Dr Ajith Sampath received a PhD in Mathematics for his ground-breaking research into the complex instrumentation challenges of next-generation radio telescopes.
Supervised by Professor Kavilan Moodley, Sampath’s thesis titled: ‘Beam Characterisation and Foreground Removal for Intensity Mapping Experiments’, represents a major contribution to radio astronomy and cosmology.
Sampath’s work focused on the flagship HIRAX (Hydrogen Intensity and Real-time Analysis eXperiment) telescope, which aims to explore one of the greatest mysteries in physics: dark energy. His research focused on developing new mathematical methods to model and correct for the influence of the telescope’s instrument beam, namely, the way the antenna responds to signals from different directions and frequencies.
“HIRAX’s scientific goal is to detect faint radio signals from the universe’s ‘teenage years’ to understand the nature of dark energy,” explained Sampath. “But these signals are incredibly faint, and even small imperfections in the telescope’s design can interfere. My research focused on characterising and correcting these effects so that the cosmological signal can be accurately extracted.”
Sampath applied his techniques not only to the HIRAX array, but also to the Atacama Cosmology Telescope (ACT), where he investigated how beam asymmetries and polarisation leakage affect data quality. “I developed mathematical models to describe the angular and spectral structure of the beam, which are crucial for removing foreground contamination and improving the precision of the power spectrum measurements,” he said.
Originally from a small village in India, Sampath’s journey into the world of astronomy began during his master’s studies. “I had the opportunity to attend a summer school that included visits to several observatories across India. That experience, combined with my long-standing interest in cosmology, sparked my curiosity in observational radio astronomy,” he recalled.
UKZN became a natural choice when he began looking for institutions to pursue a PhD. “As an international student eager to join a strong research environment, UKZN offered everything I was looking for – expertise in astronomy, access to cutting-edge resources and an incredibly supportive academic culture,” said Sampath. “Working under Professor Moodley on the HIRAX project opened up extraordinary opportunities, including my current postdoctoral research position at the University of Geneva.”
Now based in Switzerland, Sampath continues to contribute to HIRAX while broadening his research in the field. “I plan to stay in academia and tackle even more complex challenges. I’ve always found problem-solving in astronomy incredibly fulfilling, and I feel truly delighted with where I am today,” he said.
The impact of Sampath’s research is far-reaching. “Understanding the instrument is just as important as understanding the cosmos,” he explained. “My work contributes to improving the design and data analysis strategies for current and future instruments, including global efforts like the Square Kilometre Array (SKA) being built in the Karoo. It’s vital for us to quantify and remove the effects introduced by the telescope itself in order to measure the universe with precision.”
“Ajith has made a key contribution in his PhD towards the emerging field of hydrogen intensity mapping in cosmology,” said Moodley. “He studied the impact of the telescope antenna pattern on the leakage of the bright galaxy signal, thereby contaminating the faint cosmological signal. The novel methods he has developed will play a key role in the first detections of the hydrogen intensity mapping signal.”
Despite his many academic achievements, Sampath remains grounded and thankful. “My brother, Aravinth, played the most important role in making my Higher Education studies possible. He carried many burdens so I could focus on my education, and no words can express my gratitude,” he said. “I am also deeply grateful to Professor Moodley for his guidance, to the National Research Foundation for supporting my research through a doctoral scholarship, and to my parents, wife, family and friends for their constant support.”
Away from the world of cosmology, Sampath enjoys watching football, anime and playing video games. “During my PhD, I also played cricket every weekend with friends as it helped me keep a good balance,” he said.
Reflecting on his academic journey, Sampath shared a final thought: “Mathematics and science have profoundly shaped my life. I still remember the days when I had no internet access and had to rely on library books. That journey took me from a small village to earning a Doctorate in Science. It taught me perseverance, critical thinking and the sheer joy of discovery.”
Words: Sally Frost
Photograph: Supplied