NOAA Teacher at Sea
Aboard NOAA Ship Thomas Jefferson
June 22, 2013 – July 3, 2013
Mission: Hydrographic Survey
Geographical area of cruise: Mid-Atlantic
Date: Wednesday, June 26, 2013
Weather Data from Bridge:
Wind Speed: 8.35 knots
Surface Water Temperature: 21.29°C
Air Temperature: 22.80°C
Relative Humidity: 82.00%
Barometric Pressure: 1011.36mb
Science and Technology Log
As promised, today’s post is going to be about the Hydrographic Survey Launches. The Thomas Jefferson has two of these boats that are generally launched by 8:00am and return to the ship at 5:30pm. On Tuesday, my official role was Hydrographer in Training. I joined HIC Todd and Coxn Junior for a day of surveying on boat 3102. After a morning of seasickness, they returned me to the TJ around 11:30 to recuperate. However, I was still able to experience a little of what they do every day and the hilarious camaraderie between the two!
In general, the survey launches do the same work as the Thomas Jefferson, just on a smaller scale. The TJ can only drive on lines with a minimum depth of 30 feet, but the survey launches can go to a minimum depth of 12 feet which allows them to get much closer to shoals and the coast. Every morning, the launch survey teams have a meeting with the FOO and XO in the survey room to discuss logistics and safety. My boat was headed out to survey grounds on a new sheet near Cape May, New Jersey. Specifically, we were driving lines in the Prissy Wicks Shoal. This particular region has highly variable depths and created quite a challenge for the HIC and Coxn for two reasons: you cannot navigate in straight lines over shoals, and the shoals constantly change so you must drive slowly in case an area is shallower than charted.
Todd has been a HIC for both the Rainier and the Thomas Jefferson. In this position, he was worked with many Teachers at Sea, and gave me lots of great resources to bring back to school. The HIC sits inside the cabin and makes sure that all of the equipment is working together and logging the correct data. Just like on the ship, he has an MBES, HYPACK, and POS-MV to help him do his job. However, unlike the ship, he does not have an MVP, and must launch a CTD every four hours to measure the sound velocity profile in the water column. Measuring the sound velocity profile is an important part of correcting the MBES data for improved accuracy. Remember, the equipment is very sensitive to changes in the water because the farther the sound waves travel, the more they are affected by changes in the density of the medium through which they travel.
Junior’s job as Coxn is to work with the HIC to safely navigate the boat on the survey lines. The Coxn has a monitor controlled by the HIC to help him see the current chart and line. Junior gave me the opportunity to try driving, and I barely lasted 15 seconds before I was off the line! Tuesday was particularly complex because we were in a highly trafficked waterway, shoals appeared out of nowhere, and there was a very strong current around the cape. When another boat appears in the line, the Coxn must bring his boat to a standstill while staying on the line so that data collection does not have to stop. If the survey line goes over an area that is particularly shallow, a decision needs to be made about how to get around the shoal without hitting the bottom. A lot of good-natured yelling happens between the Coxn and HIC so that they can hear each other and be in constant communication.
Once the survey launch has returned to the main ship, the data is downloaded onto a server from which the hydrographers can move the data into CARIS. Eventually all of that data will be turned into a new nautical chart to help marine vessels maneuver through the waters.
Today’s Acronyms and Abbreviations (some old, some new)
HIC – Hydrographer in Charge
Coxn – Coxswain
FOO – Field Operations Officer
XO – Executive Officer
MBES – Multi-Beam Echo Sounder
MVP – Moving Vessel Profiler
HYPACK – Surprise, not an acronym! This is just the name of the software.
POSMV – Positioning Orientation System Marine Vessel
SSS – Side Scan Sonar
CTD – Conductivity, Temperature, and Depth
CARIS – Computer-Aided Resource Information System. This software allows scientists to process the data that comes from HYPACK. Hypack collects data one line at a time, while CARIS allows you to combine the lines into a new nautical chart.
Well, my bout of seasickness started about half an hour into my time on the survey launch. I started off in the cabin with the HIC, and the swells in the water got to me immediately. I spent the rest of the time on the deck with the Coxn trying to keep my eyes on the horizon. Through it all, I still managed to get a glimpse of some dolphins playing in the swells and saw many different types of boats and ships sailing around. When I was returned to the ship, I immediately felt better. However, the medical officer took precautionary measures and measured my blood pressure (totally normal, as usual for me) and prescribed 1.5 Liters of water before bed for the night. I took a nice long nap, and woke up in time for a delicious vegetable casserole for dinner. I am feeling back to 100% today, and hope to stay awake tonight. The TJ runs 24 hour operations, so I will pop by the bridge and survey rooms to see what it looks like after dark.
Did You Know?
While at sea, it is required to perform at least one safety drill a week. Today, we had a fire drill and an abandon ship drill.