Off the shores of McMurdo Station, Antarctica, built upon the Ross Ice Shelf, stands the United States Antarctic Program's Long Duration Balloon Facility. In the shadows of Mt. Erebus (the world's southern most active volcano), teams of scientists are working around the clock of the austral summer to launch balloons into the atmosphere in support of science. The payloads attached to these balloons can “answer whatever questions you want it to answer,” according to Carolyn Kierans, a grad student of UC Berkeley, California.
Inside the temporary tent Carolyn and her team of eight are constructing the Compton Spectrometer and Imager (COSI) -- a wide field imaging gamma ray telescope which will be the first scientific payload to fly with NASA’s newly designed Super Pressure Balloon. The team is hopeful the balloon will be afloat for over 100 days, blowing the current flight record out of the water. The main scientific goal of the COSI balloon campaign in Antarctica is to measure gamma-ray bursts and test the flight capabilities of the Super Pressure Balloon.
Gamma-ray bursts are kind of super, super nova. They are the most energetic explosions in the universe. When a large enough star ends its life, it will supernova. If the star is even more massive and energetic, it will create a gamma-ray burst. Huge amounts of gamma rays will come out of the poles of the star, creating "jets." If one of those jets is pointed towards our galaxy, we see a burst of gamma rays that lasts between a few milliseconds and tens of seconds: “You just see a crazy amount of gamma rays.” No two gamma-ray bursts are the same, and it is difficult to fathom the amount of energy created within them. Scientists don’t completely understand how this energy is made. The next step in studying them is measuring the polarization of the light. “We have one of the first telescopes that can inherently measure the linear polarization of gamma rays. If all goes well, if we get a 100 day flight, we could triple number of gamma-ray burst polarization measurements out there.” This could go a long way towards solidifying the theory of these massive explosions.
COSI has lots of scientific goals other than gamma-ray bursts. But why study gamma-rays bursts? “The why is sometimes hard to explain to non-scientists, the why is because we think it is really interesting, because curiosity is what drives fundamental science research”
Working on this project for about one and a half years Carolyn has seen this payload go “from nothing to the flight-ready payload it is today. I screwed in most of the nuts and bolts”
Carolyn “accidentally got into ballooning." Not knowing what type of physics to settle down in, she chose Berkeley for graduate school because of the numerous options it offered. Carolyn's mom is a math teacher and she was always talented in math, so people told her she would be really good at physics. Dugan O’Neil, her honor physics professor at Simon Fraser University in Vancouver, Canada, would do "mini lectures" of upper level physics and what real physicists were doing out in the field. "Special relativity, the science of the speed of light, quantum mechanics, and stuff, and I thought science is wicked cool." But she really fell in love with physics during a tour at Canada’s National Laboratory For Particle and Nuclear Physics (TRIUMF) where they were doing hands on experimental fundamental physics research. Now in Antarctica, Carolyn is working to launch her first balloon.
Carolyn explains the process of launching a balloon:
“The launch is really tricky, especially for the Super Pressure Balloon. First off, you need a "perfect" day - clear skies and minimal wind (less than 4 kts) with a constant direction. The lull in weather needs to last a few hours, long enough to choose a direction to lay down the balloon and get through inflation and launch without the winds picking up or changing direction. The tricky thing is that once you take the balloon out of the bag and start inflating it, there is no reusing that balloon.
"The whole launch process takes about 5-6 hours, if there are no weather holds. We are told a time that we need to be ready to exit our building (it was 3:30am for our launch attempt last week), and we do all of our checks before that. We take an hour or two to turn everything on and make sure it's all behaving, as it should. Then the Boss comes and picks up the gondola.
"This is when we check all of the communication pathways to make sure that's all acting as expected. Then, if the weather is still looking perfect, the Boss rolls you out to the center of the launch pad, they choose a direction to lay out the balloon (up-wind of the Boss), and bring out the balloon box and the trucks full of helium. Then, after one final check for weather, they'll start filling the balloon with helium, a process that takes a bit over an hour. Once the balloon is filled, they let it rise above the payload and try to maintain a straight path between the gondola and the balloon by driving the Boss around before finally releasing the instrument. Ideally, it's a smooth launch and the thing just starts floating straight up. It takes 2-3 hours to get to float altitude (110,000 ft.). For the Super Pressure, again, it's a little trickier. There is an extra balloon, the "tow" balloon, that gets inflated first and raises the top of the main flight balloon up for it's own inflation, this is needed because there are electronics embedded in the top of the super pressure balloon that weigh it down.
"Our balloon is filled with 18 million cubic feet of helium. At float, our balloon will measure just under 400 ft. in diameter; about the size of football field!”
After collecting and studying data of the Antarctic flight the group hopes to fly COSI with a super pressure balloon from Wanaka, NZ, where it can circumnavigate the globe. In addition to gamma-ray bursts, COSI is also designed to study nuclear decay lines emitted from our galaxy, essentially making maps of the locations of different elements that were created in supernova.
One of Carolyn’s favorite parts of working at McMurdo is that “it’s all about the science!”
Kierans is working on her PHD thesis, and her goal is to study the K 511 keV line emitted by positrons in the galaxy. She hopes to help explain their origin, possibly relating to the new physics of dark matter.
Carolyn Kierans, a woman living her life with passion and science!
George, named by the LDB science groups, has been hanging around the balloon facility on the ice shelf.