Fig. 1. Process of samples filtering between HIRAS-II and MERSI-LL

Fig. 2. Demonstration of coordinate systems. (a) ECEF (black), LLA (blue), ENU (red); (b) ENU and local spherical coordinate (green)

Fig. 3. Illustration of SAT and LOS vectors in ECEF coordinate

Fig. 4. Observation of HIRAS-II and MERSI-LL on UTC202112210050

Fig. 5. Shift along longitude of HIRAS-II FOV within band 3.8 μm of MERSI-LL. (a) Randiance brightness temperature of target; (b) Absolute bias percent of brightness temperature vs standard target; (c) Standard bias of brightness temperature vs standard target; (d) Ratio of standard bias and mean bias of standard target

Fig. 6. Relative uncertainty of background brightness temperature due to FOV shift

Fig. 7. Brightness temperature bias and uncertainty of observation geometry

Fig. 8. Collocation of HIRAS-II spectrum and MERSI-LL spectrum response function

Fig. 9. Change of spectrum equivalent radiance brightness temperature after expanding spectrum response function

Fig. 10. The uncertainty of spectrum equivalent radiance brightness temperature due to spectrum response function