Editor’s Note: Welcome to ANITA, the Antarctic Impulsive Transient Antenna! From October to December, Katie Mulrey is traveling with the ANITA collaboration to Antarctica to build and launch ANITA III, a scientific balloon that uses the entire continent of Antarctica for neutrino and cosmic ray detection. This is the fourth installment in a series, “Neutrinos on Ice,” documenting that effort.
It was 20 degrees Fahrenheit at McMurdo Station today, and it felt downright toasty! Warm summer weather means the time for neutrino detection is getting closer. We are still on track to launch our massive particle detection balloon in early December.
It is important for ANITA to see as much of the Antarctic ice as possible. Neutrinos interact in the ice, so viewing as much land area as possible increases the detection area and makes it more likely that we will see neutrinos. This means we have to fly pretty high.
Flying electronics at an altitude of 115,000 feet presents some unique problems, however. You would think that overheating wouldn’t be a problem in Antarctica, but we fly in the stratosphere, which has very low air density. Fans cool most electronics at sea level, but this technique breaks down when there is very little air. We have to make sure no individual components are generating too much heat, or if they do, that they efficiently dissipate the heat. All metal parts are connected together with very messy heat sink compound, which facilitates cooling through passive energy transfer. We also take steps to make sure sunlight reflects off the instrument by covering all metal that would conduct heat with reflective tape. The balloon’s gondola is painted white to help it stay cool, and all the cables are sheathed in white.
Speaking of the gondola, it is almost complete! We added two more levels of antennas and put all the scientific instruments on the deck of the gondola. Now we have to wear hard hats and harnesses when we need to get into the instrument to fix something. We still need to add two deployable structures to the payload. Size is the limiting factor here. When fully deployed, ANITA is larger than the hanger in which it’s being built. This means that some pieces have to be tucked up inside the payload and released once the balloon is in the air. That is always exciting, because if something goes wrong with the deployables during launch there is nothing that can be done about it! In our case we are deploying solar panels and a huge low frequency antenna. If the solar panels fail we will only have about six hours of battery life.
Another large undertaking this week was the set up of our remote antenna pulsers. It can be difficult to known what signals we are seeing while we fly unless we send some known signals up to the balloon. We can't do this from McMurdo because there is too much background radiation from wi-fi, walkie-talkies, etc. Two of our team members headed off to Siple Dome, 507 nautical miles from McMurdo Station, to set up an antenna that will send known signals to ANITA from the remote site. Siple Dome is a field camp. Only two people stay there during the Antarctic season. They are responsible for cooking, managing the station, keeping the runway clear and everything else that has to happen. The camp is primarily used as a fueling station for planes heading further out.
We had some great extracurricular activities this week. There is a tube at the base of Observation Hill that you can climb down. It goes through the sea ice and into a little room with plexiglass windows that looks out into the ocean below the ice. It is absolutely amazing. We saw some Antarctic fish and heard seals talking to each other. It is like looking out onto a different planet.
We also had the opportunity to go on a guided tour of the Ross Ice Shelf pressure ridges. These things looked like neat ocean waves in the ice from a distance, but up close they look like ice towers looming all around you. It is the bluest ice I've ever seen. There are pools of slushy snow where the sea water beaks through the ice. This is also where seals like to hang out, so we got to see some more seal pups. The wildlife here is great. The skuas are starting to arrive and harass anyone who makes the mistake of eating food outside. They are like huge, ultra aggressive seagulls. They don't even move for vehicles! Penguins are supposed to be arriving in December. Our fingers are crossed that they pass our way.
Also, while undertaking fieldwork such as this, it is important that we keep our knowledge of basic physics in tact, so we made sure to spend some time practicing the conservation of angular momentum with a bit of back-spinning fun on the ice.