The study of methane and water vapor is very important to get a deeper understanding of radiative, chemical and dynamic atmospheric mechanisms. Methane and water vapour are both greenhouse effect gases which contribute to climate evolution. Both species act as well in ozone budget.
Water vapour is a decisive element in formation of the polar stratospheric clouds.
The determination of methane vertical concentration profiles should therefore contribute to a better understanding of atmospheric transport phenomena. They provide the capabilities required for the determination of trace species by absorption spectroscopy, a very reliable single-mode emission, a tunable range of a few nanometers, a power of a few mW well adapted to the determination of absorption profiles of molecular species such as methane or water vapour, at atmospheric temperatures and pressures. Moreover, with this techology, an ordinary Peltier effect is enough to control the laser diode temperature and to get a stable optical emission. It makes possible the building up of high compacity spectrometers. These optimized laser diodes should be used later in the SDLA-LAMA project.