KM3NeT - News Archive

Archive of news items

Upgrade of ARCA infrastructure

21 December 2020 – Just in time for the winter break, a nice Christmas present was delivered to KM3NeT:  the second main cable between the ARCA detector site and the shore station in the lovely village of Porto Palo di Capo Passero at the isle of Sicily, Italy has been installed. It is an important step in the program of upgrading the ARCA seafloor network for the ARCA detector near Sicily, Italy.

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‘Draw me a neutrino’

13 December 2020 – Have a look at the banner pictures of the KM3NeT home page. During December 2020 and January 2021, we display amazing drawings of the three neutrino-flavours: muon-neutrinos, electron-neutrinos and tau-neutrinos.

The drawings are made by the winners of the KM3NeT contest ‘Draw me a neutrino‘. We invited everyone from young to old to use their imagination and picture a neutrino.


About 500 people from Ecuador, France, Georgia, Greece, India, Italy, Morocco, Netherlands, Switzerland, Russian Federation, Spain and the UK took up the challenge.

The best drawings are now on display in an online exhibition in our Virtual Neutrino Art Centre (

You can find the drawings and the names of their authors here.

And a high resolution version of the drawings .



New paper: Deep-sea deployment of the KM3NeT neutrino telescope detection units by self-unrolling

20 November 2020 – The KM3NeT Collaboration has published a new paper, in which we describe in detail the innovative deployment method for KM3NeT detection units.

No standard moorings

A custom design was necessary, because the KM3NeT mooring – the detection unit -is different from moorings typically used for oceanography.

For instance, in KM3NeT moorings the instrumentation is contained in transparent and thus unprotected glass spheres. That makes them vulnerable during deployment. Moreover, we use a long, thin and soft tube with optical fibres and thin copper wires for data transmission and electrical power for the instruments. That makes the units even more vulnerable.

On top of that, because we use thin Dyneema ropes as strength members in stead of a standard steel cable the mooring is not strong enough to carry the weight of the anchor during deployment.

All this makes it more difficult to deploy the unit without breaking it and we needed a customised deployment method.

Different from other telescopes

Compared to other neutrino telescopes such as ANTARES in the Mediterranean Sea and GVD in Lake Baikal, we designed the KM3NeT detection unit even more slender to minimise the amount of material used for support of the sensor modules. An other – economical – difference is that we have to deploy hundreds of units more for KM3NeT in a period of a few years while keeping the costs for sea operations at a minimum. These are even more reasons for innovation of the deployment method.


We developed a custom-made, fast deployment method. Despite the length of the detection unit of several hundreds of metres, we managed to compact it into a small, re-usable spherical launching vehicle instead of deploying it weight down from a surface vessel – the standard method in oceanography. We dubbed the vehicle LOM for Launcher of Optical Modules.

The tric

Once the LOM has reached the seafloor, the innovative tric begins. The buoyant LOM rolls upwards along the Dyneema ropes. While doing so, it spits out the glass spheres with instrumentation attached to the ropes. As a result, while floating to the surface, the LOM leaves the detection unit behind at the seabed, unfurled to its full vertical length. Ready for data taking during many years to come.

Cost effective

The LOM has two economical advantages. First, it does not take a lot in space. Therefore, during a sea operation many LOMs can be stored on deck of a ship. Secondly, we can lower the LOM to the seabed at high speed. As a result, we need less expensive ship time for the installation of the KM3NeT telescope.


As far as we know, the method of compact deployment of moorings with a LOM is unique. The method is the result of close cooperation between engineers and scientists in the KM3NeT Collaboration from both oceanographic and astrophysics institutes. We hope it will inspire oceanographic scientists for the design and deployment of their future moorings.


In the paper, we describe the details of the design of the LOM, the loading with a detection unit, and its underwater self-unrolling. You find the reference below.

LOM in pictures

Pictures below reflect the  process from idea to realisation. First an impression of the initial ideas for deployment by @Marijn van der Meer/Quest. Followed by the technical design of the KM3NeT detection units that must be installed and the design of the LOM launcher vehicle. Finally, photos of the first prototype of the LOM and the final version that is now regularly used for the installation of the detection units of the ARCA and ORCA detectors of the KM3NeT telescope.




Deep-sea deployment of the KM3NeT neutrino telescope detection units by self-unrolling

The KM3NeT Collaboration: S. Aiello et al 

2020 JINST 15 P11027

Successful sea operation in times of corona

17  – 24 October 2020 – After COVID tests and a few days of quarentine, a KM3NeT team of CPPM boarded the cable layer Raymond Croze late last night in the harbour of La Seyne sur Mer in the South of France

Their mission is the deployment and installation of a second node in the seafloor network for the ORCA detector.

The junction box has been ready since spring, but COVID got in the way until now.

A five day sea campaign involving three ships is ahead.

Stay tuned!

The KM3NeT team of CPPM, Marseille.

The ORCA junction box.

UPDATE on 17-10-2020

Operations at sea progressing well. Adding the second node in the network – see the layout below –  requires a lot of cabling handling, including dragging the cable already deployed earlier. For this you need dedicated tools, one of them the dragging tool in the picture below.


Notice, that the crew is following COVID-regulations wearing face masks.

Current position of the cable ship Raymond Croze: (


Update on 18-10-2020

You can follow Paschal Coyle on board of the cable ship Raymond Croze on the social media: @paschalcoyle. He is posting about the progress of the sea operation.


Update on 19-10-2020

The ship crews and the KM3NeT team on board the three ships involved, have worked hard. The input cable at the side of the junction box was extended with with 3.5 kilometre.  The 36 fibres in the cable have been spliced and connected, the quality of the splice verified using X-ray and protection of the joint applied.

Connection was made with the output cable of the junction box.  For this, the free end of the cable had to be transferred from the Raymond Croze to the Castor 2 and the joint made. This cable will used for the descend of the Junction Box, which will be managed by the Castor 2.



Currently, the deployment of the Junction Box is in progress. It will take some time before it will reach its position at the seabed at a depth of about 2500 m. It is mandatory that it will hit the seabed at the designated position with a precision of about 5 meter.


Update on 26 October 2020

The sea campaign came to a successful end! Some delay because of bad weather conditions, but all equipment is installed and working.  Congratulations to the crew and the KM3NeT staff!



Update on 22 November 2020

Here is a video summarising the operation in a few minutes:

New paper: Using convolutional neural networks for event reconstruction for ORCA

12 October 2020 – The KM3NeT Collaboration has published a new paper that aims at demonstrating the general applicability of deep convolutional neural networks to neutrino telescopes, using simulated datasets for the KM3NeT/ORCA detector as an example. To this end, the networks are employed to achieve reconstruction and classification tasks that constitute an alternative to the analysis pipeline presented for KM3NeT/ORCA in the KM3NeT Letter of Intent. They are used to infer event reconstruction estimates for the energy, the direction, and the interaction point of incident neutrinos. The spatial distribution of Cherenkov light generated by charged particles induced in neutrino interactions is classified as shower- or track-like, and the main background processes associated with the detection of atmospheric neutrinos are recognized. Performance comparisons to machine-learning classification and maximum-likelihood reconstruction algorithms previously developed for KM3NeT/ORCA are provided.

The conclusion is that this application of deep convolutional neural networks to simulated datasets for a large-volume neutrino telescope yields competitive reconstruction results and performance improvements with respect to classical approaches.


Event reconstruction for KM3NeT/ORCA using convolutional neural networks


Waves in the deep sea – a new mooring of temperature sensors

10 September 2020 – Like in all oceans, deep in the Mediterranean Sea turbulent waves occur which influence under water life because they transport water of different temperatures and important nutrition. Understanding the occurrence and behaviour of the ‘underwater waves’ is the objective of Hans van Haren and his team of the Royal Netherlands Institute for Sea Research NIOZ – member of the KM3NeT Collaboration (see article in Europhysics News 51/2 ).

The team has developed a large mooring construction comprising an array of temperature sensors that during two years will precisely measure the temperature of the deep sea water near the KM3NeT site off-shore Toulon, France. The measured temperature profiles will reveal the existence and behaviour of underwater turbulence and internal waves at the site. From a distance the image of the mooring resembles  that of the KM3NeT array of optical sensors (see picture below).

The mooring consists of a 70 m diameter large steel ring, holding a network with 3000 high-precision temperature sensors distributed over 45 vertical lines, 125 m high and 9.5 m apart. On land this already looks quite impressive (see drone video below) but in sea the whole construction will fill a half cubic hectometre seawater volume. The installation of the mooring has some resemblance with the installation of the sensor array of KM3NeT. This is not surprising since the NIOZ  is the institute where the KM3NeT compact deployment method was invented first. The lines with temperature sensors are compacted in small packets that are anchored on the seabed. Then they unfurl one by one to their full lengths. The major difference with the KM3NeT deployment technique is that the mooring structure of 45 lines is deployed as a whole, while for KM3NeT each line is deployed separately.

The deployment of the temperature mooring is planned for the second week of October after assembly in the harbor of Toulon. Stay tuned!


See also : a drone video by Hung-An Tian, NIOZ PhD student at

Pictures (courtesy NIOZ): After assembly, the mooring is towed to the deployment site and deployed using a custom-made ‘parachute’. Once in position, the lines will automatically unroll to to their full length after five days.







UPDATE on 2020/10/02

The NIOZ 3D temperature array is being assembled in the harbour of La Seyne sur Mer between 28 September and 6 October (see pictures). Today the construction had to be abandoned due to a rain-storm.

After Covid-19 tests and quarantine of the team, the RV Pelagia of the NIOZ Institute will sail out and tow the structure to its location for deployment sometime between 9 and 15 October, depending on permissions and the weather conditions.

Follow the blog van Hans van Haren (NIOZ) and stay tuned!



UPDATE on 2020/10/06

Despite the devastating storm and heavy rain of the last few days in France, the assembly of the array is almost ready.


UPDATE on 2020/10/09

The RV Pelagia of the  Royal NIOZ institute in the Netherlands has arrived in La Seyne dur Mer and departed again towing the large structure for the deployment site near the KM3NeT site.

At the moment of writing this update, the Pelagia has arrived  at the deployment site, about 40 kilometer off-shore and is maneuvering (see screen shot of the Marine Traffic site).



UPDATE on 2020/10/10

Preparations for the deployment of the structure, which in the mean time has reached its designated position at the seabed at a depth of about 2.5 km. It will stay there for 3 years.



Update on 23/11/2020

A ROV visited the structure at a depth of about 2400 m. The pictures made by the ROV show buoys at the top of the moorings and part of the steel ring on the seabed together with a few anchors of the moorings. The temperature sensors are visible as small tubes attached to the cables.



‘6 strings, 6 months’

On 27 July 2020, the ORCA detector of KM3NeT reached a milestone: its first 6 strings were continuously taking data since 6 months. With two musical productions of the amazing talents in the KM3NeT Collaboration, the milestone  was celebrated.

Enjoy ‘6 strings, 6 months’, the song of the Route 66 of KM3NeT and an instrumental piece on 6 pianos by 6 players.

Both productions were recorded in corona times – at large distances between the performers.

New paper: gSeaGen software tool

13 July 2020 – The KM3NeT Collaboration has published the details of gSeaGen, a simulation software package for efficient generation of neutrino events for the analysis of  measured light signals in the KM3NeT telescopes.  Monte Carlo simulations play an important role in the data analysis of neutrino telescopes. They are used to design reconstruction algorithms for neutrino events and to estimate cosmic and atmospheric signals in various physics analyses.

The new gSeaGen  software  tool is based on code of the GENIE Collaboration which aims at developing a global software platform for the Monte Carlo simulation of neutrino interactions with energies up to PeV scales. Currently, the GENIE simulation code focuses mainly on events in the low-energy range (5 GeV) and  is valid up to 5 TeV.

As described in the paper,  the gSeaGen tool allows for the generation of electron, muon and tau neutrino.  Its application for the KM3NeT telescopes is described in detail.

KM3NeT Collaboration, S. Aiello, et al.,  Computer Physics Communications 256 (2020) 107477

New paper: The Control Unit of the KM3NeT Data Acquisition System

17 June 2020 – The KM3NeT Collaboration has published a new paper about the control unit of the data acquisition system. The data acquisition control software  of KM3NeT is operating both the off-shore detectors in the deep sea and in the lab the testing and qualification stations for detector components. The software, named Control Unit, is highly modular. It can undergo upgrades and reconfiguration with the acquisition running. Interplay with the central database of the Collaboration is obtained in a way that allows for data taking even if Internet links fail. In order to simplify the management of computing resources in the long term, and to cope with possible hardware failures of one or more computers, the KM3NeT Control Unit software features a custom dynamic resource provisioning and failover technology, which is especially important for ensuring continuity in case of rare transient events in multi-messenger astronomy. The software architecture relies on ubiquitous tools and broadly adopted technologies and has been successfully tested on several operating systems.

KM3NeT Collaboration, S. Aiello, et al., Computer Physics Communications 256 (2020) 107433,, arXiv:1910.00112v1