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IceCube, KM3NeT and Baikal-GVD all detect neutrinos, but they are not interchangeable versions of the same instrument. IceCube uses Antarctic ice; KM3NeT instruments Mediterranean seawater with two detectors designed for different energy ranges; and Baikal-GVD operates in Lake Baikal’s freshwater. Their sites, layouts and scientific roles differ, so there is no well-supported single “best” observatory based on size alone.
At a glance: IceCube, KM3NeT and Baikal-GVD
| Observatory or detector | Location and medium | Established role | Scale and status |
|---|---|---|---|
| IceCube | South Pole; natural Antarctic ice | Neutrino astronomy and multimessenger astrophysics, along with neutrino physics, cosmic rays, dark matter and glaciology. Its collaboration describes observations spanning GeV to PeV energies. | A cubic-kilometer Cherenkov detector; the Particle Data Group’s 2025 review lists its instrumented volume as 1.0 km³. |
| KM3NeT/ARCA | Deep Mediterranean seawater off Sicily | High-energy cosmic-neutrino detection. | Design target of about 1 km³ in two building blocks, each planned with 115 detection units. Installation is ongoing, and the operating detector has a smaller, growing number of units. |
| KM3NeT/ORCA | Deep Mediterranean seawater off Toulon, France | Lower-energy atmospheric neutrinos, including studies to determine the neutrino mass hierarchy. | Designed as about seven megatonnes of instrumented seawater, with optical modules arranged more densely than in ARCA. |
| Baikal-GVD | Lake Baikal, Russia; freshwater | A large-volume underwater neutrino telescope. | KM3NeT says the project launched in 2015. The cited comparison material does not establish a current installed volume or deployment count. |
IceCube’s energy range and science areas are described by the IceCube Collaboration. KM3NeT’s detector roles, design descriptions and installation status come from its detector overview and ARCA and ORCA description. Baikal-GVD’s launch year and the project context are listed by KM3NeT in its related research projects page.
How their locations and detector media differ
IceCube: sensors embedded in Antarctic ice
IceCube is a Cherenkov detector embedded in natural ice at the South Pole. When a neutrino interaction produces charged particles, those particles can emit Cherenkov light, which the detector’s optical sensors register. IceCube’s location and medium give it a distinct geometry and environment from the underwater telescopes.
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KM3NeT places optical sensors in deep Mediterranean water. ARCA is off Sicily, while ORCA is off Toulon, France. Both use seawater, but their sensor layouts differ because their scientific targets differ: ARCA is spread over a larger volume for high-energy cosmic neutrinos; ORCA packs its optical modules more closely for lower-energy atmospheric neutrinos.
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Baikal-GVD: an observatory in freshwater
Baikal-GVD is located in Lake Baikal and uses freshwater rather than polar ice or the sea. That makes it a third site and medium in this comparison, not simply another Mediterranean detector. The cited project page identifies it as a large-volume underwater telescope, but does not provide a current installed scale suitable for a direct numerical comparison.
Why KM3NeT has two complementary detectors
ARCA is designed for high-energy cosmic neutrinos
ARCA’s sparse, large-scale layout is intended to detect high-energy cosmic neutrinos. KM3NeT describes its design target as about 1 km³, arranged in two building blocks of 115 detection units each. That figure is a planned design scale, not a claim that all units are already installed: the collaboration says installation continues while the detector operates with a smaller, growing number of units.
ORCA is denser and targets lower energies
ORCA is designed for lower-energy atmospheric neutrinos and measurements related to the neutrino mass hierarchy. Its design calls for about seven megatonnes of instrumented seawater and a denser optical-module distribution than ARCA. KM3NeT explains that this denser arrangement is suited to registering lower-energy atmospheric neutrinos needed for mass-hierarchy studies.
These are different design choices within one collaboration, not competing claims about which detector is superior. The larger, sparser ARCA and the smaller, denser ORCA are intended to address different neutrino populations and questions.
What the volume figures do—and do not—tell you
The Particle Data Group’s 2025 review lists IceCube at 1.0 km³ of instrumented volume. KM3NeT describes ARCA’s target as about 1 km³, while ORCA’s design is about seven megatonnes of instrumented seawater. These numbers describe different facilities and design quantities; they do not by themselves measure how often each detector will identify a neutrino of a given kind.
To compare scientific performance fairly, a reader needs like-for-like published measures, such as effective area, angular and energy resolution, event channel, energy range, exposure, background rejection and the date of the analysis. A detector’s sensitivity depends on those factors as well as its geometry. The cited sources do not provide a harmonized, current performance table for IceCube, both KM3NeT configurations and Baikal-GVD, so a numeric sensitivity ranking is not established.
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Operating IceCube versus a growing KM3NeT installation
IceCube is described as an existing cubic-kilometer observatory. KM3NeT’s ARCA and ORCA are already operating, but installation is still underway and their arrays are growing toward their design configurations. Comparing IceCube’s operating scale with KM3NeT’s full design target without this distinction would conflate present detector status with planned capacity.
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KM3NeT’s related-projects page gives 2015 as Baikal-GVD’s launch year. The cited material does not establish its current installed volume or deployment count, so it cannot support a precise scale comparison with IceCube or KM3NeT.
ANTARES is a predecessor, not a current competitor
ANTARES was a Mediterranean deep-sea neutrino telescope near Toulon and a predecessor to KM3NeT. KM3NeT says ANTARES was decommissioned in 2022 after 14 years of data taking. The Particle Data Group’s 2025 review lists its instrumented volume as 0.010 km³, a historical comparison rather than an operating facility’s current scale.
Where IceCube-Gen2 fits
IceCube-Gen2 is a planned extension at the South Pole, not the size of the operating IceCube detector. The Particle Data Group’s 2025 review lists a planned scale of 5–10 km³ and describes a future low- and high-energy extension with a surface array and radio detection. That planned figure should not be used to claim that IceCube currently instruments a volume of that size.
Which observatory is “best”?
There is no single winner established by the available figures. IceCube offers a cubic-kilometer Antarctic-ice detector with broad neutrino and multimessenger science goals; KM3NeT divides its effort between high-energy cosmic neutrinos with ARCA and lower-energy atmospheric neutrinos with ORCA; Baikal-GVD adds a freshwater site. Which facility is most useful depends on the neutrino energy, event type and scientific question being considered. A defensible performance judgment requires comparable measurements for the same channel and analysis conditions—not just instrumented volume or a project’s planned size.
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