The Atmospheric Remote-sensing Infrared Exoplanets Large-survey (ARIEL)1 Mission has been recently selected by ESA as the fourth medium-class Mission (M4) in the framework of the Cosmic Vision Program. The goal of ARIEL is to investigate, thanks to VIS photometry and IR spectroscopy, the atmospheres of several hundreds of planets orbiting nearby stars in order to address the fundamental questions on how planetary systems form and evolve.2
During its four-years mission, ARIEL will observe several hundreds of exoplanets ranging from Jupiter- and Neptune-size down to super-Earth and Earth-size with its 1 meter-class telescope.3 The analysis of spectra and photometric data will allow to extract the chemical fingerprints of gases and condensates in the planets atmospheres, including the elemental composition for the most favorable targets. It will also enable the study of thermal and scattering properties of the atmosphere as the planet orbits around its parent star.
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 a high resolution spectrograph built for the 3.5m telescope at the Calar Alto Observatory by a consortium formed by 11 German and Spanish institutions. CARMENES is composed by two separated highly stabilized spectrographs covering the VIS and NIR wavelength ranges to provide high-accuracy radial-velocity measurements with long-term stability. The technical and managerial complexity of the instrument, with a fixed project deadline, demanded a strong system engineering control to preserve the high level requirements during the development, manufacturing, assembly, integration and verification phases.
CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs) is an instrument consistent in two ultra-stable high resolution (R~82,000) spectrographs covering simultaneously the visible (0.5 – 1.0μm) and near-IR (1.0 - 1.7μm) ranges to provide high-accuracy radial-velocity measurements (∼1 m/s) thanks to the long-term stability. CARMENES was the initiative of a consortium of eleven German and Spanish institutions. CARMENES has been built for the 3.5m telescope at the Centro Astronómico Hipano- Alemán (CAHA), Calar Alto Observatory (Almería, Spain) and is currently in operation. CAHA is jointly operated by the Max-Planck-Society (MPG) and the Spanish National Research Council (CSIC).
The project received the green light in October 2010 and in February 2013 passed a Final Design Review. Six months later, the MPG and CSIC, the observatory’s owners, made an independent evaluation concluding that CARMENES had to be ready for operations at the end of 2015. Since then, fulfilling the calendar was the driver of all project decisions. Moreover, the observatory’s survival was linked to the instrument’s success: should the instrument fail, the observatory would be closed. On the contrary, the instrument’s success would give unique capabilities to the Observatory for Big Science. Such a challenge became to be our private Olympic Games: we had to be on time. This decision definitively impacted on the project dynamics, there was no room for a delay. The deadline, December 31st, 2015, was controlled by a strict tracking of the critical path; calendar deviations were corrected with risky decisions while fast tracking or even crashing methods were applied.
The management scenario was far from optimum: most key people in the project shared their time with other duties; the observatory funding cuts; the budget was tight and distributed among the 11 partner centers with their own different rules, etc. Despite these difficulties, the close coordination among the project manager, the system engineer and the work package managers, the hard work of the whole team, and the support from the observatory were our best bets.
Two frenetic years after the calendar decision, we had manufactured, integrated and tested the two spectrographs and we were commissioning the instrument. The instrument first light took place on November, 9th, 2015 and CARMENES entered in operation at the end of December 2015. This paper describes the keys to success.
The main goal of the CARMENES instrument is to perform high-accuracy measurements of stellar radial velocities (1 m/s) with long-term stability. CARMENES is installed at the 3.5 m telescope in the Calar Alto Observatory (Spain) and it is equipped with two spectrographs covering from the visible to the near-infrared. We present the software packages that are included in the instrument control layer. The coordination and management of CARMENES is handled by the Instrument Control System (ICS), which is responsible for carrying out the operations of the different subsystems providing a tool to operate the instrument in an integrated manner from low to high user interaction level. The ICS interacts with the following subsystems: the near-infrared (NIR) and visible channels, composed by the detectors and exposure meters; the calibration units; the environment sensors; the front-end electronics; the acquisition and guiding module; the interfaces with telescope and dome; and, finally, the software subsystems for operational scheduling of tasks, data processing, and data archiving. The software control framework and all the software modules and layers for the different subsystems contribute to maximize the scientific return of the instrument. The CARMENES workflow covers from the translation of the survey strategy into a detailed schedule to the data processing routines that extract radial velocity data from the observed targets. The control suite is integrated in the instrument since the end of 2015.
The ARIEL mission has been proposed to ESA by an European Consortium as the first space mission to extensively
perform remote sensing on the atmospheres of a well defined set of warm and hot transiting gas giant exoplanets, whose
temperature range between ~600 K and 3000 K.
ARIEL will observe a large number (~500) of warm and hot transiting gas giants, Neptunes and super-Earths around a
range of host star types using transit spectroscopy in the ~2-8 μm spectral range and broad-band photometry in the NIR
and optical. ARIEL will target planets hotter than 600 K to take advantage of their well-mixed atmospheres, which
should show minimal condensation and sequestration of high-Z materials and thus reveal their bulk and elemental
One of the major motivations for exoplanet characterisation is to understand the probability of occurrence of habitable
worlds, i.e. suitable for surface liquid water. While ARIEL will not study habitable planets, its major contribution to this
topic will results from its capability to detect the presence of atmospheres on many terrestrial planets outside the
habitable zone and, in many cases, characterise them. This represents a fundamental breakthrough in understanding the
physical and chemical processes of a large sample of exoplanets atmospheres as well as their bulk properties and to
probe in-space technology.
The ARIEL infrared spectrometer (AIRS) provides data on the atmospheric composition; these data are acquired and
processed by an On-Board Data Handling (OBDH) system including the Cold Front End Electronics (CFEE) and the
Instrument Control Unit (ICU). The Telescope Control Unit (TCU) is also included inside the ICU. The latter is directly
connected to the Control and Data Management Unit (CDMU) on board the Service Module (SVM). The general
hardware architecture and the application software of the ICU are described. The Fine Guidance Sensor (FGS)
electronics and the Cooler Control Electronics are also presented.
CARMENES, the new Calar Alto spectrograph especially built for radial-velocity surveys of exoearths around M dwarfs, is a very complicated system. For reaching the goal of 1 m/s radial-velocity accuracy, it is appropriate not only to monitor stars with the best observing procedure, but to monitor also the parameters of the CARMENES subsystems and safely store all the engineer and science data. Here we describe the CARMENES data flow from the different subsystems, through the instrument control system and pipeline, to the virtual-observatory data server and astronomers.
The main goal of the CARMENES instrument is to perform high-accuracy measurements of stellar radial velocities (1m/s) with long-term stability. CARMENES will be installed in 2015 at the 3.5 m telescope in the Calar Alto Observatory (Spain) and it will be equipped with two spectrographs covering from the visible to the near-infrared. It will make use of its near-IR capabilities to observe late-type stars, whose peak of the spectral energy distribution falls in the relevant wavelength interval. The technology needed to develop this instrument represents a challenge at all levels. We present two software packages that play a key role in the control layer for an efficient operation of the instrument: the Instrument Control System
(ICS) and the Operational Scheduler. The coordination and management of CARMENES is handled by the ICS, which is responsible for carrying out the operations of the different subsystems providing a tool to operate the instrument in an integrated manner from low to high user interaction level. The ICS interacts with the following subsystems: the near-IR and visible channels, composed by the detectors and exposure meters; the calibration units; the environment sensors; the front-end electronics; the acquisition and guiding module; the interfaces with telescope and dome; and, finally, the software subsystems for operational scheduling of tasks, data processing, and data archiving. We describe the ICS software design, which implements the CARMENES operational design and is planned to be integrated in the instrument by the end of 2014. The CARMENES operational scheduler is the second key element in the control layer described in this contribution. It is the main actor in the translation of the survey strategy into a detailed schedule for the achievement of the optimization goals. The scheduler is based on Artificial Intelligence techniques and computes the survey planning by combining the static constraints that are known a priori (i.e., target visibility, sky background, required time sampling coverage) and the dynamic change of the system conditions (i.e., weather, system conditions). Off-line and on-line strategies are integrated into a single tool for a suitable transfer of the target prioritization made by the science team to the real-time schedule that will be used by the instrument operators. A suitable solution will be expected to increase the efficiency of telescope operations, which will represent an important benefit in terms of scientific return and operational costs. We present the operational scheduling tool designed for CARMENES, which is based on two algorithms combining a global and a local search: Genetic Algorithms and Hill Climbing astronomy-based heuristics, respectively. The algorithm explores a large amount of potential solutions from the vast search space and is able to identify the most efficient ones. A planning solution is considered efficient when it optimizes the objectives defined, which, in our case, are related to the reduction of the time that the telescope is not in use and the maximization of the scientific return, measured in terms of the time coverage of each target in the survey. We present the results obtained using different test cases.
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.
The main task of a scheduler applied to astronomical observatories is the time optimization and the maximization of the scientific return. Scheduling of observations is an example of the classical task allocation problem known as the job-shop problem (JSP) or the flexible-JSP (fJSP). In most cases various mathematical algorithms are usually considered to solve the planning system. We present an analysis of the task allocation problem and the solutions currently in use at different astronomical facilities. We also describe the schedulers for three different projects (TJO, CARMENES and CTA) where the conclusions of this analysis are applied in their development.