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Summary of Proposal LAN0371

TitleTropospheric investigations with X-band polarimetric radar
Investigator Fritz, Jason - Colorado State University, Electrical and Computer Engineering
Team Member
Dr. Chandrasekar, V. - Colorado State University, Electrical and Computer Engineering
Dr. Wdowinski, Shimon - University of Miami, RSMAS/MGG
Mr. Fritz, Jason - Colorado State University, Electrical and Computer Engineering
SummaryThere are many applications for SAR interferometry (InSAR) especially for monitoring deformations in the Earth’s surface with high spatial accuracy. Unfortunately, the atmosphere of the Earth can have a detrimental effect on the quality of the interferograms due to its impact on electromagnetic wave propagation. Liquid and precipitable water in the troposphere are known to attenuate the signal and shift the observed phase due to gradients of the index of refraction along the path of the radar beam. The impact of this phenomena is also wavelength dependent and will cause more problems at shorter wavelengths where the attenuation is greater and phase will wrap and alias quicker than for longer wavelengths. Techniques to mitigate the tropospheric phase delays typically use an iterative algorithm to accumulate these errors, along with DEM and other errors, across all interferograms. The most common method examines the phase change of known stationary ground targets over many acquisitions. Studies have also shown the capability of extracting meteorological properties from SAR in the process. However, all the known algorithms have limitations. TerraSAR-X provides the unique opportunity to investigate atmospheric monitoring from space with a fully polarimetric X-band system. It has already been shown that strong precipitation will be visible in TSX imagery, and the additional of multiple polarizations can provide additional information in the effort to study these effects.

The proposed research will investigate atmospheric effects in TSX data over two study areas. Both areas have minimal topological variation and are prone to severe storms and high humidity in the summer. There is also a network of ground based weather stations in both regions to measure the temperature, pressure and humidity at various locations. S-band weather radar data can be used to assess active precipitation during a SAR acquisition, and one study area will also contain a network of 4 X-band polarimetric weather radars. During the summer of 2008, this research radar network will be estimating the near surface refractivity using algorithms similar to the InSAR method of monitoring coherent ground targets. In the other regions, periodic spaceborne precipitation radar measurements will be made, although they are not likely to coincide with TSX acquisitions. However, a proposal has also been submitted to the Italian Space Agency for similar research which will provide a second X-band SAR data pool for comparison. All of the data acquired will also be compared to the results of existing atmospheric models. The conclusions of this research will be presented in peer reviewed journals and conferences.

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