An alternative GRACE-FO K-Band Ranging System Level-1B dataset: AEI- KBR1B v50

The Gravity Recovery and Climate Experiment (GRACE) and its Follow-On (GRACE-FO) satellite missions consist of two satellites for global time-varying gravity field detection, which adopted the K-Band Ranging System (KBR) as the key payload to measure the inter-satellite distance variations with the accuracy of micrometer level. The process of converting the raw phase data (KBR Level-1A) to the inter-satellite range (KBR Level-1B) is operationally completed by the Science Data System (SDS). SDS data products such as the KBR1B RL04 datasets are publicly available (e.g. ftps://isdcftp.gfz-potsdam.de). After re-analysing the measurement principles of the KBR system, the AEI team reprocessed the data from KBR1A to KBR1B based on the SDS release of KBR1A, CLK1B, GNI1B, SCA1B, and auxiliary files. This alternative KBR1B product is called KBR1B v50 and is provided in this repository. The data product uses the same YAML format as the SDS ( Wen et al, 2019. https://podaac-tools.jpl.nasa.gov/drive/files/allData/gracefo/docs/GRACE-FO_L1_Handbook.pdf). Compared to the SDS KBR1B data, KBR1B v50 incorporates the so-called (carrier) frequency variation correction (FVC) in biased distances, an improved light-time correction with less noise, and satellite center-of-mass shifts are taken into account in the antenna-offset correction. More details can be found in the related publication. The AEI-KBR1B v50 can be used for scale factor estimation of the Laser Ranging Interferometer (LRI) and gravity signals recovery.

重力恢复与气候实验（Gravity Recovery and Climate Experiment，GRACE）及其后续任务（GRACE-FO）卫星计划由两颗卫星组成，用于开展全球时变重力场探测。该任务采用K波段测距系统（K-Band Ranging System，KBR）作为核心有效载荷，以微米级精度测量卫星间的距离变化。将原始相位数据（KBR Level-1A）转换为卫星间测距值（KBR Level-1B）的流程，由科学数据系统（Science Data System，SDS）通过业务化方式完成。SDS产出的KBR1B RL04等数据集已对外开放，公开访问地址例如：ftps://isdcftp.gfz-potsdam.de。AEI团队在重新梳理KBR系统的测量原理后，基于SDS发布的KBR1A、CLK1B、GNI1B、SCA1B数据及辅助文件，对KBR1A至KBR1B的原始数据进行了重新处理。这款替代型KBR1B数据产品被命名为KBR1B v50，并存储于本仓库中。该数据产品采用与SDS一致的YAML格式（详见Wen等人2019年发表的文献：https://podaac-tools.jpl.nasa.gov/drive/files/allData/gracefo/docs/GRACE-FO_L1_Handbook.pdf）。相较于SDS产出的KBR1B数据，KBR1B v50在偏置距离中新增了所谓的（载波）频率变化校正（FVC），采用了噪声更低的改进型光行时校正，并在天线偏移校正环节中考虑了卫星质心偏移的影响。更多细节可参阅相关学术出版物。AEI-KBR1B v50可用于激光测距干涉仪（Laser Ranging Interferometer，LRI）的尺度因子估算以及重力信号恢复。