Abstract
Fully-focusing of radar altimeters is a recent concept that has been introduced to allow further improvement of along-track resolution in high pulse repetition frequency (PRF) radar altimeters. The straight potentiality of this new perspective reflects into a more accurate estimation of geophysical parameters in some applications such as sea-ice observation. However, as documented in a recent paper, such capability leaves unsolved the problem of the high computational effort required. In this paper, we face the problem of adapting for altimeters the Omega-Kappa SAR focusing algorithm that is performed in the two-dimensional wavenumber domain, accounting for the difference existing between SAR and altimeter from geometry (looking and swath width) and instrument (echoes are deramped onboard on receiving) point of view. Simulations and an application using in-orbit data show the effectiveness of the proposed approach and the highly reduced computational effort.
Highlights
During the last 20 years, a new paradigm for radar altimeter instruments has been designed, implemented, and exploited to observe the ocean and ice environment involving an accurate estimate of the range of the sensor above the Earth surface
We face the problem of adapting for altimeters the Omega-Kappa synthetic aperture radar (SAR) focusing algorithm that is performed in the two-dimensional wavenumber domain, accounting for the difference existing between SAR and altimeter from geometry and instrument point of view
This paper presents an efficient focusing algorithm for high pulse repetition frequency (PRF) radar altimeters that is performed in a two-dimensional wavenumber domain
Summary
During the last 20 years, a new paradigm for radar altimeter instruments has been designed, implemented, and exploited to observe the ocean and ice environment involving an accurate estimate of the range of the sensor above the Earth surface. High pulse repetition frequency (PRF) altimeter instruments are able to transmit pulses at a high pulse repetition frequency simultaneously guaranteeing their coherence [1] Such instruments allow to exploit the Delay/Doppler (D/D) processing concept [2,3], which, by coherent summation of pulses within a burst, achieves an improvement in terms of along-track resolution and of Equivalent Number of Looks (ENL) compared to conventional pulse-limited altimeters. By using a nadir-looking synthetic aperture radar (SAR) instrument [15], a high PRF altimeter, as we address the problem of revising and adapting the frequency domain Omega-Kappa (WK) focusing algorithm for SAR [16,17] to high PRF altimeters.
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