Dateline: Nikumaroro, 13 July 2012
The primary search area is based upon the hypothesis that the aircraft landed safely on the reef and remained there for several days before being washed over the reef edge by rising tides and surf at or near the point where the object on the reef – thought to be a detached landing gear assembly – appears in the 1937 Bevington Photo.
Aircraft debris reportedly found and used by island residents in later years, and aircraft parts found by TIGHAR in the abandoned village strongly suggest that the aircraft broke up in the relatively shallow surf zone. No large components (engines, main beam, etc.) seem to have washed ashore, nor has any debris been seen during scuba-depth surveys of the reef slope. This expedition will test the hypothesis that the more massive parts of the aircraft traveled down the reef slope and came to rest in, as yet, unexplored depths.
The Niku VII expedition will have the capability to search with high-frequency side-scan sonar and take black & white photos down to a depth of 1,500 meters (4,921 ft). The expedition will be able to do detailed examination of sonar targets using high-definition video down to a depth of 1,000 meters (3,300 ft.). The available bathymetry indicates that the reef slope reaches that depth more than a mile out from the reef edge. If the hypothesis is correct, the wreckage should be well within the proposed search area.
02:00Z 7-13 (16:00PT 7-12 KOK)
ROV test to 800 feet. Spotted a target with the ROV’s sector-scan sonar, maneuvered to it and identified it with video – piece of Norwich City debris roughly two feet long. Excellent proof-of-concept. AUV is repaired. Prop was not turning on prop shaft. Ready to deploy on another test as soon as ROV is recovered.
02:30Z 7-13 (16:30 KOK)
AUV launched on 4-hour test mission along reef slope. If this mission is successful they'll re-program for a 12-hour all night mission.
03:15Z 7-13 (17:15 KOK)
AUV is stuck or hung-up on the reef slope off the mouth of Tatiman Passage at a depth of 1,604 feet. Mobilizing for rescue attempt with the ROV. ROV must be configured for deep mission.
06:00Z 7-13 (20:00 KOK)
ROV launched for rescue attempt and begins descent.
06:30Z 7-13 (20:30 to 21:30 KOK)
ROV unable to locate stuck AUV but, in the process of searching, the ROV's tether apparently knocked the AUV loose and it appeared on the surface.
09:00Z 7-13 (23:00 KOK)
AUV and ROV recovered aboard.
The end of the work day assessment was:
Objective: Collect SeaBeam mapping data
Accomplished except for last grid line close to reef edge.
Assessment – System provides good general picture of reef morphology. No surprises so far. The sonar map confirms what we already knew. The reef slope is extremely steep. The 3-D graphics are spectacular but, as expected, not detailed enough to guide actual search operations.
Objective: Test AUV
Assessment – Based on today's operations, the AUV may not be an appropriate search tool for this environment. Final decision tomorrow.
Objective: Test ROV
Assessment – The ROV appears to be an effective tool for searching a closely-defined area.
Further work with the AUV has resulted in a system that will work very well. The AUV will fly down the reef slope collecting data; at the end of the downward run, it will drift back up (vertically) rather than attempting to fly up and collect data on the upward run. The imagery being collected is excellent; in fact, there is already a Category 2 (Interesting) target for the ROV to look at, something about 2m x 6m, with some right angles.
So the ROV team will run during the day, doing visual searching and looking at anything the AUV has found; and during nighttime hours, the AUV will run according to the above patterns. As we spoke the AUV was about to go back in the water for another run of final tests, but the system looks good.