Friday, February 20, 2009

My day at the lab

Today was like most of my other days so far at the lab. Here's what we do:
Bernard (from EC) and I are the only two on night shift at PEARL. Constantine and Yann from U Sherbrooke are also on night shift, but their instrument is down at 0pal, right beside the weather station.

Bernard and I get driven up from the weather station around 6:30pm either by Matt or Pierre. The lab is about 20km away and 600m up a ridge, so it's a nice drive when you're able to see anything (which we could not today as it was night and hazy). As soon as we get in, we turn a small space heater on to warm up the pump which is used to pump all the old gas out of the laser. It won't turn on until it's warm. The other things we do right away are open the hatch on the roof over the telescope so that the scope can cool down to ambient temperature, and turn on all of our electronics. We wait a while until the pump decides it's going to work. While doing that we double check that we've got last night's data on another computer and backed up, and then we delete the files off the lab computers (They're both the trendy Pentium 386, complete with snazzy screensaver of what I choose to think are stars but which might just be dots). Once the pump is warm we turn it on, open the gas cylinders (these are just like helium tanks but they have HCl, Xe, Ne, air, etc in them), and pump all the old gas out of the laser. This part takes forever - about an hour. This shouldn't really be surprising seeing as we have to pump over 4000 mbar of pressure down to 35, which is a vaccuum. We wait for that. Once there's a vaccuum in the laser then we can start adding the new gasses. There's a recipe for how much of each to put in. Then we have to clean the optics. The main complicated part of the laser is a tube which has a mirror on the back end and a lense at the front. Both of these get dirty after only one day of running the laser, so we have to take them off, clean them carefully with methanol, and put them back on. Then we push a button to tell the laser we've put the optics back, and it thinks for awhile, then flushes some gas through, and after waiting for all that we can start the laser. Our laser puts out 2 wavelengths of light: 308 and 353 nm. The laser itself puts out 308 and directs some of that through a "Raman Cell" which is a long tube of Helium gas at 4atm which shifts the wavelength to 353 nm. At this point, we have to wear laser goggles which let most light through, but no UV light in the range that our laser runs. This is so we don't go blind. We start up the laser and the data acquisition programs, and align the laser. For Blessing, Andy, Paul and others who've had the pleasure (ha!) of aligning the PCL lidar in London, in the freezing cold, in the dark, doing the day to day alignment up here is rediculously simple. You watch counts come in on a screen, and push a button to jog one of the profiles up or down until it is on top of the other one. No need to even go outside for that! We do check the telescope again to make sure it isn't getting snowed on (and if it is, blow the snow off with some air), and then leave the laser well enough alone for the next 7.5 or so hours. We take turns checking on the alignment (which we usually don't need to adjust) and the telescope every half hour or so. And that's it!

As you can see, there is lots of waiting for the laser to do things, which means we also get a lot of other work done in the meantime. Usually the laser is going on its own by 9pm, and so we sit in one of the offices (there are plenty of desks here for us to use) and while Bernard looks at Ozone data (comparing it to Ozone sondes which are instruments carried up on weather balloons - side note: our data from two days ago compares quite nicely, which makes us happy), I work on Picon, the analysis code the PCL crew uses for lidar data. I'm making our code work with the Eureka data I'm getting, and writing some new routines for a kind of analysis our lab has not done in several years. Usually we work until about 1 or 2am or whenever we've both got brains that are refusing to think any more that day, and then watch a movie until it's time to shut down the lidar sometime around 4:30 or 5:30 am.

Then it's time for sleeping. Yes, we sleep at the lab. Who would want to come pick us up at 4:30 in the morning? That's right - no one. There's a room with a few sets of bunkbeds which are good for both sleeping in the morning until the truck will come get you and bring you back to the weather station, but also in case you get stranded at the lab for a few days because of weather (like Andy had the pleasure of experiencing last year, but I have not so far!) . We get anywhere between 4 and 6 hours of sleep, and then when the morning shift is driven up to the lab, we get driven back down, getting there usually just before lunch at 12 noon. That is hard decision time: Go straight upstairs and back to sleep, or eat the delicious lunch that is on the way? Invariably I cave and eat lunch, then an hour later go back to bed for the afternoon. I wake up around 4pm in time for supper, and off we go again for another night of measurements!

Of course there are always snags in the plan, so 2 days ago (which I think was the 18th to the 19th) we ended up at the lab for about 24 hours, just coming home with the day shift when they were done for the day. And then it snowed yesterday so we did not go at all. We're back up here tonight (it's 2:40 am right now), so we'll probably run for a few more hours before packing it in.

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