Jon set up some go pros around the high bay to take pictures every 10 seconds while we were closing up. The result is pretty sweet. You can see the various layers going on the cryostat, and the domes being closed up. I wore red for a couple consecutive days, so I’m easy to pick out!
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SPIDER on the Ice 
That was an amazing video! Nicely done Jon!
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Why do only three of the six “windows” (or, perhaps even less precisely, “spider holes”) have plastic disks over them? To be precise and clear, I am referring to the fact that, e.g. at the 1:00 mark of the video, the holes at 5-, 7-, and 11- o-clock around the “top” of the instrument have translucent (in visible band) plastic covers, but those at 1-, 3-, and 9- o-clock do not.
Is there a 3-3 split, in terms of frequency bands that the six different apertures study? Are only three of them in operation? I hope all’s well. (Seems to be, given the generally upbeat nature of your posts, Anne!)
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P.S.–On further reflection (pun intended), I think I can see coverings on the 1-, 3-, and 9- o-clock holes, as well. They are just colored differently. Correct? Or am I full of it? Do these windows simply cover different frequency bands, then?
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Good question, David! Yes, the black half wave plates are for 150 GHz receivers, and the white ones are for 90 GHz receivers. The color comes from the anti reflection coating, which is a different material for the different frequencies because they need to be different thicknesses. Just so happens that the material for 150 GHz only comes in black. Which is perfectly fine, but it bugs the OCD people on our team=)
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Thanks, Anne! So those are half wave plates? The grey-ish/white-ish ones are the 90 GHz ones? Interesting. When I did the HWP for ABS (experimental project from way back in the day), the best AR coatings we found for “145 GHz” were much more similar in color to your 90 GHz AR coats. Interesting. (Or not. I bet somebody found a better AR coat than I did. Experimentalist-produced theses/experiments >>> theorist-produced experimental projects!) Good luck, Anne + SPIDER!
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This is all too cool and fascinating – thanks for taking the time to share.
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Why do people in yellow jackets keep coming in a busying-up your work space?
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Yeah, I love that part of the video. A large group of Aussies was stuck in McMurdo for several days on the way to their base, Casey. Bad weather at Casey. So to kill time, they came out to LDB to see what was up. We gave short little tours of SPIDER to them. You can see my tour at some point in there.
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Hey Anne,
Just got caught up with your blog. Looks pretty incredible down there! Since you’re answering questions in the comments I will post mine here.
1. Aren’t sensors / telescopes etc. usually constructed in clean or dustfree environments? It looks like you guys aren’t worried about that here. Is that because each of the sensors is already sealed, so all you have to do is mount them, wire them in, and lock it all down?
2. Which parts are you having to depressurize? Is it just the large white shell that houses everything? Are you actually vacuuming within the optics? Or do you just need to depressurize and cool the frame, which in turn will cool the sensors?
3. Where do you launch? Once it’s up, do you still hang out at the main base, or do you have to go somewhere else to observe and monitor it? Will you be receiving relayed data, or will you have to wait until you recover the unit it at the end?
4. On a similar note, is what you’re detecting something that would start to give you measurable data quickly, or does it have to be a “long exposure” to detect whatever it is you’re looking for? I’m guessing you’re looking for evidence that’s rare, faint, or both.
Thanks again for keeping the blog updated. Keep us posted!
-Bobby
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Wow, Bobby, those are some great questions! Happy you’re finding some things of interest here.
1) If we could work in a clean room environment, we would. More for the cryostat than for the telescopes though. Unfortunately, it’s very difficult to get that much clean room space in Princeton, and totally impossible in Antarctica. But we know that going in, so we don’t make things that have to be clean room clean. The reason a lot of telescopes are made made and assembled in clean room environments is because they observe in higher frequency regions, like optical or UV. We work in lower frequency- microwave- wavelengths. So we care about dust and defects on order of the wavelength of a few mm. Optical telescopes are sensitive to much smaller defects in their line of sight. It makes working with microwaves a lot nicer, because you get to do things like machine optical parts yourself in the machine shop, whereas you could never do that for real nice optical telescopes!
2) Yeah, the whole large white shell gets depressurized. There is a big 1200 L tank in the middle of the cryostat that holds the liquid helium, and a smaller superfluid helium tank, and those are the only parts that aren’t pumped down to low vacuum. All of the optics are under vacuum. Some of those parts are delicate, so we have to pull the vacuum pretty slowly so we don’t cause too much stress in them on the way down. The whole telescope is well thermally coupled to cold stages with copper straps that get bolted on.
3) We launch from the launch pad, of course=) It’s at LDB, a short walk away. We will monitor it from some control room in town, not out at LDB. We will get some data relayed down- enough to tell us if things are working, and we’ll be able to send enough commands to fix problems, but the data rate isn’t nearly large enough to get all of it back. The data are stored on hard drives on the payload, which are the first thing we will recover after the thing lands somewhere on the continent. That’s part of why we get time off after Antarctica- we have no payload to work on, and it takes a while before the data can get back to us to start analyzing.
4) What we’re looking for is indeed very faint. It’s a pattern across the sky. So one way you work toward detecting the pattern is to have really sensitive detectors. The other way is to take lots of pictures of the same spot with the multiple detectors over a long period of time. This lets us reduce the noise in our measurement and make sure there aren’t systematic problems that we might otherwise interpret as a real signal. So yeah, it’s like a long exposure, two dimensional panorama of 10% of the sky.
I hope that answers well enough. Thanks again for the comment! I’ll try to update soon, but I want to have happy news before I do…
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