Altimetry
Coastal altimetry, delay/Doppler altimetry, parameter estimation
PhD Thesis: Satellite Altimetry Waveform Analysis
My PhD thesis focused on the estimation of ocean surface parameters from satellite altimetry waveforms. The work developed new statistical models and estimation algorithms for both conventional pulse-limited altimetry and the emerging delay/Doppler (SAR) altimetry. The thesis was conducted at IRIT/INP-ENSEEIHT, Toulouse, under the supervision of Jean-Yves Tourneret and Corinne Mailhes, in collaboration with CNES and CLS.
Conventional Pulse-Limited Altimetry
Conventional satellite altimeters transmit short radar pulses toward the ocean surface and analyze the returned waveforms to estimate geophysical parameters such as sea surface height, significant wave height, and wind speed. We developed improved parameter estimation algorithms based on the Brown model and its extensions, accounting for non-Gaussian noise and antenna mispointing effects.
Delay/Doppler (SAR) Altimetry
Delay/Doppler altimetry, also known as SAR altimetry, achieves improved along-track resolution by exploiting the Doppler information in the returned echoes. We developed semi-analytical models for delay/Doppler waveforms and proposed efficient estimation algorithms that account for the specific characteristics of SAR altimetry data, including multi-look processing and speckle noise reduction.
Coastal Altimetry
Coastal regions present significant challenges for satellite altimetry due to land contamination in the radar footprint, complex tidal signals, and rapidly varying sea state. We developed specialized algorithms for coastal waveform analysis that can handle multi-peak waveforms and separate ocean and land returns, enabling more accurate sea level measurements near coastlines.
Waveform Denoising and Parameter Estimation
Altimetry waveforms are affected by speckle noise that degrades the precision of estimated geophysical parameters. We developed denoising approaches based on Bayesian estimation and total variation regularization that improve the quality of estimated parameters while preserving the waveform shape information.
Related Publications
- A. Halimi, C. Mailhes, J.-Y. Tourneret, P. Thibaut, and F. Boy, "Parameter estimation for peaky altimetric waveforms," IEEE Trans. Geoscience and Remote Sensing, vol. 51, no. 3, pp. 1568–1577, 2013.
- A. Halimi, C. Mailhes, J.-Y. Tourneret, P. Thibaut, and F. Boy, "A semi-analytical model for delay/Doppler altimetry and its estimation algorithm," IEEE Trans. Geoscience and Remote Sensing, vol. 52, no. 7, pp. 4248–4258, 2014.
- A. Halimi, C. Mailhes, J.-Y. Tourneret, and H. Snoussi, "Bayesian estimation of smooth altimetric parameters: Application to conventional and delay/Doppler altimetry," IEEE Trans. Geoscience and Remote Sensing, vol. 53, no. 4, pp. 2200–2212, 2015.
- A. Halimi, C. Mailhes, and J.-Y. Tourneret, "Estimation of the antenna mispointing effects on altimetry waveforms," in Proc. IEEE IGARSS, 2015.
- A. Halimi, J.-Y. Tourneret, and C. Mailhes, "Denoising altimetry waveforms by adaptation of the total variation method," IEEE Geoscience and Remote Sensing Letters, vol. 14, no. 11, pp. 2091–2095, 2017.