The instrumentation plan for the ELT foresees the ArmazoNes high Dispersion Echelle Spectrograph (ANDES). The ANDES-project and consortium entered phase B in January 2022 and underwent several (internal and external) revisions by now to ensure that the requirements and eventually the challenging goals can be met by the physical design of the spectrograph.
Among its main scientific goals are the detection of atmospheres of exoplanets and the determination of fundamental physical constants. For this, high radial velocity precision and accuracy are required. Even though the ANDES-spectrograph is designed for maximum intrinsic stability, a calibration and thus a calibration unit is mandatory. To allow for maximum flexibility and modularity the calibration unit is physically split into three calibration units.
We show the design of the calibration units and their individual components, where possible. This includes the electronics, the mechanics, the software supporting and controlling the light guiding and calibration sources.
Ensuring earthquake resilience is paramount for the upcoming Extremely Large Telescope (ELT). Instruments positioned on the ELT’s Nasmyth platform are anticipated to endure substantial seismic accelerations, peaking at 3.6 g in specific scenarios. These instruments have to be designed not only to survive such events but also to only require minimal repairs for sustained optimal functionality. This paper presents our approach to mitigate the dynamic forces impacting the rotary platform. This platform hosts various critical components, including cryogenic control units and mosaic detector control systems, essential for the operation of MICADO in its mechanical de-rotating motion.
Furthermore, this paper tackles the challenge of minimizing instrument-induced vibrations affecting the telescope’s structure. Given that the ELT’s optical system, composed of 798 segments, operates very similar to an interferometer, maintaining an extremely stable wavefront is crucial - a key insight learned from the Very Large Telescope Interferometer (VLTI). Our focus is on identifying potential sources of vibration within specific frequency ranges where the telescope demonstrates increased sensitivity. We will explore strategies for mitigating these vibrations to maintain a wavefront error below 50 nm.
A major issue for project management, besides handling schedules and deadlines, is the process of finding and extracting the most relevant information from a variety of different software solutions used by the different stakeholders. This often leads to enormously large Excel sheets that try to identify the most up-to-date versions of the documents needed, which are extremely time-consuming to maintain, inefficient for finding information, and prone to errors. The contemporary methodology we introduce represents a paradigm shift in project management, eschewing the traditional model of isolated databases for documents, such as requirements, CAD data, and Gantt chart schedules. Instead, we propose an integrated database architecture that consolidates all project management needs into a single, user-friendly repository. This, coupled with a web-based interface, facilitates the retrieval of relevant information in a straightforward and dependable manner. Illustrated through the case study of ELT-MICADO, we present the implementation of this strategy using Siemens Teamcenter, an industry standard software solution that is adapted to our specific needs. This exposition is not intended as an endorsement of the product but rather as an exemplification of one potential solution. It is acknowledged that alternative software solutions may offer comparable functionality and performance.
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.
We introduce MOSES, the new High-Resolution Echelle Spectrograph designated for the 1.2m MONET telescope at McDonald Observatory, Texas, USA. The science drivers are radial velocity experiments and activity monitoring in Sun-like stars. Set for installation in the final quarter of 2025, MOSES features a white pupil design and aims for a spectral resolution greater than 80,000 over the 380-680 nm wavelength range. It incorporates a pixel sampling rate of 3.5 and uses two fibers to facilitate a simultaneous calibration mode. Encased within a vacuum vessel and operating in a temperature-stabilized environment, MOSES is expected to achieve a radial velocity precision below 2 m/s, aided by a Fabry-Pérot etalon calibration system. This paper outlines the implementation of the fiber injection unit, the optical layout of the spectrograph, and the present status of the various subsystems under development.
CARMENES consists of two high-resolution spectrographs located at the Calar Alto 3.5m telescope, covering the wavelength range from 520nm to 1710 nm. The original Fabry-Pérot (FP) units have been essential to track and remove instrumental drift while also improving the wavelength solution provided by the hollow cathode lamps. In this paper we present the second-generation FP unit that has begun operation at Calar Alto in April 2024. It features drastically improved temperature stabilization, additional temperature monitoring, and enhanced optomechanics. Temperature stabilization is improved through better vacuum vessel design, thermal shielding and improved thermal control. The temperature is now monitored with Pt-100 sensors inside the vacuum vessel, one of which is used to drive the temperature control. The new purpose-built optomechanics allow for an improved alignment procedure leading to higher line contrast. The etalon coatings now cover a broader wavelength range, the optics have been upgraded, and the fibers have been updated to an octagonal shape. In laboratory measurements with a Fourier transform spectrometer we compare the FP radial velocity (RV) drift to that of an iodine cell. In a two hour binning we achieve an RMS of the differential RVs of 6 cm s−1. The new FP unit has already been successfully integrated at CARMENES, with first calibration data indicating improved RV precision.
MORISOT (MOnet Robotic Instrument for Spectroscopy Of Transients) is a low-resolution optical spectrograph installed at our 1.2 m robotic telescope MONET/South located at SAAO. The installation of the newly designed frontend at the telescope enabled the commissioning of MORISOT in December 2023. With this frontend, MORISOT will be able to run fully robotically by using the main camera of the telescope for simultaneous guiding. Moreover, a second 25-cm-telescope, mounted at MONET/South, can be used to simultaneously perform photometric observations of the spectroscopically observed objects. The fully robotic operations will be handled by our observatory control system pyobs, which already runs our robotic telescopes for photometric observations and will be extended to handle all the operations (guiding, spectroscopy and photometry) at once. First use cases will be a high-cadence survey of changing-look AGN and a survey of transiting exoplanets.
The Institute for Astrophysics and Geophysics solar observatory is producing high-fidelity, ultra-high-resolution spectra (R > 500000) of the spatially resolved surface of the Sun using a Fourier transform spectrometer (FTS). The radial velocity (RV) calibration of these spectra is currently performed using absorption lines from Earth’s atmosphere, limiting the precision and accuracy. To improve the frequency calibration precision and accuracy, we use a Fabry–Pérot etalon (FP) setup that is an evolution of the CARMENES FP design and an iodine cell in combination. To create an accurate wavelength solution, the iodine cell is measured in parallel with the FP. The FP is then used to transfer the accurate wavelength solution provided by the iodine via a simultaneous calibration of solar observations. To verify the stability and precision of the FTS, we perform parallel measurements of the FP and an iodine cell. The measurements show an intrinsic stability of the FTS of a level of 1 m s − 1 over 90 h. The difference between the FP RVs and the iodine cell RVs show no significant trends during the same time span. The root mean square of the RV difference between the FP and iodine cell is 10.7 cm s − 1, which can be largely attributed to the intrinsic RV precisions of the iodine cell and the FP (10.2 and 1.0 cm s − 1, respectively). This shows that we can calibrate the FTS to a level of 10 cm s − 1, competitive with current state-of-the-art precision RV instruments. Based on these results, we argue that the spectrum of iodine can be used as an absolute reference to reach an RV accuracy of 10 cm s − 1.
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 Solar observatory at the Institute for Astrophysics and Geophysics Göttingen makes use of the ultra-high resolving power (R < 900, 000 at 600 nm) of a Fourier transform spectrograph (FTS) to obtain spectra of the resolved and integrated Sun. To improve the radial velocity (RV) stability of the FTS measurements we develop a new calibration unit based on a passively stabilized Fabry-Pérot Etalon (FP) (FSR= 3.6 GHz and F ≈ 7) for simultaneous calibration in the near-infrared. The FP is illuminated by two LEDs, covering the wavelength range from 800 to 1000 nm. To mitigate environmental effects, the FP is placed in a temperature and pressure controlled vessel. We explore the impact of the choice of input fiber as well as fiber coupler focal length on the calibration spectrum. In 150 laser frequency comb calibrated measurements over 8 hours we achieve an an RMS of the FP-RV of 0.58 m s−1 .
We present ExoTOM – a target-observation-manager automating exoplanet transit follow-up. ExoTOM is built upon the TOM-toolkit developed by Las Cumbres Observatory (LCO). ExoTOM keeps track of known transiting exoplanet targets (and candidates), automatically predicts their transit times and observability at several telescope sites, and plans and requests observations via the LCO observing portal API. Target selection can be constrained by magnitude, transit depth and manually set priorities. The recorded photometric data is then automatically retrieved and analyzed. A simple transit fit is performed using the batman transit modeling package. The data and analysis products can be accessed and edited via the ExoTOM web interface. An analysis procedure was developed to extract the cleanest possible transit light curves from the photometric data. The main challenge was to find the best radius for the aperture photometry and the best sample of reference stars to use for the differential photometry. The analysis procedure first removes outlier reference stars and frames and then uses a new algorithm to solve the discrete optimization problem of selecting the best reference stars and aperture. From January through September 2021, ExoTOM’s automatic observation scheduling produced 18 whole transit observations and 14 more of just the ingress or egress. The targets were TESS objects of interest ranging from TESS magnitude 8.7 to 13.5 mag and transit depth 1.5 to 118 mmag. These observations were done on the 50cm Cassegrain telescope of the Institute of Astrophysics of the University of Göttingen.
The Institute for Astrophysics Gottingen operates a solar observatory that combines a 50 cm siderostat with (1) a vacuum vertical telescope, (2) a very high resolution Fourier Transform Spectrograph (R < 900, 000 at 600 nm), and (3) a Laser Frequency Comb for extremely precise and accurate frequency calibration (< 10 cm/s). We introduce our setup that feeds the spectrograph with either a 32.5” field of view of the solar surface, or with disk-integrated sunlight for Sun-as-a-star observations and explain the necessary computational steps to guide specific positions on the solar surface into the fiber. Our instrument suite can deliver spectroscopic measurements with extremely accurate frequency calibration, which is valid across very large frequency regions (approx. 400-800 nm in wavelength). This allows precision spectroscopy of individual lines in order to study the variability of spectral lines in Sun-as-a-star observations as well as determining the convective blueshift across the solar surface from many spectral lines.
Fourier Transform Spectrographs (FTS) are versatile tools for measuring accurate, high resolution spectra. They are internally calibrated by a reference laser that runs in parallel to the science light. Therefore it is crucial to properly align these two beams with respect to each other. We show how this can be achieved by feeding a part of the reference light into the optical path of the science beam. For astronomical applications it’s often useful to use optical fibers. We present a coupling setup for our Bruker Optics IFS 125 FTS, consisting of (1) two hexagonal input fibers, (2) dichroic beam-combining for measuring two light sources simultaneously and (3) optimized optics to match the original Bruker design. The hexagonal shape of the fiber cores secures sufficient mode scrambling inside the fibers, resulting in constant beam parameters and a more homogeneous illumination of the entrance aperture of the FTS.
High resolution spectroscopy enables the detection of atmospheres of exoplanets. To reach the required radial velocity precision of about 1 m/s, calibration with even more precise sources is mandatory. HIRES will employ several calibration sources, the most important ones are an Laser Frequency Comb (LFC) and Fabry-P´erots (FP). The LFC needs to be filtered with a set of FP. One possible solution is to illuminate this set of FP with a broadband light source and use them as calibrators, when they are not used for filtering the LFC. It has been demonstrated that passively-stabilized FP can perform better than 10 cm/s per night. We give an overview of the currently used FP in different surveys and compare their individual features. For the FP which may be used in HIRES we discuss different configuration. We show that the Finesse and FSR of the FP needs to be optimized with regard to the resolution of the spectrograph and we outline how we aim to fulfill the requirements of HIRES.
The paper describes the preliminary design of the MICADO calibration assembly. MICADO, the Multi-AO Imaging CAmera for Deep Observations, is targeted to be one of the first light instruments of the Extremely Large Telescope (ELT) and it will embrace imaging, spectroscopic and astrometric capabilities including their calibration. The astrometric requirements are particularly ambitious aiming for ~ 50 μas differential precision within and between single epochs. The MICADO Calibration Assembly (MCA) shall deliver flat-field, wavelength and astrometric calibration and it will support the instrument alignment to the Single-Conjugate Adaptive Optics wavefront sensor. After a complete overview of the MCA subsystems, their functionalities, design and status, we will concentrate on the ongoing prototype testing of the most challenging components. Particular emphasis is put on the development and test of the Warm Astrometric Mask (WAM) for the calibration of the optical distortions within MICADO and MAORY, the multiconjugate AO module.
The wavelength calibration and nightly drift measurements for CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Echelle Spectrographs) are provided by a combination of hollow cathode lamps and two Fabry-Pérot units. CARMENES consists of two spectrograph, one for the visible part of the spectrum (520 -960 nm) and one for the near infrared (960 - 1710 nm). Each spectrograph has its own calibration unit and its own Fabry-Pérot. The calibration units are equipped with Th-Ne, U-Ar and U-Ne hollow cathode lamps as well as a flat field lamp. The Fabry-Pérots are optimized for the wavelength ranges of the spectrographs and use halogen-tungsten lamps as light sources. The Fabry-Pérots have a free spectral range of 15 GHz for the visible and 12.2 GHz for the near infrared which translates to 17,900 useful emission lines for the visible spectrograph and 9,700 for the infrared. These lines are used to compute the wavelength solution, and to monitor the instrumental drift during the night. The Fabry-Pérot units are temperature and pressure stabilized and designed to reach an internal stability of better than 10 cm/s per night. Here, we present the designs of both Fabry-Pérot units and the calibration units.
The instrumentation plan for the E-ELT foresees a High Resolution Spectrograph (HIRES). Among its main goals are the detection of atmospheres of exoplanets and the determination of fundamental physical constants. For this, high radial velocity precision and accuracy are required. HIRES will be designed for maximum intrinsic stability. Systematic errors from effects like intrapixel variations or random errors like fiber noise need to be calibrated. Based on the main requirements for the calibration of HIRES, we discuss different potential calibration sources and how they can be applied. We outline the frequency calibration concept for HIRES using these sources.
A. Quirrenbach, P. Amado, J. Caballero, R. Mundt, A. Reiners, I. Ribas, W. Seifert, M. Abril, J. Aceituno, F. J. Alonso-Floriano, M. Ammler-von Eiff, R. Antona Jiménez, H. Anwand-Heerwart, M. Azzaro, F. Bauer, D. Barrado, S. Becerril, V. J. Béjar, D. Benítez, Z. Berdiñas, M. Cárdenas, E. Casal, A. Claret, J. Colomé, M. Cortés-Contreras, S. Czesla, M. Doellinger, S. Dreizler, C. Feiz, M. Fernández, D. Galadí, M. Gálvez-Ortiz, A. García-Piquer, M. García-Vargas, R. Garrido, L. Gesa, V. Gómez Galera, E. González Álvarez, J. González Hernández, U. Grözinger, J. Guàrdia, E. Guenther, E. de Guindos, J. Gutiérrez-Soto, H.-J. Hagen, A. Hatzes, P. Hauschildt, J. Helmling, T. Henning, D. Hermann, L. Hernández Castaño, E. Herrero, D. Hidalgo, G. Holgado, A. Huber, K. Huber, S. Jeffers, V. Joergens, E. de Juan, M. Kehr, R. Klein, M. Kürster, A. Lamert, S. Lalitha, W. Laun, U. Lemke, R. Lenzen, Mauro López del Fresno, B. López Martí, J. López-Santiago, U. Mall, H. Mandel, E. Martín, S. Martín-Ruiz, H. Martínez-Rodríguez, C. Marvin, R. Mathar, E. Mirabet, D. Montes, R. Morales Muñoz, A. Moya, V. Naranjo, A. Ofir, R. Oreiro, E. Pallé, J. Panduro, V.-M. Passegger, A. Pérez-Calpena, D. Pérez Medialdea, M. Perger, M. Pluto, A. Ramón, R. Rebolo, P. Redondo, S. Reffert, S. Reinhardt, P. Rhode, H.-W. Rix, F. Rodler, E. Rodríguez, C. Rodríguez-López, E. Rodríguez-Pérez, R.-R. Rohloff, A. Rosich, E. Sánchez-Blanco, M. Sánchez Carrasco, J. Sanz-Forcada, L. Sarmiento, S. Schäfer, J. Schiller, C. Schmidt, J. H. M. M. Schmitt, E. Solano, O. Stahl, C. Storz, J. Stürmer, J. Suárez, R. Ulbrich, G. Veredas, K. Wagner, J. Winkler, M. Zapatero Osorio, M. Zechmeister, F. Abellán de Paco, G. Anglada-Escudé, C. del Burgo, A. Klutsch, J. Lizon, M. López-Morales, J. Morales, M. A. C. Perryman, S. Tulloch, W. Xu
This paper gives an overview of the CARMENES instrument and of the survey that will be carried out with it
during the first years of operation. CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths
with Near-infrared and optical Echelle Spectrographs) is a next-generation radial-velocity instrument
under construction for the 3.5m telescope at the Calar Alto Observatory by a consortium of eleven Spanish
and German institutions. The scientific goal of the project is conducting a 600-night exoplanet survey targeting
~ 300 M dwarfs with the completed instrument.
The CARMENES instrument consists of two separate echelle spectrographs covering the wavelength range
from 0.55 to 1.7 μm at a spectral resolution of R = 82,000, fed by fibers from the Cassegrain focus of the telescope.
The spectrographs are housed in vacuum tanks providing the temperature-stabilized environments necessary to
enable a 1 m/s radial velocity precision employing a simultaneous calibration with an emission-line lamp or with
a Fabry-Perot etalon. For mid-M to late-M spectral types, the wavelength range around 1.0 μm (Y band) is the
most important wavelength region for radial velocity work. Therefore, the efficiency of CARMENES has been
optimized in this range.
The CARMENES instrument consists of two spectrographs, one equipped with a 4k x 4k pixel CCD for
the range 0.55 - 1.05 μm, and one with two 2k x 2k pixel HgCdTe detectors for the range from 0.95 - 1.7μm.
Each spectrograph will be coupled to the 3.5m telescope with two optical fibers, one for the target, and one
for calibration light. The front end contains a dichroic beam splitter and an atmospheric dispersion corrector,
to feed the light into the fibers leading to the spectrographs. Guiding is performed with a separate camera;
on-axis as well as off-axis guiding modes are implemented. Fibers with octagonal cross-section are employed to
ensure good stability of the output in the presence of residual guiding errors. The fibers are continually actuated
to reduce modal noise. The spectrographs are mounted on benches inside vacuum tanks located in the coud´e
laboratory of the 3.5m dome. Each vacuum tank is equipped with a temperature stabilization system capable
of keeping the temperature constant to within ±0.01°C over 24 hours. The visible-light spectrograph will be
operated near room temperature, while the near-IR spectrograph will be cooled to ~ 140 K.
The CARMENES instrument passed its final design review in February 2013. The MAIV phase is currently
ongoing. First tests at the telescope are scheduled for early 2015. Completion of the full instrument is planned
for the fall of 2015. At least 600 useable nights have been allocated at the Calar Alto 3.5m Telescope for the
CARMENES survey in the time frame until 2018.
A data base of M stars (dubbed CARMENCITA) has been compiled from which the CARMENES sample can
be selected. CARMENCITA contains information on all relevant properties of the potential targets. Dedicated imaging, photometric, and spectroscopic observations are underway to provide crucial data on these stars that
are not available in the literature.
Andreas Quirrenbach, Pedro Amado, Walter Seifert, Miguel Sánchez Carrasco, Holger Mandel, Jose Caballero, Reinhard Mundt, Ignasi Ribas, Ansgar Reiners, Miguel Abril, Jesus Aceituno, Javier Alonso-Floriano, Matthias Ammler-von Eiff, Guillem Anglada-Escude, Regina Antona Jiménez, Heiko Anwand-Heerwart, David Barrado y Navascués, Santiago Becerril, Victor Bejar, Daniel Benitez, Concepcion Cardenas, Antonio Claret, Josep Colome, Miriam Cortés-Contreras, Stefan Czesla, Carlos del Burgo, Michaela Doellinger, R. Dorda, Stefan Dreizler, Carmen Feiz, Matilde Fernandez, David Galadi, Rafael Garrido, Jonay González Hernández, Josep Guardia, Eike Guenther, Enrique de Guindos, Juan Gutiérrez-Soto, Hans Hagen, Artie Hatzes, Peter Hauschildt, Jens Helmling, Thomas Henning, Enrique Herrero, Armin Huber, Klaus Huber, Sandra Jeffers, Viki Joergens, Enrique de Juan, M. Kehr, Alexis Klutsch, Martin Kürster, S. Lalitha, Werner Laun, Ulrike Lemke, Rainer Lenzen, Jean-Louis Lizon, Mauro López del Fresno, Mercedes López-Morales, Javier López-Santiago, Ulrich Mall, Eduardo Martin, Susana Martín-Ruiz, Eduard Mirabet, David Montes, Juan Carlos Morales, Rafael Morales Muñoz, Andres Moya, Vianak Naranjo, Raquel Oreiro, David Pérez Medialdea, Michael Pluto, Ovidio Rabaza, Alejandro Ramon, Rafael Rebolo, Sabine Reffert, Petra Rhode, Hans-Walter Rix, Florian Rodler, Eloy Rodríguez, Cristina Rodríguez López, Emilio Rodríguez Pérez, A. Rodriguez Trinidad, Ralf-Reiner Rohloff, Ernesto Sánchez-Blanco, Jorge Sanz-Forcada, Sebastian Schäfer, Jörg Schiller, Christof Schmidt, Jürgen Schmitt, Enrique Solano, Otmar Stahl, Clemens Storz, Julian Stürmer, Juan Carlos Suarez, Ulrich Thiele, Rainer Ulbrich, Manuela Vidal-Dasilva, Karl Wagner, Johannes Winkler, Wenli Xu, Maria Rosa Zapatero Osorio, Mathias Zechmeister
CARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs) is a next-generation instrument for the 3.5m telescope at the Calar Alto Observatory, built by a consortium of eleven Spanish and German institutions. The CARMENES instrument consists of two separate échelle spectrographs covering the wavelength range from 0.55 μm to 1.7 μm at a spectral resolution of R = 82, 000, fed by fibers from the Cassegrain focus of the telescope. Both spectrographs are housed in temperature-stabilized vacuum tanks, to enable a long-term 1 m/s radial velocity precision employing a simultaneous calibration with Th-Ne and U-Ne emission line lamps. CARMENES has been optimized for a search for terrestrial planets in the habitable zones (HZs) of low-mass stars, which may well provide our first chance to study environments capable of supporting the development of life outside the Solar System. With its unique combination of optical and near-infrared ´echelle spectrographs, CARMENES will provide better sensitivity for the detection of low-mass planets than any comparable instrument, and a powerful tool for discriminating between genuine planet detections and false positives caused by stellar activity. The CARMENES survey will target 300 M dwarfs in the 2014 to 2018 time frame.
The most frequently used standard light sources for spectroscopic high precision wavelength calibration are
hollow cathode lamps. These lamps, however, do not provide homogeneous line distribution and intensities.
Particularly in the infrared, the number of useful lines is severely limited and the spectrum is contaminated by
lines of the filler gas. With the goal of achieving sub m/s stability in the infrared, as required for detecting
earthlike extra-solar planets, we are developing two passively stabilized Fabry-Perot interferometers for the red
visible (600-1050nm) and near infrared wavelength regions (900-1350nm). Each of the two interferometers can
produce ~15,000 lines of nearly constant brightness. The Fabry-Perot interferometers aim at a RV calibration
precision of 10cm/s and are optimized in line shape and spacing for the infrared planet hunting CARMENES
spectrograph that is currently being built for the Calar Alto 3.5m telescope. Here we present the first results of
our work.
At the Institute for Astrophysics Goettingen (IAG), we are purchasing a high resolution
Fourier Transform Spectrograph (FTS) for astronomical observations and development of
calibration standards aiming at high wavelength precision. Astronomical spectrographs
that work in the regime of very high resolution (resolving powers λ/δλ≥105) now achieve
unprecedented precision and stability. Precise line shifts can be investigated to conclude for
an objects radial velocity relative to the observer. As a long-term scientific goal, the evolution
of galaxy redshift due to dark energy can be monitored. Also, the detection of lower mass,
down to Earth-like planets will become feasible. Here, M-dwarfs are promising objects where
an orbiting exo-Earth can cause a wavelength shift large enough to be detected. Emitting
mainly in the near infrared (NIR), these objects require novel calibration standards. Current
schemes under consideration are gas cathode lamps (e.g. CN, UNe) and a highly stable
Fabry-Perot interferometer (FPI) to act as a cost-efficient alternative to the laser frequency
comb (LFC, [1]). In addition to experiments exploring novel wavelength calibration types,
light will be fed from our telescopes at IAG. A Vacuum Tower Telescope (VTT) for solar
observations and the 50 cm Cassegrain telescope allow to investigate stellar and spatially
resolved light at our facilities.
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