Fig. 1. Spaceborne environmental lidar. (a) Diagram of basic detection principle^[50]; (b) schematic of emulator

Fig. 2. Signal simulation and retrieval of ACDL HSRL. (a) Attenuated backscatter coefficient of parallel channel B_∥; (b) attenuated backscatter coefficient of perpendicular channel B_⊥; (c) attenuated backscatter coefficient of molecular channel B_m; (d) layer information; (e) backscatter coefficient β_a; (f) extinction coefficient α_a

Fig. 3. Theoretical measurement error for ACDL HSRL at 1 km. (a) Relative error of backscatter coefficient;(b) absolute error of extinction coefficient

Fig. 4. Two-way optical depths for two wavelengths simulated by spaceborne IPDA lidar forward model

Fig. 5. Global distribution of XCO₂ pseudo data simulated by spaceborne IPDA lidar inversion model

Fig. 6. Wind lidar simulation results. (a) Molecular signal distribution; (b) aerosol signal distribution; (c) signal-to-noise ratio distribution; (d) detection error ξ distribution

Fig. 7. Simulation analysis of spaceborne wind lidar. (a) Scattering signal distribution; (b) signal-to-noise ratio distribution; (c) detection error distribution

Fig. 8. Spaceborne lidar return signal simulation ^[50]. (a) Input attenuation coefficients; (b) simulated lidar signals

Fig. 9. Polarized lidar signal simulation^[50]. (a) Input optical properties of water; (b) comparison of measured and simulated signals (data above 0 m is the atmospheric signal because the shipborne lidar has a certain distance from the water surface)

Fig. 10. Simulation analysis of spaceborne lidar in case I water ^[86]. (a) Lidar return signals varying with depth; (b) effective attenuation coefficients varying with depth

Fig. 11. Influence of multiple scattering of cloud on oceanic lidar detection^[85]. (a) Water cloud echo signal with different scattering times (n is the scattering times); (b) relationship among effective attenuation coefficient error, cloud base height, and optical depth

Fig. 12. Atmospheric HSRL system. (a) Internal structure diagram; (b) optical path^[132]

Fig. 13. Track distribution of field calibration test of CALIPSO and airborne laser radar from 2006 to 2011 carried out by NASA^[93]

Fig. 14. Flight tracks of validation of ALADIN and A2D in 2018^[95]

Fig. 15. Vertical distributions of phytoplankton of the Yellow Sea and Bohai Sea at different depths. (a) K_d; (b) b_bp

Fig. 16. CALIOP detects global oceanic particulate distribution

Fig. 17. Demonstration of aerosol and cloud distribution obtained by active and passive fusion^[197]. (a) CALIPSO profile and MODIS radiation data; (b) 3D extended results

Fig. 18. Retrieval results of shallow water depth (within 40 m) in Bahamas from ICESat-2 photon data and Sentinel-2 ocean color. Water depth inversion using the same remote sensing data source was published in^[163]

Fig. 19. Shipborne oceanic HSRL system^[220]

Fig. 20. GEDI multi-beam ground detection spot distribution diagram^[223]

Fig. 21. Schematic diagram of quantum wind lidar developed by University of Science and Technology of China^[229] (TA:tunable attenuator; WDM: wavelength division multiplexer; L: collimation mirror; TDFA: thulium-doped fiber amplifier; TEC: thermo electric cooler; MCS: multi-channel sample module)