A detailed infrared detectors systems overview of MOONS VLT instrument

Abstract

MOONS is a multi‐object spectrograph that will be installed at the Nasmyth focus of the VLT ESO Telescopes in Chile. The instrument has the capacity to deploy approximately 1000 fibers over a field of view of 500 square arcminutes, with a total wavelength coverage of from 0.6 to 1.8 m, offering both low‐ and medium‐resolution modes. The high demand for fast and large optics in all spectral channels prompted the use of similar Schmidt cameras. As a result, the Detector Unit (DU) must be located within the optical beam and its footprint must be minimized to reduce vignetting. The instrument consists of four H4RG‐15um pixel detectors and two fully depleted LBNL CCDs. This article provides a comprehensive description of the detector systems, focusing particularly on the H4RG‐15, including a brief overview of the newly developed cryogenic pre‐amplifier for 64‐output operation, and a detailed discussion of the woven cable technology used for signal routing. Some results of the characterization of three H4RG detectors are presented, with a focus on crosstalk and buffer output performance. The use of the buffer output for the H4RG results in a glow‐per‐read observed at the bottom of the detectors. This article also describes the trade‐offs and alternatives used to optimize detector performance in this situation.