Fig. 1. Interferogram nonlinear response schematic

Fig. 2. （a）The schematic diagram of nonlinear interferogram, （b）spectral out-of-band distortion due to quadratic nonlinearity

Fig. 3. Variation of phase angle of different blackbody brightness temperature responsivity

Fig. 4. Variation of blackbody spectral responsivity phase angle for 5 months in orbit

Fig. 5. Simulation of approximate linear relationship between spectral responsivity and spectral value

Fig. 6. Long-wave full-band responsivity correction coefficient of TVAC1-TVAC5 fitted value and average value

Fig. 7. The linear relationship between the target spectral value and the spectral responsivity of TVAC1-TVAC5

Fig. 8. Brightness temperature of radiometric calibration comparison before and after nonlinear correction

Fig. 9. Brightness temperature deviations comparison before and after nonlinear correction

Fig. 10. Brightness temperature standard deviation comparison before and after nonlinear correction

Fig. 11. Comparison of calibration deviations before and after nonlinear correction for all pixels in the range of 180-320 K of brightness temperature of the observation target: (a) 850 cm^-1, (b) 950 cm^-1

Fig. 12. The average deviation of calibration after nonlinear correction of all pixels in the range of 180-320 K brightness temperature of the observation target

Fig. 13. Observation target brightness temperature 280 K TVAC1-TVAC5 calibration average deviation after nonlinear correction