NEOWISE Observed CO and CO₂ Production Rates of 46P/Wirtanen During the 2018–2019 Apparition*

Abstract We present measurements of comet 46P/Wirtanen obtained by the NEOWISE spacecraft in 2017 through 2019. We detected signal in excess of the dust in the 4.6 μm channel attributable to the presence of CO, or more likely, CO2 emission. The excess, when the comet was outbound at a heliocentric distance of 1.9 au, was consistent with a CO2 production rate of 1.3(±0.07) × 1026 molecules per second, which is equivalent to an active area on the order of a percent of the comet nucleus’ total surface.