Miniaturized laser heterodyne radiometer for measurements of CO2 in the atmospheric column

Abstract

We have developed a low-cost, miniaturized laser heterodyne radiometer for highly sensitive measurements of carbon dioxide (CO 2) in the atmospheric column. In this passive design, sunlight that has undergone absorption by CO 2 in the atmosphere is collected and mixed with continuous wave laser light that is step-scanned across the absorption feature centered at 1,573.6 nm. The resulting radio frequency beat signal is collected as a function of laser wavelength, from which the total column mole fraction can be de-convolved. We are expanding this technique to include methane (CH 4) and carbon monoxide (CO), and with minor modifications, this technique can be expanded to include species such as water vapor (H 2 O) and nitrous oxide (N 2 O).

Potential improvements in global carbon flux estimates from a network of laser heterodyne radiometer measurements of column carbon dioxide

“…The development of the mini-LHR technology is ongoing, but this computational study already builds on a growing body of work that has characterized its error budgets and its in-field performance (Wilson et al, 2013;Clarke et al, 2014;Melroy et al, 2015).…”

“…The mini-LHR is a ground-based, passive, sun-viewing instrument that observes trace gases in the atmospheric column. It has been under development at the NASA Goddard Space Flight Center (GSFC) since 2009 (Melroy et al, 2015;Clarke et al, 2014;Wilson and McLinden, 2012), and while earlier versions exclusively measured XCO 2 , the current version observes both XCO 2 and XCH 4 . Current challenges associated with our understanding of emissions of CH 4 (Wolf et al, 2017) will result in a different network design.…”

“…Peylin et al, 2013). We conservatively assume a mini-LHR measurement precision of 1.5 ppm in our experiments; however, the current precisions for the mini-LHR and TCCON data products are < 1 ppm for 1 h data products (Wunch et al, 2010;Messerschmidt et al, 2011;Wilson et al, 2017;Melroy et al, 2015). Instrument biases were not included in these OSSE runs because our focus is the relative performance of different ground-based remote-sensing networks.…”

The Methane Isotopologues by Solar Occultation (MISO) Nanosatellite Mission: Spectral Channel Optimization and Early Performance Analysis

“…As with the TIR LHR, extensive demonstrations using ground-based prototypes have been made [30,31]. The SWIR LHR within MISO is based on the fully fiber-coupled design described in Rodin et al [31].…”

Thermal infrared laser heterodyne spectroradiometry for solar occultation atmospheric CO&lt;sub&gt;2&lt;/sub&gt; measurements

“…The use of LHR for CO 2 monitoring is also currently being investigated by Clarke et al (2014), Melroy et al (2015), and Wilson et al (2014). Their system operates in the shortwave IR (1.6 µm), leveraging telecommunication distributed feedback lasers as the LO and associated photonics components to couple the solar radiation to a single-mode optical fibre connected to the solar trackers of the AERONET Sun photometer network.…”