Carbon Monoxide Instrument for High-Altitude Science Flights

We present the Carbon Monoxide Measurement and Analysis (COMA) instrument, modified for airborne measurements of the upper troposphere and lower stratosphere (UT/LS) aboard the WB-57 aircraft. Carbon monoxide (CO) is emitted from combustion, including air pollution activities and biomass burning. In the Northern Hemisphere summer, levels in the UT/LS are enhanced by the Asian Summer Monsoon, and accurate CO measurements are important for understanding the dynamics and chemistry of the atmosphere during this meteorological pattern. COMA is a custom analyzer from Los Gatos Research based on Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS), which has flown previously inside the P-3 during the ORACLES campaigns in 2016-2018. In this work, COMA has been modified to operate on an unpressurized pallet on the WB-57 at altitudes greater than 40,000 kft. This configuration presents multiple challenges: CO concentrations are relatively low, temperature and pressure are outside of typical ambient ranges, and the instrument is subject to significant changes in conditions that can affect the stability of the measurement. To address these challenges, we have conducted laboratory as well as environmental chamber testing to simulate instrument behavior under expected flight conditions. Tests have shown electronic components remain within thermal limits up to a maximum design altitude of 65,000 kft. The laser has been replaced for optimized CO performance, and changes have been made to account for reduced ambient temperature and inlet pressures. Finally, a calibration gas system has been designed at NASA Ames to allow for periodic reference gas measurements in flight. Tests will be conducted in August under NASA Asian Summer Monsoon Chemical & CLimate Impact Project (ACCLIP) prior to the main science campaign. We will present the modifications and performance of the instrument, enabling a new airborne CO capability for airborne science.