Work, work, work

As pointed out by Boyan, my blog posts so far this year have mostly consisted of stories about being stalked by red-heads and making up routes at the climbing gym. "Ahh, so you poke the telescope once a day and mostly sit around drinking tea and schmoozing!" is what you might be thinking. As entertaining as yarns of volleyball and pub trivia are, that is certainly not the reason I was sent down here. Thus I will take the next few moments to describe what I have been doing on a daily basis down here at the Pole.

Tijmen walking through the hall in the Dark Sector Lab

I am here for my graduate research, which is in the branch of astrophysics known as cosmology. Cosmology is the study of the universe as a whole. I do this 'studying' by working on the South Pole Telescope (SPT). In one jargon-filled sentence, we are using the SPT to study dark energy (among other things) in two ways: finding and observing clusters of galaxies, and measuring the secondary anisotropies of the Cosmic Microwave Background. That should give you enough words to waste at least half a day on Wikipedia.

The lion's share of our observations are taken during the Antarctic winter. This leaves the summer season (i.e. now) open for maintenance of the telescope. As I mentioned in an earlier blog post, the main item on the agenda this summer was replacing the azimuth bearing. I was supposed to come down after the bearing had been replaced and help put the telescope back together for the next season. For better or worse - well for better - the bearing replacement went extremely well and the new bearing was in place 10 days early. For worse, this means that there isn't as much for us to do.

Tijmen and Ross controlling the telescope.

None the less, we have been keeping busy, and I have actually been working every day I have been here so far. We have been steadily working through a check-list of maintenance projects to prepare the telescope for the next season. Here are a few examples. One of the four elevation motors was making a lot of noise, which is usually a bad sign. The elevation motors move the telescope in elevation (up and down on relative to the horizon). We went up into the telescope and found that the motor was not giving any torque - to such a degree that you could stop it from rotating by grabbing it with your bare hand. So we took the motor out and replaced it with our spare motor. We have spares of just about everything - you can't just walk down to the store and buy a new part if something breaks! Another project involved me glueing thermometers into holders with stycast. The thermometers will be used in a calibration source, which is used to measure how well our detectors are responding to a known signal. In a third small project I have been writing new scan files which tell the telescope how to observe. I also fixed a heater in the receiver cabin by changing out a Solid State Relay.

Docking the telescope.

Climbing up into the receiver cabin.

Crazy British! Ross describing something, we're not sure what.

Me posing by the readout electronics.

A relatively major ongoing project involves the regenerator batteries. When the telescope slews (rotates) in azimuth, it is accelerated by power from the main station power (through a load-leveler). When it decelerates, some of that power is pushed into regenerator batteries, which store the power temporarily until the next time the telescope moves. In this manner we can be as efficient as possible with our energy use. However, there has been a miss-match in timing between the power source and the regenerator batteries. This means that if the telescope is accelerating to the left, it is pulling power from the main station. If it is suddenly commanded to move to the right, it decelerates, dumping power into the regenerator batteries, then tries to pull power to accelerate to the right. The problem comes if there is a timing miss-match between the regenerator batteries and the station power; the station power might be expecting the regenerator batteries to supply power when they can't, and the telescope receives no power. The result is that the telescope does not move when the software expects it to move, and all hell breaks lose.

We have spent the past two days working on diagnosing and fixing this problem. This involves checking voltage phases between the two regenerators, and the phases relative to the load-leveler (station power). We are talking about ~500 Volts. We do this while swinging the telescope back and forth in azimuth. We also found that one of the two regenerators was giving faults too easily, and switched it out for a spare. The spare works well. It is pretty exciting swinging the telescope back and forth as fast as possible. The whole building shakes, and when the power dumps into the regenerators the lights flicker. Sometimes the large breaker switches on the telescope flip with a loud 'snap!'

-- Update --
Today we looked at the voltage readout of the regenerator batteries as we moved the telescope. The voltage changes on the regenerator when moving were *backwards* from what we expected. It seemed that the load-leveler was over-compensating, and actually putting power *onto* the regenerator when the telescope accelerated, and *removing* power from the regenerator when the telescope was decelerating. We switched to direct station power, and the voltage changes on the regenerator were as expected. So we will now stay on station power until we can talk to Extreme Power, the company that makes and maintains the load-leveler.
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I think tomorrow I will be looking at some Python code which we use to tune the pulse tubes. The pulse tubes are mechanical cooling devices which keep our detectors at 350 miliKelvin, or 0.3 degrees above absolute zero. They use a very complicated thermodynamical process which is not thoroughly understood theoretically, but works quite well! Tuning them means adjusting the pumping frequency to get optimal cooling power. An additional bonus is that I get to learn a bit more Python.

Well, hopefully that gives you an idea of what I am doing on a daily basis down here at the Pole. It is fun to do hands-on work as a change from my usual job of primarily programming and data analysis on the computer back in Chicago. So far, the telescope looks to be in great shape for the up-coming season!