Molecular spectroscopy by laser techniques for the study of planetary atmospheres
It is becoming essential to probe certain molecular species of the Earth's atmosphere with very high precision. This is particularly true for greenhouse gases (CO2, CH4) in the context of satellite missions such as OCO-2, MicroCarb, MERLIN and will become so for other molecules thanks to the launch of new generations of satellites, requiring higher and higher quality spectroscopic data. Dedicated laboratory measurements are performed in support of these missions in order to provide spectroscopic parameters of the targeted absorption lines and their temperature dependence with reduced uncertainty. It is therefore necessary to record spectra with high signal-to-noise ratios (> 1,000) and to fit these spectra with non-Voigt line profiles including effects such as velocity dependence and collisional narrowing. In this talk, I will present our previous and ongoing works by Cavity Ring Down Spectroscopy of O2 (~1.27 µm), CO2 (~1.60 µm) and CH4 and water vapor (~1.65 µm) in support of the MicroCarb and MERLIN missions (CNES and DLR) and the ISOGG program of ESA.
The second part of my talk will be devoted to the measurements of absorption continua of H2O and H2 mixed with CO2. Indeed, measuring and modeling accurately the infrared absorption spectra of these mixtures and their temperature dependences is of great importance for planetary sciences (in particular Mars). The spectra recorded by CRDS and OFCEAS include a contribution due to the local absorption by the rovibrational lines of each species, which can be calculated from spectroscopic databases, and a broadband contribution (namely the continua). The continua are poorly characterized but crucial to account for the radiative budget and the composition of planetary atmospheres, and hence to accurately model the formation, evolution, and present atmospheric state of telluric planets from the solar system and beyond.