甚长基线干涉测量精密定轨技术
发布时间：2018-11-05 18:09
【摘要】：传统的航天测控网采用雷达测距和多普勒测速作为航天器跟踪测量的主要技术手段,但这两种无线电测量技术对飞行器的横向位置和横向速度并不敏感,随着探测距离的增加,受测量精度的制约和系统误差变大的影响,以角度表示的测量精度会变得很差,无法满足航天测控的需要。甚长基线干涉测量技术(Very Long Baseline Interferometry,VLBI)能获得极高的角分辨率,在航天测控领域发挥了重要的作用。本文围绕对探月卫星测控通信系统中的VLBI子系统仿真的研究,开展了以下三个方面的工作:对扩频VLBI子系统中的几种扩频伪随机码进行了分析比较。阐述了m序列、Gold序列以及JPL(Jct Propulsion Laboratory)快捕码的产生原理,并通过仿真结果验证了在周期长度在同一量级的情况下,JPL快捕码的捕获速度比m序列快得多;然后结合伪码测距原理,提出了扩频伪随机码在扩频以外的另一个用途,即通过计算两地面站接收信号的伪码偏移量之差求两站的时延估计值,因此特别针对JPL快速捕获码进行了仿真设计,设定合适的码周期及码速率,使其满足后续根据伪码偏移量之差求时延补偿值的精度要求。对VLBI扩频信号捕获跟踪方法进行了深入研究。针对传统的相关检测的捕获方法捕获过程困难、捕获时间长这一问题,研究了基于FFT(Fast Fourier Transformation)的并行频域搜索捕获算法,变伪码相位与频率的二维搜索为伪码相位的一维搜索,频率的搜索通过傅里叶变换一次性完成;并针对JPL复合码在此算法上做了改进,采用四路并行结构同时搜索复合码中各子码的相位,仿真验证了该算法的搜索次数大大减少。同样为获得精确的伪码相位、载波相位,研究设计非相干型DDLL(Digital Delay Lock Loop)伪码延迟锁定环及科斯塔斯载波跟踪环(Costas PLL),仿真验证了伪码及载波精确跟踪问题得以解决。对扩频VLBI系统数据相关处理机进行了深入研究。针对两路信号在相关运算前需要做时延补偿这一点,提出了一种通过计算两台站接收信号的伪码偏移量之差求得时延补偿值的方法,并用Simulink仿真验证了该方法有效可行;然后通过观察干涉条纹幅度值,进行粗搜索和精搜索两个步骤求得精确的时延值;最后,选取三条独立基线的时延值,使用卫星单点定位法进行卫星位置坐标的解算。
[Abstract]:The traditional space TT & C network uses radar ranging and Doppler velocimetry as the main technical means of spacecraft tracking and measurement, but these two radio measurement techniques are not sensitive to the lateral position and lateral velocity of the aircraft, and with the increase of the detection range, Because of the restriction of measurement precision and the increase of system error, the measurement precision expressed by angle will become very poor, which can not meet the needs of space measurement and control. Very long baseline interferometry (Very Long Baseline Interferometry,VLBI), which can obtain very high angular resolution, plays an important role in the field of space measurement and control. This paper focuses on the simulation of the VLBI subsystem in the lunar probe satellite TT & C communication system. The following three aspects are carried out: the analysis and comparison of several spread spectrum pseudorandom codes in the spread spectrum VLBI subsystem. The generation principle of m sequence, Gold sequence and JPL (Jct Propulsion Laboratory) fast capture code is expounded. The simulation results show that the capture speed of JPL fast capture code is much faster than m sequence when the period length is of the same order of magnitude. Then, combining the principle of pseudo-code ranging, the author puts forward another application of spread spectrum pseudorandom code in addition to spread spectrum, that is, by calculating the difference of pseudo-code offset between two earth stations, the time delay estimation value of two stations is obtained. Therefore, the JPL fast acquisition code is simulated and designed, and the appropriate code period and code rate are set to meet the accuracy requirements of the delay compensation value obtained by the difference of the pseudo code offset. The acquisition and tracking method of VLBI spread spectrum signal is studied in detail. Aiming at the difficulty of traditional acquisition method of correlation detection and the long acquisition time, a parallel frequency-domain search and acquisition algorithm based on FFT (Fast Fourier Transformation) is studied. The two dimensional search of the phase and frequency of the pseudo code is one dimensional search of the phase of the pseudo code, and the search of the frequency is completed by Fourier transform at one time. The algorithm is improved for JPL complex codes, and the phase of each subcode in the complex code is simultaneously searched by four parallel structures. The simulation results show that the search times of the algorithm are greatly reduced. In order to obtain accurate pseudo-code phase and carrier phase, the incoherent DDLL (Digital Delay Lock Loop) pseudo-code delay locking loop and Kostas carrier tracking loop are designed and simulated. The results show that the pseudo-code and carrier precise tracking problem can be solved. The data correlation processor of spread spectrum VLBI system is studied in detail. Aiming at the time delay compensation of two signals before the correlation operation, a method of calculating the difference of pseudo code offset between two stations is proposed, and the method is proved to be effective and feasible by Simulink simulation. Then, by observing the amplitude of interference fringes, two steps of coarse search and fine search are carried out to obtain the accurate delay value. Finally, the satellite position coordinates are calculated by using the satellite single point positioning method, which selects the delay values of three independent baselines.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P228.6
[Abstract]:The traditional space TT & C network uses radar ranging and Doppler velocimetry as the main technical means of spacecraft tracking and measurement, but these two radio measurement techniques are not sensitive to the lateral position and lateral velocity of the aircraft, and with the increase of the detection range, Because of the restriction of measurement precision and the increase of system error, the measurement precision expressed by angle will become very poor, which can not meet the needs of space measurement and control. Very long baseline interferometry (Very Long Baseline Interferometry,VLBI), which can obtain very high angular resolution, plays an important role in the field of space measurement and control. This paper focuses on the simulation of the VLBI subsystem in the lunar probe satellite TT & C communication system. The following three aspects are carried out: the analysis and comparison of several spread spectrum pseudorandom codes in the spread spectrum VLBI subsystem. The generation principle of m sequence, Gold sequence and JPL (Jct Propulsion Laboratory) fast capture code is expounded. The simulation results show that the capture speed of JPL fast capture code is much faster than m sequence when the period length is of the same order of magnitude. Then, combining the principle of pseudo-code ranging, the author puts forward another application of spread spectrum pseudorandom code in addition to spread spectrum, that is, by calculating the difference of pseudo-code offset between two earth stations, the time delay estimation value of two stations is obtained. Therefore, the JPL fast acquisition code is simulated and designed, and the appropriate code period and code rate are set to meet the accuracy requirements of the delay compensation value obtained by the difference of the pseudo code offset. The acquisition and tracking method of VLBI spread spectrum signal is studied in detail. Aiming at the difficulty of traditional acquisition method of correlation detection and the long acquisition time, a parallel frequency-domain search and acquisition algorithm based on FFT (Fast Fourier Transformation) is studied. The two dimensional search of the phase and frequency of the pseudo code is one dimensional search of the phase of the pseudo code, and the search of the frequency is completed by Fourier transform at one time. The algorithm is improved for JPL complex codes, and the phase of each subcode in the complex code is simultaneously searched by four parallel structures. The simulation results show that the search times of the algorithm are greatly reduced. In order to obtain accurate pseudo-code phase and carrier phase, the incoherent DDLL (Digital Delay Lock Loop) pseudo-code delay locking loop and Kostas carrier tracking loop are designed and simulated. The results show that the pseudo-code and carrier precise tracking problem can be solved. The data correlation processor of spread spectrum VLBI system is studied in detail. Aiming at the time delay compensation of two signals before the correlation operation, a method of calculating the difference of pseudo code offset between two stations is proposed, and the method is proved to be effective and feasible by Simulink simulation. Then, by observing the amplitude of interference fringes, two steps of coarse search and fine search are carried out to obtain the accurate delay value. Finally, the satellite position coordinates are calculated by using the satellite single point positioning method, which selects the delay values of three independent baselines.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P228.6
【参考文献】
相关期刊论文 前3条
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2 王刚;武小悦;;美国航天测控系统的构成及发展[J];国防科技;2010年05期
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