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.

The Harvard Herriott Hygrometer (HHH) is a multipass Herriott cell that measures water vapor via direct detection. Predicted accuracy and precision are ± 3–5% and ± 0.05 ppmv H2O, in the lower stratosphere, for a 10-s integration time, respectively. The theory and application of HHH as a water vapor instrument are laid out in the context of making accurate measurements traceable to laboratory standards. In conjunction with the Harvard Water Vapor (HWV) instrument, HHH will establish ultimate credibility via three, independent detection methods in-flight and five for laboratory and in-field calibration. A multi-detection, calibration system of this nature is beyond the scope of any in existence today. Because HHH promises such high reliability and slight margins of error, the data acquired by this instrument should minimize the uncertainty associated with natural and anthropogenic climate forcing. HHH may serve as a prototype instrument for the use of miniaturized, TDL systems as in situ quantifiers of atmospheric gases via the straightforward method of direct detection, thus extending the scientific payback of this new system.