Yaara Crane: Hydrography is Underway, June 24, 2013

NOAA Teacher at Sea
Yaara Crane
Aboard NOAA Ship Thomas Jefferson
June 22, 2013 – July 3, 2013 

Mission: Hydrographic Survey

Geographical area of cruise: Mid-Atlantic
Date: Monday, June 24, 2013 

Latitude: 38.81°N
Longitude: 75.10°W 

Weather Data from Bridge:
Wind Speed: 11.54 knots
Surface Water Temperature: 20.41°C
Air Temperature:  24.30°C
Relative Humidity: 86.00%
Barometric Pressure: 1018.16mb

Science and Technology Log

The plan of the day (POD) for today included launching two survey ships (also known as Hydrographic Survey Launches), fixing the MBES, and pulling up anchor. The survey launches must have at least two people aboard: the hydrographer in charge (HIC) and the coxswain. They go out most days collecting data from about 7:30am until 5:30pm. While the Thomas Jefferson (TJ) has been anchored, these small survey boats have still been able to go out and work. I will have more information about these smaller boats in my next post as I plan to go on tomorrow’s survey team to learn what these individuals do each day.

We have been anchored just off the coast of Lewes, DE in the Harbor of Refuge since Saturday morning. The CO (commanding officer) paged me at 12:30 today to observe while we were heaving the anchor in. I was allowed to stand on the bow and lean over the side of ship to watch. Pulling up the anchor was excellent news because it meant that the equipment delivery had arrived and the data collection would be able to begin again. Just after the anchor came up, I watched the FRB (fast rescue boat) make its delivery and be lifted into its cradle by the use of davits overhanging the deck.

We then sailed for a while to make it to our survey grounds. The Thomas Jefferson collects data by sailing in specified lines through the ocean; navigating to the beginning of a line takes skill and practice. NOAA assigns survey sheets which are sections of water with hundreds of lines that have earned priority to be charted on a particular leg of a journey. It is imperative that the watch standers on the bridge keep the ship on its planned survey lines to ensure that the entire ocean floor in a specific sheet is covered.  If you follow the path of the TJ on NOAA’s shiptracker, you might be able to zoom in to see the TJ going back and forth along these lines that are spaced exactly 120m apart. The 120m lines are carefully determined based on the fact that the SSS can measure 75m in either direction. Due to the nature of acoustic imaging, the farther a sound wave travels, the worse its accuracy will become. Therefore, a 30 m overlap of the SSS data occurs with 120m line spacing and the farthest distances will be able to be analyzed twice. If you remember, the MBES sends out a swath or cone of sound waves, so it will never be able to reach the farthest parts of the lines without being in extremely deep water. If the SSS picks up irregularities towards the edges of the data, the entire ship will have to break course to sweep back over the area in order to collect MBES data on that point.

Today was the first time that I really had the opportunity to see what this ship is all about, and I look forward to seeing what kinds of objects can be detected on the sea floor.

 Personal Log

 Yesterday, our kayak adventure around Lewes gave me the opportunity to chat with a lot more people about their backgrounds and roles on the ship. Although everyone is very welcoming, this is certainly a very busy vessel and I appreciated the time to talk with people when I knew I was not interrupting their work. I was buddied up with Eileen, a junior officer, and Steve, the second engineer. Eileen is the newest NOAA Corps Officer on board the TJ, and is in training for many different certifications. She and Charles, another junior officer, need to earn hours towards their FRB certification and spent some time driving the FRB on the ride back from kayaking to the ship. It is jet propelled and extremely responsive and maneuverable. I was able to drive it for a few minutes on my first day, and that thing can really move!

The mess area is still a very exciting area of the ship for me. Normally, I avoid the high school cafeteria but I just can’t get enough on the ship! It probably helps that I am only on the ship for a short amount of time, but so far I have been enjoying all of the food. The chef posts a menu every day, and meals are served at 7:00am, 11:30am, and 4:30pm. Outside of those hours, there is still food available in the form of a salad bar, ice cream bar, cold and hot drinks, cereal, and probably other things I have not yet discovered. All of these options are certainly a necessity because there is no take out or delivery in the middle of the Delaware Bay.

Did You Know?

 The anchor of the Thomas Jefferson weighs 3500 pounds. To clean off the mud from a dirty anchor, the ship will drag the anchor at surface level and let the running water of the sea do the cleaning.