Abstract: An optical pyrometer for use with jet engines is characterized by the use of three spectral areas or bands in a temperature computation. A target temperature is optically distinguished from background radiation by dividing a received optical beam into three spectral components which are comprised of emitted and reflected radiation. A controller computes the measured power in each band as a function of the emitted power by the target and a ratio of reflected power in adjacent bands to yield signals of reflection corrected radiation. These are used with the reflected power ratios to determine values of temperature in adjacent bands. The difference between these computed temperatures is iteratively adjusted until the difference therebetween is approximately equal to a preselected value.