Wednesday, December 14, 2011
I have now gone through, and laboriously re-added the photos to the blog, currently with one exception which I will fix later. Although I tried hard, it may be that one or two of the photos different from the original images; since the file names didn't survive the transfer, it is impossible to be sure.
I apologize for the length of time that the blog remained pictureless; it took some time to identify the problem, and even more time to work up the energy to re-create material that disappeared.
Wednesday, August 24, 2011
Here is the conclusion of Jordan's account:
And then came the fog. The fog drifted in from the south and obscured the helo pilot's ability to see where he was landing. After several unsuccessful attempts to descend through open patches, the pilot decided to return to McMurdo and try again the next day. Then, we saw from a distance, the helo descend through a patch of fog that had opened. The helo returned, 50 meters off of the ground, and dramatically landed right next to our camp in a whirl of snow and cheers. Although I looked forward to warm food and a hot shower back at the main base, I felt the Antarctic wilderness calling me back. I admired its raw untouched beauty as we ascended through the clouds above the glaciers, and looked back as our experiment disappeared in the distance.
The first flights leaving McMurdo were delayed, and it turned out we'd be spending Christmas in McMurdo. Steve and I had planned on this, and simply enjoyed the food and good company in the mess hall, which had quite a buffet for Christmas dinner. I also took the opportunity to hike to the top of Observation Hill, which looks out over McMurdo and the surrounding ice shelf.
After we drove to Pegasus air field, where our C-17 was supposed to embark for Christchurch, we met several physicists from the CREAM experiment. CREAM (Cosmic Ray Energetics and Mass) is an experiment designed to detect cosmic rays in the upper atmosphere by flying the detector on a balloon. We swapped stories from the field and took pictures. It was a fitting way to end the trip, in the company of fellow cosmic ray Antarctic researchers.
There has been a lot of activity since we returned to the USA. A paper on the results of our analysis of the reflecting properties of the ocean is going to be published in the proceedings of the 2011 International Cosmic Ray Conference. We are also gearing up for next season, and we plan on installing a second prototype station. We've added a new graduate student, Joulien Tatar, who is working on a way to link the two stations together via noiseless wireless communications. We are in the process of fabricating the circuit boards for the next station, which will include a new way of distinguishing the difference between an interesting neutrino-like signal, and radio noise.
Postscript from Spencer: Planning for the 2011 season is underway now.
Here is part3 of Jordan's account of the 2010 ARIANNA field season:
In addition to fixing the station, Steve and I also scheduled time to make measurements of certain properties of the ice beneath the detector. Spencer Klein and Thorsten Stezelberger had already calculated the depth of the shelf beneath the prototype using data taken in 2009. They did this by pulsing a radio signal down through the ice, and measuring the time for the signal to return after reflecting. This experiment requires very sensitive equipment, since the signal strength decreases with distance, and we're working with a total path length of over a kilometer. Steve and I repeated this measurement, and got the same answer as Spencer and Thorsten. We would also go on to use that data to measure how much power a radio wave loses as it travels through the Ross Ice Shelf. The key problem in the past was that no one knew how much power the radio wave looses when it reflects off of the ocean beneath the ice shelf.
To study this separately from the effect of the ice, I moved our transmitting equipment to the end of the 1 kilometer flag line we established on the first day of the expedition. I had the help of Leah Biezums, who flew in via helo to relieve Rebekah after the first week. Now we had a path length of one and a half kilometers, and the power loss from the ice would be stronger because of the increased distance the radio signals had to travel through the ice. Presumably, the properties of the reflecting ocean were the same. Thus, by comparing the amount of power received in the signals with different path lengths, but the same reflection properties, we could isolate and study the reflecting properties alone. We've found that the ocean/ice interface acts like a smooth mirror, reflecting a large fraction of the radio signals' power. This bodes well for detecting high energy neutrinos which create radio pulses, because neutrinos propagating downward through the ice shelf will create radio waves that reflect off of the bottom and back up towards the ARIANNA detectors.
As the expedition began to draw towards its close, Steve and I began to perform tasks that would ensure the viability of the detector throughout the rest of the summer and winter. We repositioned the “heartbeat” antenna, which is designed to pulse calibration signals at the prototype detector and tells us certain information about its ability to trigger on neutrinos and determine their direction. We chose a more ideal location based on heartbeat data taken the previous season. I later used this data to show that ARIANNA has the ability to distinguish the time of arrival of a signal in two different sensor antennas to a precision of 100 picoseconds. With Leah's help, I erected the larger, more powerful wind generator and watched as it begun to spin, providing sustainable power to the station which would eventually lead to data being taken further into the Antarctic winter. We began to pack up the gear, both survival and scientific, and awaited our helo extraction.
Monday, August 1, 2011
Here is part 2 of the guest post by Jordan Hanson, about the 2010 ARIANNA field season.
The beauty which surrounded us during our helo flight to the detector can only be inadequately described. We flew past windswept mountains covered in dark weather, accompanied by white glistening glaciers beneath. We observed rock formations and islands in the ice shelf that protruded upwards for a thousand feet, such as Minna Bluff. Finally, we passed Mount Discovery and proceeded onto the vast, open Ross Ice Shelf – a flat expanse of pristine snow-covered sea ice over half a kilometer thick. One hundred and twenty kilometers from our departure point, we located our detector.
After we touched down and the rotors of the helo stopped spinning, we began to unload the gear and set up camp. First we established a “cargo line,” a row of bags and tents that allowed us to access individual pieces of equipment easily in an environment in which it can be difficult to maneuver. We also had to scan for crevasses, potentially melted cracks in the ice that can have depths of hundreds of feet. With the help of ground penetrating radar, we were able to trace out a safe area on which we could safely build our camp. I remember it being so windy (in excess of 40 mph from the south) that my hands got numb each time I took them out of my parka pocket to take a bite of my sandwich.
Once we had constructed camp, we began cooking and boiling water to keep warm and get used to living there for two weeks. We had several tents: one for working and the kitchen, three tents for sleeping (Steve, Rebekah, and myself), and a tent which served as an outhouse. We unpacked our scientific gear and began installing it in the work tent. After we created our camp site, it was my job to establish a 1 kilometer flag line to be used in a later experiment. I went with a mountaineer from McMurdo, who examined the output of a ground-penetrating radar unit while I pulled it on a sled. Placing a bamboo flag every 100 meters, we staked out a crevasse-free line 977 meters long. Camp looked like a few yellow dots on a vast, flat white surface, backed by mountains covered with glaciers in the background. After placing the flags, we headed back to base.
I was eager to fix the detector, which had not come online yet since the sun had returned to shine on our solar panels. We had a small wind generator during the previous season, but it turned out not to draw enough power from the wind storms that happen every so often on the ice shelf. Steve injured his back the day we arrived in camp, so he returned to McMurdo for medical treatment while Rebakah mangaged the camp and I saw to the ARIANNA prototype. I had a satellite phone which I used to communicate with Thorsten Stezelberger, who installed the detector originally with Spencer Klein in the 2009-10 season. I noticed that the 12V lead-acid gel battery used to power the detector was cracked, having slightly frozen and expanded. However, it still held charge, and thus we do not expect that this was the problem.
It took us a long time to excavate the electronics box, which was buried in six feet of snow, beneath the metal rig that supports the solar cells. Once we had it in the tent, I used a Honda generator and a DC power source to power the electronics, while I checked each electronics component individually to located the problems. Before replacing anything, I extracted the data from the previous season and saved it on one of our computers and in other places. There was brand new event data that we had never seen before, since our station ran even after the wireless communications were removed. I replaced the CPU battery backup, which had lost its charge after so many months without power and in -30 degrees Celsius temperatures. I replaced the CPU itself, which appeared to be non-functional, and the analogue to digital converter (ADC) as well. After I fixed those components, I checked to see if the Iridium satellite modem began to draw current. I eventually figured out that the network settings such as port assignments had been lost and/or changed for certain systems upon shutdown, and after fixing all of that, the satellite modem began sending data North. Fixing the current prototype was a big victory for us, because it allowed us to take data during the 2010-11 season at a lower threshold, since man-made noise sources from the wireless communications equipment had been found and eliminated. In addition, I built and installed a taller, more powerful wind generator that allowed us to take data further into the winter while the sun dipped below the horizon.
Wednesday, July 27, 2011
I have been remiss about posting about ARIANNA, in particular on the 2010/11 field season. UC Irvine Prof. Steve Barwick and graduate student Jordan Hanson travelled back to the site in December, 2009. Jordan sent me some pictures and text describing that trip. Because of the length, it is divided into four posts. Here is part 1 of Jordans account:
The Journey to Moore's Bay, 2010
My name is Jordan Hanson, and I am a graduate student researcher at UC Irvine working for the ARIANNA collaboration. My research focuses on the viability of ARIANNA to detect high energy neutrinos in the background-free environment of Moore's Bay, in Western Antarctica. My adviser, Steve Barwick, and I, travelled to Antarctica in the winter of 2010 to revive the prototype station and make measurements of the properties of the ice beneath it.
Every long journey begins with a first step. Ours was to travel to Christchurch, New Zealand, which is the gateway city that coordinates flights to McMurdo Station, located on Ross Island in the middle of the Ross Ice Shelf. Christchurch hosts the United States Antarctic Program (USAP) and the clothing distribution center (CDC). Upon our arrival, Steve and I met with USAP personnel to gather our extreme cold weather (ECW) gear, necessary for landing on an ice shelf at almost 80 degrees South latitude. While staying at the Windsor Bed and Breakfast in Christchurch, we encountered other scientists traveling to the Antarctic continent to perform the season's research. There were geologists, climatologists, astronomers, and physicists like us. We even met several scientists in our field of high energy neutrino astronomy, working for the IceCube project (see recent posts on this blog). Specifically, we met a team led by Per-Olof Hulth, of the University of Stockholm. I had an interesting conversation with Reina Maruyama about DM-Ice, a project related to IceCube focusing on direct detection of dark matter.
On the morning of our departure, we had coffee with Vladimir Papitashvili, the director of the Aeronomy and Astrophysical Sciences Program (Office of Polar Programs) at the National Science Foundation. I learned about many other experiments like ours taking place around the Antarctic continent. When it was time to leave, we all boarded the bus to the C-17 and were escorted onto the aircraft by military personnel.
Although the details of McMurdo station and how it operates have been covered in previous posts, I'll recount our experiences briefly. We landed on the Ross Ice Shelf, near the southern tip of Ross Island, where there is a station called McMurdo station. In the summer months, it is home to over a thousand individuals, and it forms a scientific community complete with technical and logistical support staff. The dedication and hard work of these support staffs cannot be understated. Specifically, Steve and I worked with Jessy Jenkins, our point of contact, whose job it was to coordinate the accumulation of survival gear, our technical equipment, food and supplies, fuel, and helicopters necessary for accomplishing our mission. Rebekah Davis travelled with us initially to the field, to manage our camp and assist with things like tent building and radio communications. After assembling our gear and coordinating with helo-ops, we were ready to launch into the wilderness. We were accompanied by wireless communications technicians, led by Bill Nesbit, whose goal it was to establish wireless internet at the site of our prototype station.
Tuesday, January 4, 2011
After 7 construction seasons, IceCube is finally complete!
Construction ended quietly on Saturday, Dec. 18th(New Zealand date), as the last string was lowered into the ice, completing the 86-string, 5,160 optical module array. This was the last of 7 strings deployed in December; this was a very short season compared with the last two seasons, when 19 and 20 strings were deployed, respectively. Work at the Pole has now turned toward packing up the drill for long-term storage, upgrading the computer system on the surface, and sending now-surplus material North.
The occassion was celebrated by press-releases galore:
Several groups have issued press releases to note the occasion:
From the NSF and University of Wisconsin:
From DESY (in German):
There was also a modicum of press coverage - check out google or google news for the latest.
A belated Happy Holidays to everyone.