SKA-LOW at Imperial

2017 is the 10th anniversary of the European Research Council, who fund my FIRSTDAWN group at Imperial. For our celebratory festival, I thought it would be fun to display an SKA dipole. They’re eye catching and a good prop to explain radio astronomy and the SKA. My colleagues at Cambridge, where they were designed, kindly provided me with one. It arrived in flat pack, with some assembly required. Cue: Team assemble!

I’m fortunate to have a fairly large group – Claude and Tom are PhD students, Suman and Emma postdocs (Catherine who’ll be joining in July was off in Pisa). And a team bonding moment was definitely needed to cast off mid term blues.

We all got to work with a claw hammer to get into the box. Claude immediately had to go off with a nose bleed, prompting calls for a post-facto health and safety assessment. “It’ll be fine, but please watch the nails”.

A low frequency antenna looks pretty much like an old style TV antenna, just bigger. The size of the antenna needs to be matched to the wavelength of radio wave that you hope to detect. For SKA-LOW these are around 2m, so the antenna needs to be about a metre or so in size. Apart from that it’s really just metal wire and feels very low tech.

We collected all the bits, but couldn’t find the paper instructions with the little cartoon man (maybe that’s only IKEA?).

Most of the construction was straightforward. The four arms screw to the top and to the base. The plastic support was more fiddly (and needed one more 8mm socket wrench than we had).

There were some nice design features – slanted brackets so we couldn’t get the orientation of the tray wrong.

We got to this stage and spent a while wondering what the correct alignment of the arms was. These need to be fixed relative to one another and that alignment helps determine things like the response to different polarisation of light. Something seemed funny.

And it was, we’d missed a crucial step. The plastic tray both strengthens the frame AND holds the arms in the correct alignment. Yay, there was much rejoicing.

Tightening everything up and fending off enquiries from intrigued astronomers. The electronics would slot into the top plastic module with a plug that screws in to hold them in place. Then a cable feeds out to take off to more electronics for beam forming. 

Five happy theorists all turned experimentalist for an hour. At our rate of assembly, the 130,000 dipoles needed for SKA-LOW would take us about 12 years. Working without sleep in the heat of the Australian outback. Not sure any of us would accept those working conditions.

Well deserved rest. And already our dipole has detected the CMB!

All in all a great afternoon. Very interesting to see the design and construction. This is a SKALA2 antenna, there’s a scaled up SKALA3 version currently to be tested. The advantage of this fractal like structure is that it gives a very wide bandwidth (50-350 MHz). But that comes from having numerous resonances across the band – basically one per strut on the arms I think – which makes for a complicated frequency response. The SKALA2 has a sharp resonance at about 60MHz that would make EoR science difficult. By scaling everything up that resonance gets moved down in frequency and out of tthenobserving band. A simple fix, but it still remains to see if it’s sufficient. 

Imagine thousands of these grouped into 35m diameter stations of 256 dipoles and scattered across several km of the red dirtbof the Australian desert is quite a thing. There’s one test station already – the AAVS1. 

But for now, we’ll stick with one at Imperial. For outreach, for discussion, and as a scientifically themed Christmas tree.

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2015 Reading

My reading from 2015.



The Millstone – Margaret Drabble

The Hunger Games – Suzanne Collins

Catching Fire – Suzanne Collins

Mockingjay – Suzanne Collins

Against Method – Paul Feyerabend


Falling Upwards – Richard Holmes
Fantastic read that had me raving about hot air balloons for a while after.

The Long Mars – Pratchett and Baxter


Five Weeks in a Balloon – Jules Verne


Stuff Matters – Mark Miadownik

The Cable – Gillian Cookson

The Philosophical Breakfast Club – Laura Snyder


Great North Road – Peter F Hamilton

World War Z – Max Brooks

The Campaigns of Alexander – Arrian


The Martian – Andy Weir

The Difference Engine – William Gibson and Bruce Stirling

The Jewel House – Deborah Harkness


The Mysterious Island – Jules Verne


The First Men in the Moon – HG Wells

Annhilation – Jeff VanderMeer

A history of Wales – John Davies


Shackleton’s Way – Margot Morrel and Stephanie Capparell

The Long Utopia – Terry Pratchett and Stephen Baxter

The Original Folk and Fairy Talkes of the Brothers Grimm: The Complete First Edition – Grimms (Translator: Jack Zipes)


Sapiens – Yuval Harari


Lives of the Ancient Romans – Plutarch


The Invention of Nature – Andrea Wulf

The Shepard’s Crown – Terry Pratchett

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Don’t feed the scientists! Who knows what might happen…


This weekend was the 72nd World Science Fiction Convntion – Loncon3 – held at ExCeL in the London Docklands. It coincided with the visit by my friend and collaborator Katie Mack to work on a new paper looking at fast radio bursts as a probe of the gas between galaxies. My colleague Dave Clements leapt at the opportunity to rope Katie into a number of panels and talks at Loncon3. Seeing the time for actual scientific collaboration slipping away, we hit upon the idea of turning our collaboration into public outreach. Thus was born our Loncon3 live science installation – “Don’t feed the scientists”. We got to do research; conference goers got to see unvarnished science in action. Everyone won.

Our space was pieced together from two benches, a table, and the all important white board. Cordened off with hazard tape and a collection of warning signs, both for fun, to give a sense of what was going on, and to dissuade too many casual interruptions. There was science to do after all! All day Friday and most of Monday, Katie and I worked within our little corral. Occasionally other scientists stopped in to chat and passers asked what was going on and what we were working on. Mostly we got on with research, relatively undisturbed.

I had a blast putting these together the warning signs using Adobe Illustrator and base signs from Very easy and very satisfying. A couple of people asked for the pdfs of the signs. I’d share them, but there are copyright issues. Here are some examples though.


It seemed to be well received. There were never large crowds, but lots of people paused to read the signs and observe us for a while. Many of those stopped to take photos. And it really was research as is. For theoretical astrophysicists anyway, so no testubes or bunsen burners. Sadly, it got really cold! Lots of paper reading, writing code, pen and paper calculations, staring into space, discussing problems at the white board, debugging code, getting excited at small victories, and generating new results. Even some science dancing. Maybe not sexy or much of a spectacle, but totally genuine. Just in a drafty convention space rather than a comfortable university office. Lots of fun and solid research progress was made.

Does this count as science communication? We weren’t really communicating science ideas or the amazement of science, which is what outreach is normally about. Still, I think its good that people see the plodding side of science in events like this too and see science with the walls removed. Science, as I experience it, isn’t flash-bang-wow but usual quietly enjoyable with times of tedium and moments of total exhilaration. At Loncon3, if you blinked you might have missed the excitement, but hopefully caught the humanity.

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NAM Gender survey

(If you just want a link to the web form:

At the AAS 223 meeting as part of a hack day project, Jim Davenport and colleagues carried out a survey of the gender balance of speakers and question askers to get a better sense of the dynamics at astronomy conferences. Their results can be found here ( and in more detail here ( It makes for pretty interesting reading.

We (Karen Masters, Jonathan Pritchard, Stephen Wilkins) want to do the same at NAM2014 and, if you’re attending, we need your help! The better the coverage of parallel sessions the more interesting the results will be, so we need you to:
1) Record data on the gender of speaker, chair, and questions askers in as many NAM talks as possible using this simple web form
2) Spread word of this project to your friends/colleagues at NAM and encourage them to record data

After NAM has finished, we’ll analyse the data and share, suitably anonymised, results to get a better sense of the gender balance and dynamics of question asking at astronomy conferences. If you have ideas for how best to do this or want to help, get in touch! We’ll be discussing it in the NAM hack day on Wednesday too (

For this to work well we need to get as high a coverage of sessions and talks as possible. We’re totally dependent on volunteer effort, so any help you can offer in collecting data or spreading the word would be really appreciated.

This is the email we circulated to NAM attendees with the basic information:
Dear NAM attendees,
Following on from a similar survey that was carried out at the AAS 223 meeting, we intend to carry out a survey of the gender balance of speakers and question askers at NAM2014 in Portsmouth next week. For this we need you!

Participation is simple. All we need you to do is make use of this web form ( to submit the gender of the speaker, chair, and questioners at the NAM talks that you attend. The results will be analysed, aggregated to ensure anonymity, and then shared to get a better sense of the gender balance and dynamics of question asking at astronomy conferences.
If you’re interested in reading more about the AAS survey that inspired this, the key results are described here ( and in more detail here (

This will only work if we receive sufficient input from NAM attendees, so please consider making this a part of your NAM!

Please direct any queries to Jonathan Pritchard ( or Stephen Wilkins (, by email or in person at NAM. Please don’t query the hard working NAM local organisers about this survey, as they won’t be able to answer! This is a separate initiative conducted with the support of the RAS Diversity Committee, and not organised by the NAM LOC.

  Karen Masters
  Jonathan Pritchard
  Stephen Wilkins

P.S. If you are interested in helping to analyse the resulting data please consider attending the NAM hack day on Wednesday (


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Responsibility to Awe

One of my favourite poets is Rebecca Elson, an astrophysicist and poet, who died too young. The name of this blog is an homage to this poem of hers.


We Astronomers

by Rebecca Elson

We astronomers are nomads,
Merchants, circus people,
All the earth our tent.

We are industrious.
We breed enthusiasms,
Honour our responsibility to awe.

But the universe has moved a long way off.
Sometimes, I confess,
Starlight seems too sharp,

And like the moon
I bend my face to the ground,
To the small patch where each foot falls,

Before it falls,
And I forget to ask questions,
And only count things.

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