CAGIRE: a wide-field NIR imager for the COLIBRI 1.3 meter robotic telescope

The use of high energy transients such as Gamma Ray Bursts (GRBs) as probes of the distant universe relies on the close collaboration between space and ground facilities. In this context, the Sino-French mission SVOM has been designed to combine a space and a ground segment and to make the most of their synergy. On the ground, the 1.3 meter robotic telescope COLIBRI, jointly developed by France and Mexico, will quickly point the sources detected by the space hard X-ray imager ECLAIRs, in order to detect and localise their visible/NIR counterpart and alert large telescopes in minutes. COLIBRI is equipped with two visible cameras, called DDRAGO-blue and DDRAGO-red, and an infrared camera, called CAGIRE, designed for the study of high redshift GRBs candidates. Being a low-noise NIR camera mounted at the focus of an alt-azimutal robotic telescope imposes specific requirements on CAGIRE. We describe here the main characteristics of the camera: its optical, mechanical and electronics architecture, the ALFA detector, and the operation of the camera on the telescope. The instrument description is completed by three sections presenting the calibration strategy, an image simulator incorporating known detector effects, and the automatic reduction software for the ramps acquired by the detector. This paper aims at providing an overview of the instrument before its installation on the telescope.Comment: Accepted by Experimental Astronom

Conception et réalisation d'un magnétomètre vectoriel à pompage optique de l'hélium 4

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Sci.Terre recherche (751052114) / SudocSudocFranceF

Influence of the CdZnTe substrate thickness on the response of HgCdTe detectors under irradiation: modeling of the substrate luminescence

International audienceThe most extensively used infrared (IR) detectors in astrophysics are based on mercury cadmium telluride (MCT) technology: the MCT light-sensitive layer is grown on a cadmium zinc telluride (CZT) substrate. When launched on a satellite, these detectors are subjected to ionizing radiation from cosmic rays or solar flares (mainly protons) which degrade the detector performance. Indeed, an elevation of the detector background was noted under irradiation, which is believed to be associated with the luminescence of the CZT substrate. Complete removal of the substrate eliminates the problem, but it is a challenging step in the fabrication process. A deeper understanding of the response of IR detectors under irradiation, when the substrate is fully removed, will enable the optimization of substrate design for high-performance space-based scientific imaging. Here, the first results of proton irradiation modeling in MCT detectors, including energy deposition in the CZT substrate, are presented. The estimation of image pollution relies on GEANT4 (GEometry ANd Tracking 4) Monte Carlo simulations as well as analytical and numerical calculations of carrier transport inside the detector structure. In particular, recombination processes in the CZT substrate are taken into account to model the luminescence effect induced by proton irradiation. According to this model, considering published material properties, the diffusion of the carriers generated inside the CZT substrate toward the MCT layer is the main source of pollution. As the substrate thickness increases, more pixels are impacted by a proton impact on the IR. Consequently, depending on the targeted application, either partial or complete removal may be chosen

Use of EBIC for MTF measurement of HOT MCT focal plane planar array with very small pixel pitches

Event: SPIE Defense + Commercial Sensing, 2023, Orlando, Florida, United StatesInternational audienc

Development of a Cryogenic Test Bench for Spectral MTF Measurement on Midwave Infrared Focal Plane Arrays

International audienceThe modulation transfer function (MTF) is one of the key figures of merit for the characterization of infrared focal plane arrays (FPA). Moreover, with both the trend of reduced pixel pitch and the variety of pixel structures observed in the industry, the study of the impact of wavelength on the MTF is also of great interest, and thus needs a spectro-spatial measurement. In this paper, we demonstrate such spectral MTF measurements in the mid-wavelength infrared (MWIR) band by the use of several spectral bandpass filters. We realize those measurements at 80 K on a specific n/p 320 × 256 HgCdTe MWIR FPA, divided into different areas. The pixel pitch is the same for all areas (30 μm), the only difference being the fill factor, which differs from one zone to another. The MTF measurement bench is based on a continuously self-imaging grating interferometer integrated in a specific cryogenic set-up

ROIC glow reduction in very low flux short wave infra-red focal plane arrays for astronomy

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Caractérisation optique d'un objectif de spot scan cryogénique à faible nombre d'ouverture pour détecteurs infrarouges

International audienceInfrared focal plane arrays are widely used for astronomical observations and are constantly optimized to provide higher-quality images. The knowledge of the pixel spatial response becomes critical to extract ever more data from scientific missions. A specific cryogenic spot scan objective with an f-number of 1.2 has been developed in order to finely characterize 15 µm (or smaller) pixel pitch cooled infrared focal plane arrays in the spectral band between 3-5 µm. It will be operated in the MIRCOS test bench with different narrow-band filters. We present the first optical characterization of this objective obtained with a cryogenic wavefront analyzer-a quadrilateral shearing interferometer. The measured wavefront indicates a peak-to-valley amplitude of 2 µm, which corresponds to an optical quality of about λ/2 at 3.75 µm working wavelength. This value higher than expected might be due to a non-uniform cooling of the objective.Les détecteurs infrarouges sont largement utilisées pour les observations astronomiques et sont constamment optimisées pour fournir des images de meilleure qualité. La connaissance de la réponse spatiale des pixels devient primordiale pour extraire toujours plus de données provenant des missions scientifiques. Un objectif spot scan cryogénique spécifique avec un nombre d'ouverture de 1,2 a été développé afin de caractériser finement les détecteurs infrarouges refroidies avec un pas de 15 μm (ou moins) dans la bande spectrale entre 3-5 μm. Elle sera exploitée dans le banc d'essai MIRCOS avec différents filtres à bande étroite. Nous présentons la première caractérisation optique de cet objectif obtenue avec un analyseur de front d'onde cryogénique - un interféromètre à décalage quadrilatéral. Le front d'onde mesuré indique une amplitude peak-to-valley de 2 μm, ce qui correspond à une qualité optique d'environ λ/2 à une longueur d'onde de travail de 3,75 μm. Cette valeur supérieure à celle attendue pourrait être due à un refroidissement non uniforme de l'objectif

Status of the development of 2k2 IR FPAs for astronomy and space in Europe

International audienceWe report on the development of short wave infrared (SWIR) imaging arrays for astronomy and space observation in Europe. LETI and Sofradir demonstrated 640x480 SWIR HgCdTe (MCT) arrays geared at low flux, low dark noise operation. Currently, we are developing 2048x2048 arrays mated to a newly developed ROIC. In parallel, the European Space Agency and the European Commission are funding the development and industrialization of 4 '' CdZnTe substrates and HgCdTe epitaxy. These large wafers are needed to achieve the necessary economies of scale and address the need for even larger arrays. HgCdTe SWIR detector performance at LETI/Sofradir is known from previous programs and will be discussed here. However, we will only be able to summarize the features and specifications of the new 2048x2048 detectors which are still at a prototype stage

Luminescence Properties of CdTe and CdZnTe Materials When Used as Substrate for IR Detectors

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Développement du banc de spot scan cryogénique pour l'étude de détecteurs dans le moyen infrarouge

International audienceIn this article, we present a cryogenic spot scan bench dedicated to the 3-5.5 µm spectral band currently under development in the MIRCOS platform at ONERA. Initial tests have been carried out on a 30 µm pitch HgCdTe focal plane array, and improvements are underway to characterize the spatial response of detectors with smaller pixel pitches.Dans cet article, nous présentons un banc de spot scan cryogénique dédié à la bande spectrale 3-5,5 μm actuellement en cours de développement sur la plateforme MIRCOS de l'ONERA. Les premiers tests ont été réalisés sur un détecteur HgCdTe avec un pas pixel de 30 μm, et des améliorations sont en cours pour caractériser la réponse spatiale de détecteurs avec des pas de pixels plus petits