Description du sujet de thèse

The in situ determination of the size distribution, concentration and nature (liquid, icy, solid) of aerosols is often not well known for the different planetary atmospheres. However, these parameters are essential for assessing the planet's radiation balance, its atmospheric dynamics and the microphysical processes of aerosol formation.

The LOAC-S (Light Optical Aerosols Counter - Space) R&T study as an early development of LONSCAPE instrument (Light Optical Nephelometer Sizer and Counter for Aerosols for Planetary), supported by CNES, is underway in order to design a space-borne version (to the TRL 5 technological maturity level) of the already existing LOAC instrument which is an aerosol counter and optical nephelometer used routinely since the beginning of 2013 for flights under all types of balloons in the Earth's atmosphere. This instrument allows the in situ study of certain physical properties (concentration, size distribution, typology) of aerosols present in the atmosphere. The objective is to fly a LOAC-S/LONSCAPE prototype on the AEROSAT CNES nanosat. The continuation of this project will be carried out in the framework of a scientific collaboration between the LPC2E (Orléans) and the LAM (Marseille). A collaboration has already been established with JPL/NASA around the coupling of LOAC-S/LONSCAPE to a mass spectrometer.

The overarching advantage of LOAC-S/LONSCAPE is that it can be deployed on various space missions for key targeted moons/planets like Mars, the Moon and Encelade (e.g. Moonraker). The instrument could also be used in a project to study the atmosphere of giant planets like Saturn aboard a descent probe.

It becomes essential to think now about the modelling/simulation aspects of LOAC-S/LONSCAPE. Indeed, the overall configuration of the theoretical response of the instrument during the whole treatment process is a key step that remains to be developed.

The main objective of the thesis is to develop a generic model of the LOAC-S/LONSCAPE chain in order to have an engineering tool to adapt the instrument to future missions. Monitoring the distribution of particles as a function of their injection into the instrument, their scattering, the processing chain and the algorithm will make it possible to assess, adapt and optimise the LOAC-S/LONSCAPE parameterisation according to the targeted environment. A flight onboard AEROSAT (CNES nanosatellite) will provide data and valuable basis for instrument assessment. The accuracy of the measurement will also be addressed. Also, the work will consist, on the basis of the state of the art knowledge of the aerosols of different moons/planets, in defining the scientific objectives from theoretical approaches on the light scattering produced by the particles. This part will focus on a numerical modelling component aimed at determining the expected properties of atmospheric particles as a function of the environment considered.

Contexte de travail

The LPC2E is located on the CNRS campus in Orléans. It is a laboratory with the "space" label that develops on-board instruments for solar system exploration missions. The PhD student will work in the SAMPLE team, which specialises in instrumental development for the study of the Earth's atmosphere and in the field of planetology.
During the first part of the thesis dedicated to the development of the generic model of the instrument, the student will work in close collaboration with an engineer from the space agency CNES (co-supervisor), Toulouse. Then, for the definition of the scientific objectives inherent to the different aerosol environments targeted, the student will work at LPC2E.

Informations complémentaires

The PhD student will be co-supervised by and/or will collaborate with:

- Dr Gwenaël Berthet (gwenael.berthet@cnrs-orleans.fr) from LPC2E who is specialist of aerosol observations in the Earth's atmosphere using balloon-borne particle counters and participated to the development of the LOAC instrument.
- Dr Nicolas Verdier (Nicolas.Verdier@cnes.fr) from CNES who is developer of the LONSCAPE instrument
- Dr Jean-Baptiste Renard (jbrenard@cnrs-orleans.fr) from LPC2E who is PI of the LOAC-S R&T and of the LOAC instrument, is a specialist of light scattering by aerosols in the Earth's atmosphere and by interplanetary dust.
- Pr Olivier Mousis (olivier.mousis@lam.fr) from LAM who is a specialist of planetary atmospheres
- Clémence Agrapart (clemence.agrapart@cnrs-orleans.fr) from LPC2E who technically supervises the LOAC-S R&T
- Fabrice Colin (fabrice.colin@cnrs-orleans.fr) from LPC2E who technically supervises the LOAC-S R&T

Candidates must apply on the CNES website BEFORE 16 MARCH 2023:
https://cnes.fr/fr/theses-post-doctorats
Announement here:
https://recrutement.cnes.fr/fr/annonce/2035547-23-134-simulation-of-the-loac-s-lonscape-space-borne-nephelometer-and-counter-31400-toulouse