Synonyms: 
AJAX
Alphajet
Associated content: 
Alpha Jet

COmpact Formaldehyde FluorescencE Experiment

The NASA GSFC COmpact Formaldehyde FluorescencE Experiment (COFFEE) instrument measures formaldehyde (CH2O) using a nonresonant laser induced fluorescence (LIF) technique.  Originally designed to fly in the unpressurized pod of the Alpha Jet, COFFEE is capable of operation on both pressurized and unpressurized (high-altitude) aircraft.  COFFEE possesses the high sensitivity, fast time response, and dynamic range needed to observe CH2O throughout the troposphere and lower stratosphere.

Formaldehyde is produced via the oxidation of hydrocarbons, notably methane (a ubiquitous greenhouse gas) and isoprene (the primary hydrocarbon emitted by vegetation). Observations of CH2O can thus provide information on many atmospheric processes, including:
 - Convective transport of air from the surface to the upper troposphere
 - Emissions of reactive hydrocarbons from cities, forests, and fires
 - Atmospheric oxidizing capacity, which relates to formation of ozone and destruction of methane
In situ observations of CH2O are also crucial for validating retrievals from satellite instruments, such as OMI, TROPOMI, and TEMPO.

Instrument Type: 
Fluorescence
Measurements: 
CH2O
Aircraft: 
Alpha Jet
Point(s) of Contact: 
Jason M. St. Clair (PI)

COFFEE instrument in shipping crate

ARC Picarro

Measurements: 
CH4, CO2
Aircraft: 
Alpha Jet, DC-8 - AFRC
Point(s) of Contact: 
Warren Gore (Co-I)

NOAA Picarro

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.

Instrument Type: 
Spectrometer (in situ)
Measurements: 
CO2, CH4, CO
Aircraft: 
DC-8 - AFRC, Alpha Jet
Point(s) of Contact: 
Kathryn McKain (Co-I)

Alpha Jet O3 instrument in wing pod

O3 instrument calibration carried out on 3 July 2012 (prior to AJAX flight on 5 July 2012).

Google EarthTM plot of AJAX measured O3 during a vertical profile over Merced, California on 5 June 2012.

Timeseries of AJAX measured O3 and GPS altitude during a flight on 5 June 2012.

Alpha Jet Ozone Instrument

Alpha Jet (O3) Ozone instrument details

Measurements of ozone (O3) mixing ratios are performed using a commercial O3 monitor (2B Technologies Inc., model 205 (http://www.twobtech.com/model_205.htm)) based on ultraviolet (UV) absorption techniques and modified for flight worthiness. The dual-beam instrument uses two detection cells to simultaneously measure UV light intensity differences between O3-scrubbed air and un-scrubbed air to give precise measurements of O3. The monitor has been modified by upgrading the pressure sensor and pump to allow measurements at high altitudes, including a lamp heater to improve the stability of the UV source, and the addition of heaters, temperature controllers and vibration isolators to control the monitor’s physical environment.

Ozone inlet

The air intake is through Teflon tubing (perfluroalkoxy-polymer, PFA) with a backward-facing inlet positioned on the underside of the instrument wing pod. Air is delivered through a 5 µm PTFE (polytetrafluroethylene) membrane filter to remove fine particles prior to analysis.

Ozone instrument calibrations:

The O3 monitor has undergone thorough instrument testing in the laboratory to determine the precision, linearity and overall accuracy. Eight-point calibration tests (ranging from 0 – 300 ppbv) are typically performed before and after each flight using an O3 calibration source (2B Technologies, model 306 referenced to the WMO scale). The calibration of all 2B Technologies Ozone Calibration Sources is traceable to NIST through an unbroken chain of comparisons and is sent back to the vendor annually for calibration. Calibrations in a pressure- and temperature-controlled environmental chamber have also been carried out using the O3 calibration source over the pressure range 200 - 800 mbar and temperature range -15 to +25 ⁰C; typical pressure and temperature ranges observed in the wing-mounted instrument pod during flight.

Instrument Type: 
Spectrometer (in situ)
Measurements: 
O3
Aircraft: 
Alpha Jet
Point(s) of Contact: 
Laura Iraci (PI)

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