One element of a multi-year calibration program between the National Institute of Standards and Technology (NIST) and the National Aeronautical and Space Administration (NASA) Earth Observing System (EOS) Project Science Office has been the development and deployment of a portable transfer radiometer for verifying the thermal-infrared scales being used for flight-instrument pre-launch calibration. This instrument, the Thermal-infrared Transfer Radiometer (TXR), has been built and the first deployment test was completed successfully, as has been reported previously.1 The 5 µm channel, based on a photovoltaic Indium Antimonide (InSb) detector, so far has demonstrated a pre-deployment to post-deployment uncorrected repeatability of better than 30 mK to 60 mK, which is sufficient to enable intercomparisons at useful uncertainty levels for the EOS program. However, the 10 µm channel, based on a photovoltaic Mercury Cadmium Telluride (MCT) detector, shows uncorrected repeatability levels of about 0.5 K, the response changes being induced by cryocycling. This paper describes the technique that has been developed for correcting these changes. A portable black body check-source travels with the TXR that is used to verify the repeatability during the deployment trip. The check-source, in combination with the stability of the 5 µm channel, is used to restore a higher accuracy scale to the 10 µm channel than would otherwise be possible. This application is analogous to the use of an on-orbit calibration source to check for and correct for launch-induced or degradation-induced flight instrument detector response changes.