Fig. 1. Distribution and central height changes of sodium atom^[3]. (a) Distribution of sodium atom changes over time; (b) central height of sodium layer changes over time

Fig. 2. Energy level structure diagram of sodium atom^[4]

Fig. 3. Dye laser sodium beacon in MIT Lincoln laboratory^[6]. (a) Schematic diagram of atmospheric turbulence detection using sodium beacons; (b) field experimental equipment located at Baisha shooting range

Fig. 4. Correction effects of tilt and higher-order aberrations^[10]. (a) Image of tilt aberration corrected only; (b) image of tilt and higher-order aberrations corrected using natural beacons; (c) image of high-order aberrations corrected using sodium beacon

Fig. 5. The first field experiment of Keck II sodium beacon AO^[13]. (a) Keck II telescope and sodium beacon laser; (b) sodium beacon sub-spot image observed on the ACAM camera

Fig. 6. Sodium beacon excited at Japan RIKEN Institute of Technology^[17]

Fig. 7. 4LGSF outdoor light diagram^[23]

Fig. 8. Sodium beacon produced by Xinglong Lake field experiment^[30]

Fig. 9. Sodium beacon return light intensity detection experimental device^[33]

Fig. 10. Design and experimental scene of the sodium pool at the National University of Defense Technology^[34]. (a) Schematic diagram of the sodium pool experimental system; (b) sodium pool excitation experimental scene

Fig. 11. Schematic diagram of the new AO with sodium beacon^[46]. (a) MCAO; (b) LTAO; (c) GLAO; (d) MOAO

Fig. 12. Relationship between sodium beacon return light intensity and geomagnetic field^[62]. (a) Different power densities and different laser types; (b) sodium beacon light return efficiency at different angles between the beam direction and the geomagnetic field

Fig. 13. Evolution of the center frequency of sodium atom absorption after the laser interacts with sodium atoms for different times^[64]

Fig. 14. Village system pre-calibrates the optical path and experimental results^[71]. (a) Experimental optical path; (b) imaging results of HIP9507 after pre-correction by sodium guide star

Fig. 15. Measurement of magnetic field strength using sodium beacon^[79]. (a) Kuiper telescope receiving sodium beacon experiment; (b) signal strength of sodium beacons at different scanning frequencies

Fig. 16. Variation of sodium D2 absorption spectrum with wind speed and temperature^[80]. (a) Sodium D2 absorption spectrum at a wind speed of 0 m/s and different temperatures; (b) sodium D2 absorption spectrum at a temperature of 200 K and different wind speeds

Fig. 17. Kuiper telescope daytime sodium beacon adaptive optics system experimental field field^[86]. (a) Kuiper telescope observing sodium beacon during day and night; (b) sodium beacon observed at 7∶04 AM, exposure time is 8 s, each pixel size is 2.5″

Fig. 18. Layout and observation equipment of the sodium beacon laser communication system^[90-92]. (a) Sodium beacon laser communication layout; (b) 40 cm aperture observation telescope, DLR-OTA is used to observe sodium beacons, and ESO-OTA is used to observe natural beacon; (c) sodium beacon emission system