Correction of detector nonlinearity in Fourier transform spectroscopy with a low-temperature blackbody

The nonlinearity of a mercury cadmium telluride photoconductive detector, an integral part of a modified commercial interferometer used for airborne research, has been analyzed and evaluated against a number of correction schemes. A high-quality blackbody with accurate temperature control has been used as a stable and well-characterized radiation source. The detector nonlinearity was established as a function of scene temperature between 194 and 263 K. Second- and third-order corrections to the measured interferogram have been tested by analyzing the measured signal both within and outside the spectral response region of the detector. A combined correction scheme is proposed that best represents the real nonlinear response of the detector.