Addition of a channel for XCO observations to a portable FTIR spectrometer for greenhouse gas measurements

Abstract

Abstract. The portable FTIR (Fourier transform infrared) spectrometer EM27/SUN, dedicated to the precise and accurate observation of column-averaged abundances of methane and carbon dioxide, has been equipped with a second detector channel, which allows the detection of additional species, especially carbon monoxide. This allows an improved characterisation of observed carbon dioxide enhancements and makes the extended spectrometer especially suitable as a validation tool of ESA's Sentinel 5 Precursor mission, as it now covers the same spectral region as used by the infrared channel of the TROPOMI (TROPOspheric Monitoring Instrument) sensor. The extension presented here does not rely on a dichroic, but instead a fraction of the solar beam is decoupled near the aperture stop of the spectrometer using a small plane mirror. This approach allows maintaining the camera-controlled solar tracker set-up, which is referenced to the field stop in front of the primary detector. Moreover, the upgrade of existing instruments can be performed without alterating the optical set-up of the primary channel and resulting changes of the instrumental characteristics of the original instrument.

Separation of Methane Emissions From Agricultural and Natural Gas Sources in the Colorado Front Range

“…The EM27/SUN spectrometer is described in more detail in Gisi et al (2012), Frey et al (2015), and Hase et al (2016). CH 4 is retrieved from EM27/SUN solar spectra (5,000-11,000 cm −1 ) using the spectral region at 5,897-6,145 cm −1 and O 2 at 7,765-8,005 cm −1 (Frey et al, 2015); the PROFFIT code is used for the retrievals (Hase et al, 2004).…”

Assessment of errors and biases in retrievals of X<sub>CO<sub>2</sub></sub>, X<sub>CH<sub>4</sub></sub>, X<sub>CO</sub>, and X<sub>N<sub>2</sub>O</sub> from a 0.5 cm<sup>–1</sup> resolution solar-viewing spectrometer

“…Hase et al (2016) have also reported on X CO measurements using an EM27/SUN modified to include a second InGaAs detector with optical filters. Column CO measurements are desirable because CO is a tracer of combustion.…”

“…EGI provides a simple way to turn on and off saving of ancillary retrieval files (i.e., spectral fits and averaging kernels). EGI can run for instruments employing one or two detectors, such as the type described by Hase et al (2016). Like the GGG software suite, EGI also includes benchmark spectra acquired under different conditions to run simple tests on.…”

Towards verifying CH<sub>4</sub> emissions from hard coal mines using mobile sun-viewing Fourier transform spectrometry

“…Quality filtering, based on the unmodulated (DC) part of the recorded interferograms, removes all measurements that are affected by unstable pointing conditions, e.g., due to intermittent thin clouds disturbing solar-tracking (e.g., Klappenbach et al, 2015). The spectral bandwidth of the EM27/SUN allows for the detection of H 2 O, O 2 , CO 2 , CH 4 , CO, (CO in combination with an additional channel described 10 by Hase et al (2016)) and other gases if present in significant amounts (Butz et al, 2017). Related species for this study are O 2 and CH 4 .…”