Understanding how gas and dust in the interstellar medium evolve into stars and planetary systems is a major challenge in modern astrophysics. Magnetic fields play an important role in these processes, but their influence remains poorly understood. Measuring the polarization of thermal dust emission at submillimeter wavelengths provides a powerful way to map the structure of magnetic fields within molecular clouds.

The POLARYS camera, developed at CEA for the APEX telescope in Chile, will enable such observations at 350 µm with improved sensitivity. It will use a new generation of cryogenic detectors that are intrinsically sensitive to polarization, whose scientific potential remains to be fully demonstrated.

The main objective of this PhD project is to characterize these detectors and develop methods to efficiently extract the polarized astrophysical signal. The work will combine experimental measurements in the laboratory (sensitivity, noise, polarimetric response), modeling of the detection chain, and the development of signal-processing tools, particularly to separate the astrophysical emission from atmospheric contamination. The project will also focus on optimizing the camera’s observing modes and calibration strategies.

The final stage of the PhD will involve analyzing the first on-sky observations with POLARYS, planned for 2030. Combining instrumental development and astrophysical research, this work will also contribute to preparing the scientific exploitation of future space instruments, particularly those of the PRIMA mission.