Weather: Fluctuating almost daily between overcast and blowing snow, and cold and clear. Temperatures steadily around -65F with windchill hovering just above -100F. There is only 1 week left with the sun above the horizon.

As the sun gets lower on the horizon we can start to see some familiar sunset colors in the sky… that is, of course, when it’s not completely grey and flat-white outside. With the weather flip-flopping between near white outs and beautifully clear like the photo above, we all hold our breath and cross our fingers for a clear sunset. Nearly everyone on station has begun taking timelapses, either outside in heated boxes, or inside against windows.

Things ain’t all pretty, though. We still have some dirty jobs to do, including greasing the gears of the telescope. Soon enough it will be dark and we’ll have to use red headlamps to see our hands in front of our faces… but for now, greasing in the afternoon sunlight isn’t so bad!

Another fun thing about winter, is that there are no more outhouses. There is too much blowing snow (and will be no Sun, so the solar huts are not effective at staying warm), so the outhouses get put away in late February until next summer. Now, we have ‘The Little Boiler’s Room’ — which is actually the boiler room… with a 55 gallon drum, well two 55 gallon drums, but don’t use the 2nd one, that’s full of glycol for the heating loop!

Now for a new segment on my blog:

SCIENCE SUNDAY!

I’ll try to post some sciencey thing here each week… you know, because I do science, and I’m doing science at the South Pole, or at least that’s what I tell myself.

Today’s science: Why SPT3G is such a special CMB experiment.

The Cosmic Microwave Background is the remnant heat from the early universe. When the universe was young it was much smaller, and thus also much hotter — think of a pressure cooker; increasing the pressure makes it hot.

Since then, it has expanded and cooled to 2.7 degrees Kelvin above absolute zero (that’s really cold! in Freedom Units, that’s -454F). The heat has been streaming across the universe from the very beginning, for 13 billion years, until it finally hits our detectors. This means that when we measure the photons, we are also looking back in time at what the universe looked like 13 billion years ago. It also means that these photons who traveled to us all the way from the hot, early universe tell us about the structure in the universe. For example if a photon is traveling on it’s merry way and galaxy happened to have formed since the beginning of the universe (and they have, thankfully!), then that photon could run into the galaxy and get absorbed, or even interact with some hot, ionized gas within the galaxy and receive a boost in energy as it interacts.

Indeed, this is why the CMB is such a rich data set for studying the universe, because it not only tells us what the early universe was like, but also what our universe is like along the way. What makes the South Pole Telescope so special is the size of the primary dish. The 10m dish means that we have high angular resolution; i.e. that we can see things that appear very small on the sky such as galaxies or even distant clusters of galaxies.

Of course, SPT doesn’t see in the optical wavelengths because we want to observe the CMB, whose photons have cooled over 13 billion years to 2.7K. The majority of the photons now have a wavelength around 1mm long! Compare that to optical photons whose wavelength is a few hundred thousand times smaller! So when we ‘see’ these objects (galaxy clusters, dusty galaxies, active galactic nuclei) we’re seeing them in the microwaves. Some objects produce their own microwaves, such as active galactic nuclei (AGN) where high-energy electromagnetic jets are shot out of their central black holes, causing radiation in the mm-waves and causing warm gasses to emit in the mm waves. Other objects, like massive clusters of galaxies, actually effect the CMB photons as they travel on their way to us.

One such effect, called the Sunyaev-Zel’dovich (SZ) effect occurs when low-energy CMB photons pass through galaxy clusters and receive a net boost in energy due to interactions with hot electrons in the cluster.

Another effect, called the Sachs-Wolfe effect causes photons passing through a massive gravity well (caused, for example, by a massive cluster of galaxies) to gain or lose energy. This can only happen if the gravity well has different depths between when the photon enters and when the photon leaves the well. One such mechanism for this is inflation; since these clusters of galaxies are so large, it takes millions of years for a photon to travel through the gravity well, during such a time, the universe is expanding, and thus the gravity well is getting shallower and shallower, and thus the exiting photon doesn’t have to climb out of such a large gravity well; it then gains some energy compared to what it was before entering the well.

These and other effects change the energy spectrum of the CMB photons as they arrive at Earth. By measuring the spectrum of energies of a certain source, one can gain a better understanding of the physical mechanisms at play.

Below is a small zoomed in section of a heavily filtered SPT3G CMB map. The color scale is in micro-Kelvin (1/1,000,000th of a Kelvin), and shows the departure from average. The larger scale structure is caused by filtering our maps in the scan direction and shouldn’t be thought of as physical structure, but the small-scale structure that look like red or blue dots are indeed physical. The red dots are objects with higher-than-average signal (from things like dusty galaxies or active galactic nuclei which are generating their own source of mm-wave signals), the big blue dot near the middle of the image is a large galaxy cluster which has boosted the CMB photon energy up out of this frequency band. The image is about 4deg x 3deg on the sky, and you can see tens of sources in the map (even with this out-of-the-box filtering). Our full survey size is about 100x this area.

So why is SPT3G so special? We can not only survey 1500 sq degrees of CMB , but we can get high-resolution measurements of these ‘foreground sources’, which in turn effect the measured energy spectrum of the CMB photons. Understanding these foreground sources is instrumental to understanding the exact signal contained in those early-universe photons before they interact with all of the material along their way to us.

Whew! Hopefully that made some sense!

Next week I might talk about something completely different – the Event Horizon Telescope. Stay tuned!

Weather: It has been windy with lots of blowing snow and cloud coverage. Temperatures are getting colder. From our meteorologist: “Temperatures dropped quickly overnight and it’s relatively calm outside. However, models indicate a sharp increase in winds late afternoon into the evening. It’s unlikely to warm-up much before these winds increase. Thus, please use caution and prepare for potentially fast increase in wind-chill (down to minus 130F).” Right now it’s -67F with 15mph winds.

It’s been a busy week, getting ready for the SPT3G collaboration meeting which is today and tomorrow. I had to get up at 0330 this morning to make the start of the meeting (10am Chicago time), and present the work that I had been scrambling to get done. One cool thing about being up early is seeing the sun from an unusual angle. The light coming into the Galley and the conference room was really nice and reminded me, oddly enough, of early-morning light coming into my Mom-mom’s beach house in Rehoboth… I don’t know why.

Between doing analysis work, exercising, climbing, playing sports, and falling asleep trying to be social during meals, I’ve been really busy! I get really stressed and anxious when trying to get analysis results and things don’t work, or my code is too messy and I confuse myself or I don’t have a complete result to present, so the daily exercise regiment is really a critical function to keep me sane.

Here is a short timelapse I took out the Galley window one night during 2nd dinner (around 11pm).

And one of me dressing to walk back to the station after doing rounds out at the telescope.

The sun is now at 3.5 degrees above the horizon, and we only have 10 days until sunset!

Weather: Still cloudy and windy with low vis. The temps have been dropping a bit as the cloud layer thins out, but it’s still only about -40F. Winds up between 15-20mph. I should film myself walking outside the entrance to the station sometime in high winds… the wind really whips around the sides of the station.

Not much has changed since yesterday. We had our weekly update telecon with the North this morning.

I’ve started getting back into my polarization calibration analysis that I’ve been working on (on and off) for about 2 years now. There is a big interest from the upcoming generation 4 series of CMB telescopes because they want to understand the polarization response and efficiency and systematics, etc, of the style of antenna that SPT3G uses.

The difficulty with such a large, high angular resolution camera as SPT3G is that in order to do such optical calibrations, you need to be in the ‘far field’ such that the electric field of incoming (or outgoing, if you prefer the time-reversed field-of-thought) light is negligibly changing. Basically, you want flat, plane-waves arriving at your detector. For us to do that we need a source a few km away. This should be fine, since the South Pole is flat — we just drive out a few km, stick a source there, look at it, and boom Bob’s your uncle… Indeed that would work, but our detectors are so sensitive that if we look that close to the ground, the heat from the -50 degree ice would saturate all of our detectors and we would see nothing! So you might think, ok, just put the source up on a tower… Even if we only wanted to be 10 degrees off the horizon (which is still pretty low, I’m not sure we could even do that), that would mean we need a tower that is approximately 10% of the distance between the telescope and the tower; i.e. for a source 5km away we would need a 1/2 km high (or 1/4 mile high) tower! That’s unfortunately not feasible.

What we’ve decided to do is use a cosmic source of polarization; something that is definitely in our far-field! Centaurus A is a galaxy with an active galactic nucleus (AGN) which is spitting out two gigantic radio lobes. These lobes happen to be partially polarized in our observing frequency range (about 10-20% polarized in some parts of the lobes), which means that we should be able to measure the brightness change on the order of 10-20% depending on the angle of our detectors’ antennae.

At longer wavelengths, the dust you see in the image above (around the nucleus) becomes transparent, so for SPT3G, we observe at about 1mm wavelength, so the dust all but disappears. The radio lobes are generated from electrons which are ejected from the nuclear region and spun around magnetic field lines, producing radiation called synchrotron radiation (accelerating electric charges produce electric+magnetic fields i.e. light).

The difficulty here is that the radio lobes of CenA aren’t actually very bright, in an absolute sense. The plots above are maps made by adding up all 10,000+ detector maps for many observations. If I were to show you a single detector map (for which we care about measuring the polarization angle), for a single observation, you might think I were crazy for trying! The nice thing about the radio lobes is that they are physically large (so there can’t be short-timescale changes; this is not true for the nuclear region where the AGN is devouring dust, and who knows what else!), and also angularly large (large enough to be ‘beam-filling’, i.e. that a single detector’s beam will be fully contained within the lobe as we scan over it).

Anyway, I’ve lost track of what I was talking about… oh yea, measuring the polarization response of each detector…

Well it’s difficult, and we need many observations to build up the signal-to-noise per detector… but who is reading this blog that cares about this?? BOOORRING.

I need to take more pretty pictures…

Weather: Low-vis, high winds and blowing snow. Low cloud coverage and high winds mean warmer weather, but with strong winds it’s anything but pleasant outside. Temps around -35F with 20knt winds (windchill near -80F).

Today and yesterday have been windy and the blowing snow has reduced visibility such that you can’t even see DSL and the telescope.

Tonight we had green beef curry with rice and some delicious bread (I don’t know what kind). I then attempted to play basketball… I don’t know why but today was a struggle. Maybe the higher-than-usual effective altitude? I don’t know. I then attempted to work out in the gym. It was very lack luster.. But at least I ran something like 87 beer cans yesterday; so I’m now at 110 out of 534 for the climb-Everest challenge.

Time to read and go to bed…. or maybe eat second dinner first. Yeah, definitely 2nd dinner first.

Weather: Cold, clear, windy. Temps are now regularly down near -50C (-60F) and windchill today is nearing -100F. Sun is nearing 8 degrees elevation.

We removed the flags from the runway a few days ago. This has to be done every winter, otherwise they’ll get drifted over and a surveyor will have to come out and precisely place each flag… etc, etc. It’s just another reminder that we aren’t expecting any visitors anytime soon!

I finally set up my hockey net, and have been playing roller hockey in the gym… It actually works pretty well, until I turn a little too sharply and the wheels slide on the rubber floor tiles, and I wipe out… but other than that it’s great!

The telescope is telescoping nicely and we haven’t had to do any emergency debugging or problem solving. This also means lots of time for other activities, like the daily evening sports, or doing the physical activities for the Triple Crown.

Running outside is becoming difficult since the windchill of -100F means frostbite in < 5mins… so I have to keep everything, including my mouth, covered at all times. I get claustrophobic with a balaclava over my mouth, so I usually end up having to slow down and try to catch my breath. Hopefully I’ll get more used to it as the season goes on.

I don’t have any other news… Trying to come up with interesting tidbits of my day is difficult. I basically am doing the same things I would be doing at home; data analysis, with the added bonus of monitoring the telescope and real-time data quality.

We do have to grease the elevation gears tonight, though. Which I have a feeling will be awfully cold!

Weather: Cold, windy. Temps dropped 6C overnight, with the higher winds. Temp around -50F, winds at around 10mph, windchill near -80F.

Today I slept in till 9:00! It was great.

I also got to go out to the Atmospheric Research Observatory this morning, and up onto their instrument tower (I think something like 60ft); the view from up there was amazing.. I really didn’t expect everything to look so different.

After my mini tour of ARO, I went for an outdoor run with 2 other folks, down the access road next to the ski-way. I think it was my coldest run; -50F with windchill -80F, but I dressed appropriately and wore 2 balaclavas, so I was really quite warm the entire time.

After the run, I decided to do some beer cans. Unfortunately I was wearing the same pants as during the run, which were already sweaty… and they froze after a few minutes, making it difficult to climb 2 stairs at a time (it’s probably -50F to -60F in the beer can)! .. I only did 12 sets.. maybe I’ll have to go back for round 2 later.

I then did a 3km row in the gym to warm up. And now I need to do laundry. Sundays are fun!

Weather: Warmer , about -40 with windchill near -70. Slightly overcast.

For funsies, here’s a plot of temperature over the past 7 days:

Today I spent all day helping move the beverages into one of the empty berthing wings. We now have 9 rooms FULL of beer, wine, liquor and sodas to get us through the winter (and also to get the folks through next summer)… Hopefully I get a free beer or something for helping out 😉 .

Tonight is “Adventure Movie Night” – a night full of adventure, and movies… well one movie, about adventure, I guess… This is a weekly event put on by the station manager, Wayne White. He’s a really interesting guy who likes historical explorers and is an explorer himself. He’s managed remote stations all around the world and now is the first person EVER to be the Winter South Pole Station manager 3 times (and this year is 2 in a row, which is also unusual). Anyway, tonight’s movie is about Scott’s ill-fated Tera Nova expedition, and I think, historic Antarctic exploring in general.

I go back on-call tomorrow for the next week, but things have been going so smoothly that there haven’t been any pages all week. There have hardly even been any failed autoprocessing of data, or scanification of raw timestreams! … things seem quiet, too quiet. We also observed a new calibrator source for our low-elevation summer fields. I quickly made a map of it to check that it looks like a reasonable source and has good signal-to-noise ratio, etc.

These calibrator sources are large H-II (hydrogen) regions that have a steady signal over time. We use them to correct for the changing opacity of the sky (basically how much water vapor is in the atmosphere).

Another mini side-project I’m playing around with right now is looking at archival data for transient sources — things that appear and then disappear in the maps. It’s a very basic analysis that I’m using, but basically I just look at small chunks of our full field map (from a coadd of say, one month), find point sources, and then ask if those point sources exist in all other month’s maps. Really I want to understand how often this happens for different time frames (i.e. daily maps, weekly coadded maps, monthly coadded maps, etc) because we’re about to put an online transient analysis to work which searches for these sources in real-time. Here’s an example of a source which passed my monthly transient search:

That’s what I’ve been up to — I’ll try to post more non-work activities later, but most of that is just me in the gym… so it’s not too exciting.

Cheers!

Weather: Temperatures still hovering around -50F, winds have picked up and windchill is down near -80F. Mostly clear skies. Sun around 11 degrees elevation.

As the sun drops lower and lower in the sky, the shadows grow longer. The surrounding landscape begins to change, to appear almost alien. On clear days you can see contrast of ridges and troughs in the snow. What used to be flat white now has form. Looking out from the galley reminds me of an image of the surface of he moon (without the craters, of course). The shadow of the station almost reaches the ceremonial pole in the morning, and with the low winds we’ve been having the exhaust from the power plant looms over the berms like a fog lays over a lake on a cool morning. Shadows from thin cloud layers now cast noticeable shadows which make it feel like dusk, though we are still a month away from sundown. Even the light entering windows seems to make late-afternoon patterns in the rooms. We’re definitely getting there. Enjoy the sun while it lasts. I get irked when blinds are closed in the galley.

Hard to believe it has only been 1 week since station close. We still have 2 DC-10 airplanes here, waiting for better weather to head towards Rothera station and then on up to South America. Hopefully they’ll be gone before next week.

Also hard to believe I’ve been in Antarctica for 53 days. It doesn’t seem that long. Time moves weirdly here. It’s always been way longer, or way shorter than I recall. Then again, that seems to be true always, at least for me. My memory isn’t too good. Except for the random ones that won’t go away when I try to get to bed… why is it that my brain feels the need to keep memories of things like driving home from late-night hockey practice in Baltimore, or listening to a certain song at 6:30am in the highschool parking lot before school. The time range of recalled memories seems to be mostly from 6-10 years ago.. not sure why. I wonder if the time frame shifts or if it stays there… I don’t remember what I thought about back then haha.

Anyway, the telescope is still telescoping nicely, and the weather is nice for now. Triple crown challenge and climbing and playing sports is taking it’s toll. I’m thinking about sleeping in tomorrow, but don’t want to make it a habit. It’s already hard enough making it to breakfast (which ends at 8am).

No new pictures today, but if you have specific questions, or want certain photos/videos let me know! — I am going to try to get some time-lapses of the sun sometime before it goes down… we’ll see how that goes.

Cheers