COCAP: a carbon dioxide analyser for small unmanned aircraft systems
- 1Max Planck Institute for Biogeochemistry, Jena, Germany
- 2NOAA Earth System Research Laboratory, Global Monitoring Division, Boulder, Colorado, USA
- 3SenseAir AB, Delsbo, Sweden
- 4Ostwestfalen-Lippe University of Applied Sciences, Höxter, Germany
- 5Division of Atmospheric Sciences, Department of Physics, University of Helsinki, Helsinki, Finland
Abstract. Unmanned aircraft systems (UASs) could provide a cost-effective way to close gaps in the observation of the carbon cycle, provided that small yet accurate analysers are available. We have developed a COmpact Carbon dioxide analyser for Airborne Platforms (COCAP). The accuracy of COCAP's carbon dioxide (CO2) measurements is ensured by calibration in an environmental chamber, regular calibration in the field and by chemical drying of sampled air. In addition, the package contains a lightweight thermal stabilisation system that reduces the influence of ambient temperature changes on the CO2 sensor by 2 orders of magnitude. During validation of COCAP's CO2 measurements in simulated and real flights we found a measurement error of 1.2 µmol mol−1 or better with no indication of bias. COCAP is a self-contained package that has proven well suited for the operation on board small UASs. Besides carbon dioxide dry air mole fraction it also measures air temperature, humidity and pressure. We describe the measurement system and our calibration strategy in detail to support others in tapping the potential of UASs for atmospheric trace gas measurements.