This article describes the works we are doing for modifying the interface between the high resolution infrared spectrograph GIANO (0.97-2.4 micron) and the TNG telescope, passing from a fiber feed configuration to the original design of a direct light-feeding from the telescope to the spectrograph. So doing the IR spectrograph, GIANO, will work in parallel to HARPS-N spectrometer (0.38-0.70 micron), the visible high resolution spectrograph, thanks to a new telescope interface based on a dichroic window that simultaneously feeds the two instrumentes: this is GIARPS (GIAno and haRPS). The scientific aims of this project are to improve the radial velocity accuracy achievable with GIANO, down to a goal of 1 m/s, the value necessary to detect Earth-mass planets on habitable orbits around late-M stars, to implement simultaneous observations with Harps-N and GIANO optimizing the study of planets around cool stars. The very broad wavelengths range is particularly important to discriminate false radial velocity signals caused by stellar activity. We therefore include several absorption cells with different mixtures of gases and a stabilized Fabry Perot cavity, necessary to have absorption lines over the 0.97–2.4 microns range covered by GIANO. The commissioning of GIARPS is scheduled by the end of 2016.
The adaptive optics (AO) assisted CRIRES instrument is an IR (0.92 - 5.2 μm) high-resolution spectrograph was in operation from 2006 to 2014 at the Very Large Telescope (VLT) observatory. CRIRES was a unique instrument, accessing a parameter space (wavelength range and spectral resolution) up to now largely uncharted. It consisted of a single-order spectrograph providing long-slit (40 arcsecond) spectroscopy with a resolving power up to R=100 000. However the setup was limited to a narrow, single-shot, spectral range of about 1/70 of the central wavelength, resulting in low observing efficiency for many scientific programmes requiring a broad spectral coverage. The CRIRES upgrade project, CRIRES+, transforms this VLT instrument into a cross-dispersed spectrograph to increase the simultaneously covered wavelength range by a factor of ten. A new and larger detector focal plane array of three Hawaii 2RG detectors with 5.3 μm cut-off wavelength will replace the existing detectors. For advanced wavelength calibration, custom-made absorption gas cells and an etalon system will be added. A spectro-polarimetric unit will allow the recording of circular and linear polarized spectra. This upgrade will be supported by dedicated data reduction software allowing the community to take full advantage of the new capabilities offered by CRIRES+. CRIRES+ has now entered its assembly and integration phase and will return with all new capabilities by the beginning of 2018 to the Very Large Telescope in Chile. This article will provide the reader with an update of the current status of the instrument as well as the remaining steps until final installation at the Paranal Observatory.
The Waltz Spectrograph is a fiber-fed high-resolution échelle spectrograph for the 72 cm Waltz Telescope at the Landessternwarte, Heidelberg. It uses a 31.6 lines/mm 63.5° blaze angle échelle grating in white-pupil configuration, providing a spectral resolving power of R ~ 65,000 covering the spectral range between 450-800nm in one CCD exposure. A prism is used for cross-dispersion of échelle orders. The spectrum is focused by a commercial apochromat onto a 2k×2k CCD detector with 13.5μm per pixel. An exposure meter will be used to obtain precise photon-weighted midpoints of observations, which will be used in the computation of the barycentric corrections of measured radial velocities. A stabilized, newly designed iodine cell is employed for measuring radial velocities with high precision. Our goal is to reach a radial velocity precision of better than 5 m/s, providing an instrument with sufficient precision and sensitivity for the discovery of giant exoplanets. Here we describe the design of the Waltz spectrograph and early on-sky results.
The CRIRES+ project attempts to upgrade the CRIRES instrument into a cross dispersed Echelle spectrograph with a simultaneous recording of 8-10 diffraction orders. In order to transform the CRIRES spectrograph into a cross-dispersing instrument, a set of six reflection gratings, each one optimized for one of the wavelength bands CRIRES+ will operate in (YJHKLM), will be used as cross dispersion elements in CRIRES+. Due to the upgrade nature of the project, the choice of gratings depends on the fixed geometry of the instrument. Thus, custom made gratings would be required to achieve the ambitious design goals. Custom made gratings have the disadvantage, though, that they come at an extraordinary price and with lead times of more than 12 months. To mitigate this, a set of off-the-shelf gratings was obtained which had grating parameters very close to the ones being identified as optimal. To ensure that the rigorous specifications for CRIRES+ will be fulfilled, the CRIRES+ team started a collaboration with the Physikalisch-Technische Bundesanstalt Berlin (PTB) to characterize gratings underconditions similar to the operating conditions in CRIRES+ (angle of incidence, wavelength range).
The respective test setup was designed in collaboration between PTB and the CRIRES+ consortium. The PTB provided optical radiation sources and calibrated detectors for each wavelength range. With this setup, it is possible to measure the absolute efficiency of the gratings both wavelength dependent and polarization state dependent in a wavelength range from 0.9 μm to 6 μm.
CRIRES at the VLT is one of the few adaptive optics enabled instruments that offer a resolving power of 105 from 1 − 5 μm. An instrument upgrade (CRIRES+) is proposed to implement cross-dispersion capabilities, spectro-polarimetry modes, a new detector mosaic, and a new gas absorption cell. CRIRES+ will boost the simultaneous wavelength coverage of the current instrument (~ γ/70 in a single-order) by a factor of 10 in the cross-dispersed configuration, while still retaining a ~> 10 arcsec slit suitable for long-slit spectroscopy. CRIRES+ dramatically enhances the instrument’s observing efficiency, and opens new scientific opportunities. These include high-precision radial-velocity studies on the 3 m/s level to characterize extra-solar planets and their athmospheres, which demand for specialized, highly accurate wavelength calibration techniques. In this paper, we present a newly developed absorption gas-cell to enable high-precision wavelength calibration for CRIRES+. We also discuss the strategies and developments to cover the full operational spectral range (1 − 5 μµm), employing cathode emission lamps, Fabry-Perot etalons, and absorption gas-cells.
Hollow cathode lamps of U and Th are the standard frequency calibrators in astronomical spectrographs. In an effort to
optimize precision radial velocity measurements at near-IR wavelengths for the CARMENES survey, we are
characterizing 12 commercial U-Ne hollow cathode lamps using a high resolution Fourier Transform Spectrograph and
an InGaAs detector to analyze the wavelength range between 950 and 1700 nm. We have recorded spectral atlases of UNe
operated at 8, 10 and 12 mA, which are typical values used at astronomical observatories in order to maximize lamp
lifetimes. In addition to the spectral atlas, we analyze properties like warm-up times, average intensities from lines of
different elements, positions and the width of emission lines, and blends. None of our lamps show strong peculiarities in
the spectra or significant contamination. The identification of the uranium lines is based on the line widths and consistent
with the Redman et al. (2011) catalog. Our line list can add a significant number of lines particularly in the range around
9000 cm-1 (1.1 μm) where the catalog is incomplete because of limited detector sensitivity. We are able to identify the elements emitting additional lines by measuring the line width. The increased number of U lines at wavelengths relevant
to radial velocity surveys can yield a significant improvement in the accuracy of radial velocity measurements.
The CRIRES infrared spectrograph at the European Southern Observatory (ESO) Very Large Telescope (VLT)
facility will soon receive an upgrade. This upgrade will include the addition of a module for performing highresolution
spectropolarimetry. The polarimetry module will incorporate a novel infrared beamsplitter based on
polarization gratings (PGs). The beamsplitter produces a pair of infrared output beams, with opposite circular
polarizations, which are then fed into the spectrograph. Visible light passes through the module virtually
unaltered and is then available for use by the CRIRES adaptive optics system. We present the design of the
polarimetry module and measurements of PG behavior in the 1 to 2.7 μm wavelength range.
CRIRES, the ESO high resolution infrared spectrometer, is a unique instrument which allows astronomers to access a
parameter space which up to now was largely uncharted. In its current setup, it consists of a single-order spectrograph
providing long-slit, single-order spectroscopy with resolving power up to R=100,000 over a quite narrow spectral range.
This has resulted in sub-optimal efficiency and use of telescope time for all the scientific programs requiring broad
spectral coverage of compact objects (e.g. chemical abundances of stars and intergalactic medium, search and
characterization of extra-solar planets). To overcome these limitations, a consortium was set-up for upgrading CRIRES
to a cross-dispersed spectrometer, called CRIRES+. This paper presents the updated optical design of the cross-dispersion
module for CRIRES+. This new module can be mounted in place of the current pre-disperser unit. The new
system yields a factor of >10 increase in simultaneous spectral coverage and maintains a quite long slit (10”), ideal for
observations of extended sources and for precise sky-background subtraction.
CRIRES is one of the few IR (0.92-5.2 μm) high-resolution spectrographs in operation at the VLT since 2006. Despite
good performance it suffers a limitation that significantly hampers its ability: a small spectral coverage per exposure. The
CRIRES upgrade (CRIRES+) proposes to transform CRIRES into a cross-dispersed spectrograph while maintaining the
high resolution (100000) and increasing the wavelength coverage by a factor 10 compared to the current capabilities. A
major part of the upgrade is the exchange of the actual cryogenic pre-disperser module by a new cross disperser unit. In
addition to a completely new optical design, a number of important changes are required on key components and
functions like the slit unit and detectors units. We will outline the design of these new units fitting inside a predefined
and restricted space. The mechanical design of the new functions including a description and analysis will be presented.
Finally we will present the strategy for the implementation of the changes.
High-resolution infrared spectroscopy plays an important role in astrophysics from the search for exoplanets to
cosmology. Yet, many existing infrared spectrographs are limited by a rather small simultaneous wavelength coverage.
The AO assisted CRIRES instrument, installed at the ESO VLT on Paranal, is one of the few IR (0.92-5.2 μm) highresolution
spectrographs in operation since 2006. However it has a limitation that hampers its efficient use: the
wavelength range covered in a single exposure is limited to ~15 nanometers. The CRIRES Upgrade project (CRIRES+)
will transform CRIRES into a cross-dispersed spectrograph and will also add new capabilities. By introducing crossdispersion
elements the simultaneously covered wavelength range will be increased by at least a factor of 10 with respect
to the present configuration, while the operational wavelength range will be preserved. For advanced wavelength
calibration, new custom made absorption gas cells and etalons will be added. A spectro-polarimetric unit will allow one
for the first time to record circularly polarized spectra at the highest spectral resolution. This will be all supported by a
new data reduction software which will allow the community to take full advantage of the new capabilities of CRIRES+.