Harvard’s DCOTSS Portable Optical Particle Spectrometer (DPOPS) is an in situ instrument capable of measuring particle number density as a function of size throughout the troposphere and lower stratosphere. The core instrument (POPS, Handix Scientific, Boulder, CO), re-packaged by Harvard, uses a 405 nm diode laser to count and size individual particles in the size range 140–3000 nm. 3D printing technology was used in the construction of the instrument to reduce cost, manufacturing complexity, and weight. The DPOPS is an optimized POPS system for DCOTSS flight campaign with autonomous operation in flight that requires minimal support between flights. Three major upgrades are: (1) increasing the sampling flow with external pumps to achieve better counting statistics in light of the low particle number density, (2) achieving isokinetic sampling (the velocity of air entering the inlet is equal to the velocity of the approaching gas stream) with a custom inlet to ensure fidelity of sampling with respect to size, and (3) optimizing the tubing system to reduce the loss of particles in the sampling tubes. DPOPS can fly on pressurized or unpressurized aircraft. 
 

The Purdue PALMS-NG instrument measures single-particle aerosol composition using UV laser ablation to generate ions that are analyzed with a time-of-flight mass spectrometer.  The PALMS size range is approximately 150 to >3000 nm and encompasses most of the accumulation and coarse mode aerosol volume. Individual aerosol particles are classified into compositional classes.  The size-dependent composition data is combined with aerosol counting instruments from Aerosol Microphysical Properties (AMP), the Langley Aerosol Research Group Experiment (LARGE), and other groups to generate quantitative, composition-resolved aerosol concentrations.  Background tropospheric concentrations of climate-relevant aerosol including mineral dust, sea salt, and biomass burning particles are the primary foci for the ATom campaigns.  PALMS also provides a variety of compositional tracers to identify aerosol sources, probe mixing state, track particle aging, and investigate convective transport and cloud processing.

*_Standard data products_**: *

Particle type number fractions: sulfate/organic/nitrate mixtures, biomass burning, EC, sea salt, mineral dust, meteoric, alkali salts, heavy fuel combustion, and other. Sampling times range from 1-5 mins.

*_Advanced data products_**:*

Number, surface area, volume, and mass concentrations of the above particle types. Total sulfate and organic mass concentrations. Relative and absolute abundance of various chemical markers and aerosol sub-components: methanesulfonic acid, sulfate acidity, organic oxidation level, iodine, bromine, organosulfates, pyridine, and other species.