The new golden age of radio astronomy

By Patrick A. Woudt, Inter-University Institute for Data Intensive Astronomy, Department of Astronomy, University of Cape Town, South Africa, and Anthony J. Beasley, National Radio Astronomy Observatory, United States

The 1950s and 1960s are generally considered the golden age of radio astronomy. This was the foundational era that saw the establishment of iconic radio telescopes and the development of innovative techniques, resulting in groundbreaking discoveries.

Presently we are experiencing a second golden age of radio astronomy, enabled by technology-driven advances associated with the fourth industrial revolution that allow digital signal processing at petabyte scale, supported by global networks of scientific and technological collaborations and planet-wide networks of distributed telescopes and data centres.

Technology-driven advances

Radio telescopes routinely operate jointly through a technique called Very Long Baseline Interferometry’ (VLBI) that combines separately located telescopes across continental scales. An excellent example of a globally distributed network of radio telescopes is the Event Horizon Telescope (EHT).

Operating at sub-millimetre wavelengths and with telescopes spread across the furthest corners of the globe, the EHT achieves unprecedented angular resolution. Consequently, it was able to image the supermassive black hole at the centre of our Milky Way for the very first time in 2022.

Innovations in antenna design – such as the Gregorian offset antennas for South Africa’s MeerKAT and SKA-Mid facilities, as well as a next-generation prototype in the United States – and the ability to deal with overwhelming data rates have led to unprecedented improvements in survey speed. The resulting instantaneous sensitivity and has opened up new windows on the radio skies.

Today’s data rates are staggering: the joint Square Kilometre Array (SKA) is expected to deliver data to central data processors in Australia (SKA-Low) and South Africa (SKA-Mid) at an average rate of 8 terabits per seconds.

Planned new facilities and capabilities

Over the last 15 years, a tremendous number of new radio telescopes and arrays have been established, while existing ones have undergone major upgrades, covering the full spectral range from 10 megahertz (MHz) for the pan-European LOFAR to 950 gigahertz (GHz) for the multinational, Chile-based ALMA, with telescopes such as MWA and ASKAP (Australia), MeerKAT (South Africa), FAST (China), and the VLA (U.S.) covering the intermediate 0.1–50 GHz frequency range.

All these telescopes and arrays are breaking new scientific and technical ground in their respective frequency range.

The MeerKAT radio telescope array, for instance, is producing truly transformative images of the Galactic Centre, the central point of our Milky Way galaxy.

The combined SKA Observatory (SKAO) – currently under construction in Africa and Australia, with science commission underway – will form the world’s largest radio telescope array, operating in the ranges of 50–350 MHz (SKA-Low: Australia) and 350 MHz–15.4 GHz (SKA-Mid: South Africa). The SKA Observatory was established as an inter-governmental organization in 2019 and presently has 14 member states. This is a 2.1 billion Euro project.

The Atacama Large Millimeter/submillimeter Array (ALMA), located in Chile, remains one of the leading ground-based instruments available to the global astronomy community, observing at millimetre and sub-millimetre wavelengths. A wideband sensitivity upgrade of ALMA is underway, seeking to increase data acquisition capabilities and observing capabilities later this decade.

Over the past decade, the US radio astronomy community has pursued a next-generation Very Large Array (ngVLA) concept, seeking to combine Very Large Array and Very Long Baseline Array technical capabilities into a single instrument with five times more collecting area, operating from 1 GHz to 116 GHz across all angular scales from compact to continental scales.

The ngVLA project was well-ranked in the US Decadal Survey of Astronomy and Astrophysics, and project office activities continue, seeking a construction start later this decade.

Data-intensive radio astronomy driving innovation

A critical part of any data-driven scientific endeavour is ensuring that collected data are appropriately prepared for robust scientific analyses. Astronomical data, which are inherently complex, noisy, and high-dimensional, provide challenging use cases to improve the automation of data preparation.

The SKA is expected to archive 700 petabytes of data each year; at these data rates, automating data processing is essential.

Artificial intelligence (AI) provides powerful new tools to help automate data processing and will likely be integral to signal processing for the next generation of global observatories across the electromagnetic spectrum. However, bringing such tools to scale remains a challenge, especially with increasing data rates and complexity, making this an active area for research and development.

The CARTA visualization tool is a good example of visual analytics developed for the era of big data and federated cloud compute.

The need for quiet skies

The radio skies are increasingly getting noisy, and this presents serious concerns from modern day radio astronomy. In 2022, the International Astronomical Union (IAU) established the Centre for the Protection of Dark and Quiet Skies (CPS), co-hosted by the US National Science Foundation’s NOIRLab (responsible for optical/infrared astronomy) and SKAO (radio astronomy), aiming to preserve Earth’s best astronomy sites and manage the impact of large satellite constellations on the dark and quiet skies.

Numerous efforts are already underway to mitigate signal interference and protect radio astronomy from the massive growth of communication technologies.

At the upcoming World Radiocommunication Conference (WRC-27) being organized by the International Telecommunication Union (ITU) from 18 October to 12 November 2027 in Shanghai, China, the digital and space communities will come together from around the globe.

This is our opportunity to discuss how best to protect the quiet radio spectrum and preserve critical parts of the spectrum for humanity’s exploration of the cosmos.

Header image credit: I. Heywood/SARAO (2022)