Tall Tower!

We have had a great week of flying. We replaced the Gill AWS, swapped out an aerovane at the Marilyn AWS, installed the instruments on Tall Tower (Alexander AWS) and switched the Minna Bluff AWS over to a Freewave transmitter.

The Tall Tower installation was an exciting day. The Tall Tower project has turned into quite the "thing" in McMurdo. When people around town see someone from our team, they will often throw their arms up in the air and yell, "Tall Tower!". I think that there are many people on the base that are anxious for this project to be a success. Although, as has been proven in past seasons, the site is a difficult one to fly into. It is about 100 miles from McMurdo on the Ross Ice Shelf. This area is prone to dense fog for days on end. We had two days of weather cancellations before attempting to get to the site. The morning of our flight, the Fixed Wing coordinators (the department that coordinates the flight schedule for the Twin Otters) called and said that the weather at Tall Tower did not look good, but that we would do a flyby. If the weather had cleared up, we'd land. Otherwise, we would travel on to the Marilyn AWS and complete that work (we had about 30 minutes of work to do at this site). Then we would fly back to Tall Tower to see if the weather had cleared. We were slightly concerned about this schedule because we calculated that we would need about 8 hours of ground time at Tall Tower in order to complete everything. In the end, we figured that getting into the sit for a shorter period of time was better than not getting there are all.

We took off for Tall Tower with 2 riggers and a UNAVCO person (we were using one of their power supplies for the site) to help us with the installation. We are so grateful that these people were able to accompany us in the field. We never would have been able to complete the installation without them. Upon arriving at Tall Tower, the entire area was covered in fog. One of the riggers was able to see the top of the Tower through the fog (which means the fog was nearly 100 ft deep), but there was no opening for us to land. We headed on to the Marilyn site and completed our work there. When we arrived back at Tall Tower there was a small opening in the fog that allowed the pilots to land. We were given 6 hours of ground time, so we worked very hard to accomplish everything in time. The riggers worked on checking and realigning the guides for the tower before installing the upper four levels of instruments (the upper four levels included four aerovanes, four temperature sensors, a relative humidity sensor and a radiation sensor). The rest of us worked on installing the power supply (which had three large solar panels and six 100 amp-hr batteries), prepping the instruments for the riggers and installing the bottom two levels of instruments (two cup anemometers, two temperature sensors, a relative humidity sensor, an ADG (measures snow accumulation) and an antennae to transmit the data). We worked to the very end of our time limit, but were able to get everything installed and test that the station was transmitting. As you can see from the photos below, the weather significantly cleared up as we worked.

Tall Tower Before

Completed Tall Tower (Photo courtesy: Jonathan Thom)

Our trip to Minna Bluff this week was also quite interesting. The bluff is about 45 miles from McMurdo and protrudes out from the Transantarctic Mountains. It is one of the few sites that we install on dirt (or very hard permafrost). The wind speeds over the bluff can be very strong. Therefore, the site is a bit shorter than our normal sites and uses a high wind speed system (you'll see two wind instruments (one measures wind speed and one measures wind direction) on top of the tower, instead of the normal RM Young aerovane). Additionally, we built a rock wall around the base of the station in order to help with stability and protection. At this site, we replaced the entire station, but the main goal was to change the transmitter from Argos to Freewave. Argos uses satellites to transfer the data, while Freewave is a direct line of site transmission. Minna Bluff is within range of McMurdo for Freewave (we tested the transmission today and it seems to be working okay), which allows us to free up the Minna Bluff Argos ID to use at another site.

Minna Bluff AWS

The scenery on Minna Bluff was fantastic.

The backside of the bluff has dramatic cliffs. Our helo pilot flew over these as we left the site. The picture below doesn't do it justice, but it was the best one that I got.