12/02/2015 — admin
The R/V Kilo Moana undertook an engineering shakedown leg (KM1514) in order to assess acoustic noise issues documented during the KM1505 Quality Assessment Visit (QAT) conducted by the Multibeam Advisory Committee (MAC) in April, 2015 and documented in that report (see R/V Kilo Moana, EM122 and EM710 Multibeam Echosounder System Review, KM1505 April 28 – 30, 2015). Undertaking this assessment were Vicki Ferrini and Paul Johnson as the MAC Quality Assessment Team, Tim Gates and Marisa Yearta as the Noise Assessment Team, Scott Ferguson representing the University of Hawaii’s Ocean Technology Group (OTG), and Chuck Hohing and Travis Eliasen representing Kongsberg Maritime.
Conclusions and Recommendations
- Having the “A” team (Acoustic Noise Team, Quality Assurance Team, Kongsberg Maritime, and UH Ocean Technology Group) aboard to troubleshoot the EM122 multibeam problems worked great. Without this multidisciplinary and talented group, it is probable that the issue might not have been resolved without additional ship time.
- The EM122 accuracy assessment shows what appears to be a less accurate/noisier inner swath than that observed in 2012. Complicating this assessment, the tests were run at higher speeds and with a different engine configuration compared to 2012, due to the limited available time
and engine issues during KM1514. To truly compare the two accuracy datasets, additional runs should be undertaken at 6 kts with a starboard engine configuration.
- The assessment of swath width as a function of depth shows similar swath width at the reference surface site (~4700m) as seen in 2012. The transit line from the reference site back to Honolulu Harbor crosses the seafloor slopes at oblique angles and was run at higher than desired speeds due to time constraints. In light of these factors, there appear to be no major changes in swath width from the 2012 SAT to KM1514.
- It was noticed that there were many nadir “punch-through” artifacts seen during the transit back to Honolulu Harbor. This was a very limited sampling interval, and there was no attempt to steer the beams in order to see if this could be minimized. The MAC will follow up about this with scientists aboard during subsequent mapping cruises.
Please see the ANT report for this cruise here
|KM1514 MAC QAT Report||4.09 MB|
|KM1505 MAC QAT Report – PRIOR TO DIAGNOSIS AND CORRECTIVE ACTION||5.63 MB|