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Project Progress

We are currently developing a Cavity-Ringdown Spectrometer (CRDS) capable of measuring methane concentration and stable isotopes of hydrogen and carbon in the field with precisions comparable to standard laboratory techniques (e.g. Isotope Ratio Mass Spectrometry [IRMS]). CRDS is an infrared absorption spectroscopy technique that achieves high precisions and sensitivities by measuring the exponential decay of a specific wavelength of energy through a sample cell bounded by highly reflective mirrors. During the past 12 months, the final parts to this instrument have been procured and the fabrication, construction, and initial testing have been completed. Our CRDS is currently operational and we are measuring “ringdown events.” In order to achieve high precision isotopic measurements similar to IRMS, the exponential decay events (or ringdown times) must be measured with precisions of 0.01%. Our preliminary CRDS routinely achieves this precision. Preliminary field testing was completed this year with tests outside on the Princeton University Campus and at Goddard Space Flight Center; no decrease in precision or sensitivity occurred during this field testing. We have measured the absorption spectra for ¹²C-methane, ¹³C-methane, and carbon dioxide, as well as the first ever measurements of methane containing one atom of deuterium in the 1650 nanometer region of the spectra. A manuscript describing the methodology and first measurements is being prepared for Analytical Chemistry. A proposal to take the current instrument to Technology Readiness Level 6 was submitted to the Mars Instrument Development Program in June with collaboration from Paul Mahaffy of Goddard Space Flight Center.