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Benjamin van Ommen – A telescope for a bargain

A radio telescope that costs less than a few hundred euros. For his bachelor research project, physics and astronomy student Benjamin van Ommen created a very affordable alternative for more expensive telescopes that work with electronic hardware. Van Ommen: ‘Our creation could be very valuable for education, as students rarely have hands-on experience with radio telescopes!’

Physics in the real world

‘What gives me the most satisfaction in physics, is the ability to impact the physical world through abstract mathematics and physical models,’ says Van Ommen. ‘I like to apply what I learned to “the real world”. And that is exactly what he did during his bachelor research project. Under the guidance of Michiel Brentjens from the Netherlands Institute for Radio Astronomy he created an affordable radio telescope for less than a few hundred euros in material costs.

Dongles for astronomy

The key to making this telescope at such a low cost were so-called SDR USB dongles. SDR stands for Software Defined Radio. ‘Normally, radio telescopes work by processing the radio signal they receive with some electronic hardware, for example producing a sound,’ explains Van Ommen. ‘In contrast, SDR processes the radio signal using software. SDR is therefore very flexible: we can change the way we process the radio signal by simply editing a few lines of code.’

‘I like to apply what I learned to “the real world”. Therefore, I have designed and built an affordable radio telescope that could be very valuable for education.’

The SDR USB-dongles sample the radio signal and forward the samples to a computer. The dongles are commercially sold for receiving radio stations, but Van Ommen and his supervisor believed it might also be possible to use them for radio astronomy. To test whether this was the case, Van Ommen built a test set-up on the roof of the Huygens building of Leiden University. Van Ommen: ‘We used two antennas, forty metres of cable, four radio amplifiers, two radio filters, a laptop, and two SDR USB dongles. This set-up allowed us to track the sun’s position as it moved across the sky. The ratio between the strength of the signals and level of background noise is presumably even strong enough to detect some extra-solar radio sources!’

Telescopes for students

Since the dongles are mass-produced, they are very cheap, only 15 euros. Furthermore, used antennas are favoured by radio amateurs, and radio amplifiers and filters can also be acquired at an affordable price. ‘Of course, no groundbreaking astronomical discoveries can be made with this set-up,’ Van Ommen says. ‘Still, it is very valuable in education, as students rarely have hands-on experience with radio telescopes, especially not with one they can completely set-up themselves!’

Van Ommen himself has recently moved to Zürich, Switzerland, to study quantum engineering at the ETH (Eidgenössische Technische Hochschule). This is a new master’s programme focussed on the application of quantum mechanics to technology, for instance in quantum computers and quantum sensing.

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