Micro-SDLA: balloon-borne experiments, atmospheric compounds measurements, flight of 13 February 2004

The µSDLA (Micro Spectrometric Diode Laser) developed by CNRS-SA is a diode laser spectrometer devoted to the in-situ measurement of H2O and CH4 in the UTLS (upper troposphere low stratosphere) by infrared absorption spectroscopy. Three near-infrared telecommunication-type InGaAs laser diodes are connected by means of optical fibers to an open multipath optical cell providing an absorption path-length of 28 m. The laser beam is absorbed by ambient gas molecules as it is bouncing back and forth between the cell mirrors. CH4 is monitored at 1.65 µm and H2O at 1.39 µm using the differential detection technique. The payload also includes pressure and temperature sensors. To avoid contamination by out-gassing from the balloon or the payload, only data recorded during the slow night-time descent of the balloons are considered, continued by those during parachute descent in the lower troposphere.
This flight is involved in the HIBISCUS campaign.