WIOBSS: The Chinese low-power digital ionosonde for ionospheric backscattering detection

The ionospheric laboratory of Wuhan University has developed an ionosonde over about seven years. The prototype is designed as a portable, low-power digital MF (medium frequency) and HF (high frequency) radio system with high range and Doppler resolution. The first system is used for ionospheric oblique backscattering detection and called WIOBSS (Wuhan Ionospheric Oblique Backscattering Sounding System). WIOBSS is a portable monostatic ionosonde for both ionospheric research and HF channel management, adopting alternate transmitting and receiving patterns to transmit long coded pulse trains for high pulse compression gain. The almost perfect sequences are applied to modulate the pulse train for sounding without range sidelobes and the echo phase is used to estimate the Doppler velocity and velocity fluctuation. This paper introduces the new techniques adopted by WIOBSS and presents some observations.     

Doppler characteristics of HF spread Doppler clutter recorded at Alice Springs,Australia

Mean night-time peak power, Doppler shift and Doppler width of spread Doppler clutter (SDC) received by a high frequency backscatter radar located at Alice Springs, Australia from 2000 to 2018 is presented as a function of azimuth, sunspot number, time of year and frequency. The sampled region covers 90 degrees from West to North and includes the northern and southern equatorial anomalies.SDC peak power diminished across all azimuths during the winter solstice from around May to August (local winter) coinciding with the global decrease in F layer density due to the annual non-seasonal F2 anomaly but was generally constant during the equinoxes. In contrast, SDC Doppler width and inbound Doppler shift both increased during the equinoxes and exhibited azimuthal dependence related to the eastward equatorial plasma drift.SDC peak power increased with increasing sunspot number with frequency dependence during winter but not summer. Inbound Doppler shift and Doppler width increased with increasing sunspot number during equinox but not solstice with a strong dependence on azimuth and a weak dependence on frequency.     

用织女一号火箭在海南站探测的高空风和风切变

本文介绍了织女一号(ZN-l)火箭测风原理,数据处理方法和两次测风结果.结果指出,在我国低纬地区中层大气中存在非常明显的风切变和相当强的重力波扰动,测风数据与COSPAR国际参考大气CIRA1986及国际标准化组织航空用参考大气ISO5878-1982／ADD.1-1983存在明显差别.      

一种新型多普勒噪声抑制技术对BepiColombo任务无线电科学实验的性能提升

在欧洲空间局和日本宇宙开发机构联合开展的BepiColombo水星任务中,将开展水星轨道器无线电科学实验,包括估计水星的引力场及其旋转状态,并对广义相对论进行验证。目前地面系统和星上设备的主流配置可以在无线电科学实验中建立X/X、X/Ka和Ka/Ka多个频段的链路,测速精度可达3 um/s（1 000 s积分）,测距精度为20 cm。提出了基于时延机械噪声对消技术提高无线电科学实验性能的方案。时延机械噪声对消技术需要处理在两个测站不同时刻的测量数据,一个测站实施双向多普勒测距,对另一个单收测站的要求较为严格,该测站需要具有较好的对流层条件。这种方法能够显著降低Ka频段双向链路的主要测量噪声,包括由对流层和天线机械系统震动引起的噪声。我们给出了端到端的仿真性能,并估计了在使用时延机械噪声对消技术前提下的水星引力场和旋转状态。考虑使用NASA位于美国本土戈尔德斯敦的DSS-25天线或欧空局位于阿根廷马拉圭的DSA-3天线作为双程测量站,并考虑使用位于智力的APEX天文观测天线作为单收站。分析结果表明在最好的噪声条件下,使用DSA-3天线作为双程测量站时,时延机械噪声对消技术可将待估计的全局和局部参数的估计精度提升一倍。对于无线电科学实验的目标,这一可能的性能提升对行星地质物理学很有意义,它将有益于研究水星内部的结构。     

An innovative navigation scheme of powered descent phase for Mars pinpoint landing

Pinpoint landing (within 100 m from the target) is essential for future Mars exploration missions. This paper deals with one aspect of the pinpoint landing architecture—the navigation performance improvement during the powered descent phase, and proposes an innovative navigation scheme to obtain the vehicle complete and accurate states. On the basis of dead reckoning relying on the Inertial Measurement Unit, measurements of the Integrated Doppler Radar are adopted to correct the vehicle velocity and altitude. Distance between the vehicle and one Mars Orbiter as well as their line-of-sight relative velocity is measured by a radio sensor, and integrated in the filter to correct the vehicle horizontal position. The innovative navigation system is based on an Extend Kalman Filter. Two observation schemes are developed. One considers measurements of the Integrated Doppler Radar and radio range measurement. Another further considers radio velocity measurement. The performance of the innovative navigation scheme is greatly influenced by the position of the Mars Orbiter with respect to the target. Stochastic analyses are performed to obtain optimal locations of Mars Orbiter. Finally, the innovative navigation scheme performances are assessed through stochastic simulations. Its performance improvements are demonstrated by comparison with the Integrated Doppler Radar only navigation scheme.     

深空探测器被动式高精度多普勒测量方法与应用

针对深空探测器的单程多普勒测量需求,研究了被动式高精度多普勒测量方法及其实现技术。该方法基于探测器测控信标残留载波等点频信号和VLBI测站高精度氢原子钟频标,构造出与实际接收信号频率接近的参考信号;再通过本地相关处理,完成高精度开环多普勒测量。其特色在于完全不需要精确的先验轨道模型。所开发的专用被动式多普勒测量设备,在国内第一次成功用于欧空局环火星探测器“MEX”的多普勒测定轨试验。探测器X频段信号5s积分的单程多普勒测量精度达到 0.2mm/s ,与欧空局测量水平相当。采用该多普勒测量数据的MEX定轨结果与欧空局精密轨道在数百米至千米量级一致。     

测速雷达信标测量数据复原新方法

给出了一种测速雷达信标测量多普勒频率复原的新方法,此方法与目标运动的初始轨道参数无关。与已有方法相比较,新方法解决了已有数据复原方法对初始轨道参数的依赖性,理论上消除了初始轨道参数精度对数据复原精度的影响。通过与已有方法计算结果的比对分析表明,新方法能够满足数据处理精度要求,具有较好的适用性,是实现信标测量数据复原的有效途径。     

调频多普勒引信抗调幅干扰性能分析

为提高调频多普勒引信抗调幅干扰性能,定量研究了调幅干扰对其作用机理,以信干比(SJR)增益作为表征参量定量研究了不同调幅干扰作用下调频多普勒引信的抗干扰性能。详细推导了正弦波调幅、方波调幅和三角波调幅干扰作用下调频多普勒引信的信干比增益,并对其进行了仿真验证。定量分析、仿真与引信实验测试结果表明:在调幅干扰下调频多普勒引信总信干比增益在10 d B量级;调频多普勒引信抗各种调制样式调幅干扰能力相当,对调幅干扰调制样式不敏感;调幅指数对调频多普勒引信抗干扰性能基本无影响;减小多普勒滤波器带宽可以一定程度提高调频多普勒引信系统抗干扰性能。     

基于轨道参数和SAR回波数据的多普勒调频率快速估计

多普勒调频率是SAR方位向压缩的关键参数之一. 调频率的失配会带来严重的方位向散焦, 从而影响成像质量. 基于减灾、防灾目的, 需要对SAR数据快速成像, 从而相应要求对多普勒调频率进行快速估计处理. 根据多普勒调频率快速估计需求, 提出了一种基于轨道参数法和Map Drift算法估计多普勒调频率的综合反演算法, 利用多普勒调频率与距离的关系, 简化整个估计流程, 从而提高估计速度. 同时给出了一种块数据筛选的方法, 用于选择综合反演法中所采用的块数据. 实验结果表明, 综合反演法能够在满足成像质量要求的基础上, 快速估计出多普勒调频率.      

嫦娥一号卫星撞月时刻与坐标精确分析

针对CE-1卫星精确的撞月时刻与撞月点坐标,首先通过探测器载波信号的本地相关处理技术,精确分析了载波信号在VLBI各测站的消失时刻,进而推算了卫星的撞月时刻;通过实时单向多普勒频移测量的事后分析,核实了卫星撞月过程中的飞行姿态演化;最后结合VLBI互相关时延与测距资料,经定位归算确定撞月点坐标。分析表明,CE-1卫星撞月时刻的误差为±5μs,撞月点坐标月面切向和三维定位误差分别约为0.274km和0.319km(1σ)。