Harvard University Picarro Cavity Ring Down Spectrometer (HUPCRS)

All three measured carbon species are dominated by surface processes. CH4 and CO are primarily produced by human activity and CO2 is affected by both human activity and the Earth’s biosphere.
Therefore, tracking the concentration of these carbon species provides insights into the origin and transport rates of air into the Tropical Tropopause Layer and Lower Stratosphere.

The ATTREX observations can be used to evaluate chemistry-climate models and further our understanding of the impact of human activity on the composition of the local and global atmosphere.

The Wavelength-Scanned Cavity Ringdown Spectroscopy technique is used, which measures decay rate of light intensity at wavelengths between 1.5 and 1.65 microns to derive concentrations of CO2, CH4, CO, and H2O.

The cavity, lasers, wavelength monitor, and circuit boards are maintained in a 35 oC and 760 Torr environment inside a tubular pressure vessel. This vessel provides required operating conditions while the instrument is exposed to very cold temperatures and very low pressures during flight.

Ambient air enters the instrument through a forward-facing inlet, it is filtered and dehydrated prior to reaching the cavity where the measurement takes place.

Upstream and downstream pumps are used to deliver required and stable flow conditions to the cavity independent of air density changes that come with altitude changes.

Accuracy and stability of the analyzer are checked periodically by replacing ambient air with calibrated gas standards during flight.