The Mid-Infrared ELT Imager and Spectrograph (METIS) will be one of only three 1^st-generation science instruments on the 39m Extremely Large Telescope (ELT).METIS will provide diffraction-limited imaging and medium resolution slit-spectroscopy from 3-13 microns (L, M, and N bands), as well as high resolution (R≈100,000) integral field spectroscopy from 2.9-5.3 microns.Both imaging and IFU spectroscopy can be combined with coronagraphic techniques.After the final design reviews of the optics (2021) and the entire system (2022), most hardware procurements have started.In this paper we present an overview of the status of the various ongoing activities.Many hardware components are already in hand, and the manufacturing is in full swing in order to start the assembly and testing of the subsystems in 2024 toward first light at the telescope in 2028/29.This rather brief paper only provides an overview of the project status.For more information, we refer to the detailed instrument paper which will be published soon.

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The Mid-infrared ELT Imager and Spectrograph (METIS) will provide the Extremely Large Telescope (ELT) with a unique window to the thermal- and mid-infrared (3–13 µm). Its single-conjugate adaptive optics (SCAO) system will enable high contrast imaging and integral field unit (IFU) spectroscopy (R ~ 100 000) at the diffraction limit of the ELT. This article describes the science drivers, conceptual design, observing modes, and expected performance of METIS.@en

Ground-based thermal-infrared observations have a unique scientific potential, but are also extremely challenging due to the need to accurately subtract the high thermal background. Since the established techniques of chopping and nodding need to be modified for observations with the future mid-infrared ELT imager and spectrograph (METIS), we investigate the sources of thermal background subtraction residuals. Our aim is to either remove or at least minimise the need for nodding in order to increase the observing efficiency for METIS. To this end we need to improve our knowledge about the origin of chop residuals and devise observing methods to remove them most efficiently, i.e. with the slowest possible nodding frequency. Thanks to dedicated observations with VLT/VISIR and GranTeCan/CanariCam, we have successfully traced the origin of three kinds of chopping residuals to (1) the entrance window, (2) the spiders and (3) other warm emitters in the pupil, in particular the VLT M3 mirror cell in its parking position. We conclude that, in order to keep chopping residuals stable over a long time (and therefore allow for slower nodding cycles), the pupil illumination needs to be kept constant, i.e. (imaging) observations should be performed in pupil-stabilised, rather than field-stabilised mode, with image de-rotation in the post-processing pipeline. This is now foreseen as the default observing concept for all METIS imaging modes.@en

We present the preliminary design of the calibration unit of the future E-ELT instrument METIS. This independent subunit is mounted externally to the main cryostat of METIS and will function both as calibration reference for science observations, as well as verification and alignment tool during the AIT phase. In this paper, we focus on describing its preliminary layout and foreseen functionalities, based on the performance requirements defined at system level and the constraints imposed by warm IR background. We discuss the advantage of employing an integrating sphere as common radiation emitter, leading to a novel and versatile design, where the source's spatio-spectral properties can be varied with high fidelity and repeatability. By combining only few tuneable sources and mechanisms we show how a large instrument such as METIS can be calibrated and tested, without the need of a complex cold calibration unit.@en

The Mid-infrared ELT Imager and Spectrograph (METIS) is one the first three scientific instruments on ESO's Extremely Large Telescope (ELT). At the time of anticipated first light in 2025, METIS will provide diffraction limited imaging, coronagraphy and medium resolution slit spectroscopy in the 3-19 micrometers range, as well as high resolution (R approximately equals to 100, 000) integral field spectroscopy from 2.9-5.3 micrometers. The unique combination of these observing capabilities with an angular resolution of 0.020 sec, and the sensitivity provided by a 40m aperture, make METIS a very powerful tool to study the infrared sky - from objects in our Solar system, the Galactic center, brown dwarfs, evolved stars, and massive stellar clusters to active galactic nuclei (AGN), local starbursts, transient events, and luminous infrared galaxies at intermediate redshifts. Its main scientific focus, however, will be on the study of proto-planetary disks and exoplanets. In this paper, we describe the instrument concept and performance. We discuss the scientific performance of METIS with respect to AKARI, and elaborate on the relevance of the AKARI archive with respect to the METIS observing program.@en

METIS is one the first three instruments on the E-ELT. Apart from diffraction limited imaging, METIS will provide coronagraphy and medium resolution slit spectroscopy over the 3 - 19μm range, as well as high resolution (R ∼ 100,000) integral field spectroscopy from 2.9 - 5.3μm, including a mode with extended instantaneous wavelength coverage. The unique combination of these observing capabilities, makes METIS the ideal instrument for the study of circumstellar disks and exoplanets, among many other science areas. In this paper we provide an update of the relevant science drivers, the METIS observing modes, the status of the simulator and the data analysis. We discuss the preliminary design of the optical system, which is driven by the need to calibrate observations at thermal IR wavelengths on a six-mirror ELT. We present the expected adaptive optics performance and the measures taken to enable high contrast imaging. We describe the opto-mechanical system, the location of METIS on the Nasmyth instrument platform, and conclude with an update on critical subsystem components, such as the immersed grating and the focal plane detectors. In summary, the work on METIS has taken off well and is on track for first light in 2025.

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