The Giant Magellan Telescope, with a 25.4m primary and operating from the ultraviolet to the long wave infrared, is being built as one of the next-generation Extremely Large Telescopes. The size of the GMT and its doubly segmented design create a unique set of challenges for telescope alignment, from initial alignment during the assembly, integration, verification and commissioning phase to operational alignment between and during the telescope exposures. GMT therefore includes a Telescope Metrology System (TMS) that uses networks of laser trackers and absolute and differential distance-measuring interferometers for improved alignment efficiency and phasing of the mirror segments. The TMS has successfully passed its Preliminary Design Review and entered the Final Design phase. In this paper we present the current design and expected performance of the GMT TMS.
KEYWORDS: Software development, Control systems, Design, Software engineering, Observatories, Telescopes, Industry, Project management, Control systems design, Control software
The Giant Magellan Telescope (GMT) Software and Controls (SWC) team is responsible for designing, implementing, and maintaining the GMT Observatory Control System (OCS). GMT software modules are developed either in-house, or in collaboration with GMT partner institutions, following an Agile software development process. However, these software industry best-practices require significant tailoring to integrate well with other Engineering disciplines on a large, complex project such as GMT. In this paper we explore the various challenges in managing software development and how we are tackling them at GMT. Key areas include building the right team, handling programmatic challenges, streamlining development processes and engaging with customers and stakeholders. We’ve learned that people are at the heart of what we do, and the health of the team directly affects our ability to deliver high quality software on time and within budget. Also, managing limited resources is a common theme, requiring many different solutions in different domains. We have found the most effective to be a combination of process-optimization, resource-loaded scheduling, agile development, drastic overhead reduction and regular review of top priorities to help the team focus on what is important. Lastly, active engagement and efficient communication with customers and other stakeholders from the very beginning, help to set clear expectations and sets the team up for success. The team has made tremendous progress in the last few years in these areas and will continue to do so in the future due to a commitment to continuous improvement.
The Giant Magellan Telescope (GMT) is a next-generation ground-based segmented telescope. In the last few years, significant progress has been made by the GMT team and partners to design a natural guide-star wavefront control strategy that can reliably correct wavefront error, including the discrete piston aberration between segment gaps. After an extensive set of simulations and external reviews, the team proposed a design of a Pyramidal Wavefront Sensor (PWFS) combined with a Holographic Dispersed Fringe Sensor (HDFS) and started building a prototype for integrating a GMT simulator (High Contrast AO Testbed) with a PWFS and an HDFS. The prototype was developed in collaboration with the University of Arizona, INAF-Arcetri, and the GMT observatory. The software development of the adaptive optics controllers and the interfaces between all testbed components were done using the GMT software frameworks, as they will be implemented for the final observatory software. The GMT framework is model-based, and the software component interfaces are defined using a domain-specific language (DSL). In this paper, we show how the design of the testbed software fits within GMT's component-based architecture and what each partner was responsible for delivering. We discuss the challenge of a multidisciplinary team from multiple institutions in different time zones working together on the same software, describe how the software architecture and development process helped to ensure seamless integration and highlight other accomplishments and lessons learned.
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