• ISSN 2097-1893
  • CN 10-1855/P

基于三亚非相干散射雷达的月球正面南北半球拼接成像研究

李鸣远 王永辉 尹翰林 乐新安 丁锋 曾令旗 赵必强 魏勇 宁百齐

引用本文: 李鸣远,王永辉,尹翰林,乐新安,丁锋,曾令旗,赵必强,魏勇,宁百齐. 2021. 基于三亚非相干散射雷达的月球正面南北半球拼接成像研究. 地球与行星物理论评,52(4):450-458
Li M Y, Wang Y H, Yin H L, Yue X A, Ding F, Zeng L Q, Zhao B Q, Wei Y, Ning B Q. 2021. A mosaic imaging study of the northern and southern hemispheres of the nearside of the Moon based on the Sanya Incoherent Scatter Radar. Reviews of Geophysics and Planetary Physics, 52(4): 450-458

基于三亚非相干散射雷达的月球正面南北半球拼接成像研究

doi: 10.19975/j.dqyxx.2021-014
基金项目: 国家重大科研仪器研制项目(41427901)和子午工程资助
详细信息
    作者简介:

    李鸣远(1993-),男,博士研究生,主要从事非相干散射雷达以及月球成像的研究. E-mail:limingyuan@mail.iggcas.ac.cn

    通讯作者:

    乐新安(1981-),男,研究员,主要从事非相干散射雷达、GNSS及无线电掩星探测技术、电离层及空间天气效应、数据同化等研究. E-mail:yuexinan@mail.iggcas.ac.cn

  • 中图分类号: P165

A mosaic imaging study of the northern and southern hemispheres of the nearside of the Moon based on the Sanya Incoherent Scatter Radar

Funds: Supported by the National Major Scientific Research Instrument Development Program of China (41427901) and the Meridian Project
  • 摘要: 当使用地基雷达并应用距离多普勒算法对月球正面进行成像时,不可避免会遇到“南北模糊”问题. 这是由于距离多普勒成像算法对旋转的天体进行成像时,位于视赤道共轭的两点的回波在距离多普勒图像中是重叠在一起无法分辨的. 针对该问题并基于三亚非相干散射雷达我们提出了一种解决方案,即月球正面南北半球拼接成像技术. 该技术通过将波束指向调整到特定位置,对月球正面南北半球分开照射的方法进行两次独立的实验,最后将正面南北半球图像拼接的方法得到完整的月球成像图. 实验结果证明该技术可以得到较为理想的图像,但仍然存在一些不足需要改进.

     

  • 图  1  距离多普勒算法几何示意图. X轴为距离轴指向雷达,Z轴沿着视自转轴方向,Y轴为方位轴满足右手定则. 距离环为X轴上距离分辨率单元在月面的投影,距离环上所有点到雷达的距离相等,多普勒条带为Y轴上多普勒分辨率单元在月面的投影,多普勒条带上所有点相对于雷达的多普勒频移相等

    Figure  1.  Schematic diagram of range-Doppler algorithm geometry. The X-axis is the range axis pointing to the radar, the Z-axis is along the apparent rotation axis, and the Y-axis is the azimuth axis, which satisfies the right-hand rule. The range ring is the projection of the X-axis range resolution unit on the lunar surface, and the ranges from all points on the range ring to the radar are equal. The Doppler band is the projection of the Y-axis Doppler resolution unit on the lunar surface. The Doppler frequency shifts of all points on the Doppler band are equal

    图  2  三亚非相干散射雷达归一化天线方向图. 横轴代表天顶角,单位为度;纵轴代表归一化辐射能量,单位为dB. 波束主瓣指向天顶方向,3 dB波束宽度用红色横线上的黑点和文字标出,10 dB波束宽度用黄色横线上的黑点和文字标出,第一零点波束宽度用横轴上的黑点和文字标出

    Figure  2.  Normalized antenna pattern of Sanya incoherent scatter radar. The horizontal axis represents the zenith angle, in degrees; the vertical axis represents normalized radiation energy, in dB. The main lobe of the beam points to the zenith direction, the 3 dB beam width is noted by the black dots on the red horizontal line, the 10 dB beam width is noted by the black dots on the yellow horizontal line, and the first zero beam width is noted by the black dots on the horizontal axis

    图  3  不同波束宽度定义下进行观测时观测半球与视赤道另一侧半球照射能量对比分析图. 上半图蓝色线表示照射到观测半球的能量占主瓣总能量的比重,红色线表示照射到视赤道另一侧半球的能量占主瓣总能量的比重. 下半图绿色线表示的是上半图蓝色线与红色线的比值. 三条黑色竖虚线从左到右分别表示3 dB波束宽度、10 dB波束宽度以及第一零点波束宽度

    Figure  3.  Comparison and analysis diagram of the energy illuminated on the observed hemisphere and the hemisphere on the other side of the apparent equator using different beam width definitions. The blue line in the upper half of the figure indicates the ratio of the energy illuminated on the observed hemisphere to the total energy of the main lobe, and the red line indicates the ratio of the energy illuminated to the hemisphere on the other side of the apparent equator to the total energy of the main lobe. The green line in the lower half of the figure represents the ratio of the blue line to the red line in the upper half of the figure. The three black vertical dotted lines from left to right represent the 3 dB beam width, 10 dB beam width and the first zero beam width respectively

    图  4  月球南北半球拼接成像图. 图像数据来自2021年3月16日三亚当地时14:30~15:00的实验. 坐标系为月球投影坐标,即经纬度坐标,经度范围100°W~100°E,步长0.05°,纬度范围90°S~90°N,步长0.05°. 红字标出了一些月球标志性地质单元名称. 黄色框标出的条带斑纹状区域是由于线性插值处理产生的额外的无效区域,不属于成像范围

    Figure  4.  Mosaic image of the northern and southern hemispheres of the nearside of the moon. The data comes from the experiment of 14:30~15:00 local time in Sanya on March 16, 2021. The coordinate system is the lunar projection coordinates, that is, the latitude and longitude coordinates, the longitude range is 100°W~100°E, the step length is 0.05°, the latitude range is 90°S~90°N, and the step length is 0.05°. The red words mark the names of some lunar geological units. The striped areas marked by the yellow frames are invalid area caused by the linear interpolation process, which does not belong to the mapping region

    图  5  回波功率中已校正的三个影响因素. (a)归一化的天线方向图函数在月球正面观测半球的投影分布,该图是借助星历计算得到的2021年3月16日三亚当地时14:46:19、雷达波束仰角77.54°、方位角170.84°情况下天线方向图在月面的投影,用于校正当地时14:45:19~14:47:19这2 min积累得到的图像;(b)散射单元面积在距离多普勒二维坐标下的分布图,是根据距离多普勒二维分辨率单元在月面投影面积来计算的理论数值;(c)归一化极化回波功率随入射角变化曲线,其中蓝色线是2021年3月16日三亚当地时14:30~15:00的观测数据平均得到的变化曲线,红色点为Hagfors(1970)文献中总结的68 cm波长雷达探测数据,黑色线为文献数据拟合曲线,校正使用的是拟合曲线

    Figure  5.  Three influence factors corrected in the echo power. (a) The distribution of the normalized antenna pattern on the observed hemisphere of the nearside of the moon. It is calculated with the help of ephemeris at 14:46:19 local time in Sanya on March 16, 2021, with the radar beam elevation angle of 77.54° and azimuth angle of 170.84°. It is used to correct the images accumulated during the 2 minutes from 14:45:19 to 14:47:19 local time; (b) The area of the scattering unit in the range-Doppler domain. It is a theoretical map calculated by the projection area of the two-dimensional range-Doppler resolution unit on the lunar surface; (c) The curves of normalized polarized echo power with the angle of incidence, in which the blue curve is the average curve of the observation data from 14:30 to 15:00 local time in Sanya on March 16, 2021. The red points are the 68 cm-wavelength radar detection summarized in the Hagfors (1970) literature, and the black curve is the fitting curve of red points. The fitting curve was used for calibration

    表  1  雷达指标以及实验参数

    Table  1.   Radar index and experiment parameters

    参数名称数值或说明
    极化方式发射右旋圆极化,接收左旋圆极化
    天线增益43 dB(法线方向)
    天线孔径~778 m2
    扫描范围天顶角南北方向±48°,东西方向±25°
    发射波形线性调频
    脉宽2 ms
    波形带宽0.3 MHz
    发射峰值功率2 MW
    发射频率430 MHz
    脉冲重复周期60 ms
    相干积累时间2 min
    距离向分辨率~500 m
    方位向分辨率~2 km
    下载: 导出CSV
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出版历程
  • 收稿日期:  2021-03-28
  • 录用日期:  2021-05-09
  • 网络出版日期:  2021-05-11
  • 刊出日期:  2021-07-01

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