The following table lists the ancillary data sets that are used by SMAP algorithms to produce the SMAP science data products. The Level 1-3 ancillary data sets are used to create the SMAP L1, L2, and L3 products; the Level 4 ancillary data sets are used to create the SMAP L4 products. These ancillary data sets are made available as part of NSIDC DAAC’s mandate to preserve all SMAP data and related information for future research, per the NASA Earth Science Data Preservation Content Specification. Several of these ancillary data sets are produced by external organizations, such as NOAA, the NASA Global Modeling and Assimilation Office (GMAO), and NASA Land Data Assimilation Systems (LDAS). For more information about the creation and development of these data sets, users should refer to the originating institution.