ATBDsCollectionsSMAPDataset Id and VersionSPL2SMP8SPL2SMP_E5SPL3SMP8SPL3SMP_E5SPL2SMP9SPL2SMP_E6SPL3SMP9SPL3SMP_E6SPL2/3SMP/_E Algorithm Theoretical Basis Document [2021]Data Programnasa_nsidc_daac