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

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 μ m channel attributable to the presence of CO, or more likely, CO 2 emission. The excess, when the comet was outbound at a heliocentric distance of 1.9 au, was consistent with a CO 2 production rate of 1.3(±0.07) × 10 26 molecules per second, which is equivalent to an active area on the order of a percent of the comet nucleus’ total surface.