51³Ô¹Ï

Topic

On-sky Applications of Adaptive Optics: Performance Measurements and Globular Cluster Photometry

Department of Physics and Astronomy

Date & location

• Monday, May 26, 2025
• 10:00 A.M.
• Virtual Defence

Examining Committee

Supervisory Committee

• Dr. David Andersen, Department of Physics and Astronomy, 51³Ô¹Ï (Co-Supervisor)
• Dr. Kim Venn, Department of Physics and Astronomy, UVic (Co-Supervisor)
• Dr. Colin Bradley, Department of Mechanical Engineering, UVic (Outside Member)

External Examiner

• Dr. Benoit Neichel, Laboratoire d’Astrophysique de Marseille

Chair of Oral Examination

• Dr. Barbara Sawicka, Department of Mechanical Engineering, UVic

Abstract

With the dawn of extremely large optical telescopes (ELTs), there is a need to develop next-generation adaptive optics systems to fully exploit D⁴ capabilities. Adaptive optics is a technology-driven field that relies on new developments in photonics and electronics. Before an adaptive system is commissioned, it needs to be tested in both laboratory and on-sky conditions.

The thesis is structured around four key projects, each contributing to a better understanding of adaptive optics in astronomical applications. These projects focus on the performance of multi-conjugate adaptive optics (MCAO) systems, the development of an optical simulator, the design of a calibration unit for adaptive optics systems, and the analysis of the performance of next-generation adaptive optics technologies. These address technical challenges and innovative solutions to support next-generation extremely large telescopes such as the Thirty Meter Telescope and European-Extremely Large Telescope.

The first project centres on the photometric analysis of the globular cluster NGC 5904 (M5) using Gemini multi-conjugate adaptive optics systems, GeMS (Kumar et al., 2024a). MCAO is a significant advancement that offers a wider corrected field of view than traditional adaptive optics systems. M5 was selected for its extended structure, dense stellar population, and relevance in understanding stellar evolution and the Milky Way’s history. The data is from an ongoing survey of Galactic Globular Clusters within Milkyway using GeMS. The study demonstrates how MCAO systems can achieve near-diffraction-limited imaging over large fields, enabling deeper analysis of complex stellar systems. Using near-infrared photometry, our study reveals unprecedented depths within M5, showing multiple stellar populations. It addresses challenges related to crowded fields and proposes improved correction techniques that significantly enhance the accuracy of photometric data. This project highlights MCAO’s potential for future studies of globular clusters, especially with the advent of ELTs.

The second project involves the development and testing of the Herzberg NFIRAOS Optical Simulator (HeNOS), a laboratory simulator for the adaptive optics system of the Thirty Meter Telescope known as NFIRAOS. It is crucial to validate NFIRAOS performance before its deployment. HeNOS simulates wavefront corrections, allowing researchers to predict NFIRAOS’s performance in real-world conditions. HeNOS uses a micro-lenslet array to simulate guide stars. When imaged this micro-lenslet array suffers from aberrations. In this project, we developed a simple imaging system to address the cause of the aberrations.

Challenges like interference from camera windows and Talbot effect distortions are explored, and the results contribute to refining NFIRAOS’s design. This work not only ensures NFIRAOS’s optimal performance for the TMT but also provides valuable insights for other MCAO systems. The development of HeNOS is vital for the successful implementation of adaptive optics in future large telescopes.

The third project focuses on the design and implementation of a precision calibration unit for the Keck Telescope’s adaptive optics systems (Lin et al., 2020). This unit is essential for achieving precise astrometric measurements, particularly by minimizing geometric distortion. It employs a pinhole mask with known reference points to calibrate the telescope’s adaptive optics instruments, offering significant improvements over traditional on-sky calibration techniques, which are limited by observing time and atmospheric conditions. One key advancement is the ability to perform calibrations during the day, saving valuable on-sky time. By addressing geometric distortions in the telescope’s optical system, the precision calibration unit enhances the accuracy of instruments like NIRC2 and OSIRIS which are the adaptive optics instruments of Keck I and Keck II telescopes. This project lays the groundwork for future calibration systems for adaptive optics systems like NFIRAOS for Thirty Meter Telescopes to support high-precision astrometric science.

The fourth project is a performance analysis of the REVOLT (Research, Experiment and Validation of Adaptive Optics with a Legacy Telescope) instrument at the McKellar Telescope at NRC 51³Ô¹Ï, BC (Kumar et al., 2024b). REVOLT tests AO performance under real observational conditions, focusing on the instrument’s response to environmental changes and atmospheric turbulence. This project examines the opto-mechanical design of REVOLT and its integration with the telescope, analyzing the performance of the science camera and wavefront sensors. REVOLT successfully demonstrated closed-loop single conjugate adaptive optics operation with the HEART (Herzberg Extensible Adaptive Realtime Toolkit) as Real-Time controller and First Light Imaging’s C-Blue One detector as wavefront sensor. Both of these technologies will be implemented in TMT and Gemini Telescope. The research identifies residual wavefront errors, vibration-induced distortions, and overall temporal performance, providing critical data to improve the development of REVOLT. Simulations also validate the wavefront error budget, offering insights into areas for further development.

This thesis is situated at the intersection of technological innovation and scientific discovery. By addressing both this research contributes to the development of tools and techniques that will shape the future of NIR astronomy.