Physics Department Seminar University of Alaska Fairbanks

J O U R N A L    C L U B

Mapping ionospheric total electron content using
Faraday rotation in L-band SAR data
Franz Meyer and Jeremy Nicoll
Alaska Satellite Facility

With the SAR sensor PALSAR on board the Advanced Land Observing Satellite, the first spaceborne fully polarimetric L-band SAR instrument has been launched into orbit. For L-band, Faraday rotation can reach significant values degrading the quality of the received SAR data. Therefore, the estimation and correction of Faraday rotation effects is a prerequisite for data quality and continuity. Vertical total electron content (TEC) values available from Global Ionosphere Maps are generated on a daily basis at the Center for Orbit Determination in Europe, using data from about 150 GPS sites of the International GNSS service and other institutions. However, the spatial resolution of these maps is very low comprising a grid spacing of only 2.5° (lat) and 5° (lon). Also the overall accuracy is limited and is generally considered to be within 5 x 1016 e-/m2. In the course of developing methods for estimating Faraday rotation, datasets were found that demonstrated the utility of SAR data to measure ionospheric events with unprecedented precision and spatial resolution. With a priori knowledge of the satellite pointing geometry and local geomagnetic field, the contribution of TEC to the Faraday rotation can be estimated with ~50-m spatial resolution and a standard deviation of about 1 TECU (1016 e-/m2). Therefore, L-band SAR data has high potential to significantly contribute to the study of small scale ionospheric turbulences. We will demonstrate localized ionospheric effects within the 15x60-km frame size of a given PALSAR image, as well as more regional effects over the course of hundreds of kilometers in a swath.

Friday, 21 September 2007
Globe Room, Elvey Building
3:45 PM