1. IGARSS 2011, Vancouver, Canada Session: TU4.T02.2 - Ionospheric Effects on SAR, PolSAR and InSAR, Tuesday, July 26, 15:20 - 17:00 Ionospheric Effects in SAR Interferometry: An Analysis and Comparison of Methods for their Estimation Ramon Brcic 1 , Alessandro Parizzi 1 , Michael Eineder 1 , Richard Bamler 1 and Franz Meyer 2 1 Remote Sensing Technology Institute (IMF), German Aerospace Center (DLR) 2 Geophysical Institute, University of Alaska, Fairbanks

6. Ionospheric Effects in InSAR Existing and future SAR systems: interferometric phase sensitivity to VTEC at 35° incidence angle Band P L C X Carrier Frequency 435 MHz 1.27 GHz 5.405 GHz 9.65 GHz Agency ESA NASA/DLR JAXA ESA DLR Mission or Sensor BIOMASS DESDynI/ TerraSAR-L ALOS-PALSAR Sentinel-1 TerraSAR-X, TanDEM-X Range Bandwidth [MHz] 6 80 14, 28 100 100, 150, 300 Range Delay [m / TECU] 5.2 0.61 0.034 0.011 Interferometric Phase Advance [cycles / TECU] 7.5 2.6 0.61 0.34 Assumed Swath Width [km] 100 50 250 30 Interferometric range phase change over swath for constant Δ TEC [cycles / TECU] 0.89 0.15 0.18 0.012

10. Split Spectrum Method interferometric phase at carrier frequency Subband Range Spectra Lower Subband Upper Subband non-dispersive topography, atmosphere dispersive ionosphere Optimal subband bandwidth? b = B / 3 (same as split spectrum/delta-k absolute phase estimator)

12. Range Group – Phase Delay Method unwrapped interferometric phase at carrier frequency shift from crosscorrelation between master and slave non-dispersive topography, atmosphere phase delay = group delay dispersive ionosphere phase delay = – group delay take difference perform averaging

15. Theoretical Performance Theoretical standard deviation of split-spectrum ΔSTEC and ionospheric phase for various SAR systems. Averaging over constant area of 1 km slant range x 1 km azimuth. Mission, Sensor Azimuth Resolution [m] Range Bandwidth [MHz] Resolution Cells Averaged Range Phase Change [cycles / TECU] BIOMASS 12.5 6 3.2k 0.27 0.89 ALOS-PALSAR 4.5 14 21k 0.13 0.15 4.5 28 42k 0.047 DESDynI / TerraSAR-L 10 80 53k 0.015 Sentinel-1 6 100 110k 0.034 0.18 TerraSAR-X 3.3 100 200k 0.045 0.012 3.3 300 610k 0.0087

19. Experiments Fullband coherence average = 0.5 Topographic phase from external DEM 250 m change in topography 0.5 cycles at 512 m h amb

20. Experiments Fullband differential phase (DEM compensated) 6 cycles in unwrapped phase – 0.5 cycles due to elevation = 5.5 cycles in differential phase = 5.5 cycles of ionosphere Fullband unwrapped phase Fullband Phase

21. Experiments Ionospheric phase rewrapped Ionospheric phase Split Spectrum Estimates Ionospheric phase ~5.5 cycles

22. Experiments Split spectrum res. 1 km x 1 km Range group–phase delay res. 2 km x 2 km ΔSTEC Estimates average coherence 0.5 split spectrum σ ( Δ STEC) 0.04 TECU or 0.09 cycles