NICER observation list: Target ID 855512

We request 200 ks of NICER observing time to study the interaction between the solar wind and two bright comets, C/2023 A3 (Tsuchinshan-ATLAS) and P/2010 H2 (Vales). Utilizing NICER's agility and sensitivity, we aim to compare charge-exchange spectra arising from the comets interaction with varied solar-wind states. Simultaneous observations of both comets at distinct solar latitudes allow us to compare spectra from differing solar-wind conditions. This offers a unique opportunity to map the solar wind during solar maximum and explore charge-exchange reactions in astrophysical plasmas spanning a 0.1 10 MK temperature range. By comparing the cometary spectra we will investigate the source of unexplained emission features between 1-2 keV.