title: Lightweight diode laser spectrometer CHILD (Compact High-altitude iN-situ Laser Diode) for balloonborne measurements of water vapor and methane.
abstract: 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.
authors.affiliation: Institute of Environmental Physics, University of Bremen, 28201 Bremen, Germany. gurlit@iup.physik.uni-bremen.de
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Gurlit
authors.forename: Rainer
authors.initials: R
authors.lastname: Zimmermann
authors.forename: Carsten
authors.initials: C
authors.lastname: Giesemann
authors.forename: Thomas
authors.initials: T
authors.lastname: Fernholz
authors.forename: Volker
authors.initials: V
authors.lastname: Ebert
authors.forename: Jürgen
authors.initials: J
authors.lastname: Wolfrum
authors.forename: Ulrich
authors.initials: U
authors.lastname: Platt
authors.forename: John P
authors.initials: JP
authors.lastname: Burrows