Astrobites on the Ice, Part 1: Halfway to Pole

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The past year has been extremely busy, with lots of labwork, classes, and exams to complete. Luckily, I’ve recently had a change of pace. This afternoon, I left my hotel in Christchurch, New Zealand and walked across the street to eat wonton noodle soup with a few people I met yesterday at the airport.  After lunch, we took a bus to the city center.  I ended up spending a few hours in the Christchurch Botanic Gardens, meandering up and down the Avon river and enjoying the idyllic summertime scenery while resisting the urge to feed all of the ducks I saw.  After a relaxing day, I came back to the hotel and took an entirely gratuitous two hour nap.  But while it may look like I’m on winter break, really the opposite is true: I’m just here in transit, getting ready to spend a month working on a telescope at the South Pole.

Sightseeing in Christchurch, New Zealand.

Ducks at the Christchurch Botanic Gardens.










I work on the BICEP2/Keck Array projects, which are extremely targeted cosmology experiments.  Our telescopes are custom-built to detect the inflationary B-mode polarization of the Cosmic Microwave Background (CMB).  For a more detailed review of how and why experiments hope to achieve this detection, see this Astrobite I wrote about a similar project in Chile.  Here’s the gist: the theory of inflation — the idea that the early universe experienced a violent, exponential expansion — solves many problems in cosmology, and most of its predictions have been observed experimentally.  The detection of one final prediction, a background of gravitational waves in the early universe — would be the “smoking gun” for this theory.  If these gravitational waves existed, they would have created a specific polarization pattern, called “B-mode,” in the CMB.  Our experiments, along with many others around the world, hope to measure CMB polarization extremely carefully to tease out the faint B-mode signal, and thus confirm that inflation occurred.

CMB polarization maps from BICEP, the predecessor to BICEP2.  Red and blue spots show significant deviations from noise; E-modes in the top panel are clearly detected. The bottom panel shows B-modes, which are still consistent with noise in these data.

BICEP2 and Keck Array are located in at the Amundsen-Scott South Pole Station.  The first question we always get when describing the experiment is: “why the South Pole?”  There are of course good reasons why you wouldn’t want to have your telescope there!  First, the Pole is inaccessible for 9 months out of the year (during the Austral winter, approximately mid-February to October).  Second, it’s basically as far away from civilization as possible, meaning it takes a lot of effort to get equipment and people in and out.  Finally, it’s cold!  Winter temperatures average around -72 degrees Fahrenheit, while the warmest recorded temperature was still only 9 degrees Fahrenheit.

Despite all of these factors, Pole’s benefits outweigh its downsides.  Our telescopes observe microwaves, which are heavily absorbed by water vapor in the Earth’s atmosphere.  The South Pole offers one of the best microwave observing sites in the world, due to its dry atmosphere (often less than 0.5 mm of precipitable water vapor), height above sea level (about 9300 feet), and ambient temperature.

Atmospheric transmission at two good sites (South Pole, the Atacama Desert) and one terrible site (Hanoi, Vietnam). Most CMB experiments operate in the 40-220 GHz range; BICEP2 and Keck are at 150 GHz.

With its one day and one night per year, the atmosphere is extremely stable, and solar contamination is absent for six months.  Fields on the sky remain at constant elevation and never set.  Finally, there is significant infrastructure already in place at South Pole Station, supporting a large variety of scientific experiments.  For all of these reasons, CMB telescopes have been operating at Pole since the early 1990s.

Some of the first few CMB experiments at Pole.

These telescopes tend to have several-year lifespans — an experiment will be built Stateside, shipped to Pole, installed in one summer season, and remain to observe for a few years before being dismantled.  BICEP2 has been observing since 2009, and one of our goals this season is to decommission it so we can focus on data analysis.  Keck, on the other hand, will continue observing for several more years, so it requires extensive calibration and upgrades before the season is over.

How do we get to Pole in the first place?  The US Antarctic Program (USAP) operates out of Christchurch, New Zealand.  So the first part of my journey involved flights from Boston to Los Angeles, Los Angeles to Sydney, and Sydney to Christchurch.

The route I’m taking to Pole. Clearly this isn’t the best projection to use!

I arrived in Christchurch yesterday, exhausted after about 23 hours of flying and several delays along the way.  Next came the clothing issue.  As we’ve established, Antarctica is cold!  Luckily, USAP provides all the warm weather clothing we need.  This morning, all of us scheduled to fly to Antarctica tomorrow gathered at the Clothing Distribution Center to pick up our Extreme Cold Weather (ECW) gear.  My full list of clothing contained 21 items, including a bright red parka, heavy-duty work overalls, and insulated rubber thermal boots.  I made sure that all my gear fit correctly before stowing it in two orange bags.

Examples of the ECW clothes available.

Partially decked out in my ECW gear.













I then got the rest of the day off, which brings me back to my Christchurch “vacation.”  It was great to have a bit of time to relax in between all the traveling!  However, this break won’t last long.  My “ice flight” is scheduled for tomorrow morning.  Most people flying to Antarctica don’t go to the South Pole; the main US base on the continent is McMurdo Station, on the coast.  So I will first fly to McMurdo and stay there for a day or two before the final flight to Pole.

In the next installment: the trip from Christchurch to Pole!

About Kirit Karkare

I am a third-year graduate student in the Astronomy Department at Harvard University, and am interested in cosmology and instrumentation for radio telescopes. I work with John Kovac on several telescopes at the South Pole designed to detect the signature of inflation in the cosmic microwave background. In 2011, I graduated from Caltech with a degree in physics. I worked with Tony Readhead to build a Ku-Band polarimeter for the 40-Meter telescope at the Owens Valley Radio Observatory, and with John Johnson on M Dwarf Metallicities.

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1 Comment

  1. I am INCREDIBLY jealous that you are going to the south pole. It is on my bucket list to go to Antarctica and you have the opportunity to go there for research purposes.

    Very jealous!

    I will be waiting to see lots of pictures from the trip! (perhaps a link to a public Dropbox or Google Drive folder with many?)



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