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Vibration measurements at the Gemini South observatory were conducted in February 2020, in order to experimentally determine acceleration transfer functions between the instrument support structure and key locations on the telescope, including the optics. An electrodynamic exciter was used to impart known dynamic forces into the telescope structure. Acceleration responses were measured at numerous locations on the telescope, including on M1 and M2, using the facility Vibration Monitoring System (VMS) accelerometers. This paper describes the equipment, the experimental approach, and will summarize initial results from these tests., Ground-based and Airborne Telescopes VIII, December 14-18, 2020, Online Only, United States, Series: Proceedings of SPIE

The adaptive optics system for the Thirty Meter Telescope (TMT) is the Narrow-Field InfraRed Adaptive Optics System (NFIRAOS). Recently, INO has been involved in the optomechanical design of several subsystems of NFIRAOS, including the instrument selection mirror (ISM), the beam splitter (NBS), and the source simulator system (NSS) comprising the focal plane mask (FPM), the laser guide star (LGS), and natural guide star (NGS) sources. This paper presents an overview of these subsystems and the optomechanical design approaches used to meet the optical performance requirements under environmental constraints., Optomechanical Engineering 2017, 9 - 10 August 2017, San Diego, California, United States

The Dish Verification Antenna 1 (DVA-1) is a 15m aperture offset Gregorian radio telescope featuring a rim-supported single piece molded composite primary reflector on an altitude-azimuth pedestal mount. Vibration measurements of the DVA-1 telescope were conducted over three days in October 2014 by NSI Herzberg engineers. The purpose of these tests was to measure the first several natural frequencies of the DVA-1 telescope. This paper describes the experimental approach, in particular the step-release method, and summarizes some interesting results, including unexpectedly high damping of the first mode over a narrow range of zenith angles.

The early-light facility adaptive optics system for the Thirty Meter Telescope (TMT) is the Narrow-Field InfraRed Adaptive Optics System (NFIRAOS). The science beam splitter changer mechanism and the visible light beam splitter are subsystems of NFIRAOS. This paper presents the opto-mechanical design of the NFIRAOS beam splitters subsystems (NBS). In addition to the modal and the structural analyses, the beam splitters surface deformations are computed considering the environmental constraints during operation. Surface deformations are fit to Zernike polynomials using SigFit software. Rigid body motion as well as residual RMS and peak-to-valley surface deformations are calculated. Finally, deformed surfaces are exported to Zemax to evaluate the transmitted and reflected wave front error. The simulation results of this integrated opto-mechanical analysis have shown compliance with all optical requirements.

Radio telescopes striving for orders of magnitude more sensitivity in the cm-wave band require reflector antennas with high performance at low relative cost compared to conventional approaches. The Composite Applications for Radio Telescopes (CART) programme at the National Research Council's (NRC's) Dominion Radio Astrophysical Observatory, near Penticton Canada has been investigating ways to build such telescopes since 2005. In 2010 a collaboration between NRC and the US-Technology Development Project (US TDP) was formed to develop a prototype 15m Gregorian offset antenna for the Square Kilometre Array (SKA). The telescope uses NRC's composite carbon fibre reflector technology to implement the highly optimized shaped optics design and innovative mechanical concepts developed by the US TDP. The result is Dish Verification Antenna-1 (DVA1), a next generation antenna that has exceptional sensitivity (> 9 m2/K), with low monotonically decreasing far out sidelobes (< −50 dB), and high stability over environmental conditions. As well, it is modular, highly reliable, and can be produced at competitive cost using mass production techniques., 2015 1st URSI Atlantic Radio Science Conference (URSI AT-RASC), 2015-5-16 - 24, Gran Canaria, Spain

We describe measurements of both the vibration forces imparted by various types of observatory equipment, and the transmission of these forces through the soil, foundations and telescope pier. These are key uncertainties both in understanding how to mitigate vibration at existing observatories and for developing a vibration budget in the design of future observatories such as the Thirty Meter Telescope. Typical vibration surveys have measured only the resulting motion (acceleration); however, this depends on both the source and the system being excited (for example, isolating equipment results in less force being transmitted, but greater motion of the equipment itself). Instead, here we (a) apply a known force input to the pier from a shaker and measure the response at different locations, and (b) use isolator properties combined with measured acceleration to infer the forces applied by various equipment directly. The soil foundation and pier transmission can then be combined with a finite element model based vibration transmission analysis to estimate the optical consequences. Estimates of plausible source levels supports the development of a vibration budget for TMT that allocates allowable forces to the sources of vibration; this is described in a companion paper., Ground-Based and Airborne Telescopes V, June 22-27, 2014, Series: Proceedings of SPIE; no. 9145

NFIRAOS is a diffraction-limited, near-IR, multi-conjugate adaptive optics system. We present an overview of the optical design and design drivers, with particular attention given to the challenges of the laser guide star wavefront sensing optics.