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Time to resume data taking in ARCA!

15 September – after the recovery of two old detection units, already left disconnected after previous sea campaigns – the so-called PPM-DU (Pre-Production Model of Detection Unit), a 3-digital optical module unit used for qualification of the project in the sea as early as in 2014, and one of the first prototype full-size detection units deployed in spring 2016, the sea campaign of ARCA has been completed today.

A lot of good work has been done in this intense week – and we are very grateful for that to the onshore and offshore teams. We also thank all the various institutes which contributed to the construction and preparation to deployment of the detection units – in next entries on this blog we will report on these demanding activities.

As a summary, during this sea campaign:

  • the positioning system has been maintained by installing two acoustic beacons and recovering an exhausted one (these are autonomous devices running on batteries which need to be refurbished in due time)
  • five interlink cables were installed on the sea bottom
  • three new detection units were installed, i.e.: deployed to the sea bottom, connected to the submarine infrastructure, unfurled to their nominal shape (standing for almost 700 m above the sea floor) and proved to work
  • the launcher vehicles of the three installed detection units and the cable trays used for deploying the cables were of course recovered, to be reused for next campaigns

After completing this set of operations, Handin Tide safely sailed back to the port of Malta.

Note that it was decided not to install the remaining two detection units which were onboard the ship, due to a mechanical issue that will be solved. These two detection units have been taken back to shore. After adequate refurbishment, they will be added to those already in preparation. Nothing is lost therefore: they will be included in the next sea campaign.

In the end… it’s time to resume detector operation of ARCA now!

The KM3NeT Collaboration is very grateful to the onshore (in the picture) and offshore teams for their hard work, instrumental for the success of this sea campaign – note that the full operation was performed respecting all applicable rules against COVID-19: our onshore team got so close together only for the time of a… “cheese”!

ARCA enlarged with 3 new detection units!

14 September – the ARCA telescope is now enlarged with 3 new detection units.

The procedure for installing a detection unit in ARCA is as follows: firstly the detection unit is lowered from the deck of the ship. When it reaches a low level above the sea floor, the ROV (the submarine vehicle operated from the ship) comes in play: it takes a bridle and helps to guide the detection unit to its target position on the sea bottom; it also rotates it so that the panel for connection of the submarine cable faces the direction of the submarine junction box. Only at that point, the detection unit is lowered on the sea floor. After a quick visual check, the ROV detaches the deployment line. The ROV then picks up the cable which had been previously routed on the sea bottom and which is connected to the junction box on the opposite end, and plugs it to the detection unit. Then the onshore team is asked to perform a first round of test to ensure that the detection unit meets its functional requirements. After that, the ROV opens a release mechanism that lets the deployment vehicle on which the detection unit is furled free to go. The vehicle is buoyant and starts coming up; while doing so, it rotates, leaving the detection unit, which is tied to the anchor on the sea floor, upright – a sort of giant, and reversed yo-yo!

After unfurling, the deployment vehicle is recovered from the ship, to be reused for next deployments.

A final test of the newly installed and unfurled detection unit is then performed to confirm that the detection unit works as expected.

This happened three times today!

An optical spectrum analyzer is used in the shore station for a check of the quality of the communications with the detection unit (almost 100 km away, 3,500 m deep). Each signal (in the form of a peak) in the plot corresponds to one of the optical modules of the detection unit. Believe it: when this plot appears on the screen of the instrument, it is a fantastic reward for all the hard work done in the sea campaign and before!

 

 

 

 

 

 

 

 

 

 


A very busy day, offshore and onshore

13 September – Still a day packed of activities today!

The status at the moment is that all interlink cables have been layed down on the sea floor and two detection units have been deployed and connected to the junction box. The detection units are still furled on their launcher vehicles; they will be allowed to unfurl tomorrow – since the launcher vehicle has to be recovered from the ship after it reaches the surface, it is better to perform this operation in the daylight.

Pre-unfurling functional tests performed from the onshore control station show that those first two detection units are in good order.

Deployments of the next detection units will continue during the night.

The onshore team in the control station at Portopalo di Capo Passero, Sicily, Italy.

 

 

 

 

 

 

 

 


Good progress, despite adverse sea condition

12 September – there has been good progress in the operation so far!

The two cable reels are also deployed. The cables for connecting four detection units are already layed on the sea bottom and connected to the junction box. There is only one cable left to install.

While proceeding with these activities, however, the weather conditions worsened. The sky was still sunny, but waves mounted high: “We have a lot of sun here, but we are dancing a lot” commented Daniele Vivolo, who is among the KM3NeT team onboard the ship.

In such situation the risks when putting the equipment in water increase significantly. It was therefore decided to put the operation on hold, waiting for an improvement of the sea state.

In late afternoon, the sea had calmed down significantly, and the operations were resumed.

As we write this post, the first detection unit of the set of five included in this campaign is already in water, travelling into the deep, dark sea, down to 3,500 meters depth. There it will meet the ROV (the submarine vehicle operated from the ship), which will take care of the next steps: to assist in carefully positioning the detection unit on the sea bottom and to connect it to the cable already in place. Have a safe trip!

In the movie: the first detection unit is prepared for deployment.


First day of deployments at the ARCA site

11 September – operations are proceeding smoothly on Handin Tide.

The two new optical beacons of the positioning system are already placed on the sea bottom – these are autonomous devices not requiring a connection to the sea-floor network.

The deployment of the two reels carrying the long interlink cables for the detection units is proceeding. Installation of these cables requires time, because once a reel has reached the sea bottom, each cable has to be spooled off and layed down on the sea floor. These cables will be later used for connecting each detection unit to the submarine junction box which is already at the site (and connected to the 6 detection units already installed).

Once installation of the cables is completed, the deployment of the detection units can start – tomorrow!

The deck of the Handin Tide at the start of the operations (note that the yellow vehicle on the left is the Remotely Operated Vehicle – ROV – to be used for underwater operations).

 

 

 

 

 

 

 

 

 

 


Handin Tide left the harbour of Malta

10 September – the Handin Tide left the port of Malta around 5 p.m. CEST.

The navigation to the KM3NeT site is estimated to take about 10 hours.

The weather forecast is good. The activity on site will start early morning tomorrow.

Keep following the KM3NeT blog.


Blog posts about the sea campaign of September 2021

09 September 2021 – KM3NeT is getting ready for a new sea operation at the ARCA site near Sicily, Italy.

Five new detection units for ARCA are ready to board the ship in the harbour of Malta.
The ship is scheduled to set sail in the evening of 10 September 2021.

We will report on this operation with posts in the social media and in this live blog.