DC-8 - AFRC

Targeting Fourier Transform Spectrometer (FTS) measuring infrared spectra from 4.5 to 13.4 µm. AES was the airborne testbed for the EOS/Aura TES instrument and operated ~1994-2000.

The NASA Rapid OZone Experiment (ROZE) is an in situ instrument capable of measuring ozone (O3) throughout the troposphere and lower stratosphere on airborne platforms. The instrument uses cavity-enhanced absorption to measure the amount of ozone in a sampled volume flowing through an optical cell. The high-sensitivity of the cavity-enhanced detection scheme and the small sample volume enable high precision measurements in short integration times, making this instrument suitable for measuring O₃ fluxes (the exchange between the Earth's surface and atmosphere) with the eddy covariance technique. The instrument is designed for autonomous operation and requires minimal support (and no gases or dry ice) in the field. An inlet mounted in the free stream is needed to sample ambient air.

CARE consists of three instruments: an Optical Particle AnaLyzer (OPAL), a second generation Cloud, Aerosol and Precipitation Spectrometer (CAPS), and a Precipitation Imaging Probe (PIP). CARE detects the size distributions of aerosol and cloud particles in the size range between 0.5 µm and 6.2 mm, provides information about particle shape and cloud phase, and allows the retrieval of refractive index of single particles in the size range between ~0.5 and 2 µm.

Iodide Ion ToF (Time-of-Flight) CIMS (Chemical Ionization Mass Spectrometer)

Principle of the Measurement

Chemical ionization mass spectrometric detection of gas phase organic and inorganic analytes via I- adduct formation

Species Measured

Reactive nitrogen species: HNO3 (nitric acid), HONO (nitrous acid), HO2NO2 (peroxynitric acid), N2O5 (dinitrogen pentoxide), HNCO (isocyanic acid) 
Halogen Species: ClNO2, HCl, HBr, HOBr, HOCl, Cl2, Br2
Low to intermediate volatility organic species

Time Response

Instrumental response <1 sec, Field response is limited by inlet surface affinity for a particular species

Detection Limit

Precision on 1s data various by species

Accuracy

(15% + 1 pptv) for N2O5
(20% + 1 pptv) for ClNO2
(30% + 15 pptv) for HONO
(25% + 10 pptv) for HO2NO2
(15% + 15 pptv) for HNO3
(20% + 5 pptv) for HNCO
(20% + 15 pptv) for HCOOH
(30% + 1 pptv) for halogenated species

Manufacturer

TOFWERK/Aerodyne Research Inc. (modified)

Principle: The CU aircraft Extractive Electrospray Time-of-Flight Mass Spectrometer (EESI-TOFMS) detects the chemical composition of submicron particulate matter by simultaneous dissolution of the aerosol and soft ionization of its molecular components in an electrospray, followed by detection using time-of-flight mass spectrometry. When operated with positive ion polarity analytes are detected intact as adducts with sodium ions. When operated with negative ion polarity analytes are detected as deprotonated anions.

Aircraft Operation: Operated with positive or negative ion polarity, depending on mission goals.
Pressure-controlled EESI region with a maximum sampling altitude of 23 kft. Sensitivity can be increased for boundary layer  sampling by increasing the pressure of the electrospray region.
Calibrated relative to AMS on flight days, and confirmed with absolute calibrations on maintenance days
1s time resolution with 15s background measurements every 4 min.

Data Products:
Positive ion polarity EESI(+): C6H10O5 calibrated as levoglucosan and C6H5NO4 calibrated as nitrocatechol
Negative ion polarity EESI(-): C6H5NO4 calibrated as nitrocatechol
Additional species under development. Species of interest for specific campaigns can be tested and calibrated for.

Detection Limits (1s):
C6H10O5 as levoglucosan: 200 ng sm^-3
C6H5NO4 as nitrocatechol: 20ng sm^-3 EESI(-), 400 ng sm^-3 EESI(+)

The APR-3 is a three frequency (13, 35, and 94 GHz), Doppler, dual-polarization radar system. It has a downward looking antenna that performs cross track scans, covering a swath that is +/- 25 to each side of the aircraft path. Additional features include: simultaneous dual-frequency, matched beam operation, simultaneous measurement of both like- and cross-polarized signals at both frequencies, Doppler operation, and real-time pulse compression (calibrated reflectivity data can be produced for large areas in the field during flight, if necessary).

The Picarro G2401m is a commerical instrument that measures CO2, CH4, CO, and H2O. The analyzer is based on Wavelength-Scanned Cavity Ring Down Spectroscopy (WS-CRDS), a time-based measurement utilizing a near-infrared laser to measure a spectral signature of the molecule. Gas is circulated in an optical measurement cavity with an effective path length of up to 20 kilometers. A patented, high-precision wavelength monitor makes certain that only the spectral feature of interest is being monitored, greatly reducing the analyzer’s sensitivity to interfering gas species, and enabling ultra-trace gas concentration measurements even if there are other gases present. As a result, the analyzer maintains high linearity, precision, and accuracy over changing environmental conditions with minimal calibration required.

The measurement software of the NOAA Picarro has been modified to have a shorter measurement interval (~1.2 seconds instead of ~2.4 seconds) by reducing the number of scans of the CO spectroscopic peak and therefore yielding a less-precise CO measurement (1σ on 1-2 second measurements is ~9 ppb instead of ~4 ppb). The instrument was also modified to have a lower cell pressure set point (80 torr instead of 140 torr) to allow it to operate across the full pressure altitude range of the DC8 without requiring upstream pressurization of the sample stream.