Abstract: An apparatus and process for a temperature measuring pyrometer probe that measures gas temperatures above the melting point of conventional thermocouple material. The apparatus is used to calculate radiation heat losses and compensate for pneumatic cooling from the thermocouple junction of the pyrometer probe. The pyrometer probe has an inner hollow body which defines an inner chamber. The inner hollow body has an open end and the inner chamber is in communication with ambient gas surrounding the pyrometer probe. The inner hollow body is mounted within an outer hollow body and such mounting defines cooling channels. The cooling channels accommodate fluid flow which cools the inner hollow body. The ambient gas is directed into a converging-diverging nozzle, mounted within the inner hollow body, toward a thermocouple junction. The converging-diverging nozzle has a wall suction channel through which a boundary layer of the ambient gas is drawn away from the thermocouple junction.