A numerical solution is attempted for the steady state temperature distribution in a two dimensional rectangular radiating fin with single heated footprint. The solution is presented for problems similar to spacecraft doubler plate with single heated footprint. The spacecraft thermal doublers are used to spread the localized heat dissipation by some electronic packages over large area and thus ensure the operating temperature of the package within the specified maximum temperature. The results of this analysis are presented as the design charts for the design of doubler plates in a spacecraft environment. Basically, design of doubler plate is meant to find out the required radiator area and the thickness of the plate for given heat dissipation and the maximum operating temperature of the electronic package.