Seven years later, the IceCube Upgrade has now been successfully deployed, marking the first significant expansion of the Observatory since its completion 15 years ago, and U.S. Senator John Curtis (R-UT) was recently on hand in part to acknowledge the historic benchmark.
The University of Utah’s Department of Physics & Astronomy is a critical collaborator of the Observatory. At the start of the construction of the detector in 2005, current Department Chair Carsten Rott performed detector calibration and verification efforts for the Observatory as a postdoctoral researcher at Penn State University. Faculty member Dennis Soldin who last year was installed as analysis coordinator of the global project during the annual collaboration meeting held in Salt Lake City is responsible for the oversight, management and approval of all physics analysis at the IceCube Neutrino experiment which includes any analysis of the data with the newly deployed strings, part of the multi-year-long IceCube upgrade.
Significantly, during the upgrade, the added strings consist of six more closely spaced and more densely instrumented cables of light sensors at the bottom center of the 86 existing strings, adding more than 600 new and enhanced light sensors and calibration instruments already embedded in the ice.
One km3 of ice
Located at NSF’s Amundsen-Scott South Pole Station, the IceCube Neutrino Observatory uses one cubic kilometer (1km3) of Antarctic ice to detect nearly massless particles called neutrinos that travel through outer space. Because they rarely interact with matter, neutrinos can provide a lens into otherwise obscured extreme cosmic environments, carrying valuable information about their sources. Thus far, the Observatory has discovered astrophysical neutrinos, identified two galaxies as neutrino sources and observed neutrinos from our own Milky Way galaxy.
The IceCube Neutrino Observatory uses more than 5,000 light sensors to capture the faint light emitted by secondary charged particles produced by neutrino interactions in the ice. The pristine quality of the Antarctic ice makes it an ideal medium for detecting this light. The IceCube Collaboration, with over 450 scientists from around the world, then takes these light patterns to reconstruct the energy and direction of the neutrino in order to determine its origin.
The upgrade will allow more precise measurements of neutrino properties like neutrino oscillations, a phenomenon where atmospheric neutrinos can morph into different types or “flavors”—electron, muon, and tau. With these improvements, the Observatory will be the premier neutrino experiment for long-baseline oscillation measurements using atmospheric neutrinos.
Utah contribution
Contributing to the upgrade, Carsten and the U team were instrumental in securing a new camera system from Korea to better understand the environment and the ice properties of the operation. The system will improve the scientists’ ability to determine the cosmic ray composition and measure neutrinos from galactic supernovae. The U team is also helping to develop solar panels, tested on Utah’s salt flats, to replace kerosene-powered components of the operation, which can result in substantial cost saving in the future.
“Using the enhanced devices deployed in the ice,” said Soldin, “scientists will be able to better characterize the surrounding ice, leading to improved reconstruction of neutrinos and a [retroactive] reanalysis of 15 years of archived data.”
“My group,” said Rott, “designed and built a novel camera-based calibration system, which has now been deployed with the IceCube Upgrade and consists of over 2,000 cameras and LED light sources. It will be used to better understand the properties of the Antarctic ice that is used as a detector medium for the neutrinos. It might uncover new phenomena, which have so far been hidden in the data.”
The U is currently represented onsite in Antarctica by post-doctoral researcher Vedant Basu using an ice water drill at the center of the construction of the detector. “Vedant is like a universal talent," said Carsten. "He is good at data analysis, but also has a really strong engineering background. He has fit really well into this drilling team and is playing a pretty cool role there.” Basu, who has been abroad since last October—much of his time spent in Antarctica—was present to meet U.S. Senator John Curtis, from Utah, who toured the site this month.
Hot water drill system
A team of IceCube Neutrino Observatory engineers and scientists and additional engineers from the U.S., Sweden, Thailand, New Zealand, Taiwan, Germany, Australia and Japan, in coordination with the Antarctic Support Contract, overcame numerous challenges and the harsh working conditions at the South Pole to complete the upgrade. During the third and final field season, a five-megawatt hot water drill system, the largest such system in the world, was used to drill the six holes for the upgrade. The drill team worked around the clock, with each hole taking approximately three days to complete.
“The successful completion of the IceCube Neutrino Upgrade relied on the critical support of the South Pole station and Antarctic service contractors,” said Project Director Vivian O’Dell. “Their essential contributions allowed us to complete the entire installation in one drilling season despite extreme weather conditions and logistical constraints, for which I am deeply grateful.”
As soon as each hole was drilled, the installation team went to work deploying the upgrade’s higher performing light sensors. Two new types of light sensors, the multi-PMT digital optical module (mDOM) and the “Dual optical sensors in an Ellipsoid Glass for Gen2” (D-Egg), boast two to three times more sensitivity than the sensors that make up the current detector.
Global collaboration
A true global collaboration, the upgrade tapped international institutions in Germany and Japan, which contributed the light sensors, and Sweden, which contributed the surface cables. The US provided the main cables and played a central role in project coordination, logistics, drilling, and sensor construction and testing.
In addition to the mDOMs and D-Eggs, teams based in the U.S., Germany, Sweden, and Korea contributed precision calibration devices and special modules, such as cameras and prototype sensors for the proposed extension of the Observatory, IceCube-Gen2.
The upgrade also presented an opportunity to support other scientific endeavors along the way. In collaboration with the U.S. Geological Survey, the crew installed two seismometers beneath the Antarctic ice. These seismometers are the deepest in the world and will help scientists monitor earthquakes with unprecedented clarity. The team has also collected water samples for microbiologists in the U.S. who are looking for signs of life in the deep ice.
Now that the upgrade is finished, commissioning will continue to be the top priority in order to verify functionality of the newly deployed devices. The Upgrade, a steppingstone to the proposed IceCube-Gen2, which is eight times the instrumented volume of its predecessor, will ensure that the Observatory remains at the forefront of neutrino astronomy for years to come.
Back in Utah, aligned with the aspiration to be an “impact university,” results from the IceCube Neutrino Observatory will be integrated into The IceCube Masterclass at the U April 25, 2026 in which high school students and their science teachers participate in an “authentic physics experience,” according to Soldin. This includes hands-on activities such as building tabletop cloud chambers, working with real IceCube cosmic-ray data and participating in a Zoom call with IceCube scientists at the South Pole in concert with other participating institutions worldwide.