In situ sensing of the atmosphere with telecommunication laser diodes

Summary form only given. For issues in climatology, chemistry or dynamics of the atmosphere, laser diode absorption spectroscopy can be of high interest because it provides precise in situ trace-gas measurements at high temporal resolution (ranging from 10ms to is). Furthermore, current telecommunication distributed feedback InGaAs laser diode emitting in the 1-to-2/spl mu/m spectral range are convenient spectroscopic tools as no cryogeny is required for stabilizing the laser emission and a reliable single mode emission with no mode-hops over the tunability range is obtained. In addition, functional highly linear room-temperature detectors are available to detect the laser beam and optical fibers can be used to ensure light connections with the purpose of designing compact sensors. These monitoring capabilities were a strong impetus for the authors to start from year 1997 the development of the Spectrometre a Diodes Laser Accordables (SDLA), a laser diode sensor operated from a stratospheric balloon and devoted to the measurement Of CH/sub 4/ and H/sub 2/O. The science objectives were to study the water vapor and ozone budgets in the lower stratosphere. To reach the science objectives, a good spatial resolution in the vertical concentration profile and an inaccuracy of within 5% to 10% in the mixing ratio retrieval were needed.