Assessment of the SMAP Passive Soil Moisture Product

The National Aeronautics and Space Administration (NASA) Soil Moisture Active Passive (SMAP) satellite mission was launched on January 31, 2015. The observatory was developed to provide global mapping of high-resolution soil moisture and freeze-thaw state every two to three days using an L-band (act...

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Bibliographic Details
Published in:	IEEE transactions on geoscience and remote sensing 2016-08, Vol.54 (8), p.4994-5007
Main Authors:	Chan, Steven K., Bindlish, Rajat, O'Neill, Peggy E., Njoku, Eni, Jackson, Tom, Colliander, Andreas, Chen, Fan, Burgin, Mariko, Dunbar, Scott, Piepmeier, Jeffrey, Yueh, Simon, Entekhabi, Dara, Cosh, Michael H., Caldwell, Todd, Walker, Jeffrey, Wu, Xiaoling, Berg, Aaron, Rowlandson, Tracy, Pacheco, Anna, McNairn, Heather, Thibeault, Marc, Martinez-Fernandez, Jose, Gonzalez-Zamora, Angel, Seyfried, Mark, Bosch, David, Starks, Patrick, Goodrich, David, Prueger, John, Palecki, Michael, Small, Eric E., Zreda, Marek, Calvet, Jean-Christophe, Crow, Wade T., Kerr, Yann
Format:	Article
Language:	eng
Subjects:	Agriculture Algorithms Brightness temperature Channels Data centers Data models Earth Resources And Remote Sensing L-band land emission Level 2 Passive Soil Moisture Product (L2_SM_P) Level 3 Daily Composite Version (L3_SM_P) Microwave radiometry Missions NASA passive microwave remote sensing Radar Radiometers Soil moisture Soil Moisture Active Passive (SMAP) Spatial resolution tau–omega ( tau-\omega) model validation
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Summary:	The National Aeronautics and Space Administration (NASA) Soil Moisture Active Passive (SMAP) satellite mission was launched on January 31, 2015. The observatory was developed to provide global mapping of high-resolution soil moisture and freeze-thaw state every two to three days using an L-band (active) radar and an L-band (passive) radiometer. After an irrecoverable hardware failure of the radar on July 7, 2015, the radiometer-only soil moisture product became the only operational soil moisture product for SMAP. The product provides soil moisture estimates posted on a 36 km Earth-fixed grid produced using brightness temperature observations from descending passes. Within months after the commissioning of the SMAP radiometer, the product was assessed to have attained preliminary (beta) science quality, and data were released to the public for evaluation in September 2015. The product is available from the NASA Distributed Active Archive Center at the National Snow and Ice Data Center. This paper provides a summary of the Level 2 Passive Soil Moisture Product (L2_SM_P) and its validation against in situ ground measurements collected from different data sources. Initial in situ comparisons conducted between March 31, 2015 and October 26, 2015, at a limited number of core validation sites (CVSs) and several hundred sparse network points, indicate that the V-pol Single Channel Algorithm (SCA-V) currently delivers the best performance among algorithms considered for L2_SM_P, based on several metrics. The accuracy of the soil moisture retrievals averaged over the CVSs was 0.038 m 3 /m 3 unbiased root-mean-square difference (ubRMSD), which approaches the SMAP mission requirement of 0.040 m 3 /m 3 .
ISSN:	0196-2892 1558-0644