MEX-M-MARSIS-3-RDR-SS

Data Set Overview MARSIS Level 2 data products consist of Level 1b data that have been uncompressed, corrected for Automated Gain Control, aligned to a reference altitude and, except for data acquired using the SS2 mode, rangeprocessed after correcting for the distortion of the transmitted signal caused by the ionosphere. Echoes collected in the acquisition (ACQ) phase, having a much smaller bandwidth, do not have a vertical resolution sufficient for scientific analysis, and thus are not used in generating Reduced Data Records. Geometric information needed to locate observations in space and time is also provided in the Data Set. Parameters MARSIS data are the result of the processing of groups of echoes called frames. A frame is produced by the coherent summation of many tens of echoes. Each frame is recorded as a time series of complex signal samples. Scientific data in a frame are complemented by a set of engineering data, produced by the instrument and recording parameter values used in pulse transmission, echo reception and onboard processing, and by geometric information needed to locate observations in space and time. Processing Level 2 processing of subsurface sounding data consists of several steps, needed to convert the instrument telemetry into a collection of radar echoes that can be used for geological analysis and interpretation of the Martian subsurface. These are: Data decompression: 8bit spectrum samples are converted back to 4byte real numbers. AGC compensation: the gain scaling factor, applied during Automated Gain Compensation, is applied to the data. Receiving time compensation: echoes are shifted in time to refer them to a common altitude above the Martian ellipsoid. Range compression: the received signal is convolved with the transmitted signal to increase range resolution and signaltonoise ratio. Ionosphere distortion correction: an algorithm to c truncated!, Please see actual data for full [truncated!, Please see actual data for full text]

数据集概述
MARSIS 第二级数据产品由未压缩的 Level 1b 数据构成，这些数据经过自动增益控制校正，与参考高度对齐，并且除使用 SS2 模式获取的数据外，均在纠正由电离层引起的传输信号畸变后进行距离处理。在采集阶段收集到的回波，由于其带宽较小，垂直分辨率不足以进行科学分析，因此未用于生成简化数据记录。数据集中还提供了定位观测在时空中的几何信息。
参数
MARSIS 数据是处理称为帧的回波组的产物。一个帧是通过数十个回波的相干叠加生成的。每个帧被记录为复信号样本的时间序列。帧中的科学数据由一组工程数据补充，这些数据由仪器产生，并记录脉冲传输、回波接收和机载处理中使用的参数值，以及用于在时空定位观测所需的几何信息。
处理
地下探测数据的第二级处理包括多个步骤，旨在将仪器遥测数据转换为可用于地质分析和解释火星地下结构的雷达回波集合。这些步骤包括：
数据解压缩：将 8 位频谱样本转换回 4 字节实数。
自动增益控制补偿：在自动增益补偿期间应用的增益缩放因子应用于数据。
接收时间补偿：将回波在时间上移动，以将其参照到火星椭球体上方的共同高度。
距离压缩：将接收到的信号与传输信号卷积，以增加距离分辨率和信噪比。
电离层畸变校正：一种算法，用于纠正截断，请参阅实际数据以获取完整内容。