The Observatory Control System (OCS) for the Giant Magellan Telescope (GMT) includes all the software and hardware components necessary to control and monitor the GMT optical and electromechanical subsystems and to safely and efficiently operate the GMT observatory. The OCS architecture follows both a component-based and a model-based approaches. Software components are specified using a Domain Specific Language (DSL) which enables codegeneration in several languages and automatic validation of architectural conformance and interfaces. This paper describes the agile development process to generate the final software components from the specifications and the status of the whole development effort.
The Giant Magellan Telescope Project is in the construction phase. Production of the primary mirror segments is underway with four of the seven required 8.4m mirrors at various stages of completion and materials purchased for segments five and six. Development of the infrastructure at the GMT site at Las Campanas is nearing completion. Power, water, and data connections sufficient to support the construction of the telescope and enclosure are in place and roads to the summit have been widened and graded to support transportation of large and heavy loads. Construction pads for the support buildings have been graded and the construction residence is being installed. A small number of issues need to be resolved before the final design of the telescope structure and enclosure can proceed and the GMT team is collecting the required inputs to the decision making process. Prototyping activities targeted at the active and adaptive optics systems are allowing us to finalize designs before large scale production of components begins. Our technically driven schedule calls for the telescope to be assembled on site in 2022 and to be ready to receive a subset of the primary and secondary mirror optics late in the year. The end date for the project is coupled to the delivery of the final primary mirror segments and the adaptive secondary mirrors that support adaptive optics operations.
The Giant Magellan Telescope active optics system is required to maintain image quality across a 20 arcminute diameter field of view. To do so, it must control the positions of the primary mirror and secondary mirror segments, and the figures of the primary mirror segments. When operating with its adaptive secondary mirror, the figure of the secondary is also controlled. Wavefront and fast-guiding measurements are made using a set of four probes deployed around the field of view. Through a set of simulations we have determined a set of modes that will be used to control fielddependent aberrations without degeneracies.
The Giant Magellan Telescope (GMT) is a 25.4-m diameter, optical/infrared telescope that is being built by an international consortium of universities and research institutions as one of the next generation of Extremely Large Telescopes. The primary mirror of GMT consists of seven 8.4 m borosilicate honeycomb mirror segments that are optically conjugate to seven corresponding segments in the Gregorian secondary mirror. Fabrication is complete for one primary mirror segment and is underway for the next two. The final focal ratio of the telescope is f/8.2, so that the focal plane has an image scale of 1.02 arcsec/mm. GMT will be commissioned using a fast-steering secondary mirror assembly comprised of conventional, rigid segments to provide seeing-limited observations. A secondary mirror with fully adaptive segments will be used in standard operation to additionally enable ground-layer and diffraction-limited adaptive optics. In the seeing limited mode, GMT will provide a 10 arcmin field of view without field correction. A 20 arcmin field of view will be obtained using a wide-field corrector and atmospheric dispersion compensator. The project has recently completed a series of sub-system and system-level preliminary design reviews and is currently preparing to move into the construction phase. This paper summarizes the technical development of the GMT sub-systems and the current status of the GMT project.
The Giant Magellan Telescope (GMT) adaptive optics (AO) system will be an integral part of the telescope, providing laser guidestar generation, wavefront sensing, and wavefront correction to every instrument currently planned on the 25.4 m diameter GMT. There will be three first generation AO observing modes: Natural Guidestar, Laser Tomography, and Ground Layer AO. All three will use a segmented adaptive secondary mirror to deliver a corrected beam directly to the instruments. The Natural Guidestar mode will provide extreme AO performance, with a total wavefront error less than 185 nm RMS using bright guidestars. The Laser Tomography mode uses 6 lasers and a single off-axis natural guidestar to deliver better than 290 nm RMS wavefront error at the science target, over 50% of the sky at the galactic pole. The Ground Layer mode uses 4 natural guidestars on the periphery of the science field to tomographically reconstruct and correct the ground layer AO turbulence, improving the image quality for wide-field instruments. A phasing system maintains the relative alignment of the primary and secondary segments using edge sensors and continuous feedback from an off-axis guidestar. We describe the AO system preliminary design, predicted performance, and the remaining technical challenges as we move towards the start of construction.
The Giant Magellan Telescope (GMT) is a 25-meter extremely large telescope that is being built by an international
consortium of universities and research institutions. Its software and control system is being developed using a set of
Domain Specific Languages (DSL) that supports a model driven development methodology integrated with an Agile
management process. This approach promotes the use of standardized models that capture the component architecture of
the system, that facilitate the construction of technical specifications in a uniform way, that facilitate communication
between developers and domain experts and that provide a framework to ensure the successful integration of the
software subsystems developed by the GMT partner institutions.
The Giant Magellan Telescope Organization is designing and building a ground-based 25-meter extremely large telescope. This project represents a significant increase in complexity and performance requirements over 8-10 meter class telescope control systems. This paper presents how recent software and hardware technologies and the lessons learned from the previous generation of large telescopes can help to address some of these challenges. We illustrate our model-centric approach to capture all the functionalities and workflows of the observatory subsystems, and discuss its benefits for implementing and documenting the software and control systems. The same modeling approach is also used
to capture and facilitate the development process.
The Giant Magellan Telescope (GMT) is a 25-meter optical/infrared extremely large telescope that is being built by an
international consortium of universities and research institutions. It will be located at the Las Campanas Observatory,
Chile. The GMT primary mirror consists of seven 8.4-m borosilicate honeycomb mirror segments made at the Steward
Observatory Mirror Lab (SOML). Six identical off-axis segments and one on-axis segment are arranged on a single
nearly-paraboloidal parent surface having an overall focal ratio of f/0.7. The fabrication, testing and verification
procedures required to produce the closely-matched off-axis mirror segments were developed during the production of
the first mirror. Production of the second and third off-axis segments is underway.
GMT incorporates a seven-segment Gregorian adaptive secondary to implement three modes of adaptive-optics
operation: natural-guide star AO, laser-tomography AO, and ground-layer AO. A wide-field corrector/ADC is available
for use in seeing-limited mode over a 20-arcmin diameter field of view. Up to seven instruments can be mounted
simultaneously on the telescope in a large Gregorian Instrument Rotator. Conceptual design studies were completed for
six AO and seeing-limited instruments, plus a multi-object fiber feed, and a roadmap for phased deployment of the GMT
instrument suite is being developed.
The partner institutions have made firm commitments for approximately 45% of the funds required to build the
telescope. Project Office efforts are currently focused on advancing the telescope and enclosure design in preparation for
subsystem- and system-level preliminary design reviews which are scheduled to be completed in the first half of 2013.
The Inspector is the graphical user interface of the GTC Control System. It is implemented in Java and gives a unified
view of the whole system by representing it as hierarchical browser of distributed objects.
The ability to resolve at runtime the domain objects running distributed on the real time systems and use that domain
information to dynamically generate different views of the system.
Using the exact same set of tools and edition capabilities, it is as simple to create an engineering view of the GCS as it is
to create a science view. Such flexibility and simplicity, have made the Inspector be, not only the interface of the final
system, but also one of the most important tools used by the engineers from very early in the development process to test
the functionality of their respective components.
Persistency of dynamically created views, commands execution flows, visualization of system alarms and logs, are also
important aspects of the Inspector which will be explained in this paper.
The aim of a data reduction process is to minimize the influence of data acquisition imperfections on the estimation of the desired astronomical quantity. For this purpose, one must perform appropriate manipulations with data and calibration frames. In addition, random-error frames (computed from first principles: expected statistical distribution of photo-electrons, detector gain, readout-noise, etc.), corresponding to the raw-data frames, can also be properly reduced. This parallel treatment of data and errors guarantees the correct propagation of random errors due to the arithmetic manipulations throughout the reduction procedure. However, due to the unavoidable fact that the information collected by detectors is physically sampled, this approach collides with a major problem: errors are correlated when applying image manipulations involving non-integer pixel shifts of data. Since this is actually the case for many common reduction steps (wavelength calibration into a linear scale, image rectification when correcting for geometric distortions,...), we discuss the benefits of considering the data reduction as the full characterization of the raw-data frames, but avoiding, as far as possible, the arithmetic manipulation of that data until the final measure of the image properties with a scientific meaning for the astronomer. For this reason, it is essential that the software tools employed for the analysis of the data perform their work using that characterization. In that sense, the real reduction of the data should be performed during the analysis, and not before, in order to guarantee the proper treatment of errors.
This paper is focused on how the features and object services provided by CORBA (Common Object Request Broker Architecture) can be applied to solve the specific needs of a modern telescope control system. The solutions presented in this paper are based on TAO, which is the ORB (Object Request Broker) implementation selected by the GTC Control Group, although any ORB implementing OMG's CORBA 2.3 standard could be used.
Last two years the GTC control system has continued its design and prototyping activity. This paper presents the current state of the GTC control system architecture. The overall architecture is already designed and the main subsystems have been specified and are being designed. Design patterns have been applied to the architecture design and are also used as an effective way to document the design.
The GTC project is in charge of the construction of an optical/IR 10-meter class telescope at the Observatorio del Roque de los Muchachos in Canary Islands. The GTC control system (GCS) will be responsible for the management and operation of the telescope, including its instrumentation. Its conceptual design has been completed in summer 1997. The continuous and rapid development of hardware, software and communications technology has permitted a greater complexity in control systems. In their turn, the development of active and adaptive optics, the new methods of optimizing available observing time and the continuous development programs to maintain telescope competitiveness present new challenges in the design of control systems. During its life-cycles, the GCS will be subject to continuous changes brought about by different factors, such as the advent of new technologies, the evolution of the requirements, the development of new instruments and fault correction. These factors must be taken on board with the minimum possible impact, not only on the project but also on the availability of the GTC once it enters into operation. This will only be possible through the selection and planning of an adequate technological framework that enables these changes to be assimilated throughout the life-cycle of the telescope. In this presentation the fundamental aspects of this framework along the current status of the control system design are outlined.
The Gran Telescopio Canarias (GTC) project office is in charge of the construction of an optical/IR 10-meter class telescope at the Observatorio del Roque de los Muchachos, in Canary Islands. The conceptual design phase has been completed in summer 1997, and the design of the control system has already started its initial phases. Recently, the complexity of the control system for large telescopes has increased. More and more functions are computer controlled. Distributed computer systems are an effective architecture for these telescope control systems, but distributed semantics are more difficult to deal with. This gives complex architectures that are hard to develop and maintain. Additionally, technological change is continuous in computing, as the periodic reports of control system upgrade programs show. To keep these architectures in step with change is not an easy task. In the GTC control system these issues are being taken into account from the beginning of the project. This paper is focused no how recent advances in distributed computing can help to deal with these problems.