Measuring air speed at high altitude by lidar is very important for aeronautical (notably for future low-consumption aircraft) and space applications: Cal/val and future Aeolus family missions whose usefulness is now essential for weather forecasts. This measurement, carried out by direct detection molecular UV lidar, is an important subject at ONERA and LATMOS. For several years, we have been developing a solution comprising an innovative spectral analyzer of the quad Mach-Zehnder (QMZ) interferometer type which is the best compromise between measurement precision and robustness. Such a system seems a particularly advantageous solution for future versions of the AEOLUS 2 satellite [D. Bruneau and J. Pelon, Atmos. Meas. Tech.,14, 4375–4402, 2021]. It would allow an improvement in speed measurement performance and the simultaneous measurement of wind and the radiative properties of clouds with the same analyzer, which would constitute a significant gain compared to the current system.

The objective of this thesis is to study the possibilities of using the QMZ as a spectral analyzer for future versions of AEOLUS. An essential point to make a space system, particularly in the case of an interferometer, is to make any misalignment impossible. This is why we recently designed a new monolithic version of the QMZ made up of several prisms glued together. A first challenge of the thesis will be to study the performance of this interferometer and integrate it into current lidar. Additionally, as current lidar was developed to perform short-range measurements in front of an aircraft, the lidar architecture will need to be modified. A second challenge will be to modify the architecture of the current lidar to carry out long-distance wind measurements (up to 10-20 km altitude), which will notably involve the use of photomultipliers and a probable modification of the signal processing algorithms to move to photon counting. Finally, a third challenge will be to set up a treatment to determine the radiative properties of clouds from the outputs of this analyzer. At the end of the thesis, the addition of a depolarized channel could be considered to study the properties of backscattering aerosols more precisely.

The thesis has 3 stages. The first step will consist of experimentally studying the performance of the new interferometer and then integrating it into the lidar. During the second step, the student will determine, via existing modeling code, a configuration allowing a long-range lidar measurement then set it up and demonstrate the measurement. The third step will consist of simulating the measurement of the radiative properties of clouds, developing suitable QMZ processing algorithms allowing these properties to be determined and testing the method experimentally. During the different stages, the performances obtained will be evaluated with regard to the needs of AEOLUS.

=================

For more Information about the topics and the co-financial partner (found by the lab!); contact Directeur de thèse - david-tomline.michel@onera.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!