# A SLR Pre-Processing Algorithm Based on Satellite Signature Effect
## 5 Conclusions  
Scientific demands of millimeter precision ranging give aggressive performance requirement to the pre-processing data algorithms for SLR system. We simulate the satellite signature effect removal process of normal point algorithm based on a revised model of satellite response, which fully takes the structural and distribution characteristics of corner reflectors into account. The simulated results show that the waveform of return signal processed by a normal point algorithm is improved by the reduction in long tail, but there remains some distortion at the front and back edge. The distribution of return signal for each observation is not stable, and the difference between the maximum and minimum of CoM for fit residuals can reach up to 3.79 mm. This means that a normal point algorithm can reduce the effect of long-term satellite signatures on observation data but cannot eliminate the systematical errors introduced by the variation of satellite signature effect for each observation.  
On this basis, a new clipping method is proposed and applied for SLR data processing of Changchun SLR station. We adopt Poisson filter and rejection of 2.5 \(\times\) RMS to reduce noise points but retain the most of returned waveform. Defining clipping location as 5.6 mm away from the mean value of the long-term fit residuals is important to select the effective returns for normal points. The experimental results illustrate that, compared to normal point algorithm, the RMS per NP for LAGEOS-1 processed by the new clipping method is reduced from 62.90 \(\pm\) 9.9 mm to 56.07 \(\pm\) 4.69 mm, and the stability of observation data is improved 53%. Both the stability of skewness and Kurtosis for LAGEOS-1 also improved. It is concluded that the clipping method can minimize both long-term and short-term satellite signature effect and improve the ranging precision and stability of SLR observation data. This study improves the satellite signature effect model. In this paper, the fluctuation of CoM value caused by satellite signature effect is simulated for the first time. By simulating the effectiveness of different clipping location, the pre-processing algorithm is successfully improved and achieved good results. This paper provides a reference for other stations to build their own data processing algorithm and further enriches the theory of system errors for SLR systems.  
Conceptualization, B.G. and N.A.; methodology, B.G.; software, C.F., X.D. and J.G.; Formal analysis, B.G. and C.F.; Project administration: R.C.P., D.A.P., X.Y. and X.D.; Data curation, B.G. and J.G. writing-original draft, B.G.; writing--review and editing, B.G. and N.A. supervision, B.G.; Funding acquisition, R.C.P., D.A.P., C.F. and N.A. All authors have read and agreed to the published version of the manuscript.  
This research was funded by National Natural Science Foundation of China No. 12073052, Jilin Province Science and technology development program No. 2020081050 GH.  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
The authors declare no conflict of interest.  
The following abbreviations are used in this manuscript:  
SLR Satellite Laser Ranging  
NP Normal Point  
CoM Centre-of-Mass  
LEHM Leading-Edge-Half-Maximum  
LAGEOS-1 LASer GEOdynamics Satellite-1  
FWHM Full Width at Half Maximum  
SPAD Single Photon Avalanche Diode