Fig. 1. Lightning spectrum detected by NASA U-2 aircraft^[35]

Fig. 2. Details of three characteristic spectral lines of lightning's oxygen atom^[35-36]

Fig. 3. Polar orbital lightning imager TRMM-LIS of the United States^[41-43]

Fig. 4. GLM on the GOES-R and GOES-S satellite of the United States^[45-47]

Fig. 5. CCD sensor of the GLM on the GOES-R satellite of the United States^[48-49]

Fig. 6. Geostationary lightning imager MTG-LI of Europe^[50-51]

Fig. 7. ISUAL on the Formosat-2 satellite^[59]. (a) SP; (b) imager; (c) AP

Fig. 8. Research and development process of FY-4A lightning mapping imager

Fig. 9. Difference between ground observation and space observation of lightning. (a) Lightning observed on ground; (b) lightning observed on space

Fig. 10. Response range of the sensor used for the lightning detector

Fig. 11. Spatial resolution selection of FY-4A lightning mapping imager. (a) Lightning and background observed on space; (b) lightning detection resolution of lightning mapping imager

Fig. 12. Lightning pulse duration and the lightning detection frame period selection

Fig. 13. Comparison between lightning and sunlight background spectra^[54]

Fig. 14. Relationship between center wavelength and incident angle drift of ultra narrow band filter

Fig. 15. Test curves of center wavelength and bandwidth of ultra narrow band filter

Fig. 16. Overall technology for real-time detection of weak targets from multiple transient point sources in a complex background on space

Fig. 17. FY-4A lightning mapping imager and its installation on satellite

Fig. 18. Some application results of FY-4A lightning mapping imager^[68]

Fig. 19. Schematic diagram of polar lightning optical stereo detection on space

Fig. 20. Lightning types in low altitude, high altitude and near space