NOAA Teacher at Sea
Onboard NOAA Ship Thomas Jefferson
September 2 – September 19, 2014
Mission: Hydrographic Survey
Geographical area of cruise: North Atlantic Ocean
Date: September 17, 2014
Location of ship (at the Troydon Wreck): 41o 08′ 14.459″ N, 71o 21′ 42.987″ W
When I say we have “holidays” on the Thomas Jefferson, I’m not talking about Saint Patrick’s Day or 4th of July. I’m referring to gaps in previously-collected data we need to fill. Let me explain by taking you through life on the TJ on Monday, September 15.
Science and Technology Log
The day started just like any other day (we actually use the day of the year to designate days – today was Day #258):
|0000||Ship anchored West Passage|
|0730||HSL 3101 Safety Briefing|
|0800||Deploy HSL 3101|
|1730||Recover HSL 3101|
|2400||Ship U/W on Survey H12651|
Every day we have been out at sea, our launch has been out collecting data in the shallow-water areas of the coast. Today, the launch was working on filling in polygons (geographic regions designated for charting) close to the shore. The Thomas Jefferson was off on its own survey, revisiting areas the ship charted earlier this year that had gaps that needed to be filled in.
First, I should explain the technique the ship uses with side-scan sonar or multibeam echo sounding. You are all familiar with “mowing the lawn,” where a lawn mower will go across the lawn in one line, then turn 180 degrees and travel back down next to the grass just mowed, and then this linear pattern continues across the lawn. This is the same pattern hydrographic surveys use when collecting their data – except the lawn is the ocean, and the mower is the ship! At times, there may be gaps along these lines. The ship may have to navigate around a buoy or a lobster pot, or another boater may be on an intersect course with our ship. So there were several small gaps along and between lines that we needed to go back and “mow” over. Why go back and fill in the data? On this particular project, we were charting every square foot along the coast. That’s a lot of lawn to mow!
The ship is driven by the helmsman on the bridge (Deck 03), but the hydrographic survey laboratory, or plot room, is on Deck 1. This means that communications must be frequent and clear between the two decks, so that the helmsman can accurately navigate while a survey technician starts and stops the data collection along the existing gaps in the lines.
In the photo above, you can see me at the station in the plot room where the action takes place. Each computer screen displays a specific part of the data collection (today, we were collecting multibeam and not side scan). The crew in the lab was able to train me enough to actually run part of the survey and work with the bridge to identify our next holidays to fill in.
The other instrument used during our survey is called a MVP – no, not a “most valuable player” but a Moving Vessel Profiler. The MVP weighs 72 pounds and looks like a torpedo. The weight is important, as the ship will, at set intervals, let the MVP freefall (while tethered to a line). The MVP measures sound velocity vertically in the water column. These data are important, as they help the survey technicians apply necessary corrections to the water depth measurements collected by the multibeam echosounder. I must admit, it was a true test of my multitasking abilities to navigate and collect multibeam data over the holidays, while releasing the MVP and saving that data! But I had so much fun being involved, I stayed on this work station for two four-hour shifts!
One of the many incredible opportunities I’ve had while at sea is to be able to get hands-on with the varied activities of the ship – from handling the lines of the launch, to hauling the anchor, to actually sitting at the computers and running the software collecting the multibeam echosounding data. It is not just the “cool factor” of being able to communicate with the bridge and start the data collection. It is definitely “cool” being able to see the different people, their content knowledge and skill sets, and the technology involved in conducting a hydrographic survey. And it is important to know when to ask for help, when to step back, and when to say, “I’m not ready for that yet.” I am so eager to learn, but I have to balance jumping in to help, with making sure that my involvement doesn’t interfere with the ship’s activities and mission. Students, I’m sure you also find it tricky to balance your enthusiasm and desire to participate in activities, versus knowing when you are trying to take on too much. Here’s my take-home message – always ask! If you can’t get hands-on, you will most likely be able to observe your surroundings and still learn so much. There is one activity I’m nervous to try – today, the Commanding Officer (CDR Crocker) asked me if I was going to drive the ship (yes, the 208-foot long Thomas Jefferson!). I wasn’t ready today, but before this cruise ends, I will drive this ship! You just may want to stay out of the ocean until I get back to campus…
OK GEOSC 040 students at Penn State Brandywine, here is your next question (just one for this post). Please answer this question online in ANGEL in the folder “Dr. G at Sea” in the link for Post #9.
- Why do you think it is important that the Thomas Jefferson go back and fill in the holidays? (*this answer is not directly in the text above – think about why it is a good idea to fill in the gaps, not “just because” NOAA is surveying every square foot)
Random Ship Fact!
As mentioned in previous posts, the Thomas Jefferson does not focus its activities just on collecting data on the depth of the ocean. In fact, we continued surveying today through the evening over the Troydon Wreck. The wreck was first picked up by a survey from another NOAA Ship, and we then moved in to measure water data above the wreck. We had to narrow our multibeam echosounder to try to pick up as much detail in the water column – for example, would we be able to find a mast sticking up from this wreck? Check out these images and check out what we found!