Parasol Mission: to understand the role of clouds and aerosols

PARIS, 16 Dec 2004 (AFP) - The CNES Parasol micro-satellite, to be launched on Saturday by an Ariane 5 with six other passengers, should make it possible to better understand 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 the sun like a parasol, tend to cool the Earth-Atmosphere system on the contrary.

Modeling work has shown that natural aerosols (volcanic ash or sea spray), or those created by human activity, play a crucial role in the evolution of the climate and even constitute, according to the Academy of Sciences, "the greatest source of uncertainty ”in the study of climate.

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The whole question is to determine what is for the planet, globally but also according to the regions, the final balance of the competition which is played 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 of the Myriade sector developed by CNES, it will measure polarized light in several directions, in order to best characterize clouds and aerosols, other than by their spectral signature observed more conventionally.

To this end, the micro-satellite will take on a Polder wide-field imaging radiometer, designed thanks to the contribution of the Laboratory of Atmospheric Optics 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 materials in suspension) over land surfaces. They will also contribute to the detection of clouds, the determination of their thermodynamic phase, their altitude and the estimation of the flux reflected in the solar domain. The water vapor content will also be estimated.

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Parasol, whose expected lifespan is two years, was produced under the supervision of the CNES. Its development was very strongly based on that of the Polder program for the payload, and of Demeter, the first CNES microsatellite, for the platform, this in order to reduce costs and lead times.

The scientific responsibility for the mission rests with the Atmospheric Optics Laboratory of the CNRS (LOA, Lille).

Parasol will be positioned relative to the Aqua and Aura satellites (Nasa), Calipso (NASA / Cnes), Cloudsat (NASA / Canadian Space Agency) to complete the training called "A-Train", an exceptional space observatory to be completed in 2008 by another NASA satellite, Oco.

source: AFP

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