NICER observation list: Target ID 672216

We propose to use the exceptionally bright comet C/2022 E3 (ZTF) as a natural laboratory to study solar-wind charge-exchange reactions. The combination of the comet's brightness, orbit, and timing during the solar cycle will allow us to probe all main solar-wind states with nearly constant cometary parameters. We will analyze the evolution of the spectrum over time, systematically relating changes of line fluxes with variations in the velocity, density, and freeze-in temperature. We will look for the presence of emission features between 1-2 keV and use time-resolved spectra to determine whether individual exposures can be associated with solar flares. NICERs combination of high sensitivity and rapid follow capabilities make it uniquely suitable for our science goals.