http://hdl.handle.net/2248/5842 2026-04-15T14:21:39Z http://hdl.handle.net/2248/8513 Feasibility Study for Adaptive Optics Implementation on the 2m Himalayan Chandra Telescope Gurwinder Singh Hundal Atmospheric turbulence in the Earth’s atmosphere significantly impacts the performance of ground-based telescopes. Adaptive Optics (AO) has emerged as an indispensable technology in ground-based astronomy, revolutionizing our ability to observe celestial objects with unprecedented clarity. Recognizing the increasing importance of AO in enhancing the capabilities of telescopes, it is imperative for the Indian Institute of Astrophysics (IIA) to explore the potential integration of AO into its 2m Himalayan Chandra Telescope (HCT) located in hanle, where the median seeing condition is 1 arcsec. This project focuses on the comprehensive study of implementing AO on the HCT and is based on end-to-end AO simulations. Our study identifies that the most suitable AO system for HCT is a Dual Adaptive Optics system, incorporating both Natural Guide Star (NGS) and Rayleigh Laser Guide Star (LGS) techniques. Deformable mirror and wavefront sensor are identified as two crucial components in any AO system, and this study includes a meticulous quantification process to inform the selection of these components. Our AO simulations indicate that a Shack-Hartmann Wavefront Sensor (SHWS) with an 11 x 11 lenslet array and a Micro Electro-Mechanical System (MEMS) deformable mirror with 12 x 12 actuators provide optimal Strehl performance in the R, J, H, and K bands. For the LGS AO system, we selected a 10 W UV pulsed laser to generate a bright laser beacon, defining a range gate length of 800m at a 10 km altitude above hanle. We find that the limiting magnitude for a bright guide star is 9th magnitude, and a faint star upto 15th magnitude is sufficient for tip-tilt sensing. Sky coverage, which is the probability of finding a suitable guide star near the science target, is a critical performance metric. It depends on guide star magnitude, guide star density, and the separation between the guide star and the science target. Using the Besancon Model for guide star density in optical wavelengths, our calculations show that sky coverage for NGS AO is less than 1 %, whereas it is approximately 100 % for LGS AO, including tip-tilt sensing. Due to the inadequate sky coverage with NGS AO alone, the implementation of a dual adaptive optics system is necessary. This integration aims to significantly enhance the observational capabilities of the HCT, providing valuable insights for advancing ground-based astronomy at the challenging hanle site. Thesis Supervisor Dr. Ravinder Kumar Banyal © Indian Institute of Astrophysics 2024-07-01T00:00:00Z http://hdl.handle.net/2248/8052 A tip-tilt correction system for the 30-inch telescope Parvathy, M Atmospheric turbulence degrades the image formed by ground-based telescopes. It causes the image to be spread over a large area known as the seeing-disk in a typical long exposure. In a short exposure, the image is spread into a bunch of speckles, each of angular size equal to the diffraction-limit. In short, there are two distinct components to image degradation. One is the motion of the overall image, and the other is the blurring of the image. The aim of this project is to develop a system that will arrest the overall motion of the image. The main objective of this project is to design, deploy and test a tip-tilt system (as a black box) at the 30-inch telescope at the Vainu Bappu Observatory (VBO), Kavalur, while at the same time retaining the existing on-axis imaging instrument with minimal change. In other words, the aim is to augment the 30-inch telescope with a tip/tilt correction facility as an additional, optional feature. Also, this project aims to test the ability to ”off-load” tip/tilt correction (provided by the fast piezoelectric actuator) periodically (e.g., every 1 minute) to the telescope control system (along the RA. and DEC. axes) and thus enabling tip-tilt correction from the piezoelectric actuators for long duration. (e.g., several hours). The major focus is to gain expertise and confidence in developing a tip-tilt correction system so that it can be easily extended to the 90-inch telescope having a similar f-number. Thesis Supervisor Dr. R. Sridharan 2022-07-01T00:00:00Z http://hdl.handle.net/2248/8051 Design and development of a digital micromirror device (DMD) based multi-object spectrograph (MOS) for the Indian spectroscopic and imaging space telescope (INSIST) Jaini, Akhil The coming decade in astronomy focuses on large widefield imaging and spectroscopic surveys. No widefield imaging facility extends to the UV region, which represents an important window into a wide variety of astrophysical problems. Also, spectroscopy would be essential to understand the physical and chemical properties of several stars, star forming regions and galaxies. INSIST (the INdian Spectroscopic and Imaging Space Telescope) is a proposed future space UV mission to be able to observe in the UV (150nm-300nm), u (300nm-400nm) and g (400nm550nm) bands. Multi Object Spectrograph (MOS) is one of the key instruments proposed for INSIST to work in the UV band and efficiently obtain spectroscopic data for a large number of objects at a much shorter timescale. MOS is designed with a programmable reflective slit through a Digital Micromirror Device (DMD), which is an innovative opto-electro-mechanical component consisting of a 2-dimensional array of tiny mirrorlets that can be flipped to two orientations by command. DMD is to be used in a telescope in the UV region for MOS application for the first time in space. Hence, it is necessary to understand and study the functionality of DMD and its suitability to space telescopes. As part of this project, a spectrograph was designed with the DMD and set up on an optical bench in the laboratory. The performance and various parameters of the DMD were tested and the results are reported. Models were made for fabrication of an assembly to be tested at the J. C. Bhattacharya Telescope (JCBT) at Vainu Bappu Observatory in optical region. Thesis Supervisors S. Sriram and Prof. Annapurni Subramaniam 2022-07-01T00:00:00Z http://hdl.handle.net/2248/8050 Design and Development of DMD Controller Interface for INSIST Jain, Shubhangi The INSIST (Indian Spectroscopic and Imaging Space Telescope) is a UV-optical 1m class telescope expected to produce high quality imaging and moderate resolution spectra of astronomical sources. A DMD is an optical microelectrical-mechanical system (MEMS) that contains an array of highly reflective aluminum micromirrors. A Digital Micromirror Device (DMD) will be used in front of the onboard spectrograph for sampling light coming from astronomical sources of interest in the light path. The role of DMD here is similar to the slit mask used in the conventional spectrographs. DMD comprises tiny mirror lets arranged in the form of pixels which can be flipped between two predefined positions by applying digital signals. Here DMD acts as a slit for spectrograph with capability of forming multiple slits. This feature enables Multi Object Spectrograph (MOS) capability. By selecting the appropriate pixels on the DMD the required slit mask shape can be configured. The INSIST DMD Controller consists of three levels of cards stacked on one another. The base card being the User Interface Controller (UIC) FPGA Card, middle one being Chipset Card and top most card is DMD DLP9500UV Card. In this project, a controller interface module to transfer the slit mask pattern to the DMD device is under development. Here the user interface controller (UIC) FPGA card is capable of generating and receiving signals required for Chipset Card and communicating with external users. DMD Chipset Card mainly consist of DLPC410 controller chip, DLPR410 PROM chip on board system clock of 50MHz and DLPA200 (2x) driver chips for DLP9500UV. This controller interface takes the data from the user, which contains how many rows and columns of DMD to be flipped for particular observation. DMD DLP9500UV card has 1920X1080 micromirror that can be tilted by +/-12 and the positive (+) state is tilted toward the illumination and is referred to as the "on" state. Similarly, the negative (–) state is tilted away from the illumination and is referred to as the "off" state. At the initial stage of development, this slit mask input will be directly in the form of row and column numbers. The user interface FPGA card is responsible for receiving user data in terms of 1920 × 1080 Array states corresponding to Micromirror states. Each element in this data array is 1-bit binary. This received data needs to be forwarded to DLPC410 controller at the clock rate of 400 MHz At a later stage we will derive the row and column based on the acquired image from the imaging channel. This module will convert Row and Column data in a format which is suitable to the DMD chipset and transfer it to chipset with suitable command format. Controller interface module will receive telemetry of the DMD chipset and display the health of the DMD. Thesis Supervisors Amit Kumar and Dr. Prasanna Deshmukh 2022-07-01T00:00:00Z