Skip to main content
ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Hydrology and Remote Sensing Laboratory » Research » Publications at this Location » Publication #336124
Title: Combined active and passive microwave remote sensing of vegetated surfaces at l-band

Author
item HUANG, H. - University Of Michigan
item LIAO, T. - University Of Michigan
item TSANG - University Of Michigan
item NJOKU, E. - Jet Propulsion Laboratory
item COLLIANDER, A. - Jet Propulsion Laboratory
item Jackson, Thomas
item BURGIN, M.S. - Jet Propulsion Laboratory
item YUEH, S. - Jet Propulsion Laboratory

Submitted to: Progress in Electromagnetics Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2017
Publication Date: 9/1/2017
Citation: Huang, H., Liao, T., Tsang, L., Njoku, E., Colliander, A., Jackson, T.J., Burgin, M., Yueh, S. 2017. Combined active and passive microwave remote sensing of vegetated surfaces at l-band. Progress in Electromagnetics Research. 78:91-124.

Interpretive Summary: A consistent model for combined active and passive microwave remote sensing is formulated where the same physical model is used to calculate both backscatter and brightness temperature. This approach has the advantage that the active and passive microwave remote sensing models are founded on the same theoretical basis and use the same physical parameters such as crop density, plant height, stalk orientation, leaf radius, surface roughness, and others. The model results are validated by coincidental airborne low-altitude radiometer data and radar data taken during a 2012 field campaign. The brightness temperature results from the model using the physical parameters are comparable to those from the omega-tau model that uses empirical parameters. Combined active and passive microwave remote sensing of vegetated surfaces is of great interest and importance given the increasing number of active and passive satellite microwave missions and datasets available for studies of land surfaces for application in hydrology and terrestrial ecology.

Technical Abstract: In previous work the distorted Born approximation (DBA) of volume scattering was combined with the numerical solutions of Maxwell equations (NMM3D) for a rough surface to calculate the radar backscattering coefficient for the Soil Moisture Active Passive (SMAP) mission. The model results were validated with the Soil Moisture Active Passive Validation Experiment 2012 (SMAPVEX12) data. In this paper, we extend this model to calculate the bistatic scattering coefficients for each of the three scattering mechanisms: volume, double bounce and surface scattering. By integrating the bistatic scattering coefficients of the hemispherical solid angle, the emssivities are calculated. The backscatter and emissivity values calculated using this approach form a consistent model for combined active and passive microwave remote sensing. It has the advantage that the active and passive microwave remote sensing models are founded on the same theoretical basis and use the same physical parameters such as crop density, plant height, stalk orientation, leave radius, surface roughness, and so on. In this paper, this combined active and passive model is applied to various vegetation types: wheat, winter wheat, pasture and canola, to calculate both the backscattering coefficient and brightness temperature. The model results are validated by using concurrent airborne Passive Active L-band System (PALS) low-altitude radiometer data and Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) data taken during the SMAPVEX12 field campaign. The average root mean squared error (RMSE) is 1.04 dB and 1.21 dB for backscatter VV and HH, respectively; 4.65 K and 6.44 K for brightness temperature at V-pol and H-pol, respectively. The results are also compared with the omega-tau model.