High-Altitude Fast-Response CO2 Analyzer


 

Instrument:High-Altitude Fast-Response CO2 Analyzer
Principal Investigator:Steven C. Wofsy
Co-Investigators:Arlyn E. Andrews, Bruce C. Daube, Jr.
Organization:Department of Earth and Planetary Sciences
Harvard University
20 Oxford Street
Cambridge, MA 02138
Measurement Description: Similar to the ER-2 instrument, the high-altitude fast response CO2 instrument measures CO2 concentrations in situ using the light source, gas cells, and solid-state detector from a modified nondispersive infrared CO2 analyzer (Li-cor, Inc., Lincoln, NE). These components are stabilized along the detection axis, vibrationally-isolated, and housed in a temperature-controlled pressure vessel. Stratospheric air enters a forward-facing inlet and is compressed by a Teflon diaphragm pump. The CO2 mixing ratio of air flowing through the sample gas cell is determined by measuring absorption at 4.26 relative to a reference gas of known concentration. In-flight calibrations are performed by replacing the air sample with reference gas every 10 minutes, with a low-span and a high-span gas every 20 minutes, and with a long-term primary standard every 2 hours. The long-term standard is used sparingly and serves as a check of the flight-to-flight accuracy and precision of the measurements, augmented by ground-based calibrations before and after flights. Interference from water vapor due to absorption and pressure-broadening is negligible for sampling conditions; dilution by H2O corresponds to < 0.03 ppmv (equivalent CO2) for H2O < 85 ppmv.
Accuracy:0.1 ppm
Precision:0.05 ppm
Weight:110 lbs
Power:225 W typical, 450 W maximum
Response Time:2 seconds