KM 2020 QAT Planning Overview
During the late fall of 2016 and spring of 2017 the University of Hawaii’s Ocean Technology Group (OTG) submitted bathymetric data, screen shots (Figure 1), and built in self-test (BIST) data to the Multibeam Advisory Committee (MAC) and to Gates Acoustic documenting pervasive noise which was affecting the R/V Kilo Moana’s Kongsberg EM122 multibeam echosounder system’s (MBES) ability to collect high-quality bathymetric data.
Introduction
Executive Summary
Conclusions
The EM122 and EM710 systems both appear to be configured correctly and, for the most part, adequately calibrated. Small MRU roll alignment residuals do exist and it is recommended that these be confirmed as soon as possible through acquisition of a pair of reciprocal survey lines over a flat and featureless seafloor. Verification lines should have been run for calibration tests for both systems, however, time constraints on the cruise schedule precluded this. It is standard practice to run verification lines.
KILO MOANA’s acoustic signature was higher than previous acoustical data due to electronic noise interference. The levels in the EM 122 sonar operational frequency of 12 kHz were also higher than historic data. A significant problem was noted with numerous elements of the EM 122 sonar array that is believed to be associated with electronic background noise. Electronic noise was determined to be the major deficiency during this acoustic trial.
The point of the QAT visit was to help the host institution in developing protocols and practices that are conducive to the acquisition of high quality multibeam data. Even with a finely tuned and calibrated survey system, it is still possible to collect poor quality data through poor choice of operational system parameters, etc. Software tools to aid in this regard were deployed and documentation was prepared that can help return the system to a healthy configuration such that the institution can recover from a sub-optimal system configuration.
KILO MOANA’s acoustic signature was comparable to previous acoustical data with one noted exception. The levels in the EM 122 sonar operational frequency of 12 kHz were similar to historic data. A new problem was discovered that was associated with engine and switching room air handler cooling systems. This problem created 4,000 Hz harmonics from the fundamental up through 80 kHz (the limit of onboard instrumentation). An additional problem was noted with numerous elements of the EM 122 sonar array that is believed to be associated with electronic background noise.