332 J. Eur. Opt. Society-Rapid Publ. 22, 32( 2026)
Figure 11. The sky incident radiation.
Figure
12. Atmospheric radiation characteristics calculation result.
Figure
13. Atmospheric radiation characteristics calculation result.
time. Using the solar altitude angle and MODTRAN, the incident solar radiation illuminance( E sun) can be calculated. Figure 10 shows the solar incident radiation at different solar altitude angles.
4.2 Modeling of sky radiation characteristics
Sky radiation is the scattered radiation of solar radiation. The sky background radiation is regarded as a hemispherical space that emits radiation outward. The sky radiation incident from different directions can be calculated using
MODTRAN [ 34 ]. Figure 11 shows the sky incident radiation at different wavelengths.
4.3 Modeling of atmospheric radiation characteristics
The atmospheric attenuation effect has a significant impact on the upward radiative transmission of the target and background. The atmosphere itself will generate infrared radiation. The total atmospheric path radiation in the detection direction [ 34 ] is shown: