Near Real-time SMAP L1B Radiometer Half-Orbit Time-Ordered Brightness Temperatures, Version 105

This Near Real-Time (NRT) data set corresponds to the standard SMAP L1B Radiometer Half-Orbit Time-Ordered Brightness Temperatures (SPL1BTB) product. The data provide calibrated estimates of time-ordered geolocated brightness temperature data measured by the Soil Moisture Active Passive (SMAP) passive microwave radiometer, the SMAP L-band radiometer. These Near Real-Time data are available within three hours of satellite observation. The data are created using the latest available ancillary data and spacecraft and antenna attitude data to reduce latency. The SMAP satellite orbits Earth every two to three days, providing half-orbit, ascending and descending, coverage from 86.4°S to 86.4°N in swaths 1000 km across. Data are stored for approximately two to three weeks. Thus, at any given time, users have access to at least fourteen consecutive days of Near Real-Time data through the NSIDC DAAC. Users deciding between the NRT and standard SMAP products should consider the immediacy of their needs versus the quality of the data required. Near real-time data are provided for operational needs whereas standard products meet the quality needs of scientific research. If latency is not a primary concern, users are encouraged to use the standard science product, SPL1BTB (https://doi.org/10.5067/ZHHBN1KQLI20).本近实时（Near Real-Time, NRT）数据集对应标准SMAP L1B辐射计半轨时间排序亮温（SPL1BTB）产品。该数据提供经校准的、由土壤湿度主动被动（Soil Moisture Active Passive, SMAP）无源微波辐射计——即SMAP L波段辐射计——所测得的时间排序地理定位亮温数据估算值。这类近实时数据可在卫星观测完成后三小时内对外提供。本数据集采用当前最新的辅助数据、航天器及天线姿态数据生成，以进一步降低数据延迟。SMAP卫星每2至3天环绕地球一周，可提供覆盖南纬86.4°至北纬86.4°、幅宽1000公里的半轨（升轨与降轨）观测扫描带数据。数据存储时长约为2至3周，因此在任意时刻，用户均可通过国家冰雪数据中心分布式主动存档中心（NSIDC DAAC）获取至少14天连续的近实时数据。用户若需在NRT与标准SMAP产品间进行选择，应权衡自身需求的时效性与所需数据的质量要求：近实时数据面向业务运行需求提供，而标准产品则可满足科学研究的数据质量标准。若数据延迟并非核心考量因素，建议用户使用标准科学产品SPL1BTB（https://doi.org/10.5067/ZHHBN1KQLI20）。