3:54 p.m., Dec. 20, 2010----Culminating a decade of planning, innovation and testing, construction of the world's largest neutrino observatory, installed in the ice at the geographic South Pole, was successfully completed Dec. 18, 2010, New Zealand time.

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The last of 86 holes had been drilled and a total of 5,160 optical sensors are now installed to form a cubic kilometer of instrumented ice -- of the IceCube Neutrino Observatory -- located at the National Science Foundation's Amundsen-Scott South Pole Station.

The announcement was made in a news release issued jointly by the National Science Foundation (NSF) and the University of Wisconsin-Madison, the lead coordinating institution for the $279 million project, which included the University of Delaware as a major scientific collaborator.

The IceCube Neutrino Observatory is among the most ambitious and complex scientific construction projects ever attempted, encompassing an expanse of almost 200 football fields across and a mile-and-a-half deep in the Antarctic ice sheet. From its vantage point at the end of the world, the observatory provides an innovative means to investigate neutrinos -- fundamental particles that originate in some of the most spectacular phenomena in the universe.

Trillions of neutrinos stream through the human body at any given moment, but they rarely interact with regular matter, and researchers want to know more about them and where they come from.

In the deep, dark stillness of the Antarctic ice, IceCube records the rare collisions of these elusive sub-atomic particles with the atomic nuclei of water molecules of the ice. Some neutrinos come from the sun, while others come from cosmic rays interacting with Earth's atmosphere, and dramatic astronomical sources such as exploding stars in the Milky Way and other distant galaxies.

The size of the observatory is important because it increases the number of potential collisions that can be observed, which appear as flashes of light in the dark, clear ice, making neutrino astrophysics a reality.

Eighty-six strings, each with 60 sensors, make up the main IceCube detector. It was installed using a special hot-water drill, which bored holes to depths between 1,450 and 2,450 meters (0.9 - 1.5 miles) through the ice sheet. Optical sensors attached to cables were then lowered into the holes.

Above each string, on the top of the ice, sit four more sensors, forming the IceTop array. This array combined with the IceCube detector form the IceCube Observatory whose sensors record the neutrino interactions.

A University of Delaware team led by Thomas Gaisser, Martin A. Pomerantz Chaired Professor of Physics and Astronomy, was responsible for installing the IceTop surface array of detectors, which required the painstaking work of freezing digital optical modules in clear ice, without bubbles or cracks.

Gaisser and his research team from the Bartol Research Institute reported their efforts over the past four years through a popular blog series and a classroom educational experience that included a “Phone Call to the Deep Freeze,” connecting the Antarctic team with secondary school students in Delaware and across the U.S.

“With IceCube and its IceTop array on the surface working together, we will have a unique and unprecedented detector for neutrino astronomy and for cosmic-ray physics,” Gaisser said.

To build the observatory, all project personnel, equipment, food and detector components had to be transported to Antarctica from around the globe, flown in via ski-equipped C-130 cargo aircraft from McMurdo Station near the Antarctic coast, more than 800 air miles away.

The construction team worked only during the relatively warm and short Antarctic summer --from November through February, when the sun shines 24 hours a day.

“IceCube is not only a magnificent observatory for fundamental astrophysical research, it is the kind of ambitious science that can only be attempted through the cooperation -- the science diplomacy, if you will -- of many nations working together in the finest traditions of Antarctic science toward a single goal,” said Karl A. Erb, director of NSF's Office of Polar Programs.

In addition to researchers at universities and research labs in the U.S., Belgium, Germany and Sweden -- the countries that funded the observatory -- IceCube data are being analyzed by the larger IceCube Collaboration, which also includes researchers from Barbados, Canada, Japan, New Zealand, Switzerland and the United Kingdom.