When Antarctica Just Isn't Cold Enough: South Pole Telescope (SPT) Fridge Cycle

As you might have heard on my website, my newsletter, my Twitter, or, if we’re colleagues at Caltech, at work, I am currently working on the South Pole Telescope (SPT) onsite at the South Pole in Antarctica for January-November 2016 (I am employed by the University of Chicago). I have taken a sabbatical from my NSF Astronomy and Astrophysics Postdoctoral fellowship at Caltech and will return January 2017. In the meantime, over the course of my stay here in Antarctica, I hope to update with some scientific posts related to SPT to complement the science I am doing here.

SPT is a telescope operating in the microwave, submillimeter and millimeter wavelengths, designed to observe the cosmic microwave background (CMB) radiation, a relic of the Big Bang that we can see today. We can use these observations to improve our understanding of cosmology, and to point to the location and properties of galaxy clusters early on in the universe (observations which also tell us a lot cosmologically).

I’m in Antarctica because it’s an amazing opportunity to contribute to science in a unique and adventurous way. I’m growing professionally, and I have great colleagues to work with. SPT is in Antarctica as it is high and dry, with little diurnal variation due to the fact the sun rises and sets but once a year. Water vapor in the atmosphere would interfere with its observations of the cosmic microwave background radiation.

The South Pole has an average temperature of around -50ºC, last year it had a high of -18.1ºC and a low of -78ºC. -78ºC is -108.4ºF or, in the scientific temperature scale Kelvin (which is 0 at absolute 0) 195K. It might come as a surprise, but Antarctica is actually not cold enough for SPT’s electronics to function properly, to do that we have to get very close to absolute zero, around 250 millikelvin. More on why that’s the case on a future post. Today’s post is about how to get anything on Earth that cold.

The post is fashioned as a video, with animated views on a PDF illustration and a few glamour shots of the telescope and the South Pole. You can also refer to the PDF yourself as needed.