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WE ARE A TEAM OF SCIENTISTS SET OUT TO IMAGE THE 3D INTERNAL STRUCTURE OF AXIAL VOLCANO IN THE NE PACIFIC OCEAN.

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Friday, August 9, 2019

What do all of these screens actually mean?!

If you are wondering what we are doing during our shifts (2x 3 hours per day) it can be summarized in one sentence: “We are watching to see if computers are computing well” (Brian, 2019 com. perso. ). 

By Axelle Cap

What can they all possibly mean?!

In fact there are many screens (46!!) grouped on an entire screen wall
located in the lower part of the boat under the air gun deck, and we check if the acquisition is working well. Three teams can be distinguished here: the navigation team, the PSOs and the student team.


So let's break it down:

We, the student team (A), are working by groups of 2 or 3 persons. Our task is to adjust the phase (depth range) of the bathymetry to capture the seafloor depth from the Chirp. The Chirp (32) provides 2D data with accurate data until 10 m depth whereas the multibeam (33/34) provides 3D data (morphology) of the seafloor. We can adjust the incident angle of the multibeam to get greater, or lower, spatial resolution. Every 30 minutes we fill an Excel sheet (35) with various information (location coordinates, depth, shot number, direction and speed of the boat, wind force and direction, wave length, gravity, sea temp, salinity) from screen 19. On screen 33 there are waves curves indicating the heave, pitch and roll of waves (with practice you can also feel it directly when you walk in the boat). Screens 2 and 17 give the navigation direction and information about the boat. Screen 31 corresponds to water temperature according to the depth (only 4°C at 2500 m!). All this information will be used to know the environmental settings at any time of seismic acquisition.

Team A: I can see the seafloor from here!

The navigation team (B) is watching if the air guns and streamers are working properly. That means that when there is a shot every 15 seconds, the streamers receive a signal. They can have up to 4 streamers (line of receivers behind by the boat) to take care of. If there is something wrong with one of them, they launch the alert and then the team start to bring back the air guns and the failing streamer. They can contact the bridge at any time to adjust the navigation plan, depending on the needs of the science party and to fill the gaps of the navigation plan. They can control the birds (modules with wings located on the streamers) depth at distance in order to adjust the depth of the streamers down to 16 meters for our cruise. It is important to keep the streamers at the correct depth otherwise they can be damaged by a too high depth (birds have also a security system in case of issue). Screen 20 (RMS window) gives information about the velocity in the water column and noise proportion in the channels. Screens 7 and 8 give an idea of seismic signal, so if you have informed eyes you can guess shape of the magma chambers or other features.

Team B: Everything looks ship shape and in the right direction

The PSO team (C) is looking for mammals from the outside tower during the day and listening to them during the night using acoustic monitoring. If mammals are communicating, their “voice” can be detected by sonar. If they are too close (less than 1 km) from the boat we have to stop to shoot to not disturb them too much. Screen 45 shows the PSO team live acoustic signals from the water column where they can distinguish the frequency, amplitude and length of an acoustic signal; different mammals produce different sounds. Screen 46 helps them to locate any sources by bearing and distance from the ship. 

Team C: Watching for whales...

Other notable screens and devices:
Did Italy score Massimo?!
  • Camera screens (1/6/9/11): Almost every part of the boat has a camera, and most of the time there is nothing to watch on it, but there are 3 exceptions. (1) When operations on gear are taking place of the desk you can stake if other students are working efficiently and not resting! (2) “pongvision” is surely the most important and diverting one: you can watch a ping-pong match live like in a stadium but comfortably seated and without screams in your ears. (3) It is a long time that you are here in the basement/hold of the boat, so if you want to have an idea of the weather, you can have a look on the screens (S9).

  • News screen (S5): we don’t understand most of the 16 lines of this screen with so many numbers(!) but 2 things are noticeable: (1) you know that we are not shooting (turning or fixing gear) if the 15th line is red, and (2) you can get international news in English and even in French (the French community is well represented on the boat!) on the last line, if you are patient, as the words appear slowly. Newsflashes are really randomly ordered: you can learn important international news in a sentence and the next sentence will learn you that a new mosquito has been discovered in the unknown forest of somewhere unknown in the world.

  • Phone: calls from bridge to the navigation team or if the PSO see a whale from the observation tower.

  • Walky-talky: communications during operations are made by radio, you won’t understand well what is said because of crackling but it seems ok for people used to.
First discussions at the map table
  • The map table: It is here than you can have a look to know where we are. Normally you see a black triangle in the middle of a pack of red lines (shooted lines) and white lines (scheduled lines). Sometimes you see the triangle in middle of nowhere, we are not lost but just fixing the gears and out of the studied area. This table has also many other important roles. It is like the countertop of a pub... but without beers. It is THE place where: (1) Tom brings candies and sweeties every day (the best ones are the pistachios in my mind), (2) the “question of day” is located, and (3) for a week where the Cribbage tournament took place. Here you can see the best Cribbage player of all the pacific battling for the top spot!

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