TUESDAY, 03.10.09

1824: Update
Yes. We switched out the transducers on Mary Ann; the 75/410 transducers are our long range transducers at 75 kHz. We had three sets of them and as of now three individual transducers have failed. So we have one vehicle (Ginger) still operating on a 600-meter range scale and that vehicle is down to one spare. This is our only depth-related failure and is the one part that is supposed to be near bomb proof. We were hoping it was cables. It’s possible to repair them or at least try and cobble-together a fix. They will likely have to test the failed transducers at depth in a tank back in the rear to get an idea of what went wrong with them (and then literally destroy them to confirm that). They cannot be fixed as they are potted, made with a fiberglass or rubberized cement. This has turned out to be our Achilles heel, as Lee Frey said.

So Ginger is the only vehicle operating at our farthest range, and Mary Ann has our only set of 230/540 transducers. These were not spared because we never envisioned three failed transducers. I remember the conversation clearly; everyone agreed the chances of losing more than one 75/410 were slim to non-existent. We’ve run transducers into the bottom before, and they’ve kept working. We currently have one set of replacement 75/410 coming our way on the turnover on the 29th. I don’t think it has been discussed if we should spare up a set of 203/540, but I guess we should at least talk about it.

The 230/540 kHz transducers are set at 400 meters, but we don’t know whether they will give us good data that far out. We are basically hoping for 300 meters and the sortie was programmed with an overlap that factored that value in. Mary Ann will be back on the surface this afternoon. Andy Sherrell and Greg Packard are waiting until she comes back up before making a recommendation how to alter the survey to maximize the potential. The data should be smoking. The vehicle that came back last night was Ginger and it was her data I was looking at last night from box 9b. The upside is that with the shorter range transducers on Mary Ann, the data will be easier to see. It has higher frequency and shorter range, but higher resolution.

1908: From Ted Waitt
A few questions:
1. How many miles can we cover a day with the current configuration on Ginger?
2. Is the current configuration on Mary Ann capable of surveying in benign bottom conditions or any other?
3. Can we expedite a set for when I leave Saturday?

1932: Response to Ted Waitt
Ginger is running on her original configuration so that’s 28 square miles per sortie. Sorties run 23 hours, surface to surface, with four hours on average in the van (usually that is two and a half, but it only takes a couple trips changing out messed up gear or reprogramming something to screw the average) for a total of 28 miles in 27 hours.

We anticipate Mary Ann will be down to half that area in about the same amount of time due to halved coverage. We are still waiting on her first return to the ship to finalize those numbers.

Mary Ann, with her reduced range, needs to be nearer to the bottom, 30 meters rather than 60. We are looking into those terrain dangers. The solution is to perhaps slow her down so she has more reaction time if the pencil beam detects an object to be avoided. This is also being studied on her first run. While we may want to keep her on the more benign bottom, she does have a higher probability of target detection in terrain due to increased resolution. A classic Catch-22.

The latest I have heard on an expedited set of transducers is no, they won’t be available for two weeks. I know Mike Purcell and Greg Packard are still working on it with Dom Rissolo and may even have more information than I do, but the latest is they will be available for hand-carry for the changeover on the 29th, not this week.

2030: From Ted Waitt
Well, at this pace, you’ll have nothing working by the end of the week and you’ll come back early. Better to not risk a vehicle, so if you’re going that low in rough terrain, slow down.