Astrophysics Seminar

Dish Surface Characterisation for CHORD and HIRAX using Metrology and Electromagnetic Simulations

Speaker: Aditya Karigiri (McGill University)

Date and time
Venue
Library Block Lecture Hall

Abstract

The Canadian Hydrogen Observatory and Radio-transient Detector (CHORD) and the Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) are next-generation radio interferometers designed for 21-cm intensity mapping to measure baryonic acoustic oscillations, while also enabling studies of fast radio bursts and pulsars. HIRAX, located in the Karoo desert (South Africa), operates from 400–800 MHz (0.8 < z < 2.5), while CHORD, based at the Dominion Radio Astrophysical Observatory (DRAO) in Canada, spans 300–1500 MHz (z < 3.7). They will deploy 512 (HIRAX) and 256 (CHORD) six-meter composite dishes with f/0.21 focal ratio, arranged in redundant configurations. Achieving the required precision for 21-cm cosmology demands sub-millimeter mechanical tolerances across the arrays. 

To support this, the Deep-Dish Development Array (D3A) was deployed at DRAO and serves as a testbed for feed design, dish fabrication, mounts, and front-end electronic systems of HIRAX and CHORD. Systematics related to the reflector surface and receiver perturbations are among the critical factors impacting the redundancy requirements and will be the central focus of this talk. I will begin with an overview of CHORD and HIRAX, followed by my work on quantifying dish surface deformations using precise metrology techniques, emphasizing the role of redundancy in achieving the scientific objectives. I will show how these surface measurements can be incorporated into electromagnetic simulations to evaluate their effects on reflector beam patterns. Finally, I will explain how these systematics can be propagated to cosmological simulations in order the access the recovery of the 21-cm signal.

Short Biography
Aditya Karigiri is a PhD student in Physics at McGill University, specializing in 21-cm cosmology and radio astronomy. He holds a bachelor’s degree in Mechatronics Engineering from Hindustan University, Chennai, and a master’s degree in Physics from McGill. Following his undergraduate studies in 2022, Aditya worked as a visiting student at the Raman Research Institute, contributing to the VNA section of the PRATUSH receiver. At McGill, he served as Vice President Academics of the Graduate Association of Physics Students, where he helped foster a supportive academic environment and connected graduate students with key resources. Beyond academia, Aditya is also an analog astronaut. He served as Crew Executive Officer and Crew Astronomer during Mission 292 at the Mars Desert Research Station, organized by the Mars Society USA and Australia. He later joined the Between Two Worlds crew by Protoplanet, participating in a field expedition to Tso Kar, Ladakh, aimed at establishing an analog science station and observatory in the high-altitude deserts of the Himalayas. His personal interests include playing Carnatic violin, and learning ancient languages.