Synthetic Aperture Radar Signal Processing
Contact Persons
Othmar Frey | |
Keywords
SAR Signal Processing, Spaceborne/Airborne SAR, SAR Focusing, Motion Compensation, Time-Domain SAR Processing, Frequency-Domain SAR Processing
Quick Reference
Synthetic Aperture Radar (SAR) is a popular active remote sensing technique to obtain digital images of large areas, independent of the prevailing weather situation (cloud coverage, rain, snow, fog) or day- and nighttime.
SAR images need an initial focusing procedure to make the information available to the user. The Modular SAR Processor (MSP) developed at our laboratory allows the handling of complex SAR signals from spaceborne and airborne radar carriers and processes raw data from different systems of various design. Prominent sensors supported are the spaceborne ALOS PALSAR, Envisat ASAR and ERS-1/2, JERS-1, SIR-C (Space Shuttle) as well as RADARSAT-1. Airborne data may be processed from systems operating with carrier frequencies between a few hundred Megahertz (P-Band) and close to 100 Gigahertz (W-Band).
The amplitude (reflected intensity) information of processed SAR scenes may be used for land monitoring, while the phase information is often exploited much further to generate digital surface models or for temporal change detection through interferometric techniques, which are implemented in our Interferometric SAR Processor (ISP). Since these methods rely on the accurate phase information of the original complex signal, the phase-preserving capability of the processor is essential.
To retain the phase information of the SAR signal, and thus to allow physically limited focusing of the image, the processor must include special modules that handle effects of irregular motion of the (airborne) sensor platform. Hence, another main task of our research is the correct assessment of the flight track of a sensor, based on differential Global Positioning System (DGPS) and inertial measurement units (IMU).
The on-going activities are focused on the extension of the existing software packages to support new sensors and to implement additional techniques of information extraction. Several focusing techniques are implemented and integrated into the processor. The frequency domain algorithms include the classic range-Doppler approach as well as omega-k and chirp scaling implementations. In the time-domain, much work has been conducted towards a fully operational backprojection algorithm for air- and spaceborne sensors.
Partnerships
Research has been conducted in cooperation with the following organizations:
- Forschungsgesellschaft für angewandte Naturwissenschaften (FGAN)
- European Space Agency (ESA)
- German Aerospace Center (DLR)
- Swiss Federal Department of Defence, Civil Protection and Sport (armasuisse)
- OrbiSat da Amazonia s.a.
- Japan Aerospace Exploration Agency (JAXA)
Some Results
- Simulated SAR Images
- Spaceborne SAR Images
- PALSAR Image of Zurich (Detailed View)
- Envisat Image of Zurich (Detailed View)
- ERS-2 Image of Lake Konstanz (Detailed View)
- Space Shuttle SAR Images
- Airborne SAR Images
Publications
- Othmar Frey, Christophe Magnard, Maurice Rüegg, and Erich Meier. Focusing of Airborne Synthetic Aperture Radar Data from Highly Nonlinear Flight Tracks. IEEE Transactions on Geoscience and Remote Sensing, vol.47, no. 6, pp. 1844-1858, June 2009. [pdf] (PDF, 3.5 Mb)
- Othmar Frey, Felix Morsdorf, and Erich Meier. Tomographic Imaging of a Forested Area By Airborne Multi-Baseline P-Band SAR. Sensors, Special Issue on Synthetic Aperture Radar, 8(9):5884--5896, September 2008. [pdf] (PDF, 9.4 Mb)
- Othmar Frey and Erich Meier. Combining Time-Domain Back-Projection and Capon Beamforming for Tomographic SAR Processing (Invited Paper). In IEEE International Geoscience and Remote Sensing Symposium, IGARSS'08, 2008. [pdf] (PDF, 4.6 Mb)
- Othmar Frey, Christophe Magnard, Maurice Rüegg, and Erich Meier. Focusing SAR Data Acquired From Non-Linear Sensor Trajectories. In IEEE International Geoscience and Remote Sensing Symposium, IGARSS'08, 2008. [pdf] (PDF, 4.6 Mb)
- Othmar Frey and Erich Meier. Tomographic Focusing by Combining Time-Domain Back-Projection and Multi-Looking Based Focusing Techniques (Invited Paper). In Proc. of EUSAR 2008 - 7th European Conference on Synthetic Aperture Radar, 2008. [pdf] (PDF, 4.6 Mb)
- Othmar Frey, Christophe Magnard, Maurice Rüegg, and Erich Meier. Non-Linear SAR Data Processing By Time-Domain Back-Projection. In Proc. of EUSAR 2008 - 7th European Conference on Synthetic Aperture Radar, 2008. [pdf] (PDF, 4.6 Mb)
- Christophe Magnard, Othmar Frey, Maurice Rüegg, and Erich Meier. Improved Airborne SAR Data Processing by Blockwise Focusing, Mosaicking and Geocoding. In Proc. of EUSAR 2008 - 7th European Conference on Synthetic Aperture Radar, 2008. [pdf] (PDF, 313 Kb)
- Othmar Frey, Felix Morsdorf, and Erich Meier. Tomographic Processing of Multi-Baseline P-Band SAR Data for Imaging of a Forested Area. In IEEE International Geoscience and Remote Sensing Symposium, IGARSS'07, 2007. [pdf] (PDF, 1.5 Mb)
- Othmar Frey, Felix Morsdorf, and Erich Meier. Tomographic SAR Imaging of a Forested Area by Time-Domain Back-Projection. In M.E. Schaepman, S. Liang, N.E. Groot, and M. Kneubühler, editors, 10th Intl. Symposium on Physical Measurements and Spectral Signatures in Remote Sensing, volume XXXVI, 2007. Intl. Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. [pdf] (PDF, 2.0 Mb)
- Othmar Frey, Erich Meier, and Daniel Nüesch. An Integrated Focusing and Calibration Procedure for Airborne SAR Data. In Proc. of EUSAR 2006 - 6th European Conference on Synthetic Aperture Radar, 2006. [pdf] (PDF, 343 Kb)
- Othmar Frey, Erich Meier, and Daniel Nüesch. A Study on Integrated SAR Processing and Geocoding by Means of Time-Domain Backprojection. In Proceedings of the Int. Radar Symposium, Berlin, 2005. [pdf] (PDF, 2.8 Mb)
- Othmar Frey, Erich Meier, and Daniel Nüesch. Processing SAR data of rugged terrain by time-domain back-projection. In SPIE Vol. 5980: SAR Image Analysis, Modeling, and Techniques X, 2005. [pdf] (PDF, 1.9 Mb)