SATURDAY, 05.09.09

1304: Days 31-33 (May 7-9)
We have been working with no significant difficulties. The other day we had a good target and did a re-acquisition mission. Most of you have seen it, but we found a large pipe protruding from the ocean bottom, which was another pretty serious bounce for everyone. When we do these re-acquisition missions, everyone gets pretty pent up. Even when you are looking at the sonar image and you know the size does not quite match up to the expectation, you still wish — rationalize against yourself — that it could be compacted, laying at an odd angle or anything to keep the hope alive in your head.

There were 10 people in the lab watching us as we went through the high frequency, short-range sonar data while the 6,400 photographs downloaded. The anticipation can be grueling; the disappointment sharp. There is no doubt in my mind the teams working this equipment and in the analysis lab have given this job their all. They are dedicated and motivated, but our time draws to an end and each day we are that much closer to saying it’s time to pull the gear and head for home. There is no denying people are looking forward to returning to life back home; it would be foolish to expect otherwise. But I also feel if we asked them, the majority of people would opt to stay to in order to continue the search. I might be wrong, but I know I would.

Our confidence is very high we have not missed the target in our records: we have not seen it. The sonar would ring out the target, especially after ground-truthing four different contacts. Where to go from here? We could perhaps do the same search on the other side of the island that we did on this side, draw a 20-mile box around the ‘06 data and still not turn her up. There are still too many unanswered questions. As of this moment, we have covered exactly 2,100 square nautical miles of ground with good data. The vehicles have spent close to 2,000 hours in data collection at depth, run close to 700 lines, and successfully completed 80 missions. The sheer immensity of the accomplishment is hard to imagine given the depth we have seen at 17,400 feet. We are loathe to come home only to be able to say we know where she is not, but that we know to be true in an area larger than the state of Delaware.

As to the girls, we had to perform a little troubleshooting on Ginger after her last mission. It appeared the cable to her pencil beam altimeter was producing an intermittent ground fault (GFI= PITA {pain in the… well you get the idea}). We suspect there is either some moisture or a break in the cable harness that is grounding out; there were two 30-second shutdowns of the pencil beam altimeter during Ginger’s last mission. This system is one of the ways the vehicles avoid collisions and is small — roughly a two by four inch cylinder that rides in the nose of the vehicle, looking forward and slightly down. It operates in concurrence with the vehicle’s downward-looking altimeter to help the vehicle determine if it needs to stop moving forward. If the length of the horizontal component, representing the ground, drops below 70% of what the CPU calculates should be there, the vehicles props stop turning and it slowly floats up until the range is correct.

Ginger’s cable seems to be on the verge of failing, and if it does, it would likely kill the pencil beam (we have no spare to replace it since the one we brought is already in service). So, rather than risk burning up the pencil beam sonar, we have turned it off. This sounds worse than it is. Ginger is running in the western column of the C boxes and the bottom has been flat and benign. Mary Ann is running in the eastern column and is one box ahead (or south) of Ginger and seeing the same bottom conditions. We expect any significant topography to be seen by Mary Ann a day in advance of Ginger. If that happens, we will turn Ginger’s pencil beam back on and risk it.

As I do not want to risk a million-dollar vehicle to save a $2,500 part, I directed Greg Packard to increase the detection threshold of the downward-looking altimeter. The vehicles are flying at 60 meters off the bottom. When the forward-looking pencil beam altimeter is working, the vehicle is allowed to drop in altitude, but not below eight meters. It’s confusing but that’s how it works. To avoid problems, I had the downward-looking altimeter threshold increased from eight meters to 35 meters. So unless a sheer wall appears directly in front of the vehicle, we will not have any issue with a ‘bottom interface’ (geek-speak for running into the ground). These were Greg’s recommendations, Andy Sherrell concurred, and so did I.

The only other option at this point is to pull Ginger from service. Given the completely flat bottom we have been seeing for days, the distance from the islands and the mosaic of the area to our east, we are confident this is safe. Especially since Mary Ann is basically running interference in the column closer to the island, in essence scouting the terrain in front of Ginger. If we see some terrain in Mary Ann’s surveys that indicates a need, we will either turn the pencil beam back on or abort Ginger and pull her from service. Lesson: bring more than one spare for any cable on the system.

The last reported activity was a recovery of Ginger at 2221 on May 6, after which we needed to get some DOTs to proceed efficiently:

May 7:
2300 (5/6)-0330 Recovered two DOTs
0418 Launched Ginger into 13C
0421-0735 Transited and deployed DOT
0815 Recovered Mary Ann
0830-1151 Transited, deployed and surveyed DOT
1325 Launched Mary Ann into 14/16C
1345-2302 Transited, recovered, deployed and surveyed DOT

May 8:
0505 Recovered Ginger
0842 Launched Ginger into 13/15C
1042 Recovered Mary Ann
1307 Deployed Mary Ann into 16/18C
1356-0030 Transited, recovered, deployed and surveyed two DOTs

May 9:
0330-0610 Conducted net trawl to 600 meters
0815 Recovered Ginger

Ginger’s data looks good and the bottom is flat.