Alaska Satellite Facility - Distributed Active Archive Center

DOI (Digital Object Identifier) 10.5067/X0P0Q3IN3Q0D


Product Description

Short name: SPL1AAV3

SMAP Overview

Launched on 31 January 2015, the Soil Moisture Active Passive (SMAP) Mission aimed to measure soil moisture and freeze-thaw state across the globe for a period of three years.

The satellite held a 685-km altitude, near-polar, sun-synchronous 6 a.m./6 p.m., 8-day, exact repeat, frozen orbit. It measured the top 5 cm of Earth’s soil every three days.

The SMAP instrument was equipped with a radiometer and a synthetic aperture radar, both of which operated on L-band, allowing the instrument to sense soil conditions through moderate vegetation. The radiometer operated on H, V, 3rd and 4th Stokes parameter polarization at 1.414 GHz, and the synthetic aperture radar operated on VV, HH and HV polarization at 1.225 GHz. The radar lost power 7 July, the same year the spacecraft was launched, though the radiometer continues to function.

The SMAP Mission data products have four levels of processing. The Level 1 radar products are distributed by ASF DAAC and Levels 2-4 are distributed by NSIDC DAAC. All products are in HDF5 Format and follow the ISO 19115-2 model.


All Level 1 SMAP Mission products are distributed in half orbit granules. An ascending half orbit starts at the southernmost area and goes to the northernmost area, viewing Earth at 18:00 local time. A descending half orbit starts at the northernmost area and goes to the southernmost area, viewing Earth at 06:00 local time.

SMAP_L1A_Radar_V3 data is the least processed of the Level 1 products and contains raw radar data. The product orders its data into groups of Synthetic Aperture Radar processing, Real Aperture Radar processing, loop back data used for calibration processing, instrument Health and Status, antenna rotation conditions, and satellite position and altitude and antenna azimuth. While in orbit, this radar data can be downlinked continuously.

Data Access

Data Service Name: Vertex
Data Service Description: Search, visualize, and download data in GeoTIFF format
Data Service Access

Data Service Name: Alaska Satellite Facility Application Programming Interface (API)
Data Service Access

Data Service Name: Earthdata Search
Data Service Description: This application allows you to search, discover, visualize, refine, and access NASA Earth Observation data.
Data Service Access

Data Citation

Citing SMAP Level 1 Datasets

Cite datasets in publications such as journal papers, articles, presentations, posters, and websites. Each SMAP Level 1 dataset has an assigned DOI. Please also send a copy of publications that cite datasets or tools obtained through ASF to [email protected].

Format Example
SMAP data [year of data acquisition] (NASA). Dataset: [name of dataset]. Retrieved from ASF [add URL if print publication:] DAAC [day month year of data access]. DOI: [doi] SMAP data 2015 (NASA). Dataset: SMAP_L1A_Radar_V3. Retrieved from ASF DAAC 7 December 2015. DOI: 10.5067/X0P0Q3IN3Q0D

Crediting SMAP Imagery

Include appropriate credit with each image shown in publications such as journal papers, articles, presentations, posters, and websites. For more information, see NASA guidelines.

Type Format Example
Imagery, primary or altered Credit: NASA data [year of data acquisition]. Credit: NASA data 2015.
Imagery, derivative Credit: [Name of image creator or institution, as appropriate], [year of image creation], contains NASA data [year of data acquisition]. Credit: Jones, D., 2015, contains NASA data 2015.