The design and construction of CARMENES has been presented at previous SPIE conferences. It is a next-generation radial-velocity instrument at the 3.5m telescope of the Calar Alto Observatory, which was built by a consortium of eleven Spanish and German institutions. CARMENES consists of two separate échelle spectrographs covering the wavelength range from 0.52 to 1.71μm at a spec-tral resolution of R < 80,000, fed by fibers from the Cassegrain focus of the telescope. CARMENES saw “First Light” on Nov 9, 2015.
During the commissioning and initial operation phases, we established basic performance data such as throughput and spectral resolution. We found that our hollow-cathode lamps are suitable for precise wavelength calibration, but their spectra contain a number of lines of neon or argon that are so bright that the lamps cannot be used in simultaneous exposures with stars. We have therefore adopted a calibration procedure that uses simultaneous star / Fabry Pérot etalon exposures in combination with a cross-calibration between the etalons and hollow-cathode lamps during daytime. With this strategy it has been possible to achieve 1-2 m/s precision in the visible and 5-10 m/s precision in the near-IR; further improvements are expected from ongoing work on temperature control, calibration procedures and data reduction. Comparing the RV precision achieved in different wavelength bands, we find a “sweet spot” between 0.7 and 0.8μm, where deep TiO bands provide rich RV information in mid-M dwarfs. This is in contrast to our pre-survey models, which predicted comparatively better performance in the near-IR around 1μm, and explains in part why our near-IR RVs do not reach the same precision level as those taken with the visible spectrograph.
We are now conducting a large survey of 340 nearby M dwarfs (with an average distance of only 12pc), with the goal of finding terrestrial planets in their habitable zones. We have detected the signatures of several previously known or suspected planets and also discovered several new planets. We find that the radial velocity periodograms of many M dwarfs show several significant peaks. The development of robust methods to distinguish planet signatures from activity-induced radial velocity jitter is therefore among our priorities.
Due to its large wavelength coverage, the CARMENES survey is generating a unique data set for studies of M star atmospheres, rotation, and activity. The spectra cover important diagnostic lines for activity (H alpha, Na I D1 and D2, and the Ca II infrared triplet), as well as FeH lines, from which the magnetic field can be inferred. Correlating the time series of these features with each other, and with wavelength-dependent radial velocities, provides excellent handles for the discrimination between planetary companions and stellar radial velocity jitter. These data are also generating new insight into the physical properties of M dwarf atmospheres, and the impact of activity and flares on the habitability of M star planets.
The CARMENES instrument is a pair of high-resolution (R⪆80,000) spectrographs covering the wavelength range from 0.52 to 1.71 μm, optimized for precise radial velocity measurements. It was installed and commissioned at the 3.5m telescope of the Calar Alto observatory in Southern Spain in 2015. The first large science program of CARMENES is a survey of ~ 300 M dwarfs, which started on Jan 1, 2016. We present an overview of all subsystems of CARMENES (front end, fiber system, visible-light spectrograph, near-infrared spectrograph, calibration units, etalons, facility control, interlock system, instrument control system, data reduction pipeline, data flow, and archive), and give an overview of the assembly, integration, verification, and commissioning phases of the project. We show initial results and discuss further plans for the scientific use of CARMENES.
CARMENES is the new high-resolution high-stability spectrograph built for the 3.5m telescope at the Calar Alto Observatory (CAHA, Almería, Spain) by a consortium formed by German and Spanish institutions. This instrument is composed by two separated spectrographs: VIS channel (550-1050 nm) and NIR channel (950- 1700 nm). The NIR-channel spectrograph's responsible is the Instituto de Astrofísica de Andalucía (IAACSIC). It has been manufactured, assembled, integrated and verified in the last two years, delivered in fall 2015 and commissioned in December 2015.<p> </p> One of the most challenging systems in this cryogenic channel involves the Cooling System. Due to the highly demanding requirements applicable in terms of stability, this system arises as one of the core systems to provide outstanding stability to the channel. Really at the edge of the state-of-the-art, the Cooling System is able to provide to the cold mass (~1 Ton) better thermal stability than few hundredths of degree within 24 hours (goal: 0.01K/day). <p> </p>The present paper describes the Assembly, Integration and Verification phase (AIV) of the CARMENES-NIR channel Cooling System implemented at IAA-CSIC and later installation at CAHA 3.5m Telescope, thus the most relevant highlights being shown in terms of thermal performance. <p> </p>The CARMENES NIR-channel Cooling System has been implemented by the IAA-CSIC through very fruitful collaboration and involvement of the ESO (European Southern Observatory) cryo-vacuum department with Jean-Louis Lizon as its head and main collaborator. The present work sets an important trend in terms of cryogenic systems for future E-ELT (European Extremely Large Telescope) large-dimensioned instrumentation in astrophysics.
CARMENES is the new high-resolution high-stability spectrograph built for the 3.5m telescope at the Calar Alto Observatory (CAHA, Almería, Spain) by a consortium formed by German and Spanish institutions. This instrument is composed by two separated spectrographs: VIS channel (550-1050 nm) and NIR channel (950- 1700 nm). The NIR-channel spectrograph's responsible institution is the Instituto de Astrofísica de Andalucía, IAA-CSIC. <p> </p>The contouring conditions have led CARMENES-NIR to be a schedule-driven project with a extremely tight plan. The operation start-up was mandatory to be before the end of 2015. This plays in contradiction to the very complex, calm-requiring tasks and development phases faced during the AIV, which has been fully designed and implemented at IAA through a very ambitious, zero-contingency plan. As a large cryogenic instrument, this plan includes necessarily a certain number cryo-vacuum cycles, this factor being the most important for the overall AIV duration. Indeed, each cryo-vacuum cycle of the NIR channel runs during 3 weeks. This plan has therefore been driven to minimize the amount of cryo-vacuum cycles. <p> </p>Such huge effort has led the AIV at system level at IAA lab to be executed in 9 months from start to end -an astonishingly short duration for a large cryogenic, complex instrument like CARMENES NIR- which has been fully compliant with the final deadline of the installation of the NIR channel at CAHA 3.5m telescope. The detailed description of this planning, as well as the way how it was actually performed, is the main aim of the present paper.
CARMENES is a high resolution spectrograph to detect planets through the variation of radial velocity, destined for the
Calar Alto Observatory in Almeria, Spain. The optical bench has a working temperature of 140K with a 24 hours
stability of ±0,1K; goal ±0,01K. It is enclosed with a radiation shield actively cooled with thermalized nitrogen gas that
flows through strategically positioned heat exchangers to remove its radiative load. The cooling system has an external
preparation unit (N2GPU), which provides the nitrogen gas through actively vaporizing liquid nitrogen with heating
resistances and a three stage circuit flow, each one controlled by an independent PID.
Since CARMENES is still in the construction phase, a dedicated test facility has been built in order to simulate the
instrument and correctly establish the N2GPU parameters. Furthermore, the test facility allows a wide range of
configurations set-ups, which enables a full characterization of the N2GPU and the cooling system.
The N2GPU has been designed to offer a wide temperature range of thermally stabilized nitrogen gas flow, which apart
from CARMENES could also be used to provide ultra-high thermal stability in other cryogenic instruments. The present
paper shows the testing of the cooling performance, the hardware used and the very promising results obtained.
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.
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 CARMENES project, which is currently at FDR stage, is a last-generation exoplanet hunter instrument to be
installed in the Calar Alto Observatory by 2014. It is split into two different spectrographs: one works within the visual
range while the other does it in the NIR range. Both channels need to be extremely stable in terms of mechanical and
thermal behavior. Nevertheless, due to the operation temperature of the NIR spectrograph, the thermal stability
requirement (±0.07 K in 24 hours; ±0.01 K (goal)) becomes actually a major challenge. The solution here proposed
consists of a system that actively cools a shield enveloping the optical bench. Thus, the instability produced on the shield
temperature is further damped on the optical bench due to the high mass of the latter, as well as the high thermal
decoupling between both components, the main heat exchange being produced by radiation.
This system -which is being developed with the active collaboration and advice of ESO (Jean-Louis Lizon)- is composed
by a previous unit which produces a stable flow of nitrogen gas. The flow so produced goes into the in-vacuum circuitry
of the NIR spectrograph and removes the radiative heat load incoming to the radiation shield by means of a group of
properly dimensioned heat exchangers.
The present paper describes and summarizes the cooling system designed for CARMENES NIR as well as the analyses