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@ARTICLE{Kloss:894289,
      author       = {Kloss, Corinna and Tan, Vicheith and Leen, J. Brian and
                      Madsen, Garrett L. and Gardner, Aaron and Du, Xu and
                      Kulessa, Thomas and Schillings, Johannes and Schneider,
                      Herbert and Schrade, Stefanie and Qiu, Chenxi and von Hobe,
                      Marc},
      title        = {{A}irborne {M}id-{I}nfrared {C}avity enhanced {A}bsorption
                      spectrometer ({AMICA})},
      journal      = {Atmospheric measurement techniques},
      volume       = {14},
      number       = {8},
      issn         = {1867-8548},
      address      = {Katlenburg-Lindau},
      publisher    = {Copernicus},
      reportid     = {FZJ-2021-03161},
      pages        = {5271 - 5297},
      year         = {2021},
      abstract     = {We describe the Airborne Mid-Infrared Cavity enhanced
                      Absorption spectrometer (AMICA) designed to measure trace
                      gases in situ on research aircraft using Off-Axis Integrated
                      Cavity Output Spectroscopy (OA-ICOS). AMICA contains two
                      largely independent and exchangeable OA-ICOS arrangements,
                      allowing for the simultaneous measurement of multiple
                      substances in different infrared wavelength windows tailored
                      to scientific questions related to a particular flight
                      mission. Three OA-ICOS setups have been implemented with the
                      aim to measure OCS, CO2, CO, and H2O at 2050 cm−1; O3,
                      NH3, and CO2 at 1034 cm−1; and HCN, C2H2, and N2O at
                      3331 cm−1. The 2050 cm−1 setup has been
                      characterized in the laboratory and successfully used for
                      atmospheric measurements during two campaigns with the
                      research aircraft M55 Geophysica and one with the German
                      HALO (High Altitude and Long Range Research Aircraft). For
                      OCS and CO, data for scientific use have been produced with
                      $5 \%$ accuracy $(15 \%$ for CO below 60 ppb, due to
                      additional uncertainties introduced by dilution of the
                      standard) at typical atmospheric mixing ratios and
                      laboratory-measured 1σ precision of 30 ppt for OCS and
                      3 ppb for CO at 0.5 Hz time resolution. For CO2, high
                      absorption at atmospheric mixing ratios leads to saturation
                      effects that limit sensitivity and complicate the spectral
                      analysis, resulting in too large uncertainties for
                      scientific use. For H2O, absorption is too weak to be
                      measured at mixing ratios below 100 ppm. By further
                      reducing electrical noise and improving the treatment of the
                      baseline in the spectral retrieval, we hope to improve
                      precision for OCS and CO, resolve the issues inhibiting
                      useful CO2 measurements, and lower the detection limit for
                      H2O. The 1035 and 3331 cm−1 arrangements have only
                      partially been characterized and are still in development.
                      Although both setups have been flown and recorded infrared
                      spectra during field campaigns, no data for scientific use
                      have yet been produced due to unresolved deviations of the
                      retrieved mixing ratios to known standards (O3) or
                      insufficient sensitivity (NH3, HCN, C2H2, N2O). The
                      ∼100 kg instrument with a typical in-flight power
                      consumption of about 500 VA is dimensioned to fit into one
                      19 in. rack typically used for deployment inside the
                      aircraft cabin. Its rugged design and a pressurized and
                      temperature-stabilized compartment containing the sensitive
                      optical and electronic hardware also allow for deployment in
                      payload bays outside the pressurized cabin even at high
                      altitudes of 20 km. A sample flow system with two parallel
                      proportional solenoid valves of different size orifices
                      allows for precise regulation of cavity pressure over the
                      wide range of inlet port pressures encountered between the
                      ground and maximum flight altitudes. Sample flow of the
                      order of 1 SLM (standard litre per minute) maintained by
                      an exhaust-side pump limits the useful time resolution to
                      about 2.5 s (corresponding to the average cavity flush
                      time), equivalent to 500 m distance at a typical aircraft
                      speed of 200 m s−1.},
      cin          = {IEK-7},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-7-20101013},
      pnm          = {2112 - Climate Feedbacks (POF4-211)},
      pid          = {G:(DE-HGF)POF4-2112},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000680811200001},
      doi          = {10.5194/amt-14-5271-2021},
      url          = {https://juser.fz-juelich.de/record/894289},
}