PARIS, Dec 16, 2004 (AFP) - The CNES Parasol micro-satellite, which is to be launched on Saturday by an Ariane 5 with six other passengers, should provide a better understanding of the impact on the climate of clouds and aerosols, these fine particles suspended in the air.
For a long time, only greenhouse gases were taken into account to study the phenomenon of global warming, recalls the National Center for Space Studies. But apart from the warming greenhouse effect, aerosols and clouds, by shielding solar radiation like a parasol, tend on the contrary to cool the Earth-Atmosphere system.
Modeling work has shown that natural aerosols (volcanic ash or sea spray), or those created by human activity, play a crucial role in climate change and even constitute, according to the Academy of Sciences, "the greatest source of uncertainty ”in the study of climate.
The whole question is to determine what is for the planet, globally but also according to the regions, the final result of the competition which plays out between this parasol effect and the greenhouse effect.
Parasol (Polarization and Anisotropy of Reflectances at the top of the Atmosphere, coupled with an observation satellite carrying a Lidar) should provide some answers. Second satellite in the Myriade sector developed by CNES, it will measure light polarized in several directions, in order to better characterize clouds and aerosols, other than by their spectral signature observed more conventionally.
To this end, the micro-satellite will carry a large-field Polder imaging radiometer, designed with the contribution of the Atmospheric Optics Laboratory of Lille (CNRS-USTL).
The information provided will make it possible to specify the quantity and size distribution of aerosols over the ocean as well as their turbidity index (content of suspended materials) above the land surface. They will also contribute to the detection of clouds, to the determination of their thermodynamic phase, their altitude and the estimation of the reflected flux in the solar domain. The water vapor content will also be estimated.
Parasol, whose expected life is two years, was built under the supervision of CNES. Its development relied heavily on those of the Polder program for the payload, and of Déméter, CNES's first microsatellite, for the platform, in order to reduce costs and lead times.
Scientific responsibility for the mission falls to the Atmospheric Optics Laboratory of the CNRS (LOA, Lille).
Parasol will be positioned in relation to the Aqua and Aura (Nasa), Calipso (Nasa / Cnes), Cloudsat (Nasa / Canadian Space Agency) satellites in order to complete the training called “A-Train”, an exceptional space observatory which will be completed in 2008 by another NASA satellite, Oco.