Title: OSCAR: Online Services for Correction of Atmosphere in Radar
Author: Paul von Allmen
Organization: Jet Propulsion Laboratory
Co-Authors: Eric Fielding, Eric Fishbein, Zhangfan Xing, Lei Pan, Martin Lo and Zhenhong Li

Interferometric Synthetic Aperture Radar (InSAR) imaging combines two phase images of the same scene observed at different  times into an interferogram. Since tropospheric water vapor causes a phase delay in the radar signal, changes in the tropospheric water content from the first to the second acquisition time can lead to errors in the interferogram. These errors are often large enough to obscure the motion and deformation of the terrestrial crust, which are the primary motivation of obtaining interferograms. We will present a tool that corrects for the delays caused by the tropospheric water vapor.

The delays can be calculated if the total amount of precipitable water vapor in the relevant column is known. OSCAR currently retrieves the column water vapor content from MODIS remote sensing data and from ECMWF weather forecast analysis products. Other products will be added in the future. We will present the Information Technology infrastructure and the algorithms used to produce a map of signal delay for an InSAR scene predefined by the user. The IT technology relies on webservices to achieve a flexible and seamless integration of data from different sources. The correction algorithm includes an error analysis for both the MODIS and the ECMWF data, and correction for topographic errors in the ECMWF product.