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Deutsches Zentrum Fur Luft-und Raumfahrt E.v.

Deutsches Zentrum Fuer Luft-und Raumfahrt E.v

Deutsche Forschungsanstalt Fur Luft-und Raumfahrt E.v.

Josef Mittermayer

Alberto Moreira

Gerhard Krieger

Rolf Scheiber

Pau Prats

Thomas Kraus

Pau Prats-Iraola

Paco López-Dekker

Prats-Iraola Pau

Hauke Fiedler

Marc RODRÍGUEZ-CassolÀ

Elke Boerner

Sub-aperture processing is carried out. Within each sub-aperture, range compression and a correction for the target range variation are carried out. Baseband azimuth scaling is used for processing the azimuth signal, wherein a long azimuth reference function and thus a wide azimuth dimension are prevented. The scaling range is not constant and depends on the range, which is not equal to the original range vector. It is calculated such that, in combination with a subsequent derotation step, constant azimuth scanning is achieved for all ranges. The selected derotation function, which is applied in the azimuth time domain, makes it possible for all the targets to be in base band, in this way varying the effective chirp rate. Since the phase is purely quadratic because of the azimuth scaling step, it is thus possible to use an optimal filter which takes account of the effective chirp rate. IFFT results in a focused image, and a final phase function in the time domain allows phase maintenance. Application for SAR, SONAR and seismic raw data processing in the TOPS mode, as well as other modes which make use of the antenna polar diagram being scanned in the azimuth and/or elevation direction.

Method for processing TOPS (terrain observation by progressive scan)-SAR (synthetic aperture radar)-raw data

For interferometric and/or tomographic remote sensing by means of synthetic aperture radar (SAR) one to N receiver satellites and/or transmitter satellites and/or transceiver satellites with a horizontal across-track shift the same or differing in amplitude form a configuration of satellites orbiting at the same altitude and same velocity. Furthermore, a horizontal along-track separation, constant irrespective of the orbital position, is adjustable between the individual receiver satellites. In this arrangement one or more receiver satellites orbiting at the same altitude and with the same velocity are provided with a horizontal across-track shift varying over the orbit such that the maximum of the horizontal across-track shift occurs over a different orbital position for each satellite, the maxima of the horizontal across-track shifts are positioned so that the baselines are optimized for across-track interferometry. A transmitter or transceiver satellite is positioned either separate from the configuration without across-track shift or as part of the configuration with horizontal across-track shift.

Satellite configuration for interferometric and/or tomographic remote sensing by means of synthetic aperture radar (SAR)

For two-dimensional processing of spotlight SAR data into exact image data, the spotlight SAR raw data are divided into azimuth sub-apertures and transformed into the range-time/azimuth-frequency domain through short azimuth FFTs. The obtained data are multiplied by a frequency-scaling function H,(f,, t,; r,) and transformed into the two-dimensional frequency domain through short range FFTs, multiplied by an RV-phase-correction function H,(f,) and subsequently transformed back into the range time/azimuth-frequency domain through short range IFFTs. The data formed in this manner are multiplied by the inverse frequency-scaling function H,(f,, f,), then transformed back into the two-dimensional frequency domain, multiplied by the phase-correction function H,(f,, f,) and the azimuth-scaling function H,(f,, f,), and transformed back into the range-frequency/azimuth-time domain through short azimuth FFTS. Then the azimuth sub-apertures are re-assembled, multiplied by a de-ramping function H,(t,) and transformed into the two-dimensional frequency domain through long azimuth FFTs.

Method of processing spotlight SAR raw data

In a method for azimuth scaling of SAR data without interpolation, raw SAR data in azimuth are multiplied with a phase function H.sub.5 (f.sub.a ;r.sub.o), where f.sub.a denotes the azimuth frequency and r.sub.o denotes the range to a target point, and where a desired scaling factor is entered into the phase function. An azimuth modulation of the SAR data is subsequently adapted with the phase function H.sub.5 (f.sub.a,r.sub.o) to that of a reference range, in a manner so that the azimuth modulation no longer depends on the range. In a last step of the process, a quadratic phase modulation is performed in the azimuth so that, in order to attain an azimuth processing with a very high phase accuracy, the azimuth frequency modulation becomes exactly linear.

Method for azimuth scaling of SAR data and highly accurate processor for

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München, Germany

Josef Mittermayer