly reflected solar flux as the detector passed over the ice caps. The model for the long wavelength absorptance of the aluminum detector is incorrect. The model produced values of absorptance one-third of the value of emittance. The temperature dependence of the emittance is found to be significant in the detector behavior. The results of the non-dimensional correction factors are found to be inconclusive. The error in the long wavelength absorptance distorts the correction factors and renders them useless.