Black hole data

It turns out there's actually an IceCube connection to the black hole picture story.

The data had to be shipped back to the analysis center by freight, not by internet. If you look closely at the side of the box he's resting the server on, that's got a penguin in a tux and A-379-S on the side; it's one of our crates.(*)

The data transfer rate of a jet loaded with disks is very good. The transfer rate from the Pole by satellite is pretty slow, though between some US sites it can be much better. For example from NERSC to Madison it would take a little less than 6 months do move 5 PB. And 5TB is supposedly the total data set from all sites, not the amount of data each one sent.

If you remember your galaxy positions better than I do, you might wonder how it is that the South Pole Telescope managed to help image M87. (The EHT telescopes are in blue on that image.) After all, there's a planet in the way.

I haven't read half of their papers yet, but I know how I'd use the station. When you want to understand your detector, you need to know what it sees when part of it isn't working, and you want to know what it looks like if there is extra information. You can't bring Palomar along with you on a trip, but you can compare what your telescope sees with what Palomar sees when you are looking at the same thing, and that tells you something about what your scope can see by itself.

I'll bet they tried to use the telescopes to look at several nearby sources, and analyzed the data with and without the ones that couldn't see M87. That would have helped them calibrate their system--and it would have been even more fun if the source was near enough that they could have an optical comparison as well. That way they could get an estimate for what the resolution was--and you don't have a measurement if all you have is a number. You also need to know the uncertainty on that number. I gather that they deliberately blurred the image they reconstructed to match the actual resolution, so that people wouldn't think they saw structure in what were accidental artifacts of reconstruction. (People translate noisy pictures into "aliens on Mars" all the time.)

(*) Actually, I suspect that the photographer wanted a picture of him beside an Antarctic box, any box. The story just talks about shipping packs disk drives around, not servers--not even disk servers. (We also used Cabbage Cases). We ship our data on disks also, in two copies in case one disk fails (and they do). The summarized stuff we beam back by satellite, but sometimes you need the gory details.