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In situ Trace Gas Measuring Systems

The chemical trace gas measurement systems available at IPA include NO, NO2, NOy, O3, CO2, and CO. The instrument unit used for detection of reactive nitrogen employs a two-channel high sensitivity chemiluminescence NO detector. The measurement of NOy relies on the conversion of NOy species to NO on a heated surface of an Au-tube. The detection of NO2 is based on the conversion of NO2 to NO using photolysis . Ozone and CO2 are detected by UV and IR absorption, respectively. CO is measured by resonance fluorescence in the fourth positive band of CO. Excitation of CO occurs by radiation from a CO resonance lamp coupled to an appropriate optical filter system.

The particle measurement system includes several optical particle spectrometers (FSSP-300, FSSP-100, PCASP-100X, MASP) to measure size distributions of the aerosol in-situ and after drying the particles. The covered size range is 0.1µm < D < 100 µm. The total number and size distribution of ultrafine particles (D < 0.02 µm) is measured with a set of condensation nucleus counters (Condensation Particle Size Analyser) which are operated at different lower cut-off diameters. The chemical nature of the aerosol is characterised by the thermal stability of the aerosol at distinct temperatures to discriminate between sulphuric-acid like, ammonium-sulphate-like and mineral/soot aerosol particles. Additional filter samples are used to measure the absorption coefficient of the aerosol and to determine major chemical constituents by post-flight single particle analysis.

The instruments are used in various projects on board of research aircraft (Falcon, DO228, GEOPHYSICA) at test facilities (e.g. aircraft engine test stands) and ground-stations (e.g. High alpine research station Schneefernerhaus).