KM3NeT - News Archive

Archive of news items

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


KM3NeT against racism and discrimination

10 June 2020 – The KM3NeT  Collaboration is deeply saddened by the recent outbreaks of violence and hatred against people of colour. They once again laid bare the enduring worldwide systemic racism.

The researchers in KM3NeT are strongly against any kind of racism or discrimination. We urge all citizens of the world and their leaders to embrace all actions suited to establish equal opportunities for all, and forever.

As a collaboration, we will increase awareness on the impact of unintended racism and discrimination in our universities and research institutes and in particular in our collaboration.

KM3NeT collaboration meets online

8 June 2020 – Like so many other meetings, also the Spring Collaboration meeting of KM3NeT went online during corona times.  A week full of discussions  started today. An online concert and quiz are planned. Of course the traditional group photo has already been made.


Neutrino candidates in KM3NeT/ORCA6

05 February 2020 – The ORCA6 detector of KM3NeT is taking data since 27 January 2020  on a 24/7 scheme. Physicists are ‘on-shift’ to remotely or on-site operate the detector in the deep sea. The recorded data is stored in the computer centres of the KM3NeT Collaboration for further analysis.

The first step is to reconstruct from the recorded light flashes the path of charged particles through the ORCA6 detector.  Most of them are muon particles generated in the Earth’s atmosphere and travelling through the detector from above. We showed already an example  in the news item  of 27 January.

In the video below we show a series of five charged particles entering the detector from below or from the side. This is an indication that they have been created in an interaction of a neutrino with the matter surrounding the detector.



In the picture below, you see the plots that KM3NeT physicists like: six plots showing for each of the six detection units in ORCA6  the optical sensors that – in the pitch dark deep sea – are ‘hit’ by  faint light.  Each time a sensor is hit, the position of that sensor in the sea  and the time it was hit is recorded. The plots show on the y-axis the height of the sensors in the detector and on the x-axis the time. The red circles and the red line show how the light cone generated by a charged particle from below has crossed the detector. As function of time (in nanoseconds), the position of the next hit sensor is higher in the detector, indicating that the particle is travelling upwards. The blue circles are background hits.


ORCA6 completed

With the installation of two more detection units at the French site of KM3NeT, the first phase of building the ORCA detector is completed! Since 27 January 2020, the detector is taking data with six detection units.

During a sea operation the 24-26 January 2020, the two new detection units have been connected to the KM3NeT/ORCA seafloor network at the KM3NeT/ORCA deep sea site, 40 km offshore from Toulon, France. The detection units were successfully positioned twenty metres within a metre of their target position 2.5 km below the sea surface. This highlights the skills of the staff on board the deployment ship, the precision of the custom acoustic positioning system and the maturity of the deployment method based on an innovative launching vehicle.


Immediate data taking

Using a robot, remotely operated from a second ship, the deployed units were connected to the seafloor network of the ORCA site. After a visual inspection of the detection units by the robot, the power was switched on and data taking with ORCA6 started immediately.

The ORCA detector has now six detection units – hence ORCA6. These are six vertical lines each with 18 sensor modules. A module houses 31 light sensors (photo-multiplier tubes) to record the faint Cherenkov light generated by charged particles in the sea water. That makes now 6x18x31= 3348 photo-multipliers in total in ORCA6. Each photo-multiplier records the intensity of the light flash and when it arrives. A compass, tilt meter and acoustic receiver record the position of the module in the sea water. With these measurements the path the charged particle took through the detector is precisely reconstructed.

The video below shows a selection of down-going cosmic rays (muons) passing through the ORCA6 detector soon after power up.




Operating six detection units is an important milestone for KM3NeT as it marks the completion of the so-called ‘Phase 1’ of the project. In the next phase of KM3NeT/ORCA, the detector will be extended to 115 detection units.


Photo gallery