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Etude de la propagation des ondes térahertz en milieu diffusant pour l'imagerie pour hélicoptères en condition de brownout

Abstract : Brownouts are sand clouds stirred by the airflow of the helicopter rotor in arid areas. This cloud can be tens-of-meters thick and reduces or even cancels the pilot's visibility. A solution is to provide an imaging system embedded on the helicopter that would allow the pilot to visualize the landing area through the sand cloud. Such a system must meet specific criteria. The wave must be able to penetrate the scattering medium and give a sufficient resolution to detect obstacles. The system must also be compact and must work in real time.The sub-terahertz band seems to be the most adequate because it a priori complies with all the requirements. To our knowledge, the performance a sub-terahertz imaging system in brownout condition has never been completely evaluated yet. Besides, some of the existing experimental studies do not seem to be consistent between each other.Thus, we propose an accurate model, which was successfully compared to a Monte Carlo simulation, to evaluate the efficiency of such an imager. Second, we present an innovative experiment to measure simultaneously the attenuation by suspended sand in the terahertz and the visible bands. The extinction efficiency in the THz band can directly be known from these simultaneous measurements. The density of suspended particles and their refractive index in the THz band can also be deduced.
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Submitted on : Thursday, March 19, 2020 - 4:37:10 PM
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  • HAL Id : tel-02512448, version 1

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Clotilde Prophete. Etude de la propagation des ondes térahertz en milieu diffusant pour l'imagerie pour hélicoptères en condition de brownout. Physique [physics]. PSL Research University, 2018. Français. ⟨NNT : 2018PSLET040⟩. ⟨tel-02512448⟩

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