COCAP: a carbon dioxide analyser for small unmanned aircraft systems

摘要

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 (COsub2/sub) 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 COsub2/sub sensor by 2 orders of magnitude. During validation of COCAP's COsub2/sub measurements in simulated and real flights we found a measurement error of 1.2?μmol?molsup?1/sup 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.