The third version of the High Accuracy Radial velocity Planet Searcher (HARPS3) instrument is built for a ten-year programme aimed at achieving 10 cm/sec radial velocity precision on nearby stars to search for Earth-like planets. HARPS3 will be commissioned on the to-be-roboticized 2.54-m Isaac Newton Telescope at La Palma in 2021. One of the main changes compared to its predecessors is the novel dual-beam Cassegrain focus, featuring a stabilised beam feed into the HARPS3 spectrograph and an insertable polarimetric sub-unit. This polarimetric sub-unit enables HARPS3 to directly measure stellar activity signatures, which can be useful for correcting activity-induced radial velocity jitter in the search for Earth-like planets. The sub-unit consists of superachromatic polymer quarter- and half-wave retarders for circular and linear polarizations respectively, designed to suppress polarized fringing, and a novel polarimetric beam splitter based on a wire-grid design, separating the two polarimetric beams by 30 mm and feeding two separate science fibers. The dual-beam exchange implementation in combination with the extreme stability of the HARPS3 spectrograph enables a polarimetric sensitivity of 10<sup>−5</sup> on bright stars. One of the main challenges of such a system is in the characterization of instrumental polarization effects which limit the polarimetric accuracy of the polarimetric observing mode. By design and characterization of this subsystem and by pre-emptively mitigating possible noise sources, we can minimize the noise characteristics of the polarization sub-unit to allow for precise observations. In this paper we report on the design, realization, assembly, alignment, and testing of the polarimetric unit to be installed in the Cassegrain Adaptor Unit of the HARPS3 spectrograph
The CRIRES upgrade project (CRIRES+) will improve the performance and observing efficiency of the successful adaptive optics (AO) assisted CRIRES instrument. CRIRES was in operation from 2006 to 2014 at the 8m UT1 (Unit Telescope) of the Very Large Telescope (VLT, Cerro Paranal, Chile) observatory accessing a parameter space (wavelength range and spectral resolution) largely uncharted back then.
CRIRES+ will be commissioned in summer 2018 at UT3 of the VLT. It will provide a spectral resolution of R=50.000 or 100.000 in an accessible wavelength range of 0.95 – 5.3 μm (YJHKLM bands). For each band there is a separate, performance optimized reflection grating as the cross dispersing element. The slit length of 10 arcsec will provide, in combination with the new focal plane array of three HAWAII 2RG detectors, cross-dispersed (7 – 9 orders simultaneous) echelle spectra. In total, the observing efficiency will be improved by a factor of 10 comparing CRIRES+ and CRIRES. Furthermore, the upgraded instrument will be equipped with a number of novel wavelength calibration units, including a gas absorption cell optimized for use in K band and an etalon system. A spectro-polarimetric unit will allow the recording of circular and linear polarized spectra. The new metrology system will ensure a very high system stability and repeatability. Last but not least the upgrade will be supported by dedicated data reduction software allowing the community to take full advantage of the new capabilities.
The full system is being integrated at ESO and system testing has commenced. Acceptance of the instrument in Europe (PAE) is scheduled for the second quarter of 2018. Commissioning at the VLT observatory will start mid 2018. This article gives an overview of the final configuration of the instrument. The instrument will be available to the astronomic community from Spring 2019 with a call for proposals in October 2018.
High-resolution infrared spectropolarimetry has many science applications in astrophysics. One of them is measuring weak magnetic fields using the Zeeman effect. Infrared domain is particularly advantageous as Zeeman splitting of spectral lines is proportional to the square of the wavelength while the intrinsic width of the line cores increases only linearly. Important science cases include detection and monitoring of global magnetic fields on solar-type stars, study of the magnetic field evolution from stellar formation to the final stages of the stellar life with massive stellar winds, and the dynamo mechanism operation across the boundary between fully- and partially-convective stars.
CRIRES+ (the CRIRES upgrade project) includes a novel spectropolarimetric unit (SPU) based on polar- ization gratings. The novel design allows to perform beam-splitting very early in the optical path, directly after the tertiary mirror of the telescope (the ESO Very Large Telescope, VLT), minimizing instrumental polariza- tion. The new SPU performs polarization beam-splitting in the near-infrared while keeping the telescope beam mostly unchanged in the optical domain, making it compatible with the adaptive optics system of the CRIRES+ instrument.
The SPU consists of four beam-splitters optimized for measuring circular and linear polarization of spectral lines in YJ and HK bands. The SPU can perform beam switching allowing to correct for throughput in each beam and for variations in detector pixel sensitivity. Other new features of CRIRES+, such as substantially increased wavelength coverage, stability and advanced data reduction pipeline will further enhance the sensitivity of the polarimetric mode. The combination of the SPU, CRIRES+ and the VLT is a unique facility for making major progress in understanding stellar activity. In this article we present the design of the SPU, laboratory measurements of individual components and of the whole unit as well as the performance prediction for the operation at the VLT.
CRIRES+ is the new high-resolution NIR echelle spectrograph intended to be operated at the platform B of VLT Unit telescope UT3. It will cover from Y to M bands (0.95-5.3um) with a spectral resolution of R = 50000 or R=100000. The main scientific goals are the search of super-Earths in the habitable zone of low-mass stars, the characterisation of transiting planets atmosphere and the study of the origin and evolution of stellar magnetic fields. Based on the heritage of the old adaptive optics (AO) assisted VLT instrument CRIRES, the new spectrograph will present improved optical layout, a new detector system and a new calibration unit providing optimal performances in terms of simultaneous wavelength coverage and radial velocity accuracy (a few m/s). The total observing efficiency will be enhanced by a factor of 10 with respect to CRIRES. An innovative spectro-polarimetry mode will be also offered and a new metrology system will ensure very high system stability and repeatability. Fiinally, the CRIRES+ project will also provide the community with a new data reduction software (DRS) package. CRIRES+ is currently at the initial phase of its Preliminary Acceptance in Europe (PAE) and it will be commissioned early in 2019 at VLT. This work outlines the main results obtained during the initial phase of the full system test at ESO HQ Garching.
We present the results from the phase A study of ELT-HIRES, an optical-infrared High Resolution Spectrograph for ELT, which has just been completed by a consortium of 30 institutes from 12 countries forming a team of about 200 scientists and engineers. The top science cases of ELT-HIRES will be the detection of life signatures from exoplanet atmospheres, tests on the stability of Nature’s fundamental couplings, the direct detection of the cosmic acceleration. However, the science requirements of these science cases enable many other groundbreaking science cases. The baseline design, which allows to fulfil the top science cases, consists in a modular fiber- fed cross-dispersed echelle spectrograph with two ultra-stable spectral arms providing a simultaneous spectral range of 0.4-1.8 μm at a spectral resolution of ~100,000. The fiber-feeding allows ELT-HIRES to have several, interchangeable observing modes including a SCAO module and a small diffraction-limited IFU.
We present a description of a new instrument development, HARPS3, planned to be installed on an upgraded and roboticized Isaac Newton Telescope by end-2018. HARPS3 will be a high resolution (R≃115,000) echelle spectrograph with a wavelength range from 380-690 nm. It is being built as part of the Terra Hunting Experiment - a future 10- year radial velocity measurement programme to discover Earth-like exoplanets. The instrument design is based on the successful HARPS spectrograph on the 3.6m ESO telescope and HARPS-N on the TNG telescope. The main changes to the design in HARPS3 will be: a customised fibre adapter at the Cassegrain focus providing a stabilised beam feed and on-sky fibre diameter ≈1:4 arcsec, the implementation of a new continuous ow cryostat to keep the CCD temperature very stable, detailed characterisation of the HARPS3 CCD to map the effective pixel positions and thus provide an improved accuracy wavelength solution, an optimised integrated polarimeter and the instrument integrated into a robotic operation. The robotic operation will optimise our programme which requires our target stars to be measured on a nightly basis. We present an overview of the entire project, including a description of our anticipated robotic operation.
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<sup>+</sup>, 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<sup>+</sup>. CRIRES<sup>+</sup> 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 first generation of E-ELT instruments will include an optic-infrared High Resolution Spectrograph, conventionally indicated as EELT-HIRES, which will be capable of providing unique breakthroughs in the fields of exoplanets, star and planet formation, physics and evolution of stars and galaxies, cosmology and fundamental physics. A 2-year long phase A study for EELT-HIRES has just started and will be performed by a consortium composed of institutes and organisations from Brazil, Chile, Denmark, France, Germany, Italy, Poland, Portugal, Spain, Sweden, Switzerland and United Kingdom. In this paper we describe the science goals and the preliminary technical concept for EELT-HIRES which will be developed during the phase A, as well as its planned development and consortium organisation during the study.
We present an overview of the 4MOST project at the Preliminary Design Review. 4MOST is a major new wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope of ESO. 4MOST has a broad range of science goals ranging from Galactic Archaeology and stellar physics to the high-energy physics, galaxy evolution, and cosmology. Starting in 2021, 4MOST will deploy 2436 fibres in a 4.1 square degree field-of-view using a positioner based on the tilting spine principle. The fibres will feed one high-resolution (R~20,000) and two medium resolution (R~5000) spectrographs with fixed 3-channel designs and identical 6k x 6k CCD detectors. 4MOST will have a unique operations concept in which 5-year public surveys from both the consortium and the ESO community will be combined and observed in parallel during each exposure. The 4MOST Facility Simulator (4FS) was developed to demonstrate the feasibility of this observing concept, showing that we can expect to observe more than 25 million objects in each 5-year survey period and will eventually be used to plan and conduct the actual survey.
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).<p> </p> 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.
The current instrumentation plan for the E-ELT foresees a High Resolution Spectrograph conventionally indicated as
HIRES. Shaped on the study of extra-solar planet atmospheres, Pop-III stars and fundamental physical constants, HIRES
is intended to embed observing modes at high-resolution (up to R=150000) and large spectral range (from the blue limit to the K band) useful for a large suite of science cases that can exclusively be tackled by the E-ELT. We present in this
paper the solution for HIRES envisaged by the "HIRES initiative", the international collaboration established in 2013 to
pursue a HIRES on E-ELT.
CRIRES at the VLT is one of the few adaptive optics enabled instruments that offer a resolving power of 10<sup>5</sup> 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.
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 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.
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.
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+.
The cryogenic high resolution IR echelle spectrograph CRIRES is the ESO infrared (0.95−5.4 μm) high
resolution spectrograph operating at the Nasmyth A focus of VLT-UT1. The instrument provides long-slit
(31") spectroscopy with resolving power up to R=100,000 over a quite narrow wavelengths range, about 1/70 of
the central wavelength. Observations of compact objects (e.g. stellar photospheres) could be made much more
efficient by implementing a cross-dispersed mode, which increases the simultaneous spectral coverage by an order
of magnitude or more.
This paper presents the design of a relatively simple system to add cross-dispersed modes to CRIRES with a
minimum impact on the instrument optics and mechanics.
SIMPLE is an optimized near IR echelle spectrograph for the E-ELT assisted by adaptive optics. It delivers a complete
0.84-2.5μm spectrum in one exposure with resolution up to R=130,000, nearly diffraction limited pixel scale and
limiting magnitudes down to JHK~20. Its most prominent science cases include the study of the intergalactic medium in
the early Universe (z>6) and of the atmospheres of exo-planet transiting nearby low mass stars.
We present the design of a compact module that converts the HARPS instrument at the 3.6-m telescope at
La Silla to a full-Stokes high-resolution spectropolarimeter. The polarimeter will replace the obsolete Iodine
cell inside the HARPS Cassegrain adapter. Utilizing the two fibers going into the spectrograph, two dual-beam
systems can be positioned in the beam: one with a rotating superachromatic quarter-wave plate for circular
polarimetry and one with a rotating superachromatic half-wave plate for linear polarimetry. A large polarimetric
precision is ensured by the beam-exchange technique and a minimal amount of instrumental polarization. The
polarimeter, in combination with the ultra-precise HARPS spectrograph, enables unprecedented observations of
stellar magnetic fields and circumstellar material without compromising the successful planet-finding program.
PEPSI (Postham Echelle Polarimetric and Spectroscopic Instrument) is to use the unique feature of the LBT and its powerful double mirror configuration to provide high and extremely high spectral resolution full-Stokes four-vector spectra in the wavelength range 450-1100nm. For the given aperture of 8.4m in single mirror mode and 11.8m in double mirror mode, and at a spectral resolution of 40,000-300,000 as designed for the fiber-fed Echelle spectrograph, a polarimetric accuracy between 10<sup>-4</sup> and 10<sup>-2</sup> can be reached for targets with visual magnitudes of up to 17th magnitude. A polarimetric accuracy better than 10<sup>-4</sup> can only be reached for either targets brighter than approximately 10th magnitude together wiht a substantial trade-off wiht the spectral resolution or with spectrum deconvolution techniques. At 10<sup>-2</sup>, however, we will be able to observe the brightest AGNs down to 17th magnitude.