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Efficient scheduling of astronomical surveys is a challenge with an increasing level of complexity as the observation strategies are becoming more sophisticated and operational costs are higher. In general, any kind of astronomical survey requires the execution of a huge number of observations fulfilling several constraints. The fulfillment and optimization of these constraints is a key factor for obtaining an efficient schedule with an adequate exploitation of the resources and with a high scientific return. In this contribution, we present the framework STARS (Scheduling Telescopes as Autonomous Robotic Systems) that computes optimal schedules for a variety of space- and ground-based infrastructures and scientific exploitation plans. STARS provides methods, tools and libraries for the definition of surveys (e.g., objects to observe, features of the objects, observation constraints), the definition of the observatories (e.g., location, number of telescopes, type of telescopes, sub-array configurations), the usage of astronomical calculations (e.g., object coordinates, object elevation, Sun and Moon position, Moon phase), and the application of schedulers (e.g., long-term, short-term) based on Genetic Algorithms (GAs) and astronomy-based heuristics. In STARS, two main types of schedulers are defined: long-term and short-term. The long-term scheduler is focused on scheduling object observations with a time scope ranging from one night to several months or years. It considers the observation constraints (hard-constraints) that can be predicted beforehand, and it optimizes some objectives (soft constraints) by using GAs. The execution of the long-term scheduler can be time-expensive, but it is not time-critical because it can be run before the start of the telescope operation, so it can be used as a standalone scheduling tool. On the other hand, the short-term scheduler computes in real-time the next observation (or scheduling block) to be executed by optimizing some soft constraints, fulfilling all the hard constraints and by considering all the observations previously executed. The short-term scheduler is time-critical and reacts in less than a second to the changing conditions (weather, errors, delays, targets of opportunity). It uses astronomy-based heuristics to repair the schedule obtained by the long-term scheduler, in order to keep the long-term perspective while avoiding intensive calculations. STARS has been successfully applied in several ground and space-based observatories. It is used to operate the CARMENES instrument (Calar Alto, carmenes.caha.es) and the Joan Oro robotic Telescope (www.oadm.cat). It is used to prototype the mission planning tool for the ARIEL M4-ESA candidate mission, and in prototypes for large ground-based installations, such i.e. the Cherenkov Telescope Array (CTA). Finally, STARS is also being extended to cover multi-observatory coordinated scheduling purposes, under the framework of the EU-H2020 ASTERICS project, and in order to promote multi-messenger science. The coordination of large observatories in the northern and southern hemispheres are used as test cases to evaluate the performance of such an innovative scheduling solution. In this sense, simultaneous observations or minimal time gap between observations are promoted resulting in a challenging and complex optimization problem that will open a new era for the optimal operation of large astrophysical infrastructures.

The CARMENES instrument is a pair of high-resolution (R greater than or similar to 80, 000) spectrographs covering the wavelength range from 0.52 to 1.71 mu m, optimized for precise radial velocity measurements. It was installed and commissioned at the 3.5 m telescope of the Calar Alto observatory in Southern Spain in 2015. The first large science program of CARMENES is a survey of similar to 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 fiber-fed high-resolution Echelle spectrograph for the Calar Alto 3.5m telescope. The instrument is built by a German-Spanish consortium under the lead of the Landessternwarte Heidelberg. The search for planets around M dwarfs with a radial velocity of 1 m/s is the main focus of the planned science. Two channels, one for the visible, another for the near-infrared, will allow observations in the complete wavelength range from 550 to 1700 nm. To ensure the stability, the instrument is working in vacuum in a thermally controlled environment. The VIS channel spectrograph is covering the visible wavelength range from 0.55 to 0.95 μm with a spectral resolution of R=93,400 in a thermally and pressure-wise very stable environment. The VIS channel spectrograph started science operation in January 2016. Here we present the opto-mechanical and system design of the channel with the focus on the (re-)integration phase at the observatory and the measured performance during the testing and commissioning periods, including the lessons learned.

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.

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 echelle 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 overall purpose of the CARMENES instrument is to perform high-precision measurements of radial velocities of late-type stars with long-term stability. CARMENES will be installed in 2014 at the 3.5 m telescope in the German- Spanish Astronomical Center at Calar Alto observatory (CAHA, Spain) and will be equipped with two spectrographs in the near-infrared and visible windows. The technology involved in such instrument represents a challenge at all levels. The instrument coordination and management is handled by the Instrument Control System (ICS), which is responsible of carrying out the operations of the different subsystems and providing a tool to operate the instrument from low to high user interaction level. The main goal of the ICS and the CARMENES control layer architecture is to maximize the instrument efficiency by reducing time overheads and by operating it in an integrated manner. The ICS implements the CARMENES operational design. A description of the ICS architecture and the application programming interfaces for low- and high-level communication is given. Internet Communications Engine is the technology selected to implement most of the interface protocols.

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.

CARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs) is a next-generation instrument to be built for the 3.5m telescope at the Calar Alto Observatory by a consortium of Spanish and German institutions. Conducting a five-year exoplanet survey targeting ~ 300 M stars with the completed instrument is an integral part of the project. The CARMENES instrument consists of two separate spectrographs covering the wavelength range from 0.52 to 1.7 μm at a spectral resolution of R = 85, 000, fed by fibers from the Cassegrain focus of the telescope. The spectrographs are housed in a temperature-stabilized environment in vacuum tanks, to enable a 1m/s radial velocity precision employing a simultaneous ThAr calibration.