The Square Kilometre Array (SKA) Observatory is a next-generation radio astronomy facility that has recently entered into the construction phase, after successful completion of the design and prototyping phases during 2013–2021. Planned to be operational by the end of this decade, the SKA is expected to revolutionise astronomy by allowing cutting edge explorations in an extremely wide range of science areas, while driving the growth of many important new state-of-the-art technologies. There are more than 10 countries currentlyparticipating in the international consortium to build this facility, which will be co-located in Australia andSouth Africa with the global headquarters in the United Kingdom. Indian scientists and engineers have played a significant role since the beginning: from the definition of the SKA concept and its science case, to some important aspects of the design of the instrument and the prototyping activities. India is now getting ready to join the construction phase of the SKA with a well defined proposal for technical activities spanning a few different areas of work. Along with this, Indian astronomers are busy refining their science case for the SKA and preparing in different ways to be ready for front line science with the facility as and when it is commissioned. All these activities are coordinated by the SKA India consortium, which currently has a membership of more than 20 institutions across the country. In this paper, we describe the current status of the SKA project, and focus on India’s role—past contributions, ongoing activities and future plans.

Backed by advances in digital electronics, signal processing, computation and storage technologies, aperture arrays, which had strongly influenced the design of telescopes in the early years of radio astronomy, havemade a comeback. Amid all these developments, an international effort to design and build the world’s largest radio telescope, the Square Kilometre Array (SKA), is ongoing. With its vast collecting area of 1 km$^2$, the SKA is envisaged to provide unsurpassed sensitivity and leverage technological advances to implement a complex receiver to provide a large field of view through multiple beams on the sky. Many pathfinders and precursor aperture array telescopes for the SKA, operating in the frequency range of 10–300 MHz, have been constructed and operationalized to obtain valuable feedback on scientific, instrumental and functional aspects. This review article looks explicitly into the progression of digital-receiver architecture from the Murchison Widefield Array(precursor) to the SKA1-Low. It highlights the technological advances in analog-to-digital converters (ADCs), field-programmable gate arrays (FPGAs) and central processing unit–graphics processing unit (CPU–GPU) hybrid platforms around which complex digital signal processing systems implement efficient channelizers, beamformers and correlators. The article concludes with a preview of the design of a new generation signal processing platform based on radio frequency system-on-chip (RFSoC).

The low-frequency radio telescope of the Square Kilometre Array (SKA) is being built by the international radio astronomical community to (i) have orders of magnitude higher sensitivity and (ii) be able to map the sky several hundred times faster, than any other existing facilities over the frequency range of 50–350MHz. The sensitivity of a radio telescope array is in general, dependent upon the number of electromagnetic sensors used to receive the sky signal. The total number of them is further constrained by the effects of mutual coupling between the sensor elements, allowable grating lobes in their radiation patterns, etc. The operating frequency band is governed by the desired spatial and spectral responses, acceptable sidelobe and backlobe levels, radiation efficiency, polarization purity and calibratability of sensors’ response. This paper presents abrief review of several broadband antennas considered as potential candidates by various engineering groups across the globe, for the low-frequency radio telescope of SKA covering the frequency range of 50–350 MHz, on the basis of their suitability for conducting primary scientific objectives.