Ultraviolet (UV) observations of sunlight reflected at the cloud top of Venus have provided crucial insights into the planet’s atmosphere. They have revealed remarkable variability in trace gases such as sulphur oxides (SO and SO₂) and in the enigmatic “UV absorber,” whose exact nature remains unknown. Understanding the causes of these variabilities is essential to improve our knowledge of Venus’ climate system, including possible interactions between the atmosphere, surface, and interior through processes such as volcanic outgassing.

The most recent datasets originate from two key missions: ESA’s Venus Express (2006–2014), whose SPICAV-UV spectrometer covered the 170–320 nm range, and JAXA’s Akatsuki (2015–2025), equipped with the UVI imager observing at 283 and 365 nm. Together, they revealed distinctive spatial patterns in the SO₂ distribution. Both missions observed higher SO₂ concentrations at low latitudes, yet they disagreed on the local time variations: SPICAV-UV identified a subsolar minimum, whereas UVI detected an afternoon enhancement relative to the morning side. The latter result aligns with recent photochemical–dynamical coupled simulations. However, these studies employed different assumptions—particularly regarding the vertical distribution of gases and cloud particles—making direct comparison difficult.

The goal of this PhD project is to resolve these discrepancies by developing a unified, state-of-the-art radiative transfer model capable of interpreting both spectroscopic and imaging data. The model will combine deterministic solvers (e.g. DISORT) and Monte Carlo approaches (e.g. htrdr-planeto) to simulate radiative processes in Venus’ atmosphere. Once validated against SPICAV-UV and UVI datasets, this model will serve as a robust reference framework for current and future UV studies of Venus.

A major focus will be the preparation for ESA’s EnVision mission, scheduled to begin science operations in 2035. Its UV spectral imager, VenSpec-U, represents the main instrumental contribution of CNES to the mission. The radiative transfer model developed in this PhD will directly support both the scientific exploitation and the ongoing development of VenSpec-U, including performance assessments, sensitivity studies, and observation strategy optimization. The work will be carried out in close collaboration with the VenSpec-U science and engineering teams, ensuring strong integration with mission development and future data analysis efforts. Also, to facilitate comparisons with Akatsuki observations and strengthen international collaboration, the PhD will also include short research stays in Japan to work closely with the UVI instrument team.

The successful candidate will gain experience in advanced numerical modeling, analysis of multi-mission datasets, and active participation in an international research environment (CNES, ESA, JAXA).

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For more Information about the topics and the co-financial partner (found by the lab!); contact Directeur de thèse - emmanuel.marcq@latmos.ipsl.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!