Detailed design of the G-CLEF flexure control camera subsystem

The GMT-Consortium Large Earth Finder (G-CLEF) is one of the first instrument for the Giant Magellan Telescope (GMT). The G-CLEF is a fiber fed, optical band echelle spectrograph that is capable of extremely precise radial velocity measurement. The G-CLEF Flexure Control Camera (FCC) is included as a part in the G-CLEF Front End Assembly (GCFEA), which monitors the field images focused on a fiber mirror to control the flexure and the focus errors within the GCFEA. The five optical components constituting the FCC are aligned on a common optical bench. The order of the optical train is: a collimator, neutral density filters, a focus analyzer, a reimaging camera barrel, and a detector module. The collimator receives the beam reflected by the fiber mirror and consists of a triplet lens. The neutral density filters are located just after the collimator to make it possible a broad range star brightness as a target or a guide. The tent prism focus analyzer is positioned at a pupil produced by the collimator and is used to measure a focus offset. The reimaging camera barrel includes two pairs of doublet lenses to focus the beam onto the CCD focal plane. The detector module is composed of a linear translator and a field de-rotator. In this article, we present the optical and mechanical detailed designs of the G-CLEF FCC.