The MSE Project Office has begun planning a proposal to develop an end-to-end Pathfinder instrument for MSE but deployed on the current 4m-class Canada France Hawaii Telescope. MSE Project Office and CFHT Instrumentation Group are codeveloping the proposal along with coinvestigators from NOIRLab and collaborators from US universities. The goal of the Pathfinder is to prototype MSE by demonstrating on-sky the ability of its primary components and principal software packages. The end-to-end Pathfinder concept is a multi-object spectrograph fiber-fed from the current CFHT telescope. Utilizing the same technology, it will duplicate the MSE spectrograph, fiber positioner system with scaled down multiplexing (from 4,000 fibers to approximately 1,000 fibers), and fiber optics bundle. The Pathfinder will also develop the program execution architecture and its major software modules planned for MSE including scheduling, targeting, data reduction, analysis, management, and archiving, and database manipulation.

The Pathfinder would be an initial science product shared with the US community based on the Astro2020 survey’s strategic priorities on time-domain astrophysics and highly multiplexed spectroscopy. Examples of the primary science goals of Pathfinder include time-domain astrophysics (specifically, the spectroscopic follow-up of transients identified by facilities such as the Rubin Observatory and Zwicky Transient Factory to optimize their identification and classification) as well as Galactic archeology (chemical and kinematic studies of resident Milky Way stellar populations).