In layman’s terms what is the difference in Sonar Tech being used compared to the sonar used in the 2012 TIGHAR expedition?
Based on publicly available information, the technology Nautilus uses has advantages and disadvantages compared to what we used in 2012.
• Nautilus's hull-mounted multi-beam sonar is better than KOK's, but I can't quantify how much better. Multi-beam is useful for mapping the undersea topography (bathymetry) but its usefulness in searching for objects is a function of its resolution. KOK's multi-beam did not have sufficient resolution to see something as small as even an intact Electra.
• The best tool for spotting targets is side-scan sonar but the steepness of the reef slope at Niku makes towed-array side-scan difficult. Flying the "fish" parallel to the slope results in a fore-shortened image on the reef side while the ocean side sees only water. In 2012 we used side-scan mounted on an AUV (Autonomous Underwater Vehicle) to fly up and down, rather than across the slope. The AUV couldn't go deeper than 1,500 meters. We still had all kinds of problems but the area got covered. Nautilus uses towed-array side-scan sonar deployed from an ROV. Their ROVs can go much deeper than ours could. In theory, they'll have less capability than we had on the steep slope down to 1,500 meters but good capability at greater depths where the slope moderate.
• ROVs (Remote Operated Vehicles tethered to the ship) with HD cameras are a good way to investigate sonar targets. In 2012 we used a fairly nimble medium-sized ROV but we still had to be super careful to avoid fouling the tether on the steep reef slope. The Norwich City wreckage at about 300 meters is an especially bad neighborhood. Our ROV could only go to about 800 meters. Nautilus' ROVs can go to 4,000 and 6,000 meters respectively but they are much larger and might have a more difficult time on the shallower steep slope.
Bottom line: Nautilus might have trouble looking where we've already looked but they can look deeper than we could.