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NF-09-14-GOMDC  ------   ER013 / MM003 cruise

aboard the NOAA ship Nancy Foster.

by Arne Diercks

The first leg of our cruise aboard the NOAA ship Nancy Foster (NF-09-14-GOMDC-Leg1) was a great success. The weather and seas played along well to allow for five successful launches and an equal number of recoveries. A couple of these recoveries were some of the smoothest I have witnessed with the Eagle Ray's Launch and Recovery system in 4 to 6 foot seas.

Our initial goal was to visit 3 wreck sites and acquire high resolution Multi Beam data on these sites with the ER's EM2000 multibeam. Survey operations went smooth and timely allowing us to perform dives at two alternate sites as well. The survey areas were small enough to allow for two individual dives over each wreck per day, including launch and recovery.

Our general approach, we chose to minimize the risk to the vehicle being highest during launches and recoveries, was to perform two consecutive dives with a partial data recovery via the Data Radio.  The approach was to investigate the site with EM2000 on the Eagle Ray set to fly at a constant altitude of 30m above bottom. Once the initial survey was complete the ER would return to the surface and we would download 3 to 5 individual EM-2000 raw data files centered over the target,  via FTP over the Data Radio, while the ER was maneuvering back to the dive position of the survey. When the last file was downloaded we would dive the ER back down to a loitering depth of 30m above bottom and restart the bottom alignment of the SeaDeViL INS, while we processed the multibeam data we had just downloaded.

This processing took in the range of 10 to 20 minutes and provided us with bottom topography and potential hazards to the ER operation for the near bottom (15m altitude) for the second dive over the wreck.   The second dive provided us with higher resolution multibeam data for more detailed information about the individual targets. The timing for the AUV to reach the loitering depth and finish the alignment of the INS coincided with our analysis to confirm save diving conditions for a closer to the bottom dive and the second survey was commenced.  At the end of this survey, the AUV was programmed to return to the surface for safe recovery with the Nancy Foster.

On the first leg from 10/6 to 10/12/2009 we performed five such dives over five individual targets, confirming 3 new shipwrecks and the existence of a previously known wreck and discovering an interesting geological feature in the process. Eagle Ray worked flawlessly providing great data from every survey area. Below are a few sample images of the data collected during this cruise.

Cruise Dates: October 6 to October 28, 2009

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