Compass Calibration

We've spent a lot of time the last couple of days working on compass calibrations for the gliders.  When the gliders are at the surface, they can get a GPS fix (that is, find their position from satellites) and figure out exactly where they are.  However, when they are under water, the only way they can estimate their position is from how fast they think they're going and what direction they are heading in.  The direction comes from a magnetic compass.  Since we are so close to the magnetic south pole (which is actually north-west of where we are right now), it is kind of tricky to use a magnetic compass here and the one in the glider has to be carefully calibrated.

Compasses are affected by metal, so to calibrate it, we went a few miles out onto the sea-ice to get away from nearby mountains:

Road on the sea-ice away from base.  Way in the background you can see a couple of C-130's parked at the runway on the sea-ice.

You have to hook up a GPS antenna to the glider, stand around for a while to get the computer to be happy, and then move this bulky glider around by hand in several (48 I think for a good calibration) different positions.  Then, when the calibration is done, you have to check it by again moving the  glider in a bunch of different positions.  The first day we did this, we were out there for a few hours (had a few problems before we could even get started) before the batteries we had died due to the cold and we had to go back.

Hooking the GPS antenna (the little white thing) up to the glider (the big yellow thing).

The next day we went back out with bigger (and better insulated) batteries.  We still had some problems, which involved a couple of people going back and forth to town a couple of times.  Two of us stayed out with the gliders, which would've been OK, except the weather was getting to be more like what I expected of Antarctica:  14F, wind chill -5F, steady winds at 20-30 knots, with gusts up to 48 knots.  I ended up being out there that day for about 9-1/2 hours (other than the 20 minutes I was eating lunch in the truck).  The cold weather clothing worked pretty well (and the boots were awesome...my toes stayed toasty warm the entire time).  My drinking water bottle did freeze pretty solidly though.

We still haven't finished calibrating all three gliders, but we can wait to do the third one as it is a backup anyway.  Plus, the weather should be better if we're out there again for a while.

We got back too late to get dinner last night.  Luckily, the ice cream machine in the cafeteria is left on all day and night, so my dinner last night was leftover chips and ice cream.  I can think of worse things....