NOAA Teacher at Sea
Kathy Virdin
Onboard NOAA Ship Rainier
July 20 – 28, 2004
Mission: Hydrographic Survey
Geographical Area: Eastern Aleutian Islands, Alaska
Date: July 21, 2004
Time: 6:00p.m.
Latitude: 55 degrees 49.65 N
Longitude: 157 degrees 56 W
Visibility: 11 nautical miles
Wind direction: 350 degrees NW
Wind speed: 7 kts
Sea wave height: 0-1 ft.
Swell wave height:2-3 ft.
Sea water temperature: 12.2 C.
Sea level pressure: 1013.0 mb.
Cloud cover: Partly cloudy
Science and Technology Log
Today I was able to go out on a launch (small boat) that did survey lines for eight hours. After the launch got underway, we lowered the transducer into the water where it will send out a spray of sound (approximately 131 pings) that will be measured on the launch’s computers. We also did a Reson line measurement which can accurately measure depths of 40 meters. We drove the launch in a line that was approximately 4-5 miles long, then turned and went back on the next line. Each line took about 40 minutes and we were able to cover 7 lines today. So in all, we were able to chart an area of 4-5 square miles. We stopped every four hours to put down a CDT which checks salinity, density and temperature. This information was immediately fed into the computers so that it can adjust the speed of sound through the waters by these factors. This launch also has a motion sensor that can measure the pitch and roll of the boat and that is factored into the speed the sound travels, which gives the calculated distance to the ocean floor.
NOAA has about 8 or 9 ships that do hydrography work which is extremely important to scientific research, as well as commerce. About 90-95% of all goods used in the U.S. are brought to us by ships! So it’s vital that they have accurate information to chart their path through our waters. The RAINIER is the only ship in the world that can do all the hydrographic survey work that it does. It’s an honor to work on a NOAA vessel and all members of the NOAA corps must have a degree in one of the sciences. The swath or path of the sonar beam that our launch is sending out covers about 200 meters. We’re seeing the data that tells us that the depths in this area are 100 meters. We have successfully measured our plot of the chart today with multi-beam swaths that intersect at the outskirts with one another. This is another measure taken to ensure accuracy.
Personal Log
I asked a lot of questions today while we were surveying, as the field operations officer with us had time to answer them. The work was mostly being done by the computers, so we were watching and checking them periodically. I learned that the launches are expensive boats because of all the high-tech equipment they carry (all of it necessary to get the job done). When we came back to the RAINIER, the sun came out and we went up on the deck to enjoy the view. I saw puffins flying over the water, and one of them flapped its wings across the water as it skimmed along the surface. This was a treat to watch the puffins as they entertained us with their antics. Tomorrow, I’m looking forward to following up on the data that was gathered from the two launches that went out today. It will be scrutinized and evaluated by the survey technicians and then stored in the folder for the day.
