18-09-2023 | By Robin Mitchell
Detecting radio signals from space can be tricky business, especially when considering that large portions of modern life are dependent on radio-based systems that can all interfere with radio telescopes. A new radio telescope being developed in the Australian outback has deployed electronic assemblies that have been specially designed to be immensely quiet so as not to interfere with research. What challenges do radio telescopes face, what did researchers develop, and what challenges will radio telescopes face in the future?
The Low-Frequency Telescope of the Square Kilometer Array in Australia possesses the capability to identify the faintest radio signals emanating from the farthest corners of the cosmos. (Image credit: SKAO)
What challenges do radio telescopes face?
Ever since the dawn of time, mankind has looked up and gazed at the stars, using them to tell stories, help with navigation, and inspire all kinds of dreams. Despite the fact that we now know what stars are, we still look up at the heavens in amazement as we contemplate our place in the universe.
To help our understanding of the universe, astronomers have developed all kinds of telescopes that can operate at different wavelengths of light. Visible wavelength telescopes are great for seeing details in objects such as planets, nebulas, and galaxies, while x-ray and gamma telescopes can be great for seeing strong emissions from black holes and quasars.
When it comes to radio telescopes, being able to see such long wavelengths not only allows us to see through dust clouds but also helps us see the structure of the early universe. This is because light from the distant past becomes redshifted as it travels through expanding space. Simply put, the expanding universe “stretches” photons, which in turn shifts their frequency, so much so that visible light eventually becomes radio waves.
As these radio signals are incredibly weak, it is essential that radio telescopes are large enough to capture as much energy as possible, use amplifiers with a large gain, and reduce noise and interference as much as possible. While a radio telescope in space would be able to achieve much of this with ease, putting large telescopes into space is no small feat, as demonstrated by Hubble and the James Webb Telescope.
Thus, most radio telescopes are found on the surface of Earth, where they can be extraordinarily large. Luckily, the Earth’s atmosphere is also mostly translucent to radio waves, meaning that researchers face little attenuation as radio waves hit the Earth.
But one major problem that radio telescopes face is interference. As modern life is highly dependent on electronics and radio systems, it is very difficult to get far away enough from sources of radio waves. Considering that radio telescopes are extremely sensitive, it only takes a small Bluetooth device 10 miles away to potentially interfere with a telescope array (keep in mind that such telescopes need to amplify the radio signal from a source that can be millions of lightyears away).
So far, the only practical solution to this has been to install radio telescopes in extremely remote areas such as the Australian Outback or the forests of South America. Furthermore, researchers will often be required to obtain results from multiple telescopes so that sources of noise and potential interference can be triangulated and confirmed. This is one of the core reasons why telescopes that detect a potential signal need to confirm that with other telescope operators.
Electronics used in the new telescope are quieter than a smartphone on the moon
It clearly goes without saying that as interference needs to be reduced as much as humanly possible, the electronics used in such installations must also be extremely quiet. Achieving this can be done in a multitude of different ways, including shielded enclosers and cables, well-designed circuits, and careful component selection.
However, one area of electronics that can be particularly troublesome is power management. As efficiency is an important aspect of electronic design, the use of switch mode topologies is often popular due to its ability to minimise losses in switching devices. However, such circuits can easily emit large amounts of interference, which is why designers will often try to avoid using them in commercial products wherever possible (in favour of linear regulators, especially when microcontrollers are involved).
If such power circuits can be such a burden in a commercial environment, imagine how they must be in a radio telescope environment. Recognising the challenges faced by radio telescopes, researchers from the International Center for Radio Astronomy Research (ICRAR) have recently developed a whole range of power and signal distribution devices for the upcoming Square Kilometre Array low-frequency telescope in Australia that specialises in ultra-low interference.
The telescope itself, which began construction in 2022, will consist of 131,072 dipole antennas and, when complete, will be able to hear the faintest of signals in deep space. For perspective, a recent study has shown that the completed radio array will be so sensitive that it will be able to hear the electronic hum from Starlink satellites as they fly by, which orbit 550km above the array.
To make the new electronic devices used by the radio array as quiet as possible, the researchers not only selected radio-quiet parts but also developed a special wrapping that prevents any electromagnetic radiation from leaking into the surrounding environment. According to the researchers, the devices have been made so quiet that a smartphone on the moon’s surface would provide more interference on Earth than standing next to the device.
The Square Kilometre Array: A Revolutionary Leap in Radio Astronomy
One of the most ambitious projects in the field of radio astronomy is the Square Kilometre Array (SKA). This next-generation radio telescope is being developed with the aim of answering some of the most perplexing questions about our universe. According to Space.com, the SKA will be the most powerful radio telescope ever built, with scientific operations expected to begin in 2028–29.
What challenges will radio telescopes face in the future?
As technology continues to progress, radio telescopes will face increasing difficulties from interference. For example, the expansion of internet services into space will not only affect observations from visual telescopes but produce strong sources of radio waves that will undoubtedly upset radio telescopes.
The inclusion of more wireless networks in cities also carries risks to radio telescope arrays. Even if higher frequencies are used (which have a shorter range), the use of greater radio powers will undoubtedly raise the noise floor for any nearby radio telescope. This is also true for the steadily increasing popularity of long-range radio communications technologies such as LoRa, which are specifically designed to send signals across vast distances.
Unless radio telescopes can be placed on the far side of the moon (which is tidally locked and never in view of the Earth), radio telescopes of the future will have to continue managing sources of radio interference, and as society develops, sources of noise will only become more prevalent.
How the SKA Plans to Overcome Interference Challenges
The SKA is being constructed in remote areas to minimise interference. In Australia, it will consist of 131,072 low-frequency antennas, known as SKA-Low. These antennas will be able to detect radio waves emitted by objects in the most distant universe. Space.com reports that the SKA telescopes will be able to produce images with 10-100 times the fidelity of current instruments.