OPC-Pod: A New Sensor Payload to Measure Aerosol Particles for Small Uncrewed Aircraft Systems

Atmospheric aerosols affect human health and influence atmospheric and biological processes. Dust can be transported long distances in the atmosphere, and the mechanisms that influence dust transport are not fully understood. To improve the data base for numerical models that simulate dust transport, measurements are needed that cover both the vertical distribution of the dust and its size distribution. In addition to measurements with crewed aircraft, uncrewed aircraft systems (UAS) provide a particularly suitable platform for this purpose. In this paper we present the OPC-Pod, a payload for the small fixed-wing UAS of the type MASC-3 for aerosol particle measurements. The OPC-Pod is based on the optical particle counter (OPC) OPC-N3 (Alphasense, UK), modified by the addition of a dryer and a passive aspiration system. Based on field tests with a reference instrument in Mannheim, Germany, wind tunnel tests and a comparison measurement with the UAS-mounted aerosol particle measurement system UCASS during a dust event over Cyprus, we show that the OPC-Pod can measure particle number concentrations in the range 0.66 - 31 μm as well as particle size distributions. The agreement of ther OPC-Pod with UCASS is good. Both instruments resolve a vertical profile of the Saharan dust event, with a prominent dust layer between 1500 m and 2800 m above sea level, with particle number concentrations up to 35 cm−3 for particles between 0.66 - 31 μm.