The GTC (Gran Telescopio Canarias) is an optical and IR telescope, with a 10,4 meter segmented primary, installed at
the Observatorio del Roque de Los Muchachos (ORM) on the island of La Palma.
GTC commissioning started in July 2007 when First Light was achieved. GTC regular scientific operations started at the
beginning of 2009 with its first science instrument: OSIRIS, a visible camera with tunable filter and low-resolution
multi-object spectroscopic capability. Since that time science operation and telescope and instrument development
activities alternate in using the available telescope time. Later in 2010 the second science instrument will be
commissioned: CanariCam, a thermal-IR camera and low-resolution spectrograph with polarimetric and coronagraphic
This paper presents the telescope commissioning process, the problems encountered and shows some of the performance
aspects. First science results will also be presented to demonstrate the current capabilities of the GTC facility.
The Wind Evaluation Breadboard (WEB) for the European Extremely Large Telescope (ELT) is a primary mirror and
telescope simulator formed by seven segments simulators, including position sensors, electromechanical support systems
and support structures. The purpose of the WEB is to evaluate the performance of the control of wind buffeting
disturbance on ELT segmented mirrors using an electro-mechanical set-up which simulates the real operational
constrains applied to large segmented mirrors. The instrument has been designed and developed by IAC, ALTRAN,
JUPASA and ESO, with FOGALE responsible of the Edge Sensors, and TNO of the Position Actuators. This paper
describes the mechanical design and analysis, the control architecture, the dynamic model generated based on the Finite
Element Model and the close loop performance achieved in simulations. A comparison in control performance between
segments modal control and actuators local control is also presented.
The GTC (Gran Telescopio Canarias) is an optical/IR telescope, with a 10,4 meter segmented primary, installed at the
Observatorio del Roque de Los Muchachos (ORM), at La Palma.
Past July 2007 it saw its First Light showing a very promising behaviour. The very good image quality achieved at that
an early stage of telescope commissioning is a direct consequence of the quality of its optics, the high performances of
its primary mirror control system, and the highly engineered telescope structure and servo system.
At present, we are advancing with the telescope commissioning whose first results are presented here. The two Day One
science instruments: OSIRIS and CanariCam are being prepared for installation and commissioning on the telescope.
Science verification are planned to be initiated by the end of 2008 and regular operation by March 2009.
The European Extremely Large Telescope (E-ELT) is a 42-m class optical telescope with a segmented primary mirror
composed of 984 segments which is currently being studied by ESO (European Southern Observatory). The segment
support system combines a series of mechanical whiffletrees for the axial support, a central diaphragm for lateral support
and a torsional constrainer. These elements are fixed to a common moving frame which is actively moved by means of
three actuators in piston and tip-tilt in order to keep the whole primary mirror in phase. The moving frame is fixed to the
segments subcells, which properly attach the segments to the cell structure, by means of special flexures, allowing large
axial alignment capability combined with high lateral stiffness. This paper describes the development of the support
system for the primary mirror segments of the E-ELT, which has been specified for a high stiffness and
eigenfrequencies, 60Hz for axial modes and 40Hz for lateral ones.
In March 2004, the Commissioning Instrument (CI) for the GTC was accepted in the site of The Gran Telescopio Canarias (GTC) located in La Palma Island, Spain. During the GTC integration phase, the CI will be a diagnostic tool for performance verification. The CI features four operation modes-imaging, pupil imaging, Curvature Wave-front sensing (WFS), and high resolution Shack-Hartmann WFS. The imaging mode permits to qualify the GTC image quality. The Pupil Mode permits estimate the GTC stray light. The segments figure, alignment and cophasing verifications are made with both WFS modes. In this work we describe the Commissioning Instrument and show some tests results obtained during the site acceptance process at the GTC site.
The GTC (Gran Telescopio Canarias) is a 10,4 meter segmented telescope, whose integration is currently being completed at the ORM in La Palma, Spain. The GTC is a partnership between Spain, Mexico and the University of Florida. Main science drivers for the GTC are image quality, operational efficiency and reliability. First light is planned for late-2006. The GTC Project, initiated in 1996, is nearly complete in its integration. Groundbreaking was done in 2000. The telescope building and dome were finished by end 2002. The telescope structure was complete in early 2005. Since then this structure is being completed with the rest of the parts, i.e. M1 mirror subcells, M3 tower, main axes encoders and motors, cables, pipes and cable-rotators, electronic cabinets, etc. The mirrors will be installed at the telescope, just before First Light. All the optical elements have been finished and are being prepared to be installed. Three science instruments are being completed to be installed as first generation instruments. Two second-generation instruments, including one exploiting the future Adaptive Optics capabilities of the GTC, are under development.
In March 2004 was accepted in the site of Gran Telescopio Canarias (GTC) in La Palma Island, Spain, the Commissioning Instrument (CI) for the GTC. During the GTC integration phase, the CI will be a diagnostic tool for performance verification. The CI features four operation modes-imaging, pupil imaging, Curvature Wave-front sensing (WFS), and high resolution Shack-Hartmann WFS. This instrument was built by the Instituto de Astronomia UNAM in Mexico City and the Centro de Ingenieria y Desarrollo Industrial (CIDESI) in Queretaro, Qro under a GRANTECAN contract after an international public bid. Some optical components were built by Centro de Investigaciones en Optica (CIO) in Leon Gto and the biggest mechanical parts were manufactured by Vatech in Morelia Mich. In this paper we made a general description of the CI and we relate how this instrument, build under international standards, was entirely made in Mexico.
The 10m Gran Telescopio Canarias (GTC) is currently being installed in the Observatorio del Roque de los Muchachos (ORM) on the island of La Palma. An adaptive optics (AO) system will be installed at one of the Nasmyth foci of the telescope within a year of the telescope being commissioned. The preliminary design of the adaptive optics system is presented here. The system will initially be operated in single-conjugate mode using a natural guide star, but provisions are made for upgrade to dual-conjugate operation and the use of laser guide stars. The main system requirements and the optical and mechanical design solutions are outlined here. It is planned to employ a piezo-stack deformable mirror having approximately 350 actuators and a Shack-Hartmann wavefront sensor. The tip-tilt correction will be provided by the secondary mirror of the GTC which is a lightweighted Beryllium mirror with a drive system capable of fast tip-tilt and chopping. In preparation for dual-conjugate operation we have studied the optimal altitude of the second deformable mirror (the first will be conjugate to the telescope pupil) using numerical simulations and measurements of turbulence obtained at the ORM. We have used the GSC II catalogue to determine sky-coverage for multi-natural guide star wavefront sensing, as required for dual-conjugate operation. In addition we have investigated a novel approach to multi-object wavefront sensing based on curvature sensing.
Under a contract with the GRANTECAN, the Commissioning Instrument (CI) is a project developed by a team of Mexican scientists and engineers from the Instrumentation Department of the Astronomy Institute at the UNAM and the CIDESI Engineering Center. The CI will verify the Gran Telescopio Canarias (GTC) performance during the commissioning phase between First Light and Day One. The design phase is now completed and the project is currently in the manufacturing phase.
The CI main goal is to measure the telescope image quality. To obtain a stable high resolution image, the mechanical structures should be as rigid as possible. This paper describes the several steps of the conceptual design and the Finite Element Analysis (FEA) for the CI mechanical structures.
A variety of models were proposed. The FEA was useful to evaluate the displacements, shape modes, weight, and thermal expansions of each model. A set of indicators were compared with decision matrixes. The best performance models were subjected to a re-optimization stage. By applying the same decision method, a CI Structure Model was proposed. The FEA results complied with all the instruments specifications. Displacements values and vibration frequencies are reported.
Under a contract with the GRANTECAN, the Commissioning Instrument is a project developed by a team of Mexican scientists and engineers from the Instrumentation Department of the Astronomy Institute at the UNAM and the CIDESI Engineering Center.
This paper will discuss in some detail the final Commissioning Instrument (CI) mechanical design and fabrication. We will also explain the error budget and the barrels design as well as their thermal compensation. The optical design and the control system are discussed in other papers.
The CI will just act as a diagnostic tool for image quality verification during the GTC Commissioning Phase. This phase is a quality control process for achieving, verifying, and documenting the performance of each GTC sub-systems. This is a very important step for the telescope life. It will begin on starting day and will last for a year.
The CI project started in December 2000. The critical design phase was reviewed in July 2001. The CI manufacturing is currently in progress and most parts are finished. We are now approaching the factory acceptance stage.
During the GTC integration phase, the Commissioning Instrument (CI) will be a diagnostic tool for performance verification. The CI features four operation modes-imaging, pupil imaging, Curvature WFS, and high resolution Shack-Hartmann WFS. After the GTC Commissioning we also plan to install a Pyramid WFS. This instrument can therefore serve as a test bench for comparing co-phasing methods for ELTs on a real segmented telescope. In this paper we made a general instrument overview.
During the conceptual design of the GTC (Gran Telescopio Canarias) it was suggested to develop a Global Model of the behaviour of the GTC system to be used as a tool for the system engineering. This Global Model should be a dynamical simulation capable to predict the pointing, tracking, guiding and image quality of the GTC system in several simulation scenarios depending on the behavior of each subsystem. It was decided to develop the simulation in the Matlab/Simulink® environment. The kernel of the Global Model was a Simulink® model of the telescope mechanics. The model included the structural dynamics, control loops of the main axis (azimuth, elevation and rotators), and load models (wind, gravity, seism). Each component included error sources inherent to it (cogging and ripple on motors, encoding errors, bearing run-out, etc). The model permitted large rotations in elevation axis, which was necessary to test pointing performances. A specific simulation was developed within the project office for the analysis of the image quality of the optical system. It includes polishing defects of the optical surfaces (M1 segments, M2 and M3), low spatial frequency distortions of the optical surfaces (due to fabrication, gravity of instability) and misalignment between the primary mirror segments.
The Gran Telescopio Canarias (GTC) is a 10 m-class telescope which is under construction and will be operational at the Observatorio del Roque de Los Muchachos at the end of 2003. The goal of this paper is to describe the current status of the design and construction of the primary, secondary and tertiary mirrors of the GTC and their opto-mechanical supports. It also summarizes the optical performances expected from the GTC and the error budget of the optical system.
Modern Acquisition and Guiding systems provide a range of services with the aim of optimizing telescope performance. These include wavefront sensing for active optics, fast guiding and measurement of seeing. On a segmented-mirror telescope, the Acquisition and Guiding system may also be expected to provide measurements of the piston errors between the primary mirror segments. The Guacamole (GUiding, Acquisition and CAlibration MOduLE) system of the 10 m Gran Telescopio Canarias (GTC) has been designed to provide all of these services. Complete systems will be installed at each of the GTC Nasmyth foci. The requirements of this system are presented and a preliminary design is described.
The conceptual design of the GTC optical system was completed in summer of 1997. It will be a Richey Cretien type telescope with a flat tertiary mirror to feed Nasmyth and folded Cassegrain focal stations. The telescope will have a segmented primary mirror and an entrance pupil area equivalent to a circular aperture of 10 m diameter. The details of its optical- and opto-mechanical design have been chosen to meet the scientific requirements such as excellent image quality in a broad wavelength range (0.3 microns < (lambda) < 15 microns) and maximum operational efficiency. To achieve the required specifications, all optical elements, in particular the primary mirror segments need to be equipped with a high performance opto-mechanical support system. In this paper we present the results of the optical- and opto-mechanical design of the GTC.
The conceptual design of the Gran Telescopio Canarias (GTC) has been completed. One of the challenges facing the GTC Project is to obtain excellent image quality using a segmented primary mirror. The segmentation will introduce a physical effect that contributes to significant degradation of image quality. The image quality requirement imposes the use of an active optical system to correct figure instabilities of the optical surfaces and part of the unavoidable fabrication figure errors. The active correlation includes the capability of 5-axis motion of the secondary mirror, 3-axis motion of each primary mirror segment, and 6 active degrees of freedom to deform each segment. A mixed strategy of closed- and open-loop control of the active correction will be implemented. This paper discusses the expected wavefront errors of the GTC, how they are corrected by active optics, and the expected image quality performance in FWHM, (theta) 80 and Central Intensity ratio.
Within the preliminary developments related to the Gran Telescopio Canarias, a test rig is being designed for the active control of the support system of the segmented primary mirror. The construction of this test rig will be divided in two phases: the first one will basically consist in the implementation and testing of a displacement sensor prototype as well as an actuator prototype. Phase 2 will consist in the development and characterization of the whole test rig, including two segment simulators and a number of displacement sensors and actuators. Also, a non contact optical system for the test rig behavior verification will be constructed during phase 2. This paper presents the conceptual design adopted for the active control system proposed for the telescope and a brief description of the development program, including the requirements of the displacement sensors and actuators. We intend the test rig not only for testing the active control system components, but also for checking different control strategies.
The preservation of the excellent image quality of the 'Roque de los Muchachos' Observatory (ORM) is one of the most important design criteria for the enclosure of the future large telescope. Additionally, the cost of a large telescope and its instrumentation is so high that it would be regrettable if its own enclosure deteriorates the telescope performance for astronomical observations. For these reasons, the IAC and CEANI are conducting an aero- and thermo-dynamical study based on numerical simulations, attempting to minimize the seeing degradation due to factors within the control of the designers. This paper first describes the general concept of the enclosure we are planning for the future 'Gran Telescopio Canarias' (GTC) and second the set of three dimensional simulations we are conducting to evaluate the effect on seeing of four different enclosure topologies located at two possible sites.
This paper presents a solution to correct wind induced deformation on a 8.0 m thin meniscus mirror supported by a system of astatic active supports. The correction scheme is based on an active correction using the force actuators which support the mirror, and a passive rate dependent coupling of the mirror to the cell. The paper identifies the fundamental design parameters of the passive correction system and the active controller, and shows its wind attenuation capabilities. A 3D simulation verifies the good performance of the system for wind velocities of about 45 km/h. Furthermore, the influence of cell deflection on the mirror due to the passive coupling system is shown.
This paper presents the IAC (Instituto de Astrofisica de Canaries, Spain) proposal of a distributed control system intended for the active support of a 8 m mirror. The system incorporates a large number of compact `smart' force actuators, six force definers, and a mirror support computer (MSC) for interfacing with the telescope control system and for general housekeeping. We propose the use of a network for the interconnection of the actuators, definers and the MSC, which will minimize the physical complexity of the interface between the mirror support system and the MSC. The force actuator control electronics are described in detail, as is the system software architecture of the actuator and the MSC. As the network is a key point for the system, we also detail the evaluation of three candidates, before electing the CAN bus.