This post will be the combination of yesterday and today. My mandatory training is complete, and I’m able to spend more time in the labs writing software. I’m currently working on writing SPI (Serial Port Interface) code to talk to our 24-bit ADS1258 analog to digital converters. Analog to Digital Converters (ADCs) are precision voltage measurement devices that convert an input voltage to a digital number which can be used for digital processing. For example, the ST-110 thermistors we use to measure temperature are given a known reference voltage. The resistance of the thermistor changes with temperature based on a given equation from the manufacturer. By measuring the voltage output from the voltage divider created between the Thermistor and a 24,900 ohm resistor with an analog to digital converter, we can calculate can the temperature of the thermistor. This is generally the idea of measurement with all analog output sensors.
Last night was a blast. After 4 beers and a glass of scotch each, Aurora and I decided to go hiking up observation hill at 10:30pm Saturday night. It didn’t exactly happen that way though. We had no map and neither of us had taken survival training, so we had no idea where the trail even was. We walked around looking for a bit, and after a while we decided to turn back. On the way back, we stumbled on a group of people standing outside the BFC Outdoor Equipment Center. We thought they might have a better idea than us, so we walked up to them and asked if they knew where the trail was. While standing there talking, we couldn’t help but notice the throw-back early 2000’s pop music blasting in the background. We asked what was going on and were immediately invited inside. All of the windows were blacked out, the lights were off, and people were in robes and party cloths all around. We definitely looked out of place with our huge “big red” jackets and all of our winter gear. We threw our gear on a rack and started wandering around. Suddenly Lee appeared out of nowhere and “congratulated” us on finding the party. He told us the real party was upstairs, and we should go check it out. In the stairwell, there was an ice sculpture. We had no idea what it was, but it was really neat. Upstairs, we didn’t expect there to be a full-on dance floor with people jumping around to music, Christmas lights hanging from the walls and ceiling, and an open bar serving beer and wine. At some point late in the night Aurora and I followed a group of people out to the Science Support Center, where another party was taking place. The song Lean On Me – Bill Withers was playing when we got there, and at least 40 people doing a kick line in a huge circle to it. It was like something straight out of a college frat party. I never expected there to be legit parties in McMurdo! We danced until 2 or 3am, then got pizza in the galley. I remember making fun of Aurora by insisting that there was an M & M hidden in every picture on the walls of the galley, because the artist really liked M & M’s. The whole night turned out to be a great time. I thought Antarctica would be this refined research station full of boring people who only know their work, but I was definitely wrong. This place is awesome.
Now for today’s news. I attended a science lecture in the galley at 8pm today. The Automatic Precipitation Station grant, composed of Principal Investigator Mark Seefeldt and Co-Principal Investigator Scott Landolt, focused on the pros and cons of precipitation sensor design, snow accumulation rates in various places, and the measurement methods of sublimation. Their APS system is sort of like a drum, which terminates conically to a 6” opening at the top. The drum is positioned vertically, so the opening faces the sky. The idea is that snow falls into the drum through the opening, and the mass can be determined and converted back to a liquid volume. The trick to measuring snow precipitation is to ensure that winds do not blow snow into the drum, trapping excess snow and erroneously increasing the mass in the measurement. The APS team has spent years developing methods to protect the drum. Their latest design utilizes flaps arranged in a large ring around the barrel that deflect wind. This allows snow to freely fall into the drum.
Another study the APS team researched was on sublimation. Sublimation is the phase transition of matter in solid phase, directly into a gaseous phase. This commonly occurs on mountain sides where the sun shines at a more perpendicular angle to the surface. At low temperatures, sunlight gives snow (solid state water molecules) a chance to absorb enough energy to break their intermolecular forces and sublimate. Inside the drum, without sunlight, this occurs at a lesser but still measurable degree. By measuring small decreases in the liquid water mass of the snow in the drum over time, the rate of sublimation can be calculated. This rate of sublimation can then be correlated to effects such as temperature and humidity.
Tomorrow should be a pretty busy day for Lee and I. We have meetings with flight ops to discuss our upcoming plans to day trip to Cape Hallett. We also have a meeting with helo ops to talk about other future plans. We are loosely planning to visit 20 locations in Antarctica, many of which are only accessible by aircraft.
Josh
Josh's Antarctica Blog 