## 2 System Description  
Figure 1 illustrates the framework of the system. In the GLAO system, the atmospheric turbulent wavefront (light signal) enters the deformable mirror (DM) from the telescope, the DM performs closed-loop correction, and then the residual wavefront enters the MD-WFS for wavefront detection to obtain slope information (electrical signal). The slope information is transmitted to the RTC for processing, resulting in a closed-loop voltage to control the DM. The RTC is responsible for real-time processing and the Upper Computer (UPC) is responsible for monitoring. The measurement system relies on the GLAO system. The measurement system captures the MD-WFS slopes and the DM corrected voltages from the GLAO RTC. After preprocessing and pseudo-open-loop reconstruction, this pseudo-open-loop slope information is used for measuring the atmospheric turbulence's intensity and distribution. Finally, the measurement system displays the results to the GLAO UPC. Serving as the primary equipment for detecting atmospheric turbulence in the system, the parameters of MD-WFS dictate the specific characteristics of the measurement system. The quantity of sub-aperture pairs in a given direction determines the number of height layers that a measurement grid can probe. In contrast, the number of guide region pairs in a particular order determines the maximum number of measurement grids that can be constructed. The related parameters of the real-time measurement system are listed in Table 1.  
Figure 1: The framework of the real-time measurement system. The MD-WFS has a sub-aperture arrangement of 9 \(\times\) 8, with the shape of a regular hexagon. Figure 2 shows the configuration information of the MD-WFS. The diameter of the pupil plane is 0.98 m. Due to the secondary mirror obstruction in the telescope's center, the MD-WFS only has 48 effective sub-apertures. Combining two sub-apertures separated by a certain distance forms a sub-aperture pair, the basis for measuring atmospheric turbulence intensity. In this MD-WFS, we establish sub-aperture pairs using sub-apertures in the horizontal direction. All sub-apertures are taken into account to increase measurement accuracy and stability. Then, we can construct eight sub-aperture pairs with different interval sizes. An interval size of 0 is also included, corresponding to data from different guide regions within the same sub-aperture, which is used to probe near-ground turbulence. If two guide regions form a measurement grid in the horizontal direction, then eight sub-aperture pairs can probe eight different height layers. The MD-WFS features a 42\({}^{\prime\prime}\)\(\times\) 37\({}^{\prime\prime}\) field of view (FOV) and a pixel resolution of 0.6\({}^{\prime\prime}\)/Pixel. MD-WFS has a large FOV, and multiple small regions are cut out in the sub-images for different direction wavefront sensing. Each small region corresponds to an independent Shack-Hartmann wavefront sensor. Therefore, MD-WFS is equivalent to multiple independent WFS. Nine guide regions are set up in the sub-images of the MD-WFS, arranged in a rectangular pattern. A pair of guide regions at a certain angle apart in the horizontal direction form a guide region pair. A measurement grid can be obtained by combining the guide \begin{table}
\begin{tabular}{c c} \hline Telescope aperture & 0.98 m \\ Wavelength & 500 nm \\ Data frame rate & 200 Hz \\ Sub-aperture arrangement & 9 \(\times\) 8, hexagon \\ Number of effective sub-apertures & 48 \\ Pixel resolution & 0.6 arcsec/pixel \\ Field of view & 42\({}^{\prime\prime}\)\(\times\) 37\({}^{\prime\prime}\) \\ Guide regions arrangement & 3 \(\times\) 3 \\ Angle interval corresponding to the guide region pairs & [0 9 18]\({}^{\prime\prime}\) \\ Number of measured height layers & 12 \\ \hline \end{tabular}
\end{table} 
Table 1: System parameter.