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Soil Moisture Active Passive (SMAP) Mission

SMAP Mission Overview

Launch date: January 31, 2015
First SAR data: April 13, 2015

From mud, to permafrost, to drought-stricken cropland, Earth’s soil holds vital information about the planet’s water. Understanding where water is stored, where it is going, and how fast it is moving is critical as the human population grows, demand for water increases, the climate changes, and weather patterns shift.

The SMAP mission will provide global measurements of soil moisture and its freeze-thaw state. SMAP measures the amount of water in the top 5 cm (2 inches) of soil everywhere on the Earth’s surface every three days. These data will be used to

  •  further understanding of processes that link the water, energy, and carbon cycles;
  •  enhance weather and climate prediction models;
  •  quantify net carbon flux in boreal landscapes; and
  •  develop improved flood-prediction and drought-monitoring capabilities.

Instrument: The instrument includes a radiometer and a synthetic aperture radar (SAR), operating at L-band (1.20-1.41 GHz), that measure surface emission and backscatter, sensing soil conditions through moderate vegetation cover.

Observatory: The SMAP spacecraft features an instrument suite deployed by an expendable launch vehicle into a 680-km, near-polar, sun-synchronous orbit, with equator crossings at 6 a.m. and 6 p.m. local time. SMAP provides global coverage within three days at the equator and two days at boreal latitudes.

Operations: SMAP science measurements will be acquired for three years. A comprehensive validation program will be carried out after launch to assess the accuracies of soil-moisture and freeze-thaw estimates. Data products from the SMAP mission will be made available through the Alaska Satellite Facility DAAC and the NSIDC DAAC.

The radar instrument ceased operation in 2015 due to failure of the radar power supply. ASF continues to receive passive radar data only.  More information


"On our home planet Earth, water is an essential requirement for life and for most human activities. We must understand the details of how water moves within and between the atmosphere, the oceans, and the land if we are to predict changes to our climate and the availability of water resources."

Michael Freilich, Director, NASA Earth Science Division

SMAP – Data and Imagery

SMAP Data Products Instrument events timetable The SMAP baseline science-data products will be publicly available through two NASA-designated data centers, the Alaska Satellite Facility (ASF) and the National Snow and Ice

SMAP – Handbook

“A rare characteristic of the SMAP Project is its emphasis on serving both basic Earth System science as well as applications in operational and practice-oriented communities.” Download Handbook Contents of

SMAP – How to Cite

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

SMAP – Instrument

Soil Moisture Passive Active (SMAP) is a remote-sensing observatory with two instruments — a synthetic aperture radar (SAR) and a radiometer — that map soil moisture and determine the freeze or thaw state of the area being mapped.

SMAP – Publications and Credits

Publications Please submit additional relevant publications to [email protected], with “SMAP Publications” on the subject line. 2014 Assessment of Soil Moisture Data Requirements by the Potential SMAP Data User Community: Review

SMAP – Tools

Documents Name Description ATBD Documents Algorithm theoretical basis documents are listed with the products available for download. Product Specification Documents Product specification documents are listed with the products available for

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