In-flight calibration of optical sensors polarization sensitivity based on sunlight reflection over open oceans.

Optical radiometers are critical instruments in remote sensing, providing high-precision measurements for various applications such as vegetation monitoring, water color analysis, and Earth’s radiative balance assessment. However, these instruments are subject to imperfections that can affect data quality. Ground-based image quality processing is typically employed to correct these imperfections, ensuring accurate measurements for users. One such imperfection is polarization sensitivity, which introduces errors when not properly addressed, particularly in sensors that do not explicitly measure polarization, turning it into a poorly controlled disturbance in the signal.

Traditionally, polarization sensitivity is characterized during pre-flight tests at instrument level, with corrections applied during the satellite’s operational phase. However, this characterization has limitations. Over time, the instrument's sensitivity to polarization can change due to environmental factors, exposure to space conditions, and degradation over the satellite’s lifespan. Furthermore,

the accuracy of the correction depends on the precision of ground-based polarization measurements, resulting in residual errors in the corrected data.

The primary goal of this thesis is to develop an innovative method for modeling and correcting polarization sensitivity in-flight. This aims to improve the accuracy of in-flight evaluations to a level that allows for seamless integration into image correction pipelines. Specifically, the research will focus on sunlight reflection over ocean surfaces, a phenomenon with predictable polarization characteristics that has been successfully measured by polarized sensors like POLDER. This natural target can serve as a reliable reference to continuously monitor and characterize polarization sensitivity during the satellite’s mission. The use of in-land water bodies will also be investigated to address the specific problem of high spatial resolution sensors. 

This project seeks to refine existing techniques and expand their application, ultimately contributing to more accurate and reliable data for remote sensing. Additionally, improving in-flight polarization correction may allow for less stringent instrument specifications, as the ability to correct in-flight could reduce the need for overly constrained design requirements. Such technique could also have profound implication for the development of low cost sensors on-board cube-sat platforms.

The candidate will build upon preliminary work from a previous thesis that explored the theoretical foundations of sunglint modeling and polarization calibration. The research will combine modeling and data analysis of past, current and future polarimetric sensors (PARASOL, SGLI, 3MI, …).

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For more Information about the topics and the co-financial partner (found by the lab); contact Directeur de thèse - jerome.riedi@univ-lille.fr

Then, prepare a resume, a recent transcript and a reference letter from your M2 supervisor/ engineering school director and you will be ready to apply online before March 13th, 2026 Midnight Paris time!