Synthetic Aperture Radar (SAR)
Circular Flight Path Imaging | Terrain Characterization using Foliage Penetration
| FPGA Programming

TSC has significant experience in developing advanced radar signal processing algorithms for application to synthetic aperture radar (SAR). Our algorithms perform 3D imaging, foliage suppression and change detection.


 

3-D SAR for Enhanced Combat ID
Typical SAR systems of the past have employed a single frequency band, a single transmit/receive polarization, a single antenna and simple linear flight paths. This simplicity reduced the acquisition and operating cost of the radar, the latency of the imagery and the complexity of the CONOPS. However, the SAR imagery produced by these systems is not adequate to differentiate true targets from sophisticated decoys. Recent advances in SAR technology can be exploited to provide additional information and better support enhanced combat ID. This information can come in many forms including fully-polarimetric SAR, interferometric SAR and SAR from novel flight paths. Although fully polarimetric and interferometric systems can provide additional information, development of entirely new systems or incorporating hardware modifications to existing systems can be very expensive. Alternatively, SAR imagery produced using novel flight paths can provide a significant increase in combat ID performance using existing radar systems with only CONOPS and software changes. TSC is investigating novel flight paths and processing to aid combat ID. Under an SBIR effort, TSC is developing an automatic target recognition system that exploits SAR imaging performed using a circular flight path. TSC’s 3D-aided target recognition concept is based on 2D Circular SAR imaging and 3D Tomographic SAR imaging techniques which produce “slices” of the target at various heights to form a 3D data cube. A crisp outline of the target signature is provided as well as an enhanced set of target features. TSC is also investigating methods to find correspondence between observed signatures and CAD models and to produce true stereo displays of overlaid 3D SAR imagery and target CAD-models.


 

Circular Flight Path Imaging
TSC has developed novel image formation algorithms for application to microwave and FOPEN SAR systems. Our flexible backprojection processing focuses imagery in a manner that removes the constraint for SAR platforms to fly straight line flight paths. TSC’s backprojection algorithm enables ground areas of interest to be imaged rapidly at any desired resolution within the measurement capability of the radar. TSC has demonstrated the ability to use backprojection to view a target area from all sides by flying complete circles around a designated area. TSC is also investigating tomographic processing techniques to produce 3-D images from circular flight paths. This will supplement GeoSAR’s current mapping capabilities. TSC is additionally designing a field-deployable groundstation to provide quick-look imaging to support quality checking and intelligence analysis.


 

Terrain Characterization using Foliage Penetration
TSC is developing extensive algorithms to automatically characterize terrain by processing Foliage Penetration Synthetic Aperture Radar (FOPEN SAR) imagery on an effort for DARPA and the US Army CERDEC. FOPEN SAR is able to penetrate the foliage canopy to detect hidden targets, facilities and road networks. TSC has developed innovative stereo processing and repeat-pass Interferometric SAR (IFSAR) techniques to estimate the topography beneath the canopy, to determine trafficable areas for route planning, and to identify where enemy vehicles may be concealed. We have evaluated these algorithms on FOPEN SAR imagery collected at a variety of sites by an airborne testbed to demonstrate their robust performance.

TSC has extended our proven Automatic Terrain Classification algorithms to estimate tree density and to identify man-made features, including buildings and roads. A stereographic workstation has also been configured to provide a FOPEN SAR visualization capability, which was favorably demonstrated to National Geospatial Agency (NGA) image analysts. This workstation can display the location of individual trees, relocated targets and extracted features overlaid on terrain contours. TSC’s stereo SAR DEM generation tool has been hosted on a DARPA FOPEN SAR workstation that is being developed to aid in wide-area target detection. This tool was used with great success in a recent data collection in South America.

Additionally, TSC is developing novel image formation algorithms for application to GeoSAR and to other microwave and FOPEN SAR systems. Our flexible backprojection processing focuses imagery in a manner that removes the constraint for SAR platforms to fly straight line flight paths. TSC’s backprojection algorithm enables ground areas of interest to be imaged rapidly at any desired resolution within the measurement capability of the radar. TSC has demonstrated the ability to use backprojection to view a target area from all sides by flying complete circles around a designated area.

TSC is investigating the use of multi-pass microwave SAR imagery to identify areas of recent human activity. As shown in the figure, ground disturbances that are not evident in single pass images can be very evident when two pass Coherent Change Detection (CCD) is performed, and may even allow the detection of foot traffic, and mine emplacement. This technology could be used in a variety of applications, such as locating IED emplacements, identifying tunneling activity, and detecting illegal immigration traffic.

 



FPGA Programming
TSC has investigated the use of Field Programmable Gate Array (FPGA) based systems, such as the MAPstation from SRC Computers (www.srccomp.com), to provide improved throughput during SAR image formation using Backprojection techniques. These FPGA systems provide a reprogrammable hardware-based solution for processing large volumes of data in real-time. TSC has experience in making tradeoffs and customizing high-level code to make optimal use of their capabilities. TSC personnel have been trained in the architecture and programming of the SRC devices including their development environment and debugging toolset.