The GMT-Consortium Large Earth Finder (G-CLEF): an optical Echelle spectrograph for the Giant Magellan Telescope (GMT)

The GMT-Consortium Large Earth Finder (G- CLEF) will be a cross- dispersed, opticalband echelle spectrographto be delivered as the first light scientific instrumentfor the Giant Magellan Telescope(GMT) in 2022. G- CLEFis vacuum enclosed and fiber-fed to enable precision radial velocity (PRV) measurements, especially for the detection and characterization of low-mass exoplanetsorbiting solar-type stars. The passbandof G- CLEFis broad, extending from 3500A to 9500A. This passbandprovides good sensitivity at blue wavelengths for stellar abundance studies and deep red response for observations of high-redshift phenomena. The design of G- CLEFincorporates several novel technical innovations. We give an overview of the innovative features of the current design. G- CLEFwill be the first PRV spectrographto have a composite optical bench so as to exploit that material’s extremely low coefficient of thermal expansion, high in-plane thermal conductivity and high stiffness-to-mass ratio. The spectrographcamera subsystem is divided into a red and a blue channel, split by a dichroic, so there are two independent refractive spectrographcameras. The control system software is being developed in model-driven software context that has been adopted globally by the GMT. G- CLEFhas been conceived and designed within a strict systems engineering framework. As a part of this process, we have developed a analytical toolset to assess the predicted performance of G- CLEFas it has evolved through design phases.