The CAMS instrument’s core design and operation is similar to the DFGAS (Difference Frequency Generation Absorption Spectrometer) instrument, which has been successfully deployed for fast, accurate, and sensitive airborne measurements of the important trace gas formaldehyde (CH2O). CAMS like DFGAS is based on tunable mid-IR (3.53-μm) absorption spectroscopy utilizing advanced fiber optically pumped difference-frequency generation (DFG) laser sources. Mid-Infrared light at 2831.6-cm^-1 (3.53 μm) is generated by mixing two near-IR room temperature lasers (one at 1562 nm and the other at 1083 nm) in a non-linear crystal (periodically poled lithium niobate). The DFG laser output is directed through a multipass Herriott absorption cell (90-m pathlength in ~ 1.7 liter volume) where the laser light is selectively absorbed by a moderately strong and isolated vibrational-rotational absorption feature of CH2O. The transmitted light from the cell is directed onto an IR detector employing a number of optical elements. A portion of the IR beam is split off by a special beam splitter (BS) before the multipass cell and focused onto an Amplitude Modulation Detector (AMD) to capture and remove optical noise from various components in the difference frequency generation process. A third detection channel from light emanating out the back of the beam splitter is directed through a low pressure CH2O reference cell and onto a reference detector (RD) for locking the center of the wavelength scan to the absorption line center. The mid-IR DFG output is simultaneously scanned and modulated over the CH2O absorption feature, and the second harmonic signals at twice the modulation frequency from the 3 detectors are processed using a computer lock-in amplifier [Weibring et al., 2006].

TOGA measures volatile organic compounds (VOCs). TOGA was deployed with an Agilent quadrupole mass spectrometer from 2006 through 2018. Since 2019, the TOGA has been equipped with a TOFWERK high-resolution time-of-flight (HR-TOF) mass spectrometer detector (TOGA-TOF). Specific data will be obtained for radical precursors, tracers of anthropogenic and biogenic activities, tracers of urban and biomass combustion emissions, tracers of ocean emissions, products of oxidative processing, precursors to aerosol formation, and compounds important for aerosol modification and transformation. TOGA measures a wide range of VOCs with high sensitivity (low to sub-ppt), frequency (2 minutes or better), accuracy (20% or better), and precision (<3%). Over 100 species are routinely measured throughout the troposphere and lower stratosphere from the surface to 16 km or higher. See table for list of VOCs that have been quantified using TOGA and TOGA-TOF. The TOGA-TOF is contained in a dual extended HIAPER rack, weighs approximately 225 kg and consumes ~1 kW of power. The major components of the instrument are the inlet, cryogenic preconcentrator, gas chromatograph, time-of-flight mass spectrometer detector, zero air/calibration system, and the control/data acquisition system. All processes and data acquisition are computer controlled.

PTR-MS is a chemical ionization mass spectrometry technique that allows for fast measurements of organic trace gases. In combination with the CHARON inlet, it measures the organic composition of submicrometer aerosol particles.

The NASA Langley Airborne Differential Absorption Lidar (DIAL) system uses four lasers to make DIAL O3 profile measurements in the ultraviolet (UV) simultaneously with aerosol profile measurements in the visible and IR. Recent changes incorporate an additional laser and modifications to the receiver system that will provide aerosol backscatter, extinction, and depolarization profile measurements at three wavelengths (UV, visible, and NIR). For SEAC4RS, the DIAL instrument will include for the first time aerosol and cloud measurements implementing the High Spectral Resolution Lidar (HSRL) technique [Hair, 2008]. The modifications include integrating an additional 3-wavelength (355 nm, 532 nm, 1064 nm) narrowband laser and the receiver to make the following measurements; depolarization at all three wavelengths, aerosol/cloud backscatter and extinction at 532 nm via the HSRL technique, and aerosol/cloud backscatter at the 355 and 1064 nm via the standard backscatter lidar technique. Integration of the aerosol extinction profile at 532nm above and below the aircraft also provides aerosol optical depth (AOD) along the aircraft flight track.

The NASA Langley CO2 sampling system (AVOCET) has an extensive measurement heritage in tropospheric field campaigns, delivering high reliability over 3400 flight hours (452 science flights) and is recognized within the CO2 community as a benchmark for evaluating newly evolving remote CO2. This instrument was adapted by the investigators for airborne sampling and has been successfully deployed aboard NASA research aircraft beginning with the PEM-West A mission in 1992, and more recently during the 2016 KORUS-AQ, 2017 ACSENDS/ABoVE, and 2019 FIREX-AQ missions. The newest iteration of the technique as of 2017 has at its core a modified LI-COR model 7000 non-dispersive infrared spectrometer (NDIR). The basic instrument is small (13 x 25 x 37 cm) and composed of dual 11.9 cm^3 sample/reference cells, a feedback stabilized infrared source, 500 Hz chopper, thermoelectrically-cooled solid state PbSe detector, and a narrow band (150 nm) interference filter centered on the 4.26 μm CO2 absorption band. Using synchronous signal detection techniques, it operates by sensing the difference in light absorption between the continuously flowing sample and reference gases occupying each side of the dual absorption cell. Thus, by selecting a reference gas of approximately the same concentration as background air (~405 ppm), minute fluctuations in atmospheric concentration can be quantified with high precision. Calibrations are performed frequently during flight using WMO-traceable standards from NOAA ESRL. Precisions of ≤ 0.1 ppm (±1σ) for 1 Hz sampling rates are typical for our present airborne CO2 system when operated at 600 torr sample pressure.

Principle: The CU aircraft version of the Aerodyne High-Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) detects non-refractory submicron aerosol composition by impaction on a vaporizer at 600°C, followed by electron ionization and time-of-flight mass spectral analysis. Size-resolved composition can be quantified by measuring the arrival times of the aerosol at the vaporizer.

Aircraft Operation: (1 min cycles, can be adjusted to meet mission goals):
46 s total concentration measurements (1 s resolution, can be increased to up to 10 Hz upon request)
5 s speciated size distribution measurements (with improved S/N detection due to ePToF acquisition)
9 s Background + Overhead
Higher accuracy due to flight day calibrations using built-in system
Custom pressure controlled inlet with confirmed performance up to 45 kft

Real Time Data Products: 
PM1 Aerosol Mass Concentrations:
Organic aerosol (OA) , SO4, NO3, NH4, Chloride 
OA Chemical Markers: f44 (Secondary OA), f57 (hydrocarbon-like OA), f60 (biomass burning OA), f82 (isoprene epoxide-SOA), other fx upon request

More Advanced Products:
- PM1 Seasalt, ClO4, total I, total Br, MSA concentrations
- O/C, H/C, OA/OC, OSc
- Particle organic nitrates (pRONO2)
- Ammonium Balance, estimated pH
- OA components by positive matrix factorization (PMF)
- Particle eddy covariance fluxes of all species
- Speciated Aerosol size distributions

Detection Limits (1s, ng sm-3), (1 min, ng sm-3) from start of the flight (due to custom cryopump):
Sulfate: 40, 15
Nitrate: 15, 6
Ammonium: 3, 1
Chloride: 30, 12
OA: 200, 80
For detailed OA analysis, longer averaging (3-30 s, depending on OA concentration) is needed. A 1 min product is hence provided as well.

Langley Aerosol Research Group Experiment (LARGE).  The "classic" suite of instrumenation measures in-situ aerosol micrphysical and optical properties. The package can be tailored for specific science objectives and to operate on a variety of aircraft. Depending on the aircraft, measurments are made from either a shrouded single-diffuser "Clarke" inlet, from a BMI (Brechtel Manufacturing Inc.) isokinetic inlet, or from a HIML inlet. Primary measurements include:

1.) total and non-volatile particle concentrations (3nm and 10nm nominal size cuts),
2.) dry size distributions from 3nm to 5µm diameter using a combination of mobilty-optical-aerodynamic sizing techniques,
3.) dry and humidified scattering coefficients (at 450, 550, and 700nm wavelength), and
4.) dry absorption coefficients (470, 532, and 670nm wavelength). 

LARGE derived products include particle size statistics (integrated number, surface area, and volume concentrations for ultrafine, accumulation, and coarse modes), dry and ambient aerosol extinction coefficients, single scattering albedo, angstrom exponent coefficients, and scattering hygroscopicity parameter f(RH).

As part of the measurement team on the NASA DC-8 we operate two related installations: a mist chamber/ion chromatograph (MC/IC) sampling/analysis system providing near real time results for selected species, and a bulk aerosol system that collects particulates onto filters for subsequent analysis. We use ion chromatography on aqueous extracts of the bulk aerosol samples collected on Teflon filters to quantify soluble ions (Cl^-, Br^-, NO3^-, SO4^2-, C2O4^2-, Na⁺, NH4⁺, K⁺, Ca⁺, and Mg⁺). Filters are exposed on all level flight legs. Below 3 km exposure times are 5 minutes or less, increasing at higher altitudes to a maximum sample time of 15 minutes. Aerosols participate in heterogeneous chemistry, impact radiative transfer, and can be detected from space. Our measurements help to validate and extend retrievals of aerosol distributions and properties by MODIS, MISR and CALIPSO. In addition, several of the particle-associated ions are tracers of sources of gas and aerosol pollutants (e.g., SO4^2- from industrial emissions of SO2, enhancements of C2O4^2-, K⁺, and NH4⁺ indicate encounters with biomass burning plumes, Na⁺, and Cl^- are tracers of seasalt, Mg²⁺ and Ca²⁺ are tracers of dust). Our system has two inlets, allowing collection of paired samples simultaneously.

The CIMS instrument consists of a low pressure ion molecule reactor (IMR) coupled to a quadrupole mass filter by an actively pumped collisional dissociation chamber (CDC) and an octopole ion guide. The vacuum system is a 100 mm outer diameter stainless steel chamber evacuated with two small turbo pumps (70 l s^-1). The mass filter is a set of 9.5 mm diameter quadrupole rods housed in the main vacuum chamber. The CDC is a short 80 mm diameter chamber that houses an octopole ion guide and is evacuated with a hybrid molecular drag pump. The IMR is evacuated with a scroll pump (300 l min^-1) that also serves as the backing pump for the mass spectrometer.

Click here for the Collaborative Ground and Airborne Observations description page.

The SP2 is a laser-induced incandescence instrument primarily used for measuring the refractory BC  (rBC) mass content of individual accumulation-mode aerosol particles. It is able to provide this data product independently of the total particle morphology and mixing state, and thus delivers detailed information not only about BC loadings, but also size distributions, even in exceptionally clean air. The instrument can also provide the optical size of individual particles containing rBC, and identify the presence of materials associated with the BC fraction (i.e. identify the rBC’s mixing state). Since its introduction in 2003, the SP2 has been substantially improved, and now can be considered a highly competent instrument for assessing BC loadings and mixing state in situ.  NOAA deploys multiple SP2s with different designs: the first was built for the WB-57F research aircraft. Two others are rack-mounted units customized at NOAA; one of the rack mounted units can be humidified, and has been deployed with a paired dry rack-mounted SP2 as the "Humidified-Dual SP2" (HD-SP2). The rack mounted units are suitable for in-cabin operations.