Thirty Years of the Square Kilometre Array

If you drive from Cambridge (UK) to Wimpole, you'll see some impressively large radio telescopes that belong to the Mullard Radio Astronomy Observatory (MRAO).

However, there's much more that's not visible from the road. Hidden behind the trees, MRAO has a prototype SKA-Low array (from before the full installation in Australia), and three dishes from a HERA prototype.

The MRAO itself has a fascinating history, notably including the discovery of the first pulsar by Jocelyn Bell using the wonderfully named Interplanetary Scintillation Array, which consisted of over four thousand dipole antennas spread across nine acres. In WWI the site was a mustard gas factory, with train station and sidings. The train tracks have long since gone, but the station building remains. Inside hangs a large, coloured but faded image titled "GALACTIC RADIO EMISSION AT 38 Mc/s". This appears to be a coloured visualisation based upon the black & white figure in pages 654-655 of a 1957 paper [0].

The above 1957 paper illustrates a survey of half the celestial sphere at 38 MHz. In comparison, this specific MeerKAT image from the article [1] appears to be a 1.28 GHz measurement focusing on the galactic center (6.5 square degrees) [2]. So it's not a 100% like-for-like comparison, but interesting nonetheless to see how much the detail has improved in the past ~70 years!

[0] https://adsabs.harvard.edu/pdf/1957MNRAS.117..652B ("RESULTS OF A SURVEY OF GALACTIC RADIATION AT 38 Mc/s")

[1] https://physicsworld.com/wp-content/uploads/2025/03/2025-02-...

[2] https://arxiv.org/pdf/2201.10541 ("The 1.28 GHz MeerKAT Galactic Center Mosaic")

	▲	timthorn an hour ago \| parent [-]
		The MRAO is a fascinating place, with things left as they were the last time an instrument was used. The floor of the hut where the array cables were aggregated for connection to the cable back to the Cavendish is covered in little plastic caps from the connectors, discarded as the instrument was being set up. The article talks about HERA; MRAO hosts the prototype for that. IIRC, they experimented with methods to build the dishes with off-the-shelf parts - such as drainpipes to build the ring.

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qwertytyyuu 4 hours ago | parent | prev | next [-]

I love physics names. A array of telescopes with collecting are of 1 square kilomter. Square kilometer array. Makes it so clear what it is.

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JamesTRexx 4 hours ago | parent | prev [-]

"Makes it so clear what it is."

Well.., I've been more busy with writing code lately so that the first question coming to mind was, how many bytes is an array of one square kilometer? And I assume it's a two-dimensional array.

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Etheryte 3 hours ago | parent [-]

It's a radio telescope, how would you imagine translating that to bytes?

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stargazer-3 3 hours ago | parent | next [-]

Here's an article mentioning the data transmission rates in SKA, up to 20 terabits per second:

https://www.skao.int/en/explore/big-data

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touisteur 2 hours ago | parent | prev [-]

Every sensor in the array is sampling at frequency, so - first order - you can use that sampling frequency and the sample size, you get an idea of the input bandwidth in bytes/second. There are of course bandwidth reduction steps (filtering, downsampling, beamforming)...

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jacquesm 2 hours ago | parent [-]

Aren't they sampling broadband for later processing?

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touisteur 10 minutes ago | parent [-]

On SKA from what I understand they're sampling broadband but quickly beamform and downsample as the datarates would be unsustainable to store over the whole array.

	▲	jacquesm 6 minutes ago \| parent [-]
		Right, that makes sense, you'd be looking at an insane amount of data across the ranges that these sensors can look at. But they would still need to preserve phase information if they want to use the array for what it is best at and that alone is a massive amount of data.