RFI-shielded containers for the MeerKAT project

After I’d written that blog post about the arrival of the RFI-shielded containers at the South African Astronomical Observatory (SAAO) in Observatory on 06 May, I was asked by the SKA’s media department whether I would be willing to attend the informal function at the SAAO on Friday 29 May to celebrate the arrival of the containers, and to take some nice photographs, chat to the people there and then write a short article about the containers and their relevance for the Karoo Array Telescope (MeerKAT) project.

As I was keen to attend anyway, and thought it would be a good challenge to do some formal writing, I didn’t hesitate to say yes.

In my car on the way to the SAAO on the day of the function, though, I was fighting down a sense of increasing panic, which rather unnerved me. Here I was going to an event I was eager to attend, looking forward to speaking with people I already knew, respected and liked, and with the permission – nay, the injunction! – to take as many photographs as I wanted (Awesome! Can’t imagine anything better!).

And all I had to do afterwards was to write about the experience, which I would have done for my blog anyway!

I love writing and I love taking photographs (although I also find it rather hard to delete the ‘bumf’, much to the mounting despair of my “IT manager” who keeps tabs on the decreasing available storage space on my hard drive).

So why was I in such a tizz?

And then it dawned on me: I was experiencing performance anxiety.

On reflection, I realised that, when I write a blog post, I don’t think of someone actually reading, judging or, God forbid, criticizing what I write. I don’t agonise about the structure of the post, or whether I’ve used good English and put in the correct punctuation, or split my poor infinitives yet again. I ‘just’ tell the story, and share my thoughts and feelings. It’s fun, and I love the freedom of just writing.

This time, though, I had to make sure that I took good photos, spoke to the right people and obtained the correct facts. I had a responsibility to get everything right. Thankfully, my significant other was around so that I could cross-check the facts with him before I submitted my draft article. But it was surprisingly stressful.

I realised that being a journalist is definitely not as easy as it looks from the outside.

The function itself took place in the building that houses the fascinating McClean telescope.

McClean telescope building

McClean telescope building

And this is what the telescope looks like (sorry, it’s not the best of pictures!):

McClean telescope

McClean telescope

The building also houses a museum that is filled with the most intriguing and mysterious equipment imaginable.

Astronomy museum

Astronomy museum

I must find out whether they offer a tour of the museum, as I have no idea what all these things are or what they are used for. I hope one doesn’t have to be an astronomer to understand it all.

Mysterious pieces of equipment

Mysterious pieces of equipment

I learned quite a bit, though.

Richard explained to me, for instance, that the radio waves from pulsars, quasars, stars, galaxies and other celestial objects in the universe are extremely weak and that they compete with man-made radio waves or radio frequency interference (RFI). Most electronic appliances, for example, cell phones, laptops, microwave ovens, TVs and PCs, emit RFI. RFI is regarded by many as the greatest threat to radio telescopes all over the world.

The four containers from the outside

The four containers from the outside

And that is precisely why the MeerKAT antennas are being sited in a particularly isolated part of the Northern Cape Province. It is also the reason for the drafting of the South African Astronomy Geographic Advantage Bill (for more info this, see here; a copy of the draft bill can be downloaded here):

“The Bill’s purpose was three-fold. It aimed to protect astronomy investments already made in South Africa, to maintain an environment for a global hub that would attract international investments and to create a competitive edge for South Africa to win the bid to host the SKA and other astronomy investments.” (Parliamentary Monitoring Group Briefing)

“The AGA Bill aims to protect astronomy facilities across a wide range of wavelengths, from radio to optical and gamma-ray. This could see the establishment of frequency dependent protection areas hundreds of kilometres in extent.” (SKA Newsletter No. 7)

Opening the containers

Opening the containers

Ironically, the electronic equipment needed to operate the telescopes, and to receive, record, amplify and process the data, creates high levels of RFI, which could severely compromise the quality of the data. The solution is to confine the RFI-generating equipment within an RFI-shielded Faraday cage and to prevent RFI ‘leaking’ to the outside and interfering with the measurements. And that is why these RFI-shielded containers were commissioned.

Carel van der Merwe (SKA SA Infrastructure/Ancillary system engineer) and Richard took the time to point out some salient features of the containers:

Each container has two shielded doors. This enables a person to enter and exit a container while maintaining the shielding effectiveness at all times. Each door also has a double row of copper fingers all along the edge, thus maximising the shielding effectiveness (apparently, it exceeds 120 dB when measured up to 3 GHz, but don’t ask me what that means!).

A quick practical test to see whether the shielding did indeed work was to close one of the shielded doors and to check whether we had any cellphone reception inside the container: there was none (and for once that is a good thing!!).

Richard explaining the important features of the containers

Richard explaining the important features of the containers

In addition, the outer door has a rubber seal that helps to protect the inside from the elements and from dust (imperative in a dry and dusty place like the Karoo). Carel also showed me the false floor of the containers by lifting up one of the floor tiles; this space is used for routing cables and cooling pipes.

When you enter the container, motion detectors automatically switch on lights and a fan, which blows filtered fresh air in through a honeycomb structure; this honeycomb prevents electromagnetic waves passing through. When the doors were closed while we were all standing inside, it was quite a relief to know that there was fresh air coming in!

I can imagine that it would be quite claustrophobic working inside these sealed-off containers when the doors are shut and the equipment is humming. Someone suggested that they could put up pretty landscape pictures on the inside, so that you would have the illusion of looking out through a window. (I rather like that idea!)

And because no KAT function would be complete without a sporting event of some sort, the guys set up a volleyball net on the lawns and burnt off some of the calories they had consumed at lunchtime.

A friendly volleyball match

A friendly volleyball match

P.S. I’ve just received confirmation that the article I wrote has appeared in the SKA South Africa Newsletter No. 10 (see website or download the PDF from here). So now you can read the official version there! Yayyy!!!

P.P.S. A lengthy article about the MeerKAT and SKA projects appeared in Popular Mechanics of December 2007.

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