## 4 Conclusions  
In this paper, the KPOD for Swarm and GRACE-FO satellites was carried out simultaneously for a total of 14 days from DOY 152 to 165 in 2021 with the same processing strategy based on an undifferenced IF linear combination and a least squares batch processing method. To suppress the jumping phenomenon of the kinematic orbit and improve the accuracy of the final solution, RDPOD was performed, along with KPOD, and the calculated reduced dynamic orbit was used as the benchmark for quality control of the kinematic orbit. The accuracy of the results was evaluated by three approaches: residual analysis of phase observations, SLR validation, and comparison with a precise ephemeris. The following conclusions were obtained:  
1. The residuals of phase observations for Swarm and GRACE-FO satellites show that the models, data sets, and processing strategies are reasonable, and the orbit determination is stable. 2. According to the results of SLR validation, the accuracy of the kinematic orbit and the reduced dynamic orbit both achieved the centimeter-level. The accuracy of the kinematic orbit and the reduced dynamic orbit of Swarm satellites is better than 4 cm. The accuracy of the kinematic orbit of GRACE-FO satellites is better than 4 cm, and the accuracy of their reduced dynamic orbit is better than 2 cm. 3. After quality control for the kinematic orbit, the jumping phenomenon in the kinematic orbit was alleviated. By comparing with the precise ephemeris, the kinematic \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Satellite** & **Groups** & \begin{tabular}{c} **3D-RMS** \\ **(cm)** \\ \end{tabular} & \begin{tabular}{c} **R-RMS** \\ **(cm)** \\ \end{tabular} & \begin{tabular}{c} **T-RMS** \\ **(cm)** \\ \end{tabular} & \
\begin{tabular}{c} **N-RMS** \\ **(cm)** \\ \end{tabular} &
\begin{tabular}{c} **Improvement** \\ \end{tabular} \\ \hline Swarm-A & Group 1 & 3.53 & 3.30 & 3.97 & 3.28 & \\  & Group 2 & 3.57 & 3.39 & 3.99 & 3.29 & 1.12\% \\ \hline Swarm-B & Group 1 & 4.03 & 3.46 & 4.39 & 4.18 & \\  & Group 2 & 4.11 & 3.60 & 4.48 & 4.20 & 1.95\% \\ \hline Swarm-C & Group 1 & 3.52 & 3.27 & 3.85 & 3.41 & 2.49\% \\  & Group 2 & 3.61 & 3.42 & 3.92 & 3.45 & 2.49\% \\ \hline GRACE-C & Group 1 & 2.39 & 2.81 & 2.56 & 1.63 & \\  & Group 2 & 2.43 & 2.90 & 2.58 & 1.64 & 1.65\% \\ \hline GRACE-D & Group 1 & 3.60 & 4.06 & 3.57 & 3.12 & 6.98\% \\  & Group 2 & 3.87 & 4.56 & 3.74 & 3.19 & 6.98\% \\ \hline \hline \end{tabular}
\end{table} 
Table 5: RMS with different groups comparing kinematic orbit and reference orbit. orbit accuracy was improved by 2.49% for Swarm-C and 6.98 for GRACE-D after the quality control. Conceptualization, S.J. and P.L. ; methodology, P.L. ; software, P.L. ; validation, S.J., P.L. and Q.S. ; formal analysis, P.L. ; investigation, S.J. and P.L. ; data curation, P.L. ; writing--original draft preparation, S.J. and P.L. ; writing--review and editing, S.J. and Q.S. ; visualization, S.J. ; supervision, S.J. ; project administration, S.J. ; funding acquisition, S.J. All authors have read and agreed to the published version of the manuscript. This research was supported by the Shanghai Leading Talent Project, Grant Number: E056061 and the Jiangsu Province Distinguished Professor Project, Grant Number: R2018T20. The dual-frequency GPS observation data and precise dynamic orbit of Swarm satellites used in this paper can be downloaded from [[http://swarm-disse.oe.esa.int](http://swarm-disse.oe.esa.int)]([http://swarm-disse.oe.esa.int](http://swarm-disse.oe.esa.int)) (accessed on 1 October 2021). The dual-frequency GPS observation data and precise orbit of GRACE-FO satellites used in this paper can also be downloaded from [[ftp://isdcftp.gfz-postda.m.de/grace-fo/](ftp://isdcftp.gfz-postda.m.de/grace-fo/)]([ftp://isdcftp.gfz-postda.m.de/grace-fo/](ftp://isdcftp.gfz-postda.m.de/grace-fo/)) (accessed on 1 October 2021).