A new lightweight near-infrared tunable diode laser spectrometer CHILD (Compact High-altitude In-situ Laser Diode spectrometer) was developed for flights to the stratosphere as an additional in situ sensor on existing balloonborne payloads. Free-air absorption measurements in the near infrared are made with an open-path Herriott cell with new design features. It offers two individual absorption path lengths optimized for CH4 with 74 m (136 pass) and H2O with 36 m (66 pass). New electronic features include a real-time gain control loop that provides an autocalibration function. In flight-ready configuration the instrument mass is approximately 20 kg, including batteries. It successfully measured stratospheric CH4 and H2O profiles on high-altitude balloons on four balloon campaigns (Environmental Satellite validation) between October 2001 and June 2003. On these first flights, in situ spectra were recorded from ground level to 32,000-m altitude with a sensitivity of 0.1 ppm [(parts per million), ground] to 0.4 ppm (32,000 m) for methane and 0.15-0.5 ppm for water.
© 2005 Optical Society of America
(010.1280) Atmospheric and oceanic optics : Atmospheric composition
(120.6200) Instrumentation, measurement, and metrology : Spectrometers and spectroscopic instrumentation
(300.6260) Spectroscopy : Spectroscopy, diode lasers
Wolfgang Gurlit, Rainer Zimmermann, Carsten Giesemann, Thomas Fernholz, Volker Ebert, Jürgen Wolfrum, Ulrich Platt, and John P. Burrows, "Lightweight diode laser spectrometer CHILD (Compact High-altitude In-situ Laser Diode) for balloonborne measurements of water vapor and methane," Appl. Opt. 44, 91-102 (2005)