Soil Moisture Active Passive

Soil Moisture Active Passive
Name	Soil Moisture Active Passive
Names	SMAP
Operator	National Aeronautics and Space Administration (NASA)
Mission type	Earth observation
Mission duration	Design life: 3 years
Launch date	January 31, 2015
Launch vehicle	Delta II
Launch site	Vandenberg Space Force Base
Manufacturer	Jet Propulsion Laboratory
Instruments	L-band radar, L-band radiometer

Soil Moisture Active Passive

Soil Moisture Active Passive was a NASA Earth observation mission developed by the Jet Propulsion Laboratory and managed by NASA to measure surface soil moisture globally. The mission supported programs at Earth Science Division (NASA), engaged with agencies including the National Oceanic and Atmospheric Administration and the United States Geological Survey, and contributed to international partnerships such as European Space Agency and Japan Aerospace Exploration Agency. SMAP combined active and passive microwave sensing to address scientific challenges identified by panels including the National Research Council and the World Meteorological Organization.

Overview

SMAP was conceived following recommendations from the National Research Council's decadal survey and oversight by NASA Headquarters to provide L-band soil moisture retrievals for hydrologic and climate research. The mission architecture integrated technology heritage from missions like SMOS (Soil Moisture and Ocean Salinity), Aquarius (satellite), and instruments on Terra (satellite). SMAP aimed to bridge gaps noted by panels from Intergovernmental Panel on Climate Change assessments and to supply operational stakeholders such as United States Department of Agriculture and Federal Emergency Management Agency with routine moisture products.

Mission Objectives and Instruments

Primary objectives included measuring near-surface soil moisture and freeze/thaw state to improve understanding of land–atmosphere exchange, informed by science committees convened by NASA Science Mission Directorate and the Earth Science Division (NASA). The payload comprised an L-band synthetic aperture radar and an L-band radiometer developed with contributions from contractors and centers including JPL and industrial partners. Instrument designs drew on prior work at Lockheed Martin, Ball Aerospace, and laboratories such as Jet Propulsion Laboratory facilities, while calibration strategies referenced standards promoted by National Institute of Standards and Technology.

Spacecraft and Launch

The SMAP spacecraft bus was built by teams coordinated by Jet Propulsion Laboratory and integrated at facilities associated with NASA Ames Research Center and contractors. The 6-meter rotating deployable mesh antenna was a central element adapted from engineering studies at NASA Langley Research Center and assembly efforts linked to United Launch Alliance suppliers. SMAP launched on a Delta II rocket from Vandenberg Space Force Base into a Sun-synchronous orbit, aligning orbital parameters with missions such as Landsat 8 and Sentinel-1 to enable synergistic retrievals.

Data Products and Processing

SMAP produced calibrated soil moisture and freeze/thaw datasets, with Level 1 radar and radiometer and higher-level merged products processed by teams at JPL and distributed through systems built with Goddard Space Flight Center involvement. Processing chains used algorithms peer-reviewed by working groups including members from University of California, Berkeley, Massachusetts Institute of Technology, Colorado State University, and data assimilation centers like European Centre for Medium-Range Weather Forecasts and NOAA National Centers for Environmental Prediction. Products fed into modeling systems at institutions such as NASA Goddard and were archived following protocols harmonized with Committee on Earth Observation Satellites recommendations.

Scientific and Practical Applications

SMAP data supported research areas championed by universities and agencies including Harvard University, Princeton University, Columbia University, and the University of Maryland for studies of hydrology, carbon cycling, and permafrost dynamics. Operational users included USDA Natural Resources Conservation Service, FEMA, NOAA partners, and international agencies such as Food and Agriculture Organization and European Commission services. Applications ranged from drought monitoring, flood forecasting, and irrigation management to coupling with climate models used by groups participating in Coupled Model Intercomparison Project activities.

Mission Operations and Performance

Mission operations were overseen by teams within Jet Propulsion Laboratory in coordination with NASA Mission Control Center and ground stations affiliated with networks such as the Deep Space Network and commercial partners. Early mission performance documented by science teams reported success in radiometer calibration and challenges with the radar, prompting engineering reviews by panels with members from California Institute of Technology and Stanford University. Contingency operations and recovery plans referenced practices from prior missions like Aqua (satellite) and informed decisions about continued product generation and mission extensions.

Legacy and Impact on Hydrology and Remote Sensing

SMAP's legacy includes advancing retrieval algorithms and fostering assimilation into land surface models at institutions including NOAA, ECMWF, and national research centers in China, India, and Australia. The mission influenced subsequent satellite design discussions within NASA and ESA programs and informed international data-sharing initiatives such as those coordinated by the Group on Earth Observations. SMAP-enabled datasets remain a resource for scientific publications from teams at University of Tokyo, University of Oxford, University of Zurich, and many other research organizations, shaping policy dialogues involving agencies like United Nations offices concerned with food security and disaster risk reduction.

Category:NASA satellites Category:Earth observation satellites