Cruise ID: RR2501
Multibeam System: EM712 / EM124
Dates: April 18-29, 2025
R/V Roger Revelle (RR) received a new Seapath 380 and MGC-R3 (‘Seapath 380-R3’) in 2024, sharing the same GNSS antennas used by the Seapath 380 with MRU (‘Seapath 380-5+’); no other modifications were made. The MGC was surveyed by Westlake in March and reported in a new survey report in May 2024. The Multibeam Advisory Committee (MAC) was asked to assist with routine Quality Assurance Testing (QAT) for the ship’s EM124 and EM712 multibeam echosounders using both Seapath systems; this was incorporated into a shakedown and training opportunity during transit from Tampa, FL, to Woods Hole, MA in April 2025.
EM124 and EM712 calibrations and verifications proceeded smoothly, with the new Seapath 380-R3 applied in real time and Seapath 380-5+ applied in post-processing; results were small or zero, suggesting a high-quality offset survey as well as correct interpretations for EM and Seapath configurations. Accuracy testing was carried out at a 5200 m test site off Blake Nose that was initially occupied for EM304 MKII testing aboard Okeanos Explorer, with modification for the EM124’s broader swath capacity; crossline results in Deeper and Very Deep indicated expected performance at this depth. Swath coverage testing was carried out opportunistically on the transit toward Woods Hole, crossing a 2800 m reference surface collected by R/V Sikuliaq in 2014; the EM124 crossline over this reference surface indicated expected performance, with potential complication from refraction. EM124 coverage trends met expectations and compared favorably with another EM124 ‘benchmark’ dataset, whereas the EM712 fell short against a related ‘benchmark’ dataset for reasons that are not clear at present; future deeper testing will help to illustrate attenuation effects (both systems) and extinction limits (EM712). This report describes the procedures and results for system geometry review, calibrations, hardware health monitoring, RX noise characterization, and accuracy testing, with recommendations for future data collection. The MAC thanks the Revelle’s shipboard technicians for collecting all QAT data, re-running some tests to verify results (e.g., RX noise), and following up with questions to ensure data quality throughout the process
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