The second generation of ELT instruments includes an optical-infrared high-resolution spectrograph, ANDES, ArmazoNes high Dispersion Echelle Spectrograph. It covers a wide spectral range that goes from 0.4 to 1.8μm (goal 0.35 to 2.4μm). A common model of detector is planned for the two visible spectrographs RIZ and UBV. A total of five detectors will cover the latter spectral range. A common detector unit design has been developed based on ELT's standard components and inspired by the previous successful detector units designed for HARPS and ESPRESSO. It consists of a 9k x 9k CCD detector, a differential vacuum cryostat that keeps the detector in its dedicated vacuum chamber and a cryocooler that cools down the detector to minimize the dark noise. The required temperature, mechanical and pressure stabilities drive the design of the detector unit.
In this paper, we present an overview of the software architecture for the ArmazoNes high Dispersion Echelle Spectrograph (ANDES) spectrograph, which has been developed as part of the recent System Architecture Review (SAR) held in October 2023. Our focus in this paper is twofold: we will detail about the control software and science tools that are set to be implemented. In particular, we provide a detailed view on how the ELT Instrument Control Framework has been effectively deployed to manage the complexities of a distributed instrument like ANDES. This entails a comprehensive discussion of the key architectural decisions we have made to meet the requirements of the project. Furthermore, we offer insights into the suite of science software that will be an integral part of the ANDES instrument. This includes the Exposure Time Calculator, Observation Preparation tools, and the Data Reduction Library. Finally, we provide an overview of the Data Analysis Software and the End-to-End ANDES simulator. These tools are crucial for processing and analyzing the data collected by the ANDES spectrograph.
The first generation of ELT instruments includes an optical-infrared high resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs ([U]BV, RIZ, YJH) providing a spectral resolution of ∼100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 μm with the goal of extending it to 0.35-2.4 μm with the addition of an U arm to the BV spectrograph and a separate K band spectrograph. It operates both in seeing- and diffraction-limited conditions and the fibre-feeding allows several, interchangeable observing modes including a single conjugated adaptive optics module and a small diffraction-limited integral field unit in the NIR. Modularity and fibre-feeding allows ANDES to be placed partly on the ELT Nasmyth platform and partly in the Coudé room. ANDES has a wide range of groundbreaking science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars, tests on the stability of Nature’s fundamental couplings, and the direct detection of the cosmic acceleration. The ANDES project is carried forward by a large international consortium, composed of 35 Institutes from 13 countries, forming a team of almost 300 scientists and engineers which include the majority of the scientific and technical expertise in the field that can be found in ESO member states.
The RIZ & UBV visible spectrographs of the ANDES instrument, which are foreseen to be installed at the Extremely Large Telescope, require to be under a very stable high vacuum and at an extremely stable temperature of 1mK to reach the radial velocity goal of 10cm/s RMS over a 10-year period. The baseline design, integration and first analyses of the 5.5t aluminum vacuum tank, vacuum system, and the thermal enclosure of the two-room temperature spectrographs are presented in this paper. A very analogous configuration is proposed for both instruments in view of their similarities. In addition, this article addresses the finite rigidity of the Nasmyth platform and its consequences on the instrument design together with a potential collaborative multi-CAD Product Design Management platform description.
We present the design of the ANDES UBV module, the bluest spectrograph of the ANDES instrument. It is a fiber-fed high resolution, high stability spectrograph, which will be installed on the ELT-Nasmyth platform to minimize blue fibre losses from the focal plane to the spectrograph. In this paper we present the status of development of the spectrograph, its optical design, and auxiliary devices like exposure meter and leveling system, at the preliminary design stage. As stability is the prime design driver, a thermal enclosure is provided to keep temperature of the optical train stable at ambient conditions, and the pressure is kept constant at high vacuum level. The science, sky background and simultaneous calibration light is fed to the spectrographs via fiber bundles of 66 fibres, which are arranged in a straight row forming the spectrograph slit.
We present here the preliminary design of the RIZ module, one of the visible spectrographs of the ANDES instrument. It is a fiber-fed high-resolution, high-stability spectrograph. Its design follows the guidelines of successful predecessors such as HARPS and ESPRESSO. In this paper we present the status of the spectrograph at the preliminary design stage. The spectrograph will be a warm, vacuum-operated, thermally controlled and fiber-fed echelle spectrograph. Following the phase A design, the huge etendue of the telescope will be reformed in the instrument with a long slit made of smaller fibers. We discuss the system design of the spectrographs system.
The first generation of ELT instruments includes an optical-infrared high resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs (UBV, RIZ, YJH) providing a spectral resolution of ∼100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 µm with the goal of extending it to 0.35-2.4 µm with the addition of a K band spectrograph. It operates both in seeing- and diffraction-limited conditions and the fibre-feeding allows several, interchangeable observing modes including a single conjugated adaptive optics module and a small diffraction-limited integral field unit in the NIR. Its modularity will ensure that ANDES can be placed entirely on the ELT Nasmyth platform, if enough mass and volume is available, or partly in the Coudé room. ANDES has a wide range of groundbreaking science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars, tests on the stability of Nature’s fundamental couplings, and the direct detection of the cosmic acceleration. The ANDES project is carried forward by a large international consortium, composed of 35 Institutes from 13 countries, forming a team of more than 200 scientists and engineers which represent the majority of the scientific and technical expertise in the field among ESO member states.
The current STELLA Échelle spectrograph (SES), which records 390nm to 870nm in one shot at a spectral resolution of 55000, will be replaced by a suite of specialized spectrographs in three spectral bands. The UV will be covered by a newly designed H and K spectrograph covering 380nm to 470nm (SES-H and K), the visual band (470nm - 690 nm) will be covered by SES-VIS, which is a vacuum-stabilized spectrograph designed for high radial-velocity accuracy, and the NIR will be covered by the current SES spectrograph from 690nm to 1050 nm. In order to improve the UV transmission, and to accommodate three different fibre-feeds, the prime focus corrector of the telescope will be refurbished, leading to an optical system with the f/2 1200mm spherical primary, a 4-lens collimator with 2" aperture, atmospheric dispersion corrector (ADC), and two dichroic beam splitters, feeding 3 separate fibre feeds for the three bands. The newly designed H and K spectrograph will be an Échelle spectrograph, based on a R4-grating with 41.6 l/mm and 110mmx420mm, using a f/5 camera and the cross-disperser in double pass (as in TRAFICOS, MIKE, KPF), using 21 spectral orders. The spectral resolution of all three spectrographs will be comparable to the current SES's 55000.
The BMK10k is a 30cm-aperture lens telescope ‘Ballistische Messkammer 75/2,5/18’, now equipped with a 100Megapixel STA1600LN CCD camera. With a plate scale of 2.54 arcsec per pixel, it delivers an astrometrically well-corrected field of view of 7.25° × 7.25°. We have roboticized it with the intention of operating it from Cerro Armazones, Chile, where it saw first light in August 2019. It is currently in commissioning. Among other applications, we plan to use it to observe the Southern PLATO Field (SPF) almost continuously for three years in preparation for the PLATO satellite, which will have much reduced spatial resolution in comparison. The telescope mount was retrofitted with modern servo motors and an industrial Beckhoff programmable logic controller (PLC), allowing reliable remote telescope control, environmental monitoring, dome control, with a separate PLC ensuring safely measures to protect the telescope in case of communication loss or power failure. Communications between the TCS and the PLC firmware are accomplished with Beckhoff TwinCAT Automation Device Specification (ADS) over TCP/IP. Real-time response is realised within the PLC, and ADS has latency times on the order of a few 100 ms, sufficient for high-level control of the telescope. Using off-the-shelf industrial components has proven to be a cost-effective and reliable method of operating a fully autonomous observatory.
The new visual STELLA echelle spectrograph (SES-VIS) is a new instrument for the STELLA-II telescope at the Iza~na observatory on Tenerife. Together with the original SES spectrograph - which will still be used in the near IR - and a new H&K-optimized spectrograph, which is currently in the design phase, it will change the focus of the spectroscopic observations at STELLA towards the follow up of planetary candidates detected by upcoming surveys focusing on bright targets (TESS, PLATO2). It is optimized for precise radial velocity determination and long term stability. We have developed a ZEMAX based software package to create simulated spectra, which are then extracted using our new reduction package, which is based on the PEPSI software package. The focus has been put on calibration spectra, and the full range of available calibration sources (at field, Th-Ar, and Fabry-Perot), which can be compared to actual commissioning data once they are available. Furthermore we tested for the effect of changes of the environmental parameters to the wavelength calibration precision.
The Gregor At Night Spectrograph (GANS) is a new instrument currently being built for the GREGOR solar telescope at Iza~na observatory on Tenerife. Its primary science case will be the follow up of planetary candidates detected by upcoming surveys focussing on bright targets (TESS, PLATO2). Therefore it will be optimised for precise radial velocity determination and long term stability. We have developed a ZEMAX based software package to create simulated spectra, which are reduced using standard IRAF tasks. We used a solar model spectrum to determine the influence of S/N ratio, wavelength coverage, pixel sampling and telluric lines on the extracted radial velocities. Furthermore we derived the effect of an asymmetric spectrograph illumination on the measured radial velocity.
White pupil arrangements using parabolic off-axis mirrors are commonly used by instrument designers of high-resolution spectrographs. Their advantage is a non-chromatic, spherical free collimation, an intermediate focus providing the possibility for stray light apertures, and the compression of the beam diameter using a second, a transfer, collimator. However, these arrangements suffer from off-axis aberrations in the field. Many configurations create the intermediate focus, after double-passing the primary collimator, in the vicinity of the spectrograph input. This makes it necessary to introduce small angles at the main collimator, further increasing off-axis aberrations. Furthermore, image curvature is high and requires toroidal surfaces to be added near the spectrograph focus in front of the CCD. In high-precision radial velocity measurements, it is of great importance to properly model the spectrographs transfer function in order to derive exact line positions. Therefore, clean and very well defined spots, even when working near the sampling limit, which can simply be represented by gaussians will benefit such measurements. This point is usually considered less by instrument designers. We have studied several possible off-axis mirror arrangements for white pupil spectrographs and discuss our results here. We focus on the image quality generated by the mirrors, on-axis as well as in the field. We come to the conclusion that a fairly uncommon arrangement provides best performance in the sense of image quality and focus accessibility.
GREGOR at night spectrograph (GANS) is a high-resolution thermally-stabilised vacuum-enclosed fixed-format fiber-fed Echelle spectrograph. GANS will be installed starting 2018 alongside the daytime instrumentation in the building of the 1,5m Gregor Solar Telescope at the Observatorio del Teide at Izan˜a, Tenerife. Specified resolving power is R~55k with wavelength coverage from 470 to 680 nm in single shot on 2k 2k CCD with 3”, 50μm fiber on sky, and with space between orders for simultaneous calibration light in the form of a Fabry-Perot Etalon or a Laser-comb spectrum. The end-to-end simulated radial velocity precision performance estimate is 2 ms−1. The main observing project of GANS will be the ground-based follow-up survey of TESS and PLATO2.0 exoplanet candidates. GANS will observe its targets in autonomous operation without human intervention using the normally human-operated day-time observatory. Limited operations will begin in first half of 2019 with first science-light planned for summer 2019.
PEPSI is the new fiber-fed and stabilized “Potsdam Echelle Polarimetric and Spectroscopic Instrument” for the Large Binocular Telescope (LBT). It covers the entire optical wavelength range from 384 to 913 nm in three exposures at resolutions of either R=λ/▵λ=50,000, 130,000 or 250,000. The R=130,000 mode can also be used with two dual-beam Stokes IQUV polarimeters. The 50,000-mode with its 12-pix sampling per resolution element is our “bad seeing” or “faint-object” mode. A robotic solar-disk-integration (SDI) telescope feeds solar light to PEPSI during day time and a 450-m fiber feed from the 1.8m VATT can be used when the LBT is busy otherwise. CCD characterization and a removal procedure for the spatial fixed-pattern noise were the main tasks left from the commissioning phase. Several SDI spectral time series with up to 300 individual spectra per day recovered the well-known solar 5-minute oscillation at a peak of 3 mHz (5.5min) with a disk-integrated radial-velocity amplitude of only 47 cm/s. Spectral atlases for 50 bright benchmark stars including the Sun were recently released to the scientific community, among them the ancient planet- system host Kepler-444. These data combine PEPSI’s high spectral resolution of R=250,000 with signal-to-noise ratio (S/N) of many hundreds to even thousands covering the entire optical to near-infrared wavelength range from 384 to 913 nm. Other early science cases were exoplanet transits including TRAPPIST-1, a spectrum of Boyajian's star that revealed strong and structured but stable ISM Na D lines, a spectrum of Oph allowing a redetermination of the ISM Li line doublet, and a first Doppler image of the young solar analog EK Dra that revealed starspots with solar-like penumbrae.
Limited observing time at large telescopes equipped with the most powerful spectrographs makes it almost impossible to gain long and well-sampled time-series observations. Ditto, high-time-resolution observations of bright targets with high signal-to-noise are rare. By pulling an optical fibre of 450m length from the Vatican Advanced Technology Telescope (VATT) to the Large Binocular Telescope (LBT) to connect the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) to the VATT, allows for ultra-high resolution time-series measurements of bright targets. This article presents the fibre-link in detail from the technical point-of-view, demonstrates its performance from first observations, and sketches current applications.
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