Nitrogen Oxides in the Troposphere, Andreas Richter, ERCA 2010 20 Long Path DOAS measurements open path through the atmosphere lamp telescope retro reflectors spectrometer detector quartz fibre Instrument: open path Differential Optical Absorption Spectroscopy (DOAS) system using a lamp as light source retro reflectors for simplified set-up white cells (multi reflection) for enhanced light path possible advantages: measurements at night well defined light path extension to UV (no ozone layer in between) disadvantages: relatively short light path need for bright lamp (+ power) usually not fully automated
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