We propose a survey of Detached Eclipsing Binaries (DEBs) in the Andromeda galaxy (M31) using HSC in order to geometrically measure its distance to 1% precision. These measurements will enable us to use M31 as a new anchor for the first rung of the local distance ladder to measure the Hubble constant (H0). The distance ladder is currently anchored only by the Milky Way and a few nearby galaxies, which can cause significant systematic errors when determining H0. M31 is a great candidate for an additional anchor, but we cannot currently use it because of the lack of a precisely-measured geometric distance. We will overcome this problem by monitoring hundreds of DEBs hosted by M31. Our simulations show that we can detect a sufficient number of DEBs in the requested nights for this purpose. We have also analysed a DEB found in HSC archival data, and though the quality of its light curve satisfies the necessary conditions, it has too short a period to be used for our goal. Our proposed observations will lead to more robust measurements of H0 and tackle the Hubble tension, one of the most important problems in observational cosmology. The data will be useful to search not only for DEBs but also other time-domain astronomical events such as BH-stellar binaries or microlensing.
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