China’s Tianwen-1 probe orbiting Mars provides necessary conditions for Mars-to-Earth Mars radio occultation observation, and can effectively support the exploration of Mars atmosphere and ionosphere retrieval. In this paper, the first domestic Mars radio occultation observation experiment based on Tianwen-1 was introduced. Firstly, Tianwen-1 was used to forecast the orbit and the occultation observation arc of the ground deep space station. Then, deep space stations were organized to observe the entire process of Tianwen-1 Mars occultation, and the original downlink signals of the probe were sampled and recorded. Finally, the self-developed deep space open-loop measurement software was used to process and analyze the downlink signals of Tianwen-1, to extract the radio occultation features of Mars. The results show that the amplitude diffraction speckles and frequency warping features in the signal were successfully extracted, which confirms that the Mars-to-Earth Mars radio occultation event has been effectively observed, and important technical experience and measurement data have been accumulated for subsequent scientific research on Mars atmospheric exploration based on Tianwen-1.

Precision orbit determination of Tianwen-1 using one-way Doppler is a first trial in deep space exploration of China. In this paper, a method of orbit determination with one-way Doppler is proposed. Firstly, the observation model of one-way Doppler is established and the theoretical error is analyzed. Secondly, the orbit determination of Tianwen-1 is carried out using one-way Doppler during the relay orbit phase. The orbital accuracy is evaluated in two ways, the first one is orbital comparison with precision orbit determined using UXB and VLBI, the second one is overlap comparison. The results show that the instability of ultra-stable oscillator and phase scintillation error are the main error sources that affect the accuracy of one-way Doppler measurement. The orbital accuracy can be better than 1 km using only one-way Doppler during the relay phase, and can provide important support for China ’s future deep space exploration missions.

全相位快速傅里叶变换(all phase Fast Fourier Transform,apFFT)相位一致性特点使正弦信号相位估计不受频率估计影响,但由于频谱泄露和栅栏效应,apFFT相位估计性能受信号频率位置影响.针对该问题,提出了一种基于高精度频率估计和补偿的apFFT相位估计方法.首先,对信号进行高精度频率估计,并以此对信号进行频移补偿,然后对补偿信号进行apFFT,最后求解信号相位.蒙特卡洛仿真结果表明:所提算法的相位估计性能不受信号频率位置影响,相位估计误差性能与理论值一致,受两参数克拉美罗界(CRLB2)约束,约为1.1582倍的CRLB2;相位估计性能和抗噪声能力明显优于经典apFFT算法和其他对比算法.更进一步,利用我国首次火星探测器TW-1(天问一号)近火捕获段干涉测量数据进行算法验证,结果表明:相位估计精度约4 mrad,干涉测量时延估计精度约50 ps.

Flying on the mission orbit at the Earth-Moon L2, the Chang'e-4 relay sattellite carried out the experiment of regenerative pseudo-random code ranging, during which the regenerative pseudo-random code ranging and the sidetones ranging were both utilized. The regenerative pseudo-random code ranging data and the side tone ranging data of the Chang’E 4 relay satellite, which are flying on the mission orbit at the Earth-Moon L2 libration point, are used to evaluate their orbit determination accuracies. The results show that the RMS of the regenerative pseudo-random code ranging data is one order of magnitude better than that of the sidetones ranging data, and the orbit determination and prediction accuracy of the regenerative pseudo random code ranging data is twice as good as that of the side tone ranging data. This is a reliable reference for the application of regenerative pseudo-random code ranging in the future Chinese deep space exploration missions.

According to the interferometric observation data of Jiamusi deep space station and Kashi deep space station of China deep space network during the mission of Chang'E-4 prober, the orbit determination accuracy of real-time data and post-correction data respectively combined with the USB data is analyzed. The difference between the Earth Moon transfer section and the precise orbit is 100 meters, and the difference between the ring moon section and the precise ephemeris is 10 meters. At the same time, the influences of VLBI data weight setting on the orbit accuracy is analyzed. In view of theChina deep space network in subsequent deep space missions such as Chang’E 5, a time-sharing acquisition mode is proposed to reduce the amount of VLBI data. The influence of this mode on orbit accuracy is analyzed by using the measured VLBI data of Chang’E 4 prober. The results show that the real-time data accuracy of China’s deep space network VLBI data has reached the accuracy of post-correction data, which can support the follow-up deep space exploration tasks in China. At the same time, for 2 to 3 hours per day of common viewing time of two stations, in the time-sharing acquisition mode, the total 20 minutes per day data and 1 minute acquisition step can ensure that the orbit accuracy does not decrease.

低轨非合作空间目标的测定轨对于地面重要目标或区域的空间态势感知、安全防卫具有十分重要的作用.地基无线电测量方式是对低轨非合作目标最有效的监测手段之一,但其面临难快速跟踪、难精确测量、难精密定轨等问题,开展实际低轨非合作目标的实测验证试验,将对关键技术验证与性能评估具有重要意义.首先,介绍了基于连线干涉测量(CEI)系统对低轨非合作目标的跟踪试验情况;然后,采集与记录目标外测信号;接着,通过事后信号处理方式,获取了非合作卫星的干涉测量时延观测量、单向开环测速观测量.在有效信号带宽300kHz条件下,干涉测量时延精度为30ns,多普勒频率测量精度为50mHz;最后,通过单基线时延参与定轨验证,成功实现了对于低轨非合作目标从跟踪、测量到定轨的全链条、全系统验证.

针对嫦娥四号着陆器环月飞行阶段的轨道,开展基于多普勒测量数据的精密轨道计算与精度分析.首先给出了多普勒测量数据的精确观测建模方法.然后,从着陆器姿控力影响,重叠弧段轨道比较,以及独立轨道比较几个方面开展计算与分析,结果表明:姿控喷气会对探测器产生细微的加速度,对轨道计算产生20～50 m的影响;通过重叠弧段的比较,稳定飞行阶段多普勒数据独立解算轨道的精度优于30 m;与测距与VLBI测量联合解算轨道的比较,轨道之间的差异小于50 m.

针对航天器未搭载干涉测量信标机的情况,提出了一种基于通用下行信号相关处理的干涉测量方法.首先分析了通用下行信号相关处理中载波重建、整周模糊解算和系统时延偏差估计等技术;然后,结合试验,针对某地球同步卫星下行信号特点,提出了一种递进解模糊的载波提取方法;最后,对同步卫星实测数据进行了处理,得到了1.03 ps量级的时延估计精度,验证了所提方法的有效性.

A radio interferometry method is proposed to resolve the problems of the process of weak spacecraft signal received in deep space exploration. Firstly，based on the analysis of the original wavelet correlation filter，an improved one is proposed which contains shift correlation，the processing order from higher scale to lower one and the threshold filtering of the highest scale coefficients. Secondly，the wide band signal model in deep space exploration is analyzed and constructed，and the radio interferometry scheme based on wavelet correlation filter is provided. Finally，results of Monte Carlo simulation and data processing for some GEO satellite measured signal prove a better performance of the interferometry measurement，and the group delay accuracy of the GEO satellite is improved by 10%.

An open loop velocity measurement scheme is proposed for the high accuracy orbit measurement mission of deep space probes. Firstly,deep space probe's downlink signal is sampled and recorded by narrow band model. Then,the probe's carrier signal is processed to extract carrier frequency based on the combining signal processing method,which contains FFT,CZT and local re-construction algorithms. Then,the probe's Doppler frequency is obtained and Doppler frequency's random noise level is estimated. Finally,thethe Doppler frequency obtained by the proposed method is compared with the Doppler frequency based on the deep space station's baseband velocity measurement and the accumulation carrier phase velocity measurement. The three types of Doppler frequency are utilized for the input observations of orbit determination system to evaluate the absolute accuracy of the three types of Doppler frequency. The real signal processing and analysis of the on-orbit CE-4 relay satellite shows that, the Doppler frequency accuracy in this paper is at the level of 10 mHz,which is better than the Doppler frequency based on the deep space station's baseband velocity measurement and the accumulation carrier phase velocity measurement. The probe high accuracy orbit determination results show thatthe velocity measurement absolute accuracy in this paper is at the level of 0.2 mm/s. The effectiveness of the open loop measurement technology is successfully evaluated for China's future deep space missions.

The orbit determination of lunar probes is the basis of lunar exploration. With the development of deep space TT&C (Tracking, Telemetry and Command systems) in China, the technology of orbit determination has made rapid progress driven by the lunar exploration mission. The space-time reference and dynamic mode are presented for the development of orbit determination. Based on this, the orbit determination performance and precision of lunar probes are continuously improved in China, which is a good reference for lunar exploration mission for now and future.

角位置是深空探测航天器导航定位的重要观测量信息,相对于获取航天器距离、速度信息的统一载波测量体制,甚长基线干涉测量(Very Long Baseline Interferometry,VLBI)技术的原始数据量呈几何式增长,海量数据的实时、准实时处理对航天器高精度导航定位提出了新的挑战.依托中国深空网干涉测量中心,论述了基于高性能集群平台环境的航天器干涉测角数据相关处理系统的设计实现,并利用探月工程的实测数据进行了验证分析.分析结论对推进我国深空网干涉测量信号处理中心建设、优化相关处理系统资源配置具有一定的参考价值.

针对深空差分干涉测量(DOR)信号受数传副瓣信号干扰问题,首次研究了数传副瓣信号(泄露频谱)的干涉测量,建立了数传副瓣信号干涉测量优化模型,并利用嫦娥三号着陆器实测数据验证比对了数传干涉时延与DOR干涉时延.实验结果表明,干涉带宽相仿条件下,数传信号干涉时延随机误差约0.02 ns(STD),优于DOR干涉时延0.17 ns(STD)的随机误差;利用射电源差分观测后,DOR干涉时延与数传干涉时延基本吻合;以干涉相时延为基准,数传干涉时延的波动误差约为0.14 ns(STD),稳定性优于波动误差约为0.46 ns(STD)的DOR干涉时延.该结论对嫦娥五号、载人登月等任务中下行数传信号阶段提高干涉测量精度、火星探测任务中DOR信号与数传信号分时工作模式下增加干涉测量覆盖弧段具有直接的工程价值.

Limited by the poor observation geometry,a long-term joint tracking data from the ground-based USB/UXB and the astronomical VLBI is required to get the accurate orbit of spacecraft located at the Earth-Moon L2 Libration point. A dual-station tracking mode is proposed to obtain two-way and three-way Ranging and VLBI tracking data to solve the precision orbit. Taking the "Magpie Bridge" satellite as the analysis object,the tracking ability of Chinese deep space network is analyzed first. Then the accuracy of orbit determination with different observation combination is simulated. The results show that under the common-view constraint,the deep-space stations can track Magpie Bridge more than 5 hours per day. To determine the orbit with tracking data longer than 6h,it is better to estimate the systematic bias of ranging data. Once the tracking arc reaches more than 2 days,the solar radiation pressure is expectedto achieve an orbital accuracy better than 100 meters.

The very long baseline interferometry (VLBI) in China Deep Space Net (CDSN) mainly uses the classical model for tropospheric delay modification in real-time processing, while the measuring accuracy is constrained by the model performance. In view of this problem, an accurate regional tropospheric delay model is constructed. Firstly, the correction factor of Saastamoinen zenith tropospheric delay is determined by comparison of measured and estimated value, which leads to the zenith delay estimation bias reducing to about 0.9 ps from 1.24 ns. Secondly, in order to overcome the restriction of meteorological data, the UNB3m model with height correction is introduced to construct reginal atmospheric parameter estimation model, and results show that the estimation bias of atmospheric pressure, temperature and vapor pressure is about 3.9 mbar, 6.7 K, 0.63 mbar, respectively, moreover, the difference of zenith delay is about 14 ps when the measured and modeled meteorological data are as input, which enhances the real-time performance of zenith delay estimation. Finally, the characteristics of Niell mapping function are analyzed and the factor a in dry function is confirmed as the key parameter, whose optimal value is obtained by least-square processing. The measured data processing results show that the tropospheric delay estimation bias is about 0.3 ns when the elevation angle is 10°, which decreases nearly an order compared with the original model. Furthermore, the orbit determination error of Chang’E-4 detector is basically identical when using measured and the proposed tropospheric delay model, both results are significantly better than that of the original model. The regional model proposed here is of meteorological data independence and of high accuracy, which improves the support ability of VLBI system in CDSN for real-time orbit determination.

在嫦娥四号中继星任务期间某次干涉测量标校射电源观测无效、微卫星轨控后预报星历无法提供精确时延模型的背景下,提出了一种为微卫星轨控后轨道确定提供辅助约束测量信息的方法.该方法通过迭代相关处理修正时延模型,解决了轨控后微卫星预报星历不准的难题;利用中继星观测估计系统时延并修正微卫星干涉测量观测量,得到了实时条件下微卫星干涉测量观测信息,与事后相关处理结果的偏差约为4.2ns(约1.2m).进一步分析了相对干涉测量中的误差因素,结果表明相对干涉测量的随机误差约2ns,与事后相关处理精度相当.最后,给出了应用于辅助探测器轨道确定的相对干涉测量数据处理方案,为后续相关背景下的干涉测量提供参考.

中国深空探测网(CDSN)干涉测量系统目前由佳木斯深空站(JM01)、喀什深空站(KS01)、纳米比亚深空天线(NB01)和南美深空站(NM01)及北京相关处理中心组成,系统最长基线达到12000km.首先以嫦娥三号着陆器、嫦娥四号中继星和火星为目标,分析CDSN干涉测量系统的覆盖性.结果表明在统计时段内,NB01和NM01的建成将系统单站观测弧段及干涉测量观测弧段均提高一倍以上,显著增强了系统的定轨支持能力.然后利用嫦娥三号着陆器开展干涉测量观测试验.数据处理结果表明,干涉测量时延随机误差达到0.2ns,其中KS01-NM01基线的时延随机精度接近0.1ns,相应测角精度约为1.2nrad;KS01-NB01-NM01的闭合时延平均值约为0.1ns,显示了CDSN干涉测量系统具备较好的系统误差性能.最后分析CDSN干涉测量系统的限制因素及后续工作方向.

The construction of China's deep space network supports China's deep space missions,such as explorations of Lunar,Mars,Small planets,Jupiter,and etc. To validate China's deep space network performance and obtain the radio measurement raw data,dozens of radio open loop measurement experiments of Juno which is one of Jupiter's probe on orbit were accomplished. These open loop measurement experiments are the first time conducted by the China's deep space stations tracking a in-orbit probe in Earth-Jupiter distance. VLBI terminate sampling and recording facilities were utilized to record Juno's raw carrier signal,which was processed to extract Doppler frequency between Juno and the deep space station. In this paper,the combining method of Fast Fourier transform,Chirp Z transform and signal local reconstruction was utilized to obtain Juno's Doppler frequency. The results show that Juno's open loop Doppler frequency is at the level of 10 μHz,which effectively validated the method of deep space open loop measurement and provide valuable reference for China's future deep space missions.

In Queqiao mission, the first stage of Chang'e-4 mission，Queqiao mission，Jiamusi and Kashi deep space stations were used to conduct VLBI（Very Long Baseline Inteferometry） observation to the relay satellite. Real-time and post-time high-precision angular measurement results were obtained，which effectively supported the mission implementation. In the mission，the two deep space stations need to complete the TT&C tasks at the same time，so they cannot alternate the radio source and spacecraft observation to calibrate the system error. Based on this system，a long time interval calibration method was adopted to observe the radio source before and after the spacecraft observation. Multiple interferometric measurements were carried out in the lunar transfer section，the Lunar to L2 transfer section and the Halo orbital formation section. The results show that the observation accuracy of the deep space network is about 3ns.

由于探测距离远,火星探测任务对干涉测量具有很强的精度需求.首先描述了相位参考甚长基线干涉测量(Very Long Baseline Interferometry,VLBI)原理,介绍了弧段内干涉相时延解模糊方法,阐述了弧段之间相互参考解算干涉相时延流程,给出了测量误差分析,并利用中国佳木斯深空站、喀什深空站针对射电源对1633+38和1641+399开展了相位参考VLBI试验验证.结果 表明,消除模糊度后,相位参考时延精度优于0.1 ns.这为提高中国未来深空探测器角位置精度提供一种可行的技术途径.