Pasadena, CA – 16 September, 2019 – The TMT Telescope Control System (TCS) successfully passed its Preliminary Design Review (PDR) and is now ready to enter its final design phase.
The primary goal of TCS is to provide and maintain high-quality stable images to the science instruments located at the telescope’s Nasmyth focal planes. TCS is a software-only system whose main functions are to (1) control, synchronize, and monitor the telescope subsystems, (2) convert the position of celestial targets into coordinates relevant to each subsystem, and (3) continuously integrate optical corrections for seeing-limited and adaptive optics instruments.
During nighttime observations, the TCS provides high level control for the telescope mount, the enclosure, and the secondary and tertiary mirrors to secure proper pointing and acquisition of the observed targets. It also provides telemetry for precise target tracking by the telescope, the science instruments and various adjustable devices (rotators, wavefront sensors, guiders, atmospheric dispersion compensators).
During the segment exchange procedures (after the mirror segments have been replaced for cleaning), the TCS works with the alignment and phasing system and the primary mirror control system to ensure that the new mirror segments are properly aligned and phased.
Figure 2 shows a preliminary concept of the web-based ‘TCS overview’ engineering user interface that was presented at the review. The information is distributed over four areas: The top left quadrant is used to enter the target position and telescope offsets. The top right quadrant shows the current and future telescope positions as well as the location of the azimuth cable wrap. The lower left quadrant displays information about the status of M3, M1 and the science instruments. And the lower right quadrant provides the status of M2 and the telescope enclosure.
“We have achieved a significant milestone within TMT,” says Jimmy Johnson, TMT Lead Software Engineer, who is responsible for the delivery and integration of the TCS software. “This successful PDR allows the TCS to progress to its final design phase, where the design will be further enhanced to the point that implementation and testing can begin.”
The review covered all technical aspects of the TCS design. This included requirement and interface definitions, use cases, hazard and risk analysis, failure mode analysis, system architecture, and software designs for all components such as the pointing kernel, adaptive and active optics integration, control and monitoring of all the telescope control subsystems.
An expert panel of external reviewers from the Daniel K. Inouye Solar Telescope, Gemini North Observatory, W.M. Keck Observatory, Las Cumbres Observatories and the National Research Council Canada attended the two-day review, which was held at the Pasadena Project Office on September 11-12, 2019.
The TCS is part of India’s workshare and is being managed by the Inter-University Centre for Astronomy and Astrophysics, in Pune, on behalf of the India TMT Coordination Centre. The TMT Telescope Controls group provides the overall leadership of the work package.