Characterization of Aeris MIRA Ultra CH4/C2H6 and CO/N2O Gas Analyzers

Gas analyzers are essential for projects that involve atmospheric chemical composition, especially those related to the emission of greenhouse gases. Each successive generation of modern commercially available gas analyzers has strived to be smaller, lighter, and more accurate than the previous generation of analyzers. The new Aeris MIRA Ultra gas analyzers are no exception, as they are lightweight and user-friendly, claim to have unmatched sensitivity and accuracy, and may be particularly suitable for aircraft and drone deployments. For this study, we completed a comprehensive characterization of two Aeris analyzers: the rack mounted CH₄/C₂H₆ Ultra (Ultra 460) and N₂O/CO Ultra (Ultra 505). The methane/ethane model looks to measure natural gas leaks with a superior thermogenic vs biogenic discrimination at sub-ppb per second scales, while the second model is described as the world’s first truly portable, simultaneously measured nitrous oxide and carbon monoxide gas analyzer. Together, the precision and drift of these analyzers were evaluated by comparison with the performance of four fully characterized reference instruments: (1) a Picarro G2401-m cavity-ringdown spectrometer, an Aerodyne (2) C₂H₆ and (3) N₂O Tunable Infrared Laser Direct Absorption Spectroscopy (TILDAS) analyzer, and (4) a Differential Absorption Carbon monOxide Measurement (DACOM) laser spectrometer system. Instrument reference and dilution calibrations were conducted in-lab, while deployment tests and comparisons were executed elsewhere during multiple field projects. Most notably, the Ultra 460 (ethane/methane) was deployed in the winter of 2024 for the Airborne and Satellite Investigation of Asian Air Quality (ASIA-AQ) campaign aboard the NASA DC-8 aircraft in the Philippines, South Korea, Thailand, and Taiwan, and it was also deployed in the summer of 2024 in Salt Lake City, Utah aboard the University of Wyoming Department of Atmospheric Science Mobile Lab for ground-based monitoring during Salt Lake City - Summer Ozone Study (SLC-SOS). The performances of the instruments during these periods were analyzed and their implications are addressed at length, particularly the impact of high humidity conditions on Ultra 460 CH₄ observations. A simple statistical analysis of this relationship is performed using the ratio between DACOM and Ultra 460 CH₄ observations, and it is found that the Ultra 460 performance begins to degrade above ~9000 ppmv of H₂O and breaches -3σ at concentrations of ~35000 ppmv. This relationship is demonstrated to be quadratic and, when used as a correction factor, dramatically reduces error in Ultra 460 CH₄ observations relative to DACOM. The benefits and limitations of these instruments for aircraft and drone deployments, in comparison to existing equipment, are discussed.