Alain Hauchecorne

Complex organic matter in Titan's atmospheric aerosols from in situ pyrolysis and analysis.

Aerosols in Titans atmosphere play an important role in determining its thermal structure. They also serve as sinks for organic vapours and can act as condensation nuclei for the formation of clouds, where the condensation efficiency will depend on the chemical composition of the aerosols. So far, however, no direct information has been available on the chemical composition of these particles. Here we report an in situ chemical analysis of Titans aerosols by pyrolysis at 600u2009°C. Ammonia (NH3) and hydrogen cyanide (HCN) have been identified as the main pyrolysis products. This clearly shows that the aerosol particles include a solid organic refractory core. NH3 and HCN are gaseous chemical fingerprints of the complex organics that constitute this core, and their presence demonstrates that carbon and nitrogen are in the aerosols.

Think the way to measure the Earth Radiation Budget and the Total Solar Irradiance with a small satellites constellation

Within the past decade, satellites constellations have become possible and practical. One of the interest to use a satellites constellation is to measure the true Earth Radiation Imbalance, which is a crucial quantity for testing climate models and for predicting the future course of global warming. This measurement presents a high interest because the 2001-2010 decade has not shown the accelerating pace of global warming that most models predict, despite the fact that the greenhouse-gas radiative forcing continues to rise. All estimates (ocean heat content and top of atmosphere) show that over the past decade the Earth radiation imbalance ranges between 0.5 to 1W-2. Up to now, the Earth radiation imbalance has not been measured directly. The only way to measure the imbalance with sufficient accuracy is to measure both the incoming solar radiations (total solar irradiance) and the outgoing terrestrial radiations (top of atmosphere outgoing longwave radiations and shortwave radiations) onboard the same satellite, and ideally, with the same instrument. The incoming solar radiations and the outgoing terrestrial radiations are of nearly equal magnitude of the order of 340.5W-2. The objective is to measure these quantities over time by using differential Sun-Earth measurements (to counter calibration errors) with an accuracy better than 0.05Wm-2 at 1σ. It is also necessary to have redundant instruments to track aging in space in order to measure during a decade and to measure the global diurnal cycle with a dozen satellites. Solar irradiance and Earth Radiation Budget (SERB) is a potential first in orbit demonstration satellite. The SERB nano-satellite aims to measure on the same platform the different components of the Earth radiation budget and the total solar irradiance. Instrumental payloads (solar radiometer and Earth radiometers) can acquire the technical maturity for the future large missions (constellation that insure global measurement cover) by flying in a CubeSat. This paper is intended to demonstrate the ability to build a low-cost satellite with a high accuracy measurement in order to have constant flow of data from space.

The PICARD Scientific Mission: status of the program

PICARD is an investigation dedicated to the simultaneous measurement of the absolute total and spectral solar irradiance, the diameter and solar shape, and to the Suns interior probing by the helioseismology method. The spacecraft was successfully launched into a Sun-synchronous dawn-dusk orbit on 15 June 2010 by a DNEPR-1 launcher for a life expectancy of 2 years; its operational mission ended in March, 2014. nThe payload consists of the SODISM imager (SOlar Diameter Imager and Surface Mapper) and of two radiometers, SOVAP (SOlar VAriability PICARD) and PREMOS (PREcision MOnitoring Sensor), which measure Total Solar Irradiance. Filter radiometers on PREMOS monitor the Solar Spectral Irradiance in six selected bands in the near UV, visible, and near IR wavelength regions. The SODISM telescope monitors continuously solar activity from the middle ultraviolet (UV) to the near infrared (IR) spectral domains. nWe shall give an overview of the mission, as well as the behaviour of the instruments in orbit, and the scientific results.

Refroidissement de la stratosphère : Détection réussie mais quantification encore incertaine,

La stratosphere se refroidit sous leffet de la diminution dozone et de laugmentation de leffet de serre. Meme si les observations disponibles, qui nont pas ete prevues initialement pour des etudes climatiques, presentent toutes de fortes discontinuites temporelles, on identifie clairement ce refroidissement, avec des variations en fonction de laltitude et de la latitude. Cependant, les incertitudes concernant la quantification de ces tendances varient dun facteur 2. Dans le futur, la synergie entre les mesures spatiales et celles depuis le sol devra se renforcer afin dassurer notamment une meilleure continuite entre les instruments SSU et AMSU.