Exp397T Underway Geophysics Technical Report

Eric Moortgat

Expedition 397T - Return to Walvis Ridge Hotspot & Transit

Expedition 397T officially got underway at 10h18 on September 12 and ended at 08h00 on October 11. Expedition 397T occupied two new sites from Exp391: U1584 & U1585.

Instrumentation

Navigation

• The Marine Computer Specialists tried to configure a NaviPac shortcut that would start the application as an 'elevated user' from the Active Directory (AD) DAQ account, but NaviPac online would not start. We are currently launching NaviPac/Helmsman from the local DEV account (.\dev). The password is in the ALO safe.

• The remote Helmsman is not connecting to the Nav1 NaviPac master. Limited troubleshooting was performed as coring duties, Physical Properties Scientist and ALO duties kept me busy. During L1T & L2T, remote desktop to Nav1 was used on the video distribution PC and it worked great. On L3T we used Google Earth per the LO's request.

• The MRU data through the Black Box is now going to NaviPac via comm 10.

Echosounder

• Acquiring PDR data for U1584 & U1585 was done using the 12 kHz EDO transducer. We tried the 3.5 kHz transducer array during L1T, but even on power level 3, the CHIRP amp shut itself down. Use/troubleshooting was discontinued until post-relocation.

• The 12 kHz transducer offers very little bottom identification at 11+ knots but once the vessel slowed down, as the site was approached, it immediately locked on to bottom and a successful PDR was obtained.

• After obtaining the water depth for U1585, we moved the CHIRP amp from the UWGL to the gym network locker. We unfortunately quickly discovered that the incorrect type of USB over gigabit extender was purchased so we have to improvise until the correct one arrives (hopefully for Exp398). The MCSs quickly configured a laptop with the EchoSuite software for us to use.

• The one 'issue' with this situation, until we can get the proper USB extender into the locker, is that the laptop will not be able to get GPS position from NaviPac. Not sure how much an 'issue' this is, because like was mentioned, we are going to have to get by with the EDO until the 3.5 array can be looked at. Hard to say during 397, with the water depths and 12 kHz combinations, if a bottom lock can be achieved during a transit. I am 100% confident that a correct PDR measurement can be made once the vessel slows down on approach to a site. That is its main function.

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  • I was in contact with Nolan Pretty at Knudsen. He wanted us to perform some tests using the EchoSIM.

  • The first figure is from the impendence tests in Transducer Test Mode. The orange traces are from Exp397T and the blue traces are from Dec 2020 when we were also troubleshooting. The left plot is from the Thyrig Room junction box to the dome. The right plot is from the amp to the dome.

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  • Both cables measure continuity. The 3.5 kHz is 2 ohms and the 12 kHz is 0.9 ohms.

  • The next figure is from the Simulator Mode. Nolan wanted to confirm that the amp is working correctly, and the test confirmed. You set the EchoSIM software to a certain depth and then check if the EchoControl software receives the same values. A nice test. Just remember to use the internal impedance of 50 ohms using the EchoSIM cable. 

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  • The next test is the Transmitter Analysis Mode.

  • The test gave disturbing results. For the most part we received values as shown in the figure below. Nolan responded with : "The strange results while in this mode further indicate an issue within the cables/connections or transducers (possibly).

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  •  Here is the QSG for the EchoSIM modes:

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• Oct 8, 2022 We opened the Thyrig Room hull hatch. We took this opportunity to replace the 3.5 cable to the O'Brien connection. It was suggested to replace for a couple of years now. All the pins on the O'Brien connection were measured going to the sonar dome. All five pins gave approximately the same ohm value. This is an indication that the cable down to the junction box, or even the junction box itself, is compromised; or both.

• The MRU heave data is coming through a new comm port over previous configuration but could not be tested as the Black Box and RS232 convertor was not temporarily relocated to the gym locker. The need is not urgent.