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Summary of Proposal MTH0224

TitlePotential of TerraSAR-X advanced modes for SAR interferometry
Investigator Pourthié, Nadine - CNES, DCT/SI/AR
Team Members
Mrs. Pourthié, Nadine - CNES, DCT/SI/AR
Mr. Gaudin, Jean-Marc - CNES, DCT/SI/AR
SummaryTerraSAR-X will provide very innovative SAR data and very promising images for science, including high resolution, X-band, polarimetry and interferometry. Moreover several acquisition modes (Stripmap, ScanSAR and Spotlight) will be available.
This proposal is dedicated to the assessment of advanced modes (ScanSAR, Spotlight) for interferometry. We identify two major axes: assessment of advanced modes for interferometry and study of a new SAR synthesis approach in order to simplify the interferometric process.
Classically, interferometry is derived from stripmap images. What about using other modes ? does it have an impact on interferometric phase quality ? Is it possible to merge different modes to create an interferogram ?
The second issue will be developed in the framework of a PhD thesis that will start in 2006 on advanced SAR synthesis methods. The overall objective is to synthesize a single look complex SAR image directly on a DTM (for instance, SRTM). Subsequent interferometric processing would thus be very easy. Throughout this AO response, we propose to validate the PhD work on TerraSAR-X data.
The study will be conducted by people of the SI/AR group of CNES. There is no external co-PI. In addition, no external funding is required. The work is conducted on CNES fund and may also be extended in the framework of CNES research and development plan, if needed.
CNES has submitted three proposals to the TerraSAR-X AO :
1. “Singular point monitoring with different TerraSAR-X modes”,
2. “Potential of new TerraSAR-X modes for SAR interferometry”,
3. “TerraSAR-X contribution to reference remote sensing data base”.
The two first ones address different theoretical problems of SAR methods , whereas the last one is more dedicated to applications with land cover, risk management or costal monitoring thematics. Two CNES departments are involved in these works. Of course, these three works will share their results in order to improve the global quality of the final work that will be delivered to the TerraSAR-X mission.
Detailed report- A new release of the CNES/Altamira Diapason Software have been done in order to produce SpotLight interferograms: compared with conventional stripmap mode processing, the Insar SpotLight data processing requires some precautions and algorithmic modifications according [Eineder 2009]. Doppler centroïd and PRF variations inherent to Spotlight acquisitions are taken into account. The Insar processing software at CNES is now able to process Spotlight TERRASAR-X data. - Stripmap and SpotLight comparison: High resolution Spotlight mode with short temporal baseline (very high coherence) revealed interesting topographic details for volcano studies. Spotlight interferometric acquisitions focussed the study on the very active volcano of Piton de La Fournaise (10x10 km2- Reunion Island). The high resolution of the Spotlight mode is a real asset to fully monitor 3D ground deformations and update precisely DTM. (see the corresponding uploaded images included in this report) - SpotLight mode for 3D urban studies: Severe decorrelation occurs on vegetated areas (as expected for X-band). Filtering of the interferograms is needed in order to reduce the noise and to allow exploitation of the temporal stability of small scatterers on buildings. - Haiti co- and post-seismic Stripmap interferograms: A good interferometric coherence is observed between images with a temporal baseline of 11 days, even 22 days. The coherence on urban areas remains acceptable with a one year temporal baseline. Despite a lot of atmospheric artefacts, inevitable in X-band under the tropical latitudes, thin networks of interferometric fringes appears to the Southeast of Leogane town and to the South of Carrefour town (at the Enriquillo Fault level). (see the corresponding uploaded images included in this report)

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