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Data for new versions of SMAP Level-1, -2, and -3 data sets are currently available from 27 August 2020 onward. Data since 31 March 2015 will become available as they are reprocessed.
Antenna scan angle (ASA) errors affected a large number of data files between 05 Oct and 23 Nov 2019, as well as a handful of dates within 2020 (04 and 05 Feb, 09 Apr, 30 May, and 18 Jun). The bad data are not currently identified by data quality flags. The ASA errors disrupt the proper geolocation of half-orbits, which may be off by as much as 99 km in the along scan direction. The affected half-orbits are in the Version 5 SPL1BTB product (specifically half-orbits 24977.5 - 25691, 26765 - 26781, 27709 - 27713, 28458~28459, and 28733.5 – 28739.5), but the most recent version of all upstream products are similarly impacted. The cause of the ASA errors has been identified and all affected products will be reprocessed. This reprocessing is scheduled to begin in March, 2021.
Data Set ID: 
SPL2SMAP_S

SMAP/Sentinel-1 L2 Radiometer/Radar 30-Second Scene 3 km EASE-Grid Soil Moisture, Version 3

This Level-2 (L2) soil moisture product provides estimates of land surface conditions retrieved by both the Soil Moisture Active Passive (SMAP) radiometer during 6:00 a.m. descending and 6:00 p.m. ascending half-orbit passes and the Sentinel-1A and -1B radar. SMAP L-band brightness temperatures and Copernicus Sentinel-1 C-band backscatter coefficients are used to derive soil moisture data, which are then resampled to an Earth-fixed, cylindrical 3 km Equal-Area Scalable Earth Grid, Version 2.0 (EASE-Grid 2.0).

Note: These data are Beta-release quality. Additional analyses of in situ soil moisture stations will be conducted over the next several months, which should move the data quality to the validated category.

This is the most recent version of these data.

Version Summary: 

Changes to this version include:
- An improved calibration methodology was applied to the SMAP Level-1B brightness temperatures.
- Revised the coefficients in the land surface temperature computation to be consistent with the SMAP Level-2 soil moisture passive enhanced product. The new coefficients are C=0.246, K=1.007 for AM passes and C=1.0, K=1.007 for PM passes.
- Changed the omega parameter of the tau-omega model for forest landcover classes (1-5) from 0.05 to 0.07.
- Uses a new high-resolution soil database (SoilGrid250m; Hengl et al., 2017).
- Uses bulk density to set the upper limit of the soil moisture retrievals. Previous versions used a fixed value of 0.65 m3/m3.
- Enhanced documentation on Data Flags in the User Guide to help data users to better understand and use the flags.
- Added a bit in the TB Disaggregation QC flag to indicate (1) the use of SMAP AM or PM data; and (2) the time difference (greater or less than 36 hours) between the SMAP and Sentinel observations overlap.
- Fixed the EASE_[row/column]_index_apm_[1km/3km] data fields to make them 0-based.
- Fixed the range beginning and ending time in the file metadata.

For the full major and minor version history, go to https://nsidc.org/data/smap/data_versions.

COMPREHENSIVE Level of Service

Data: Data integrity and usability verified; data customization services available for select data

Documentation: Key metadata and comprehensive user guide available

User Support: Assistance with data access and usage; guidance on use of data in tools and data customization services

See All Level of Service Details

Parameter(s):
  • MICROWAVE > BRIGHTNESS TEMPERATURE
  • RADAR > SIGMA NAUGHT
  • SOILS > SOIL MOISTURE/WATER CONTENT > SURFACE SOIL MOISTURE
Data Format(s):
  • HDF5
Spatial Coverage:
N: 60, 
S: -60, 
E: 180, 
W: -180
Platform(s):SENTINEL-1A, SENTINEL-1B, SMAP
Spatial Resolution:
  • 3 km x 3 km
Sensor(s):C-SAR, SMAP L-BAND RADIOMETER
Temporal Coverage:
  • 31 March 2015
Version(s):V3
Temporal Resolution30 secondMetadata XML:View Metadata Record
Data Contributor(s):Das, N., D. Entekhabi, R. S. Dunbar, S. Kim, S. Yueh, A. Colliander, P. E. O'Neill, T. Jackson, T. Jagdhuber, F. Chen, W. T. Crow, J. Walker, A. Berg, D. Bosch, T. Caldwell, and M. Cosh.

Geographic Coverage
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Download Via HTTPS: An Earthdata Login account is required to access these data.

Once you have logged in, you will be able to click and download files via a Web browser. There are also options for downloading via a command line or client. For more detailed instructions, please see Options Available for Bulk Downloading Data from HTTPS with Earthdata Login.

Earthdata Search: This application allows you to search, visualize, and access data across thousands of Earth science data sets. Additional customization services are available for select data sets, including subsetting, reformatting, and reprojection.

Worldview: This application allows you to interactively browse global satellite imagery within hours of it being acquired. You can also save it, share it, and download the underlying data.

Subscription Service: Subscribe to have new data automatically delivered to you as they become available at NSIDC. Subscriptions apply only to future data as they are delivered to NSIDC; they cannot be used to receive data already in NSIDC's archive.

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Das, N., D. Entekhabi, R. S. Dunbar, S. Kim, S. Yueh, A. Colliander, P. E. O'Neill, T. Jackson, T. Jagdhuber, F. Chen, W. T. Crow, J. Walker, A. Berg, D. Bosch, T. Caldwell, and M. Cosh. 2020. SMAP/Sentinel-1 L2 Radiometer/Radar 30-Second Scene 3 km EASE-Grid Soil Moisture, Version 3. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/ASB0EQO2LYJV. [Date Accessed].

Literature Citation

As a condition of using these data, we request that you acknowledge the author(s) of this data set by referencing the following peer-reviewed publication.

  • Das, N., D. Entekhabi, S. Dunbar, J. Chaubell, A. Colliander, S. Yueh, T. Jagdhuber, F. Chen, W. T. Crow, P. E. O'Neill, J. Walker, A. Berg, D. Bosch, T. Caldwell, M. Cosh, C. H. Collins, E. Lopez-Baeza, and M. Thibeault. 2019. The SMAP and Copernicus Sentinel 1A/B microwave active-passive high resolution surface soil moisture product, Remote Sensing of Environment. 233. 111380. https://doi.org/10.1016/j.rse.2019.111380

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What data subsetting, reformatting, and reprojection services are available for SMAP data?
The following table describes the data subsetting, reformatting, and reprojection services that are currently available for SMAP data via the NASA Earthdata Search tool and a Data Subscription... read more
How do I convert an HDF5/HDF-EOS5 file into binary format?
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Read and plot SMAP/Sentinel-1 data with Matlab
This articles provides an example MATLAB snippet to read and plot SMAP/Sentinel-1 L2 Radiometer/Radar 30-Second Scene 3 km EASE-Grid Soil Moisture HDF5 soil moisture and brightness temperature data, as well as the related surface and quality flags. These flags are useful for determining the overall... read more
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