|
The effects of the ionosphere on spaceborne synthetic aperture radar (SAR) systems have received attention since the development of ALOS PALSAR (L-band). One of them is the Faraday rotation (FR) due to the dispersive nature of ionosphere and the existence of Earth’s magnetic field. The FR error is obviously embedded in polarimetric data of PALSAR systems, which destroys the scattering matrix. Nevertheless, distorted echoes contain abundant ionospheric information, the ionospheric sounding based on the scattering matrix data can become possible if the mechanisms of ionospheric interference can be understood and accurately modeled. SAR systems are generally characterized by high spatial resolution, this powerful technique can detect kilometer-scale ionospheric information where such unprecedented spatial resolution was previously inaccessible (e.g., such resolution is 1 to 2 orders of magnitude higher than that obtained by GPS). In this paper, by using the ALOS PALSAR full-polarization data sets, we quantitatively evaluate the reliability and accuracy of retrieved TEC information. We have used the observation results of incoherent scattering radar (ISR) to verify the accuracy of our results, given that ISR is currently the most powerful ground means for ionospheric monitoring and the ideal means for ionospheric data verification. In our work, the AMISR data for the Alaskan region in the United States is selected. After screening the data, we have selected and compared three sets of SAR and ISR results obtained at the same observation time (universal time: 8/6/2010, 21:6:25; 3/19/2011, 7:32:50; 3/31/2011, 7:28:16) and place. Our results show that the deviation between the results of SAR and ISR is only 0.1-0.35 TECU accounting for different factors, such as system and geographical deviations. However, the accuracy of the most widely used GPS data can only up to 1-2 TECU. Both accuracy and resolution of ionospheric sounding using fullpolarization SAR are therefore superior to those of ionospheric sounding using GPS.
|
