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United States Department of Agriculture

Agricultural Research Service

Research Project: Soil Moisture Active Passive (Smap) in Situ Sensor Testbed

Location: Hydrology and Remote Sensing Laboratory

2011 Annual Report


1a.Objectives (from AD-416)
Work with Oklahoma State University (OSU) to evaluate the quality and accuracy of in situ soil moisture monitoring instrumentation in a rangeland field. Large scale sampling of soil moisture and co-location of a variety of soil moisture sensor technologies will be implemented in a rangeland field on OSU property under the management of their Range Research Station. Physical collection of soil moisture samples and characterization of the field on a routine basis for the term of this agreement will be the primary objective.


1b.Approach (from AD-416)
The cooperative work proposed here will assess the accuracy and representativeness of the soil moisture studies included in the project, based upon physical collection of soil moisture. This assessment will guide the NASA Soil Moisture Active Passive (SMAP) Science Definition Team in their calibration and validation activities for the satellite mission.

ARS will direct the research aspects of the project, leading the investigation and analysis of the results for incorporation into the SMAP Science Team Data Archive. Provide equipment and installation of in situ soil moisture sensors and assist in the collection of physical samples for calibration and validation of the sensors installed in the testbed.

OSU will be providing local logistical support for the project including field site maintenance and communications support for the instrumentation. Also administer a gravimetric and vegetation sampling regimen on a regular basis for calibration and validation of the sensor estimates with the support personnel funded by this agreement.


3.Progress Report

In support of USDA ARS, Soil Moisture Active/Passive validation activities in central Oklahoma, scientists at the Oklahoma State University (OSU) installed an in situ sensor test bed in coordination with USDA ARS HRSL. The location is managed by OSU as a part of their rangeland management research station. OSU has collected soil texture and moisture information on a regular basis as a validation of the in situ sensor. In addition, they have conducted vegetation sampling protocols for the purpose of quality controlling of some of the larger scale sensors which have vegetation dependence.

Data from four base stations can be downloaded via cellular technology, but OSU is maintaining and downloading data from several other satellite stations which have larger data production rates and cannot be easily transferred via cellular networks. Many of the sensors required a settling time before the data could be considered accurate. Several sensors were re-installed because of equipment defects or installation errors. Sensors were calibrated using in situ gravimetric methods and because of an ongoing drought, soils were brought into a laboratory for further calibration.

As part of the SMAP Validation Experiments 2011, (SMAPVEX11), aircraft overflights were conducted in June of 2011 using a Passive Active L-band Radiometer in coordination with gravimetric sampling. Additionally, a mobile cosmic-ray soil moisture rover has been deployed on multiple occasions to have spatial maps of the surrounding region.

Future research will include a vegetation removal experiment, where portions of the field will be burned as part of another experiment and will influence how some of the sensors respond to moisture.

The ADODR has monitored the progress of this project through email correspondences, conference calls and periodic meetings with Oklahoma State University scientists.


Last Modified: 11/28/2014
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