Precise calculation of the integrated emissivity of a multiple-celled large-area blackbody source

Precise calculation of integrated emissivity of a multiple-celled large-area blackbody source has been a very complex problem. The kernel of the problem is to compute radiant exchange between the sub-cavities and a non-coaxial detector. On the basis of the method for computing radiant exchange between a cavity and a coaxial detector, a method has been developed in this paper to calculate the noncoaxial radiant exchange by which the integrated emissivity of the multiple-celled large-area blackbody source was computed accurately. The emitting area of the blackbody is of 200x200 ma that includes more than 1600 sub-cavities.