Ultra-rapid optronic processor for instantaneous ENVISAT/ASAR scene observation

Long-range land surveillance is a critical need in numerous military and civilian security applications, such as threat detection, terrain mapping and disaster prevention. A key technology for land surveillance, synthetic aperture radar (SAR) continues to provide high resolution radar images in all weather conditions from remote distances. Recently, Interferometric SAR (InSAR) and Differential Interferometric SAR (D-InSAR) have become powerful tools adding high resolution elevation and change detection measurements. State of the art SAR systems based on dual-use satellites are capable of providing ground resolutions of one meter; while their airborne counterparts obtain resolutions of 10 cm. DInSAR products based on these systems can produce cm-scale vertical resolution image products.Certain land surveillance applications such as land subsidence monitoring, landslide hazard prediction and tactical target tracking could benefit from improved resolution. The ultimate limitation to the achievable resolution of any imaging system is its wavelength. State-of-the art SAR systems are approaching this limit. The natural extension to improve resolution is to thus decrease the wavelength, i.e. design a synthetic aperture system in a different wavelength regime. One such system offering the potential for vastly improved resolution is Synthetic Aperture Ladar (SAL). This system operates at infrared wavelengths, ten thousand times smaller radar wavelengths. This paper discusses an initial investigation into a concept for an airborne SAL specifically aiming at land surveillance. The system would operate at 1.55 µm and would integrate an optronic processor on-board to allow for immediate transmission of the high resolution images to the end-user on the ground. Estimates of the size and weight, as well as the resolution and processing time are given.

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“…After digital (such as the Range -Doppler algorithm [2][7]) or optronic [8][9] processing, the SAR image is given by:…”

Section: Synthetic Aperture Radar (Sar)mentioning

confidence: 99%

“…SAR image reconstruction may be performed either digitally [2] [7] or optronically [8] [9] and similarly for SAL. Indeed, the demonstration of SAL image reconstruction from optronic processing has recently be shown in Refs.…”

Section: Introductionmentioning

confidence: 99%

Investigation of synthetic aperture ladar for land surveillance applications

et al. 2013

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“…Optronic processing is based on digital holography. In this technique [8] [9], the raw data are coherently illuminated and lenses are inserted into the beam's path focusing the raw data to form the image that is in turn captured by a digital camera or a film. The main difference between the optronic processor and the more commonly used digital approach is the ultra-fast processing capability of optronic processing.…”

Section: Introductionmentioning

confidence: 99%

An all-optronic synthetic aperture lidar

et al. 2012

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Synthetic Aperture Radar (SAR) is a mature technology that overcomes the diffraction limit of an imaging system's real aperture by taking advantage of the platform motion to coherently sample multiple sections of an aperture much larger than the physical one. Synthetic Aperture Lidar (SAL) is the extension of SAR to much shorter wavelengths (1.5 μm vs 5 cm). This new technology can offer higher resolution images in day or night time as well as in certain adverse conditions. It could be a powerful tool for Earth monitoring (ship detection, frontier surveillance, ocean monitoring) from aircraft, unattended aerial vehicle (UAV) or spatial platforms. A continuous flow of high-resolution images covering large areas would however produce a large amount of data involving a high cost in term of post-processing computational time.This paper presents a laboratory demonstration of a SAL system complete with image reconstruction based on optronic processing. This differs from the more traditional digital approach by its real-time processing capability. The SAL system is discussed and images obtained from a non-metallic diffuse target at ranges up to 3m are shown, these images being processed by a real-time optronic SAR processor origiinally designed to reconstruct SAR images from ENVISAT/ASAR data.

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“…A SAL system is basically the equivalent of a SAR system where the radar wavelength is replaced with an infrared wavelength, a thousand time smaller, yielding a more compact system and eventually much higher resolution. Figure 3 presents an image (left) and schematic drawing (right) of a prototype optronic SAR processor designed to reconstruct SAR images from specifically from ENVISAT/ASAR data [9]- [10]. In this implementation, the SAR raw data is fed into the system through two spatial light modulators, one for the amplitude component and one for the phase component, illuminated by a coherent laser beam.…”

Section: Synthetic Aperture Systemsmentioning

confidence: 99%