Randol, the other BICEP2 grad student down here, left on thursday which meant I was in charge of the telescope. Every three days, we need to refill the liquid helium tank and cycle the fridge. It just so happened that friday was the first time I would have to refill the helium. Liquid Helium, like all cryogens, is very dangerous if not handled properly. If it contacts your skin, it will burn it badly. If too much of it is released into the air around you, you will asphyxiate immediately. If you aren't careful about the container it is in, it will form an ice plug, pressure will build, and it will explode. Fortunately, I don't think there's ever been a death attributed to liquid helium so the procedures to deal with it are very safe and very proven. Still, it always makes me nervous the first time I have to deal with it--especially filling the telescope because if I get an ice plug, we lose a lot of time (and Helium which is in short supply) trying to un-plug it. The other major concern is that the telescope will run out of helium sooner than expected and then it warms up and again, you'll lose time and helium to cool it back down.
So my first night with the telescope, I watched the helium level as it slowly ticked down, figuring I should have more than enough to last until the morning. I go to bed at around 12:30 and at 2am, my radio starts going off that there is trouble with BICEP2. I look at the viewer on my computer that shows what all the thermometers are reading, mount position, helium level, etc. and they are all reading zero. I then check my email for the auto-generated message to see what happened. Apparently, the alarm for low liquid helium was triggered. The problem is that we should have had plenty to last the night and with everything reading zero, I had no idea what was going on. So I threw on some clothes and ECW gear and ran out to the telescope. I was nauseas from the effort but I pulled it together and checked the instruments. Again, everything was reading zero so I took a manual reading from the LHe level meter and it was reading what I was expecting. With that, I was much more relaxed. I power cycled some of the monitoring programs that we run and once everything was back online, everything was reading out normal. Thus, in the end, there was really nothing wrong. I babysat the telescope for about an hour and then went back to the station. At that point, I could maybe get 3-4 hours of sleep before having to go back out the following morning to refill the helium, cycle the fridge, and start the next schedule. Everything went off without a hitch but it made me panic for just a little bit. It was a helluva way to start my time as the responsible party down here. Since then, everything has been fine. This morning I did another fill and fridge cycle and now I'm waiting to queue up another schedule. All is well.