HR: 09:00h
AN: G41D-05    [Abstracts]
TI: Integration of ERS and ASAR Time Series for Differential Interferometric SAR Analysis
AU: * Werner, C L
EM: cw@gamma-rs.ch
AF: Gamma Remote Sensing AG, Worbstrasse 225, Gümligen, 3073 Switzerland
AU: Wegmüller, U
EM: wegmuller@gamma-rs.ch
AF: Gamma Remote Sensing AG, Worbstrasse 225, Gümligen, 3073 Switzerland
AU: Strozzi, T
EM: strozzi@gamma-rs.ch
AF: Gamma Remote Sensing AG, Worbstrasse 225, Gümligen, 3073 Switzerland
AU: Wiesmann, A
EM: wiesmann@gamma-rs.ch
AF: Gamma Remote Sensing AG, Worbstrasse 225, Gümligen, 3073 Switzerland
AB: Time series SAR interferometric analysis requires SAR data with good temporal sampling covering the time period of interest. The ERS satellites operated by ESA have acquired a large global archive of C-Band SAR data since 1991. The ASAR C-Band instrument aboard the ENVISAT platform launched in 2002 operates in the same orbit as ERS-1 and ERS-2 and has largely replaced the remaining operational ERS-2 satellite. However, interferometry between data acquired by ERS and ASAR is complicated by a 31 MHz offset in the radar center frequency between the instruments leading to decorrelation over distributed targets. Only in rare instances, when the baseline exceeds 1 km, can the spectral shift compensate for the difference in the frequencies of the SAR instruments to produce visible fringes. Conversely, point targets do not decorrelate due to the frequency offset making it possible to incorporate the ERS-ASAR phase information and obtain improved temporal coverage. We present an algorithm for interferometric point target analysis that integrates ERS-ERS, ASAR-ASAR and ERS-ASAR data. Initial analysis using the ERS-ERS data is used to identify the phase stable point-like scatterers within the scene. Height corrections relative to the initial DEM are derived by regression of the residual interferometric phases with respect to perpendicular baseline for a set of ERS-ERS interferograms. The ASAR images are coregistered with the ERS scenes and the point phase values are extracted. The different system pixel spacing values between ERS and ASAR requires additional refinement in the offset estimation and resampling procedure. Calculation of the ERS-ASAR simulated phase used to derive the differential interferometric phase must take into account the slightly different carrrier frequencies. Differential ERS-ASAR point phases contain an additional phase component related to the scatterer location within the resolution element. This additional phase varies over several cycles making the differential interferogram appear as uniform phase noise. We present how this point phase difference can be determined and used to correct the ERS-ASAR interferograms. Further processing proceeds as with standard ERS-ERS interferogram stacks utilizing the unwrapped point phases to obtain estimates of the deformation history, and path delay due to variations in tropospheric water vapor. We show and discuss examples demonstrating the success of this approach.
DE: 1243 Space geodetic surveys
DE: 1294 Instruments and techniques
DE: 6924 Interferometry (1207, 1209, 1242)
DE: 6969 Remote sensing
SC: Geodesy [G]
MN: Fall Meeting 2005