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United States Department of Agriculture

Agricultural Research Service

Title: Estar Measurements During the Southern Great Plains Experiments

Authors
item Levine, D - NASA/GSFC
item JACKSON, THOMAS
item Swift, C - UNIVERSITY OF MASS
item Haken, M - NASA/GSFC
item Bidwell, S - NASA/GSFC

Submitted to: IEEE Transactions on Geoscience and Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2001
Publication Date: N/A

Interpretive Summary: The measurement of soil moisture from space presents a significant technological challenge. That is, an engineering challenge in addition to the issues associated with the retrieval algorithm and science. The technological challenge associated with mapping soil moisture from space occurs because the measurement is optimally done at the long wavelength end dof the microwave spectrum. Long wavelengths permit penetration into the soil and mitigate the effects of roughness and vegetation canopy. However, at these wavelengths the antennas required in orbit to achieve the resolution goals present a significant engineering challenge. The L-band measurements of brightness temperature made by ESTAR during the Southern Great Plains experiment in 1999 reflect the spatial and temporal patterns of soil moisture within the study area. The data compare well with previous observations made earlier during SGP97 under very similar conditions and provided a validation of the technology of aperture synthesis for remote sensing from space. The engineering problems associated with large, scanning antennas of this has limited the deployment in space of passive sensors at this frequency, and similar problems can be expected in the future at higher frequencies as the demand increases for improved resolution from space. The results of this study provide valuable information on a potential solution to the problem.

Technical Abstract: The synthetic aperture radiometer, ESTAR, supported the Southern Great Plains experiment in 1999, by providing maps of L-band brightness temperature over the large study area in Oklahoma. ESTAR flew on the NASA P-3B Orion aircraft at an altitude of 7.6 km and mapped a swath about 50 km wide and about 300 km long, extending west from Oklahoma City to El Reno and north from the Little Washita River watershed to the Kansas border. Maps were made on 6 days between July 8-19, 1999. The brightness temperature maps reflect the patterns of soil moisture expected from rainfall. The data are consistent with observed values of soil moisture at the research sites within the SGP99 study area and are consistent with previous measurements in this area. The data add to the resources for hydrologic modeling in this area and are further validation of the technology represented by ESTAR as a potential path to a future mission to map soil moisture globally from space. Dynamics of five emission parameterizations during diurnal cycles and gradual dry-down of the simulated soil.

Last Modified: 9/10/2014
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