Fiber Optic Characterization for Unprecedented Sky Subtraction (FOCUSS)

Abstract

Observations taken from ground-based telescopes and large spectroscopic facilities are contaminated by emission from the Earth’s atmosphere and must be subtracted from astronomical measurements to recover the true target spectrum of an object. Precise and accurate sky subtraction is imperative to achieving reliable science results since many astronomical objects are fainter than the sky background. The Fiber Optic Characterization for Unprecedented Sky Subtraction (FOCUSS) project aims to obtain an accurate subtraction of the sky background using calibrated fiber-fed spectroscopic instruments for the next generation of spectroscopic facilities such as the Maunakea Spectroscopic Explorer (MSE). The fundamental basis of FOCUSS is to take detailed measurements of individual fibers that will be used in these spectroscopic facilities, locate and analyze the primary depreciators of fiber performance, and identify solutions and techniques to limit these effects. The fiber characteristics tested in the project include focal ratio degradation (FRD) and the relative transmission of the fibers. Ultimately, we should be able to choose a group of fibers for any spectroscopic facility that effectively minimize the effect of fiber differences to achieve accurate sky subtraction and maximize the accuracy of the spectroscopic data collected.