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A Semi-Analytical Model for Delay/Doppler Altimetry and Its Estimation Algorithm

Halimi, Abderrahim and Mailhes, Corinne and Tourneret, Jean-Yves and Thibault, Pierre and Boy, François A Semi-Analytical Model for Delay/Doppler Altimetry and Its Estimation Algorithm. (2014) IEEE Transactions on Geoscience and Remote Sensing, vol. 52 (n° 7). pp. 4248-4258. ISSN 0196-2892

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Official URL: http://dx.doi.org/10.1109/TGRS.2013.2280595

Abstract

The concept of delay/Doppler (DD) altimetry (DDA) has been under study since the mid-1990s, aiming at reducing the measurement noise and increasing the along-track resolution in comparison with the conventional pulse-limited altimetry. This paper introduces a new model for the mean backscattered power waveform acquired by a radar altimeter operating in synthetic aperture radar mode, as well as an associated least squares (LS) estimation algorithm. As in conventional altimetry (CA), the mean power can be expressed as the convolution of three terms: the flat surface impulse response (FSIR), the probability density function of the heights of the specular scatterers, and the time/frequency point target response of the radar. An important contribution of this paper is to derive an analytical formula for the FSIR associated with DDA. This analytical formula is obtained for a circular antenna pattern, no mispointing, no vertical speed effect, and a uniform scattering. The double convolution defining the mean echo power can then be computed numerically, resulting in a 2-D semi-analytical model called the DD map (DDM). This DDM depends on three altimetric parameters: the epoch, the sea surface wave height, and the amplitude. A multi-look model is obtained by summing all the reflected echoes from the same along-track surface location of interest after applying appropriate delay compensation (range migration) to align the DDM on the same reference. The second contribution of this paper concerns the estimation of the parameters associated with the multi-look semi-analytical model. An LS approach is investigated by means of the Levenberg–Marquardt algorithm. Simulations conducted on simulated altimetric waveforms allow the performance of the proposed estimation algorithm to be appreciated. The analysis of Cryosat-2 waveforms shows an improvement in parameter estimation when compared to the CA.

Item Type:Article
Additional Information:Thanks to IEEE editor. The original PDF of the article can be found at IEEE Transactions on Geoscience and Remote Sensing website : http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=36
HAL Id:hal-01057698
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National des Etudes Spatiales - CNES (FRANCE)
French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
French research institutions > Institut Français de Recherche pour l'Exploitation de la MER - IFREMER (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Université de Toulouse > Université Paul Sabatier-Toulouse III - UPS (FRANCE)
Université de Toulouse > Université Toulouse - Jean Jaurès - UT2J (FRANCE)
Université de Toulouse > Université de Toulouse I-Sciences Sociales - UT1 (FRANCE)
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Deposited By: Jean-yves TOURNERET
Deposited On:25 Aug 2014 09:37

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