Fig. 1. Schematic diagram of the imager's on-star calibration

Fig. 2. Incident envelope of sunlight throughout the year

Fig. 3. Schematic diagram of a diffuse plate with sunlight incident

Fig. 4. Schematic diagram of the outfield scaler solar observation system

Fig. 5. Solar irradiance spectra (Thuillier2002)

Fig. 6. Diffuse plate radiant brightness varies with air quality

Fig. 7. Atmospheric vertical optical depth obtained from diffuse plate exit radiance brightness

Fig. 8. BTDF spectral distribution of diffuse plate

Fig. 9. BTDF of diffuse plate with solar pitch angle

Fig. 10. BTDF of diffuse plate with solar horizontal angle

Fig. 11. 2D BTDF of diffuse plate with solar incident angle