![]() The Deep Space Network (DSN) developed the capability for VLBI measurement, and both the implementation performance and importance to flight projects have evolved over the past several decades. Taking planet orbit insertion maneuver as a typical scenario, DeltaDOR measurements could ensure more reliability and accuracy in orbit determination than only relying on conventional ranging and Doppler data. While DeltaDOR is a technique that is highly efficient in determining spacecraft angular position in the plane of sky, it could be used in conjunction with conventional Doppler and ranging data to improve spacecraft navigation. Conventional earth-based tracking technique, ranging and Doppler could precisely measure the distance and velocity along the line of sight between the spacecraft and station however, they suffered from a poorer ability to take angular measurement. The year 1977 is a keystone in DeltaDOR history, a proposed system that featured a custom signal generator onboard was published, the spacecraft could produce a series of tones for differential one-way ranging. Very-Long-Baseline Interferometry (VLBI) was firstly used in radio astronomy, and since the 1970s, it has been introduced in deep spacecraft navigation by differential measurement of angular nearly calibration quasar, which is known as Delta-Differential One-Way Ranging (DeltaDOR). All the baselines are induced to evaluate the accuracy of the spacecraft orbit determined and predicted by CLTC, and the DeltaDOR residuals have a root-mean-square (RMS) better than 0.5 ns (the goal is 1 ns), which could enhance the confidence of the orbit accuracy and the effectiveness of control parameters during critical orbit operation. Observables from CLTC and ESOC are consistent with each other, and the difference in observables is in the order of tens of ps. Results of the cross-support interferometry tracking activities are also analyzed. This paper discusses the new method and algorithm adopted in joint cross support, especially for spacecraft tone signal processing and clock estimation when correlating with the data of two stations from different agencies. Cross-support interferometry is a new challenge to CLTC, as the correlator for routine DeltaDOR measurements do not fit for cross support, because of observable definition, blind station clock searching, and so on. In China Mars mission Tianwen-1, formal joint cross-support interferometry tracking between China Satellite Launch and TT&C General (CLTC) and European Space Operations Center (ESOC) under commercial contract was conducted around the critical stages of the mission, such as Mars orbit insertion. Delta-Differential One-Way Ranging (DeltaDOR) is widely used in deep spacecraft navigation, and cross support could enhance navigation accuracy with more interferometry baselines and longer baseline. ![]()
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