Validation of soil moisture data products from the NASA SMAP mission

Andreas Colliander, Rolf Reichle, Wade Crow, Michael H. Cosh, Fan Chen, Steven K. Chan, Narendra Narayan Das, Rajat Bindlish, Mario J. Chaubell, Seungbum Kim, Qing Liu, Peggy E. Oneill, Scott Dunbar, Land B. Dang, John S. Kimball, Thomas J. Jackson, Hala Khalid Aljassar, Jun Asanuma, Bimal Kumar Bhattacharya, Aaron BergDavid D. Bosch, Laura Louise Bourgeau-Chavez, Todd Caldwell, Jean Christophe Calvet, Chandra Holifield Collins, Karsten H. Jensen, Stan Livingston, Ernesto Lopez-Baeza, Jose Martinez-Fernandez, Heather Mcnairn, Mahta Moghaddam, Carsten Montzka, Claudia Notarnicola, Thierry Pellarin, Isabella Pfeil, Jouni Pulliainen, Judith Ramos, Mark Seyfried, Patrick Starks, Bob Su, R. Van der Velde, Yijian Zeng, Marc Thibeault, Mariette Vreugdenhil, Jeffrey P. Walker, Mehrez Zribi, Dara Entekhabi, Simon H. Yueh

Research output: Contribution to journalArticleAcademicpeer-review

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NASAs Soil Moisture Active Passive (SMAP) mission has been validating its soil moisture (SM) products since the start of data production on March 31, 2015. Prior to launch, the mission defined a set of criteria for core validation sites (CVS) that enable the testing of the key mission SM accuracy requirement (unbiased root-mean-square error <0.04 m3/m3). The validation approach also includes other (sparse network) in situ SM measurements, satellite SM products, model-based SM products, and field experiments. Over the past six years, the SMAP SM products have been analyzed with respect to these reference data, and the analysis approaches themselves have been scrutinized in an effort to best understand the products performance. Validation of the most recent SMAP Level 2 and 3 SM retrieval products (R17000) shows that the L-band (1.4 GHz) radiometer-based SM record continues to meet mission requirements. The products are generally consistent with SM retrievals from the ESA Soil Moisture Ocean Salinity mission, although there are differences in some regions. The high-resolution (3-km) SM retrieval product, generated by combining Copernicus Sentinel-1 data with SMAP observations, performs within expectations. Currently, however, there is limited availability of 3-km CVS data to support extensive validation at this spatial scale. The most recent (version 5) SMAP Level 4 SM data assimilation product providing surface and root-zone SM with complete spatio-temporal coverage at 9-km resolution also meets performance requirements. The SMAP SM validation program will continue throughout the mission life; future plans include expanding it to forested and high-latitude regions.

Original languageEnglish
Article number9599364
Pages (from-to)364-392
Number of pages29
JournalIEEE Journal of selected topics in applied earth observations and remote sensing
Publication statusPublished - 13 Nov 2021


  • Core Validation Sites
  • NASA
  • Remote sensing
  • Satellite broadcasting
  • Sea surface
  • SMAP
  • SMAP mission
  • Soil measurements
  • Soil moisture
  • Soil Moisture
  • Validation


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