A detailed infrared detectors systems overview of MOONS VLT instrument

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.mu m, offering both lowand medium-resolution modes. The high demand for fast and large optics in all spectral channels prompted the use of similar f /0.95 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 theH4RGresults 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.