Abstract: A mathematical model is presented for the local hemisphericaleffective emissivities of isothermal and non-isothermal cylindro-inner-coneswith a cone opening by application of the stokes theorem and contour inte-gration on the assumption that the emission and reflection are diffusive.Aprecise calculation is made for a blackbody.

Key words: Blackbody, Emissivity, Environmental simulation, Satellite