# Reduction of Satellite Signature Effect in High-Accuracy Satellite Laser Ranging to Etalon
## 4 Discussion  
Based on one month of kHz SLR passes of Etalon-1 collected by the Changchun observatory, we demonstrate that the new method provides different results from the previous method. Figure 8 illustrates the processed observation data for the period from 1 January to 26 January in 2022. The RMS for each normal point processed by the new proposed algorithm is significantly reduced. In addition, the kurtosis as well as skewness for the observed distribution in actual residuals are smaller, as well. It is important to note that the noise signals originating from the tails of post-fit range residual distributions are eliminated, as a result the residual waveform, is more similar to that of a normal distribution. An improvement in the quality of the SLR data collected by the observatory has been demonstrated with the introduction of the center of mass corrections filter.  
In order to verify the applicability of this new algorithm, we also analyze Etalon-2 observation data with the same procedures, as shown in Figure 9. Based on the results of the analysis, Etalon-2 observation data processed by the new algorithm show superior accuracy and stability in comparison to Etalon-1 observation data.  
In Table 1, we summarize the statistical observations related to Etalon-1/2 processed via these two methods. Compared to the results calibrated with the normal point algorithm, the new algorithm with the center of mass corrections filter has a better performance. For Etalon-1, the average RMS per normal point (NP) is decreased from 163.7 \(\pm\) 41.8 ps to 118.2 \(\pm\) 8.94 ps while the stability of normal point is improved by 79%. As for Etalon-2, the average RMS per NP is reduced from 145.4 \(\pm\) 34.3 ps to 120 \(\pm\) 7.47 ps, while the stability of normal point is improved by 78%. Both kurtosis and skewness per NP are significantly reduced, which indicates that satellite signature effect has a minimal impact on temporal spread. It can be believed that the new processed observation data are more stable and reliable.  
Figure 7: The diagram of the new proposed SLR algorithm.  
Figure 8: Etalon-1 satellite data processing results (**a**) RMS of NPT, (**b**) skewness of NPT, (**c**) kurtosis of NPT.  
Figure 9: Etalon-2 satellite data processing results (**a**) RMS of NPT, (**b**) skewness of NPT, (**c**) kurtosis of NPT.  
As a further verification of the efficacy of the new proposed SLR processing algorithm, Etalon-1/2's external precision is calibrated using the precise satellite ephemeris SP3 of the International GNSS Service (IGS). Figure 10 illustrates the residual distribution of Etalon-1/2 computed using the two approaches outlined above.  
The calibrated results indicate that the external precision of Etalon-1 normal points processed by the new algorithm has been reduced from 8.4 cm to 7.5 cm. By introducing the center of mass corrections filter, the external precision of Etalon-1 satellite observation results has been improved by 0.9 cm. However, it was not successful on Etalon-2. RMS of the residuals obtained by the standard point algorithm for Etalon-2 normal points is 9.4 cm, while RMS of the residuals obtained by the new algorithm is 9.7 cm. A possible explanation may be the small number of Etalon satellite observation points or the long observation interval.