## 6 Conclusions  
This paper presents a novel joint processing interferometric measurement method, utilizing pseudo-noise ranging clock tones for integer ambiguity resolution, aimed at enhancing the power utilization efficiency of weak downlink signals in deep space exploration. First, the fundamental principles of \(\Delta\)DOR are introduced and the error budget analysis is conducted. Then, the detailed analysis of several factors is provided: the power ratio of each signal component, the precision of the interferometric measurement time delay model, the measurement accuracy requirements, and the improvement of power utilization efficiency under typical downlink signal modulation parameter settings. On this basis, the on-orbit measured data of the Queqiao-1 lunar relay satellite and the static test data of a typical spacecraft were processed, analyzed, and verified. The results show that the interferometric measurement processing method combining pseudo-noise ranging and  
Figure 12: The coarse time delay estimation results of the two signal combinations (**upper** half) and their deviation (**lower** half).  
Figure 13: The final time delay estimation results of the two signal combinations (**upper** half) and their deviation (**lower** half).  
DOR beacons can achieve the measurement accuracy of traditional processing methods. If the modulation parameters of the downlink signal are maintained, approximately 13% of the X-band signal power can be saved, while the detection range can be increased by roughly 6.5%. If the power of other signal components remains unchanged, the power of the DOR signal can be increased by more than 100% to improve the accuracy of the interferometric measurements. Therefore, in future, deep space exploration missions where the probe-ground station distance is very far and the downlink signal is extremely weak, it may be feasible to adjust a set of DOR beacon signals to effectively improve the downlink signal power and its utilization efficiency. The PN code ranging clock tones can be comprehensively utilized to achieve interferometric measurement, improve the measurement accuracy, and increase the range of deep space exploration. Without additional design requirements for deep space transponders, the efficient tracking and measurement of deep space probes can be achieved.  
Conceptualization, W.L. and M.F.; data curation, W.L., L.C. and Y.Z.; formal analysis, L.C.; funding acquisition, W.L.; investigation, W.L., M.F., D.X. and T.R.; methodology, W.L. and M.F.; software, W.L.; validation, W.L., M.F. and T.R.; writing--original draft, W.L.; writing--review and editing, W.L., M.F. and L.C. All authors have read and agreed to the published version of the manuscript.  
This research was funded by [PERSON] of the National Key Laboratory of Science and Technology on Aerospace Flight Dynamics Foundation grant (No. KGJ6142210220106); [PERSON] of the National Key Laboratory of Science and Technology on Aerospace Flight Dynamics Foundation (No. KGJ6142210210201); [PERSON] of the open project of the Key Laboratory in Xinjiang Uygur Autonomous Region of China (No. 2023D04058).  
Not applicable.  
This study used the measured data from Chinese Deep Space Stations, but according to the copyright, we cannot afford an open dataset. But the method proposed here is general, and can be applied to process any data which have the PN Clock component and DOR tone signals.  
This study made use of data collected through the Chinese Deep Space Stations. The authors wish to thank the staff of the radio telescopes and radar team for participating in the experiments. The authors wish to thank [PERSON] from Xinjiang Observatory and [PERSON] from Beijing Aerospace Control Center for the improvement of the English in this paper.  
The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of the data; in the writing of the manuscript, or in the decision to publish the results.