CYGNSS Level 1 Climate Data Record Version 1.2

This Level 1 (L1) dataset contains the Version 1.2 Climate Data Record (CDR) of the geo-located Delay Doppler Maps (DDMs) calibrated into Power Received (Watts) and Bistatic Radar Cross Section (BRCS) expressed in units of m2 from the Delay Doppler Mapping Instrument aboard the CYGNSS satellite constellation. Other useful scientific and engineering measurement parameters include the DDM of Normalized Bistatic Radar Cross Section (NBRCS), the Delay Doppler Map Average (DDMA) of the NBRCS near the specular reflection point, and the Leading Edge Slope (LES) of the integrated delay waveform. The L1 dataset contains a number of other engineering and science measurement parameters, including sets of quality flags/indicators, error estimates, and bias estimates as well as a variety of orbital, spacecraft/sensor health, timekeeping, and geolocation parameters. At most, 8 netCDF data files (each file corresponding to a unique spacecraft in the CYGNSS constellation) are provided each day; under nominal conditions, there are typically 6-8 spacecraft retrieving data each day, but this can be maximized to 8 spacecraft under special circumstances in which higher than normal retrieval frequency is needed (i.e., during tropical storms and or hurricanes). Latency is approximately 1 week. The Version 1.2 CDR is a collection of reanalysis products derived from the SDR v3.1 Level 1 data (https://doi.org/10.5067/CYGNS-L1X31 ). Calibration accuracy and long term stability are improved relative to SDR v3.0 using the same trackwise correction algorithm as was used by CDR v1.1 (https://doi.org/10.5067/CYGNS-L1C11 ), which was derived from SDR v2.1 Level 1 data (https://doi.org/10.5067/CYGNS-L1X21 ). Details of the algorithm are provided in the Trackwise Corrected CDR Algorithm Theoretical Basis Document. Trackwise correction is applied to the two primary CYGNSS L1 science data products, the normalized bistatic radar cross section (NBRCS) and the LES. The correction compensates for small errors in the Level 1 calibration, due e.g. to uncertainties in the GPS transmitting antenna gain patterns and the CYGNSS receiving antenna gain patterns. It should be noted that the trackwise correction algorithm cannot be successfully applied to all v3.1 SDR L1 data, so there is also some loss of samples that were present in v3.1.

本一级（L1）数据集包含地理定位延迟多普勒图（DDMs）的版本1.2气候数据记录（CDR），经过校准为功率接收（瓦特）和双基地雷达散射截面（BRCS），并以平方米为单位表达，源自CYGNSS卫星星座上的延迟多普勒映射仪器。其他有用的科学和工程测量参数包括归一化双基地雷达散射截面（NBRCS）的DDM、NBRCS在镜面反射点附近的DDM平均（DDMA）以及综合延迟波形的尖端斜率（LES）。L1数据集还包含一系列其他工程和科学测量参数，包括质量标志/指示器集、误差估计和偏差估计，以及多种轨道、航天器/传感器健康状况、时间同步和地理定位参数。每天最多提供8个netCDF数据文件（每个文件对应CYGNSS星座中独特的一艘航天器）；在正常条件下，通常每天有6-8艘航天器收集数据，但在需要高于正常收集频率的特殊情况下，该数量可以增加到8艘航天器（例如，在热带风暴和飓风期间）。延迟时间大约为一周。版本1.2的CDR是从SDR v3.1一级数据中派生出的再分析产品集（https://doi.org/10.5067/CYGNS-L1X31）。与SDR v3.0相比，通过使用与CDR v1.1相同的轨迹校正算法（https://doi.org/10.5067/CYGNS-L1C11），该算法源自SDR v2.1一级数据（https://doi.org/10.5067/CYGNS-L1X21），校准精度和长期稳定性得到提升。算法的详细信息可在轨迹校正CDR理论依据文档中找到。轨迹校正应用于CYGNSS L1科学数据产品的两个主要方面，即归一化双基地雷达散射截面（NBRCS）和尖端斜率（LES）。该校正补偿了一级校准中的微小误差，例如由于GPS发射天线增益模式的不确定性以及CYGNSS接收天线增益模式的不确定性所引起的误差。需要注意的是，轨迹校正算法不能成功应用于所有v3.1 SDR L1数据，因此也存在一些在v3.1中存在的样本损失。