Performance Assessment of Portable Optical Particle Spectrometer (POPS).

Fan Mei,Gavin Mcmeeking,Hagen Telg,Ru-Shan Gao,Gourihar Kulkarni,Swarup China,Jason Tomlinson,Darielle Dexheimer,Beat Schmid,Mikhail Pekour

doi:10.3390/s20216294

Abstract

Accurate representation of atmospheric aerosol properties is a long-standing problem in atmospheric research. Modern pilotless aerial systems provide a new platform for atmospheric in situ measurement. However, small airborne platforms require miniaturized instrumentation due to apparent size, power, and weight limitations. A Portable Optical Particle Spectrometer (POPS) is an emerged instrument to measure ambient aerosol size distribution with high time and size resolution, designed for deployment on a small unmanned aerial system (UAS) or tethered balloon system (TBS) platforms. This study evaluates the performance of a POPS with an upgraded laser heater and additional temperature sensors in the aerosol pathway. POPS maintains its performance under different environmental conditions as long as the laser temperature remains above 25 °C and the aerosol flow temperature inside the optical chamber is 15 °C higher than the ambient temperature. The comparison between POPS and an Ultra-High Sensitivity Aerosol Spectrometer (UHSAS) suggests that the coincidence error is less than 25% when the number concentration is less than 4000 cm−3. The size distributions measured by both of them remained unaffected up to 15,000 cm−3. While both instruments’ sizing accuracy is affected by the aerosol chemical composition and morphology, the influence is more profound on the POPS.

Highlights

This paper described evaluating the variability of operational parameters using the commercial versions of Portable Optical Particle Spectrometer (POPS), especially with the laser heater and temperature sensor upgrade
The counting efficiency is defined as the ratio of the particle number concentration counted by POPS to the particles’ total particle number concentration within a specific size range
We did not put x-axis error bars in the figure. They are theoretically equal to the sizing uncertainty of the Differential Mobility Analyzer (DMA)

Summary

Introduction

Atmospheric aerosols have a broad size range, which covers more than four orders of magnitude. From newly formed nanometer clusters to super-micron cloud droplets and dust particles, ambient aerosols actively affect and are affected by atmospheric processes and human activities [1,2,3]. High-quality measurements with suitable temporal and spatial resolutions are essential for addressing the research questions in meteorology, atmospheric processing, severe weather monitoring, and in many other areas of human activity, like industrial hygiene and the semiconductor and pharmaceutical industries [4,5,6,7]. A high-resolution real-time technique is critical to capture aerosol properties and their space and/or time variations, especially from a fast-moving platform (manned or unmanned).

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Conclusion