The Soil Moisture Active Passive (SMAP) mission is a NASA directed mission to map global land surface soil moisture and freeze-thaw state. Instrument  and mission details are shown. The key SMAP soil moisture product is provided at 10 km resolution with 0.04cubic cm/cubic cm accuracy. The freeze/thaw product is provided at 3 km resolution and 80% frozen-thawed classification accuracy. The full list of SMAP data products is shown

Colliander, A.

Cosh, M.

Entekhabi, D.

Jackson, T.

Kimball, J.

Njoku, E.

ONeill, P.

Spencer, M.

NASA Technical Reports Server

The algorithms are calibrated and validated pre-
launch using both simulated and experimental
data. Global end-to-end simulations with
representative land surface and observational
conditions are performed to exercise all
algorithms. The simulation runs are tied to the
real world by utilizing experimental data from field
campaigns and actual satellite observations (e.g.
SMOS). An Algorithm Testbed has been
implemented on the SMAP Science Data System
[3] for running the simulations. The Testbed also
includes a Cal/Val Database that stores a wide
range of experimental data. Establishment of
procedures for timely transfer of required in situ
data to the Cal/Val database is a key objective in
the pre-launch phase. Methodologies for up-
SMAP Mission Cal/Val Overview
Timeline
The key SMAP soil moisture product is
provided at 10 km resolution with 0.04 cm3/cm3
accuracy. The freeze/thaw product is pro-
vided at 3 km resolution and 80% frozen-
thawed classification accuracy. The full list of
SMAP data products is shown Table 1.
SMAP utilizes a conically scanning 6 m reflector antenna, yielding a 
swath width of 1000 km and spatial resolutions of 40 km and 1-3 km 
for the radiometer and radar, respectively.
The Soil Moisture Active Passive (SMAP)
mission [1] is a NASA directed mission to map
global land surface soil moisture and freeze-
thaw state. Instrument and mission details are
shown below.
[1]  D. Entekhabi et al., “The Soil Moisture Active Passive (SMAP) Mission”, Proc. IEEE, Vol. 98, No. 5, May 2010.
[2]  T. Jackson et al., “SMAP Science Calibration and Validation Plan”, Preliminary Release, Ver. 1.0, November 2010.
[3]  W. Crow et al., “The SMAP Science Data System Algorithm and Application Simulation Testbed”, IGARSS10, July 2010.
The objective of the SMAP Cal/Val Program is to
calibrate and validate Level 1 through Level 4
algorithms and products relative to the mission
requirements. The overall strategy to meet this
objective includes: (1) cold-sky and
homogeneous, stable Earth surface targets; (2)
in-situ monitoring using ground-based
observation networks; (3) intensive field
campaigns using airborne sensors and ground-
data acquisition; (4) comparative satellite-based
soil moisture products, and (5) land surface
modeling. Spatial and temporal scaling
techniques are used to make the connection
between satellite and in situ observations. The
Algorithm Theoretical Basis Documents (ATBD)
will define the cal/val approach and requirements
for each of the Level 1 through 4 data products.
IOC for Level 1 products and during the first
twelve months after IOC for Level 2 and higher
products. The cumulative mission science data
will be reprocessed as needed to improve data
product quality and accommodate upgrades in
processing algorithms.
This poster was prepared at the Jet Propulsion Laboratory, California Institute of Technology,
under contract to the National Aeronautics and Space Administration
Data Product Description
L1B_S0_LoRes Low Resolution Radar σo in Time Order
L1C_S0_HiRes High Resolution Radar σo, on Swath Grid
L1B_TB Radiometer TB in Time Order
L1C_TB Radiometer TB
L2_SM_A Radar Soil Moisture*
L2_SM_P Radiometer Soil Moisture
L2_SM_A/P Radar/Radiometer Soil Moisture
L3_F/T_A Daily Global Composite Freeze/Thaw State
L3_SM_A Daily Global Composite Radar Soil Moisture*
L3_SM_P Daily Global Composite Radiometer Soil Moisture
L3_SM_A/P Daily Global Composite Radar/Radiometer Soil Moisture
L4_F/T Freeze/Thaw Model Assimilation on Earth Grid
L4_SM Soil Moisture Model Assimilation on Earth Grid
Instruments:
 Radar:  L-band (1.26 GHz)
− High resolution, moderate accuracy soil moisture
− SAR mode: 3 km resolution
− Real-aperture mode: 5 x 30 km resolution
 Radiometer:  L-band (1.4 GHz) 
− Moderate resolution, high accuracy soil moisture
− 40 km resolution
 Shared Antenna:
− 6-m diameter deployable mesh antenna
− Conical scan at 14.6 rpm
− Constant incidence angle: 40 degrees
 1000 km-wide swath
 Swath and orbit enable 2-3 day revisit 
Orbit:
 Sun-synchronous, 6 am/pm orbit
 680 km altitude
Operations: 
 3-year baseline mission
Methodology
During the pre-launch phase the instruments (radar
and radiometer) will be calibrated to the required
accuracy. Pre-launch instrument calibration will
include modeling, analysis, simulations, and
laboratory and test facility measurements.
Fig. B: Installation at one of the four sites at  In Situ Sensor 
Testbed in Oklahoma.
Cal/Val Activities
National Aeronautics and Space Administration
Jet Propulsion Laboratory
California Institute of Technology
Pasadena, California
www.nasa.gov
DEVELOPMENT OF SMAP MISSION CAL/VAL ACTIVITIES
A. Colliander1, T. Jackson2, J. Kimball3, M. Cosh2, M. Spencer1, D. Entekhabi4, E. Njoku1, P. O’Neill5
(1) Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA; (2) USDA Agricultural Research Service, Beltsville, MD, USA;
(3) University of Montana, Missoula, MT, USA; (4) Massachusetts Institute of Technology, Cambridge, MA, USA; (5) NASA Goddard Space Flight Center, Greenbelt, MD, USA
Fig. A: In situ observations are the key for validation of SMAP 
products. The in situ samples require up-scaling to the satellite 
footprint size.
SMAP Cal/Val activities are divided into pre- and
post-launch phases. Emphasis during pre-
launch is on algorithm development and charac-
terization of uncertainties (parameterizations and
algorithmic implementation). During this phase
the infrastructure and methodologies for post-
launch validation will also be established.
Emphasis during post-launch is on algorithm
refinement and L1 through L4 product accuracy
assessments over different regions and spatial
and temporal time scales.
In situ observation networks are classified in two
categories: 1) Core Sites - dense networks,
limited extent of a watershed or region, with
multiple samples within a SMAP footprint, and 2)
Sparse Networks - with perhaps just one or a few
samples within a SMAP footprint (but covering a
large extent; continental or global). SMAP
product validation efforts in the post-launch
phase will emphasize primarily the Core Sites for
quantitative accuracy assessments due to their
better representation of footprint-scale values. In
situ network observations will be augmented by
field campaign observations to implement the
scaling methodology. Satellites with products
similar to SMAP can be used for inter-
comparisons and trend analysis. Land surface
models can be used to extend the validation
domains in space and time. All validation data will
be utilized to calibrate and improve the
algorithms to yield the best possible products.
scaling in situ observations to the SMAP footprint
scale (see Fig. A) will be established before
launch and the processing for the scaling will be
implemented on the Testbed. Intermediate-
resolution airborne field observations and dense-
observation networks are essential for
development of reliable up-scaling functions.
The SMAP Science Cal/Val Plan (preliminary version) [2] is available at http://smap.jpl.nasa.gov
NASA plans to coordinate with operational
observation networks to acquire in situ
measurements globally. The objective is to gain as
extensive coverage as possible encompassing the
maximum diversity of conditions over the land
surface of the Earth. Both the Core Sites and the
Sparse Networks will be connected to the Cal/Val
Database in order to ensure timely data availability
from these sites for the calibration and validation
activities.
Instruments
The post-launch calibration will make use of
instrument parameters measured before launch,
internal calibration sources, and external targets
including cold-sky. During cold sky calibration the
antenna is pointed to measure the known cosmic
microwave background. Homogeneous well known
Earth surface targets will also be utilized to calibrate
and validate the L1 products. These sites include
oceans, Antarctica ice sheets, rain forests and
possibly deserts. The instrument Cal/Val includes
verification of geolocation accuracy, Faraday
rotation correction, and antenna pattern correction.
Special attention is paid to RFI in the hardware
design and post-processing.
Algorithm Pre-Launch Validation
Field Campaigns
Numerous SMAP-relevant field campaigns have
been carried out over the years. The SMAP project
has plans for two major field campaigns: one before
launch (SMAPVEX12) and one after launch
(SMAPVEX15). In addition, SMAP plans to
collaborate in SMAP-related field campaigns
conducted by international partners both pre- and
post-launch.
The Science Data System Algorithm Testbed [3]
plays a key role in pre-launch algorithm calibration
and validation. The Testbed enables full end-to-end
simulations of the algorithms. Land surface models
are used as inputs to the forward models, and
instrument characteristics are accounted for in
simulating radar and radiometer outputs. Various
algorithm options can be tested, including
uncertainties in parameterizations and ancillary
data, to test and compare the performance of the
algorithms for each product. Field campaign data
will also be used to improve the parameterizations
and performance of the algorithms.
smap.jpl.nasa.gov
The primary objectives of SMAPVEX12 are: 1) to
address unresolved algorithm issues from earlier
campaigns, and 2) to contribute to establishment of
scaling methodologies. Both SMAPVEX12 and
SMAPVEX15 are planned to take place over a
subset of the Core Sites.
In Situ Networks
Several challenges exist in utilizing in situ sensors
for SMAP product validation. Not only do sensor
measurement technologies vary among networks
but also the installation of the sensors varies. To
investigate these issues, an In Situ Sensor Testbed
activity was initiated by the USDA in Oklahoma in
2010 (see Fig. B). Utilization of results from this
study, and application of robust inter-sensor
calibration based on the thermo-gravimetric soil
moisture sampling, will improve the reliability and
consistency of the in situ data record for SMAP
product validation.
SMOS (Soil Moisture and Ocean Salinity) satellite
will be exploited to exercise the SMAP radiometer
based soil moisture algorithm with realistic
brightness temperature fields. Other satellite data
sets will also be utilized, including ALOS PALSAR
and others.
SMAP Radar pixels 
SMAP Radiometer Pixel 
Existing stations
New stations
SMAP Combined radiometer/radar soil moisture
Fig. C: Validation site at Yanco Australia matching the validation 
site components with the nested SMAP grid (courtesy J. Walker, 
Monash University, Australia).
Up-Scaling and Validation Measurements
Several methods have been proposed for scaling
point in situ measurements to satellite footprint
scales. The SMAP Science Definition Team will
select the appropriate methodologies to be used for
SMAP. An experimental Core Site design,
accounting for up-scaling to SMAP grid resolutions,
The baseline validation source for the freeze/thaw
state product is the air temperature. However, the
effect of snow, soil surface, and land cover
temperatures on the L-band backscatter need to be
quantified in the pre-launch phase in order to
develop a comprehensive validation approach.
Furthermore, an approach to account for the
typically high landscape heterogeneity of northern
latitudes will be developed. The Alaska Ecological
Transect (ALECTRA) Network provides a basis for
investigating these effects.
A primary objective of the post-launch Cal/Val
phase is to validate science products for release to
the public. In order to accomplish this objective
within the twelve-month period, validation data must
be ingested into the Cal/Val database in timely
manner. Tools for comparing SMAP products with
the validation data must be in place before launch.
Validation will be performed by assessing product
accuracies relative to the specified requirements for
each product. Beyond the twelve-month intensive
Cal/Val phase, continuing product accuracy
assessments and algorithm refinements will be
performed over the entire mission lifetime.
Post-Launch Priorities
*) Research product not for official release
SMAP is currently in Phase B and scheduled for
launch in November 2014. The post-launch
period (Phase E) is divided into In-orbit Checkout
(IOC), Cal/Val and Routine Observation phases.
An intensive calibration and validation program
will be conducted during the first six months after
has already been implemented in Yanco, NSW,
Australia. Each grid cell includes at five least
measurements, and lower resolution cells include at
least two sampled higher resolution cells (see Fig.
C).
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( )...,,iVV g θθ ′=′Up-Scaling
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Table 1: SMAP Mission Products
Satellite data will be utilized for testing and
validation of algorithms as well. In particular, the
L1C product of the European Space Agency’s
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Development of SMAP Mission Cal/Val Activities

Development of SMAP Mission Cal/Val Activities

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