Images of

ANTARCTICA

Dark Sector

Photos © 2004 Seth White

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Approximately grid north of the station, there is a region called the 'dark sector'. This area is set aside to keep it free from optical and electromagnetic pollution which would interfere with the extremely sensitive measurements being conducted here. By the way, the normal compass directions start to mean less and less when you get closer to the Pole. The lines of longitude converge, and obviously all directions are north from the South Pole. So a grid system has been implemented for aircraft navigation in these regions. It's a rectangular grid with 'north' defined in one certain direction. The planes take off from the skiway headed about 'grid north', and they fly just to the 'grid east' of the dark sector.

This is the main dark sector facility, the Martin A. Pomerantz Observatory or MAPO. Pomerantz is one of the luminaries of Antarctic Science, going back to the IGY days. He was instrumental in many projects, including the cosmic ray research at Pole and McMurdo. In fact, some of the old communication logs in Cosray from the observers in the 60's are addressed to him.

This is a unique looking creation. It looks like something I might have built out of my space legos when I was younger. Actually, I still build stuff out of space legos. My brother and I had tons of these when we were kids (thanks mom) and they're still around, sitting in my storage unit back home. Another thing is that I'm almost becoming one of those itinerant ice people...the ones that when you ask them 'so where's home for you?', they reply 'well, my storage unit is in Obscura, Maine' or something like that. I thought it odd that I ran into so many people like that during my first months on the ice, but now I'm becoming one of them. I don't think of myself as a vagabond, and Denver will probably always be my home. But I haven't had an actual residence in a year and a half, and I don't know how long it's going to be before I get a 'real' job which will last long enough for me to move my stuff out of storage. Hmmm. I kind of miss the regular routine - seeing friends and family, riding trails around Colorado, going to the Falling Rock Tap House with some buddies and swilling fine American Ales, etc. etc. But then again, I was technically getting paid last week to gawk out the window as I flew over the Transantarctic Mountains and the Beardmore Glacier. Hmmm. I don't think I'm finished with Antarctica quite yet, and I'm not sure I will ever completely be. And as my friend Dan says about himself, Antarctica isn't finished with me either.

Another one of the MAPO structure. The two dishes are parts of telescopes which study cosmic microwave background radiation (CMBR). The one on the right will house the QUEST instrument, while the one on the right is the VIPER telescope which currently houses the ACBAR instrument.

I had been wanting to get out to the dark sector for a tour before I left, but it's bad form to just wander out and bug somebody for a tour. I hear most of the scientists out there are pretty friendly and generally enjoy giving tours, but I'm not such much the gregarious type so I hadn't managed to hook up with anyone during my first week at Pole. I was talking to Al Baker one day (he's the science support coordinator for Pole, and a good ping pong player) and he suggested I come out for a tour while he was there. Excellent...so that's what I did. One of the first doors I went through in MAPO opened up to this picture. Is it called the dark sector because it's supposed to stay dark, or is there another reason? The winter is long at McMurdo, but the winter is LONG at Pole....

From up on the roof of the building, this is the view of the new Dark Sector Lab (DSL). It's currently uninhabited, but soon will be full of beakers and their instruments.

This is the VIPER telescope. I asked what VIPER stood for, and the surprising answer was that it wasn't an acronym at all. South Pole is acronym-world, so this was a shock. As it turns out, there was a previous telescope here named PYTHON. I'm not sure if this stood for anything or not, but when the time came to build a replacement, they stuck with the snake theme. The telescope itself can house different instruments, and this year it's home to ACBAR.

The dish again.

There are three platforms from which you can access the interior of the dish. This is a view from the bottom.

As I was taking the above picture, a hatch opened above me and I found myself being observed by a guy working inside the dish. Didn't expect that. The instrument itself is on the left side of this picture.

A view into the dish from the top floor. The ACBAR instrument is on the right side, opposite the larger reflector.

A better view of the guts. ACBAR is on the right again, inside the layers of padding.

ACBAR stands for Arcminute Cosmology Bolometer Array Receiver. I am painfully ignorant of cosmology and most other astronomical disciplines, however, so if you want more info just click here. You will find a much better description of the whole thing than my regurgitation of what Al told me during our tour. Information overload was definitely a factor as we walked around. One interesting item that stuck in my mind was the cooling this device requires. In order to measure the minute anisotropies in the CMBR, the sensor itself must be cooled almost to absolute zero. To do this, two cryogens are used. First, liquid nitrogen is used as a cooling jacket for the sensing area. The sensor itself is then cooled by liquid helium. Paola had given me a book on how the scientific study of cold evolved through the centuries, and after reading it I had a great appreciation for how momentous it was when people were first able to liquify nitrogen, then helium, then hydrogen. It took a lot of clever people many years to do this. And it's now routine. There is even a small liquid nitrogen plant inside MAPO. Next year, they are planning to install a liquid helium plant as well. Nitrogen can be captured from the atmosphere and liquified fairly easily these days, but helium is a different animal. There is only a limited supply of this stuff on earth, and all your bottled helium comes from a very few natural reservoirs. In fact the National Scientific Balloon Facility is located in a small Texas city, because it's one of the largest supplies of helium in the world. So helium has to be shipped down here, and the increased demands of modern astronomical systems is pushing the logistical envelope. The solution is to build a plant to capture the waste helium (as it evaporates) and re-liquify it. Yes, this is expensive, but it's all they can do for now. But couldn't you just ship more helium dewars down? Well yes, but you're limited by the physical size of what you can fit inside an LC-130. A helium dewar is just about the biggest and heaviest thing they fly here, and it's not feasible to ship anything bigger. The problem arises because helium will evaporate and be lost at a certain fixed rate inside the dewar. So even if you have 50 dewars, each of the current size (3000 gallon, I think), they will all naturally empty out in the same time. Again, the winter is LONG at Pole, and the months during which planes can't fly is approaching the time limit during which helium will 'keep' inside this size dewar. So, they're going to start recycling what they use.

Here's yet another hero shot of me, this time with the VIPER dish. A couple hundred meters behind me is a little marker denoting the position of an entrance to the Old Pole station. It's moved out here from its original location due to the flow of the ice sheet below.

Looking out from the VIPER dish toward station, you see the dish which will house the QUEST instrument.

Again, I defer to the experts for a description of the QUEST instrument...click here. The device itself is being positioned on the mount which used to hold the DASI (Degree Angular Scale Interferometer, see here.) instrument. In the last year of its life, DASI was the first to detect polarization in the CMBR. This is an important finding, and has a large effect on our understanding of the early moments of the universe. Now, QUEST is seeking to map this polarization.

A composite picture of the dish. I couldn't get up high enough for a look inside, so this is the best I could do.

On the side of MAPO facing the station, there is the AST/RO facility. This acronym stands for Antarctic Submillimeter Telescope and Remote Observatory. Again, for more details see here.

Another one of AST/RO. The South Pole is an good location for this type of measurement, because radiation in this wavelength range is easily absorbed by water in the atmosphere. The Pole is at a high elevation and the air is extremely dry, so less water is present overhead to absorb the incoming radiation.

Inside the accordion-like dome, this is the telescope apparatus.

A mirror inside the dome. This year, an instrument called SPIFI (South Pole Imaging Fabry-Perot Interferometer) will be used with AST/RO. This instrument, however, is only one of five different sensors which will be used at various points during the winter. They each will run at different times, in a specific sequence which is optimized depending on the time of year and ambient weather conditions. And this is about all the information I retained while listening to one of the researchers during dinner one day. This, and the fact that SPIFI is a ravenous consumer of liquid helium.

Right outside the MAPO entrance is a little marker sticking out of the ground. There are a series of these markers in the dark sector, each denoting the location of one element of the AMANDA array. This project, the Antarctic Muon And Neutrino Detector Array, was the forerunner to the new ICE CUBE project. The idea is to use the polar ice cap as a medium in which to construct a telescope to detect neutrinos. Neutrinos are subatomic particles which have extremely little mass, interact very weakly with other matter, and are unaffected by interstellar magnetic fields (thus they travel in a straight line, which clearly shows their point of origin). Most of them will pass right through the earth as if it wasn't there, however on rare occasion a neutrino will hit a bit of matter just right...and will leave a trace of its existence. In this case, when a neutrino which hits a water molecule in precisely the right way, a muon will be produced which travels in roughly the same direction as its parent neutrino. The muon will cause a faint flash of blue light, which will be visible for a relatively large distance inside the crystal clear polar ice. One problem however, is that other particles coming along will also cause little streaks of light. But this problem can be eliminated by observing the direction of travel of the incoming particles. Whereas all other particles will leave traces indicating they came from above, only neutrinos can come from 'below', i.e. through the earth. So AMANDA and ICE CUBE only look for traces of particles moving upward, toward the sky.

Another pic of an AMANDA marker. The boreholes extend two miles underneath the surface, and along the way are placed little photodetector units to record the flashes of light. AMANDA and ICE CUBE are similar in design, however ICE CUBE is a three dimensional array which will cover a much larger area - 1 cubic kilometer. See here for more ICE CUBE info.

This is the SPASE hut, as seen from MAPO. SPASE is the South Pole Air Shower Experiment. Outside the hut is an array of scintillator detectors, which seek to monitor the flux of high energy cosmic rays (higher energies than the ones tracked by the neutron detector instruments). Like the Cosray project at McMurdo and the similar neutron monitors at Pole, this project is also run by the Bartol Research Institute at U. of Deleware.

This is actually the SPASE-2 array, a improved (and larger) version of the original SPASE-1 array which was installed in 1987. There is overlap between the studies conducted by the SPASE guys and the ICE CUBE guys, and it is convenient that both arrays are located so close together. For more on SPASE, click here.

Near the SPASE hut are two little pits in the snow, each containing a surface detector for the ICE CUBE array. The sensors located at the surface of the snow must operate quite differently than the buried photodetectors which comprise the main body of ICE CUBE. Paul Evenson from Bartol was at Pole the same time as I was, and he is one of the principal people involved in developing the surface detectors. These are the test units, and once they are fully refined, a slew of them will be scattered over the surface of the dark sector to complete the ICE CUBE array.

This isn't in the dark sector, but I believe it recently was...and was moved over near ARO this year. It's the Automated Astrophysical Site Testing Observatory, or AASTO. This year it's home to a telescope searching for planets orbiting other stars - project Vulan South. The project is a joint affair between the US and Australia, and will operate during the winter. Some of the guys dropped by ARO to set up a couple computers, and later in the week I stopped by to see the systems they were installing.

The green hut is very similar to the huts you would find at the AGO (Automated Geophysical Observatory) sites. The AGO's contain various geophysiscal instruments, and there are 6 of them scattered around the polar plateau (some of the researchers I supported last year as McMurdo science tech are involved in the AGO project, and I wondered what an actual AGO site would look like). The telescope itself is an optical device, mounted on the elevated platform. It looks for planets by observing the intensity of various stars. It looks for periodic dips in the intensity as a planet passes in front of the star. It can resolve only the larger planets, on the order of 1% of the star's size (similar to Jupiter's size relative to the sun). Also, only planets with orbits measured in days can be found (and of course only ones that orbit the star in a plane parallel to the line of sight). But relatively few planets have been found orbiting other stars, so a yield of just a handful of new planets would be significant. The bubble hanging off the platform is a webcam (!).

Here is Douglas Caldwell, the PI of the project, standing outside the hut. The project has ties to the SETI program, and there are more details here.