  Characterizing rocky exoplanet atmospheres is a key goal of exoplanet
science, but interpreting such observations will require understanding the
stellar UV irradiation incident on the planet from its host star. Stellar UV
mediates atmospheric escape, photochemistry, and planetary habitability, and
observations of rocky exoplanets can only be understood in the context of the
UV SED of their host stars. Particularly important are SEDs from
observationally favorable but poorly understood low-mass M-dwarf stars, which
are the only plausible targets for rocky planet atmospheric characterization
for the next 1-2 decades. In this work, we explore the utility of AstroSat UVIT
for the characterization of the UV SEDs of low-mass stars. We present
observations of the nearby M0 star HIP 23309 in the FUV and NUV gratings of
UVIT. Our FUV spectra are consistent with contemporaneous HST data and our NUV
spectra are stable between orbits, suggesting UVIT is a viable tool for the
characterization of the SEDs of low-mass stars. We apply our measured spectra
to simulations of photochemistry and habitability for a hypothetical rocky
planet orbiting HIP 23309 and elucidate the utility and limitations of UVIT in
deriving UV SEDs of M-dwarf exoplanet hosts. Our work validates UVIT as a tool
to complement HST in the characterization of exoplanet host stars and carries
implications for its successor missions like INSIST.
