## 3 XNAV for Spacecraft in Formation
### Procedure of Pulsar-Based Navigation Using Pulse Phase Delay
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\begin{tabular}{c c c} \hline \hline
**Method** & **RMS Error [cycle]** & **Mean CPU Time Cost [s]** \\ \hline Proposed direct estimation method & 1.83 \(\times\) 10\({}^{-3}\) & 0.0092 \\ Respective estimation method & 1.71 \(\times\) 10\({}^{-3}\) & 0.0146 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: RMS error and mean CPU time cost for different pulse phase delay estimation methods. [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON] [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; et al. TanDEM-X: 10 Years of Formation Flying Bistatic SAR Interferometry. _IEEE J. Sel. Top. Appl. Earth Obs. Remote Sens._**2021**, _14_, 3546-3565. [CrossRef]
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