A compact near-infrared diode-laser analyser for the measurement of atmospheric methane profiles on an airborne platform

摘要

In the frame of an interdisciplinary research project, in-situ measurements of atmospheric methane profiles have been made during mid-latitude and polar field campaigns on board of the "Geophysica M55" stratospheric aircraft, operating up to an altitude of 22 km. A prerequisite for these measurements is a reliable, compact gas analyser for unattended operation during several hours of flight. The spectrometer specially designed for this application is based on a room temperature, distributed feedback laser emitting at the wavelength of 1.651 micron. The instrument is located in the bay in front of the rear left wheel of the aircraft. The air is sampled through a pipe pointing in the aircraft forward direction and is heated up to about 0 C before entering the instrument, to prevent condensation of water vapour on the mirrors. For the same reason a computer driven valve stops the air inlet at altitudes below 5000 m.