One of the critical questions regarding radiation thermometers
is how to obtain the true temperature of an emitting opaque body with
an unknown emissivity and with unknown circumferential radiations. We
suggest that two enclosed chambers with given temperatures and emissivities
be used to cover part of the area of the emitting body. By use of
two simultaneous radiothermometer readings, both the true temperature
and the emissivity of the graybody can be calculated.