| Abstract: India has played a pioneering role in radio interferometry, with facilities such as the Ooty Radio Telescope (ORT) and the Giant Metrewave Radio Telescope (GMRT) delivering internationally competitive science, and with SKA India poised to extend high-angular-resolution radio astronomy to unprecedented scales. However, many fundamental stellar properties surface structure, rotation, limb darkening, and localized inhomogeneities, are most directly probed at optical and near-infrared wavelengths. Achieving comparable angular resolution in the optical remains a major challenge.
Conventional Michelson-type optical interferometers, including facilities such as CHARA, have demonstrated sub-milli-arc-second resolution using baselines of a few hundred meters. Yet extending these techniques to resolve finer stellar surface features faces significant technical and atmospheric limitations. An alternative approach is offered by Hanbury Brown Twiss (HBT) Interferometry, a photon-correlation technique that is inherently robust against atmospheric turbulence and optical path imperfections, and is well suited for ultra-long baselines.
In this talk, I outline a staged strategy toward optical intensity interferometry in India. As an intermediate and accessible step, Speckle Interferometry (SI) using existing CCD/CMOS detectors on modest optical telescopes can already deliver diffraction-limited information and serve as a testbed for high-resolution analysis techniques. Building on this foundation, I discuss the prospects for implementing optical Intensity Interferometry (II) using Cherenkov telescope arrays in India, enabling angular resolutions far beyond current optical interferometers for bright stellar targets.
By integrating speckle interferometry, intensity interferometry, and a distributed optical infrastructure, India has the opportunity to extend its interferometric legacy from radio to optical wavelengths and emerge as a major contributor to high-resolution stellar surface imaging. |
