09/06/2017 — admin
The E/V Nautilus undertook a multibeam echosounder quality assurance test from May 1 to May 5, 2017 during an engineering shakedown leg (NA079) in order to perform an assessment of the vessel’s Kongsberg EM302 multibeam echosounder. Data were collected near the Southern Channel Islands (Figure 1), offshore from San Pedro, California. Paul Johnson and Lindsay Gee provided logistical and technical support for mission planning, data collection, and analysis.
Summary and Recommendations:
- Heading into the 2017 operating season, the EM302 and associated sensors aboard E/V Nautilus are working fairly well compared to previous evaluations and to other EM302 systems examined recently. The patch test showed very slight pitch and heading adjustments, indicating no major changes to the system geometry. That said, the swath performance data appears to show a decreased swath width as a function of depth when
compared to other years. This is more apparent in the shallower and deeper portions of the range of depths that we tested in during NA079. It is highly desirable to collect more data and submit it to Johnson for analysis and revision of this report. This data can be transit data or mapping data, as long as the system is opened to its maximum range and distance, and the depth mode is set to Auto to correctly adjust the system for the depth it is operating in.
- Initial RX ship self noise testing revealed that the noise floor of the ship has risen significantly since last year. However, after changing the surface sound speed pump and replacing the shock mounts, it appears that the noise floor has dropped closer to that observed during previous tests. It is recommended that a full set of RX noise tests be conducted when it is convenient.
- Sensor positions and SIS Installation Parameters have not been changed (except for the pitch and yaw calibration results from the 2017 patch test discussed above) and should not be changed. A PU Parameters file containing all SIS Installation Parameters and Runtime Parameters was written to disk on the primary acquisition machine at the end of NA079. If any problems or questions arise with any parameters, this file should be
reloaded to restore a functional configuration for SIS.
- The onboard technical staff have collected routine BIST results throughout the previous year. This practice provides excellent information for tracking system health and should be continued moving forward.
- As discussed in the NA055 and NA070 report, the Ethernet cables between the switch and TX boards in the TRU cabinet are extremely sensitive to vibration and deformation, resulting in lost connectivity to individual boards. During the update process of bring SIS from version 4.1.3 to 4.3.2 a reboot of the TRU was required. It was necessary to “jiggle” the cables in order for all of the boards to boot correctly.
- The servicing and reinstallation of the SeaPath MRU appears to be successful with little change to the installation angles of the system.
- The new Sound Speed Manager software was installed and configured on the Subbottom / SVP Editor machine. The previous install of the SVP Editor is still active and available, but it is recommended that the new SSP Manager software be used as it is currently supported if any issues arise.
- A very large backlog of SIS surveys has been maintained on the MB Acquisition computer. As noted last year, it is highly recommended that these be removed from the SIS database in order to avoid potential SIS instability issues observed on other vessels.
- The Knudsen subbottom profiler was operated during NA079, providing the chance to confirm synchronization with the EM302 and general data quality.