Chris Murdock: Calibration Time! June 9, 2017

NOAA Teacher at Sea

Chris Murdock

Aboard NOAA Ship Oregon II

June 7 – June 20, 2017

Mission: SEAMAP Groundfish Survey

Geographic Area of Cruise: Gulf of Mexico

Date: June 9, 2017

Weather Data from the Bridge

Latitude: 27.193 N
Longitude: 93.133 W
Water Temperature: 28.8 C
Wind Speed: 10.5 knots
Wind Direction: 92.59 degrees
Visibility: 10nm
Air Temperature: 25.9 C
Barometric Pressure: 1012.6 mbar
Sky:  Clear

Science and Technology Log

Prior to our departure from Pascagoula, the ship anchored approximately 8 miles off the coast in order to run a calibration test. This is done in order to calibrate the ship’s multi-beam echosounders. Echosounders emit sound waves downward towards the ocean floor that measure and record the time it takes an acoustic wave signal to travel to the ocean floor, bounce off, and return back to the receiver. Think of this like a dolphin’s echolocation. Dolphins emit sound waves that bounce off objects and allow the dolphin to determine the distance that object is. As you can imagine, this is incredibly important!

How an echosounder works Source:

The Oregon II echosounders
The entire calibration process takes a long time, and that time drastically varies depending on the amount of sensors a ship has. The Oregon II has two echosounders, so this whole process took roughly 6-8 hours. The calibration process works like this: Calibration requires deploying one or more calibration spheres under the ship. These are lowered into deep waters, or in wave terms the farfield (the outer limits of the sensors). Each sensor is tethered to a series of down-riggers mounted on the upper deck of the ship, on both the starboard (right) and port (left) sides of the ship. This essentially centers the sphere allowing the operator to control where under the boat the calibration sphere is. The controllers of the down-riggers move the spheres in specific locations until the sensor on deck is fully calibrated.

Diagram of calibration set up (

The calibration of the echosounders is vital to the success of this study, as well as studies like hydrography.  Knowing the proper depth of the ocean underneath the ship is used to determine when and where to trawl for stock assessment (which I will talk about in later blog posts!)


Personal Log

So far, life aboard the Oregon II has been smooth sailing (pun intended). We finished the sensor calibration on Wednesday, and have spent the past two days traveling to our first sampling location, so I have had sufficient time to become acclimated to the way things work out in open waters. Thankfully, I am used to being on a rocking ship, so I don’t foresee seasickness being an issue (fingers crossed). I have gotten to know most of the crew, as well as all of the other volunteers aboard the ship. Most of the volunteers/interns are graduate students from schools scattered around the south. I look forward to sitting down with each of them to learn more about their specific fields of study and why they chose marine science.

Headed out to open sea!

It has been nice to have this downtime, because it has allowed me to become familiar with how things work on board.  With the calibration and travel time, I have really fallen in love with being out on the open water. I spent most of my time on the flying bridge of the Oregon II, or as many of the crew call it the “steel beach”. There is a plethora of workout equipment up there, as well as chairs to have a cup of coffee between shifts. Exercising on the top of a rocking boat is not easy! I have come to find it quite peaceful, however. There is something about being able to look out at the vastness of the open water, with only the occasional speckling of oil rigs and tankers off in the distance, that allows you to separate yourself from everything else and be in that moment. Sometimes, I even spot large numbers of flying fish leap from the boat’s wake and travel just above the surface of the water for large distances, only to watch them disappear into the blue void. For a Midwestern kid, they are truly fascinating animals.

Oregon II rescue boat
Crew lounge
My stateroom
Laundry facilities
Stairs from the bottom deck up to the crew’s lounge
Chem lab
TAS Chris Murdock wearing helmet and life jacket
Yesterday was also the time for our first series of drills. We conducted a fire safety drill, as well as the all-important abandon ship drill. In the later, we don our survival suits and life jackets and head to muster (gather) at the bow of the ship (remembering the directions and other ship lingo is taking a little bit to get used to, but after the first day or so it has just become second nature. Port is left, starboard is right, the bow is the front, and the stern is the back). You then have two minutes to properly put it on. The suit itself looks and feels like a giant red Gumby costume, but immediately you can see the benefit of it. It completely surrounds your body with watertight neoprene, and has specially located lights and floats to keep you insulated and on the surface of the water. While you may think the Gulf is very warm (it is), the temperature is roughly 86 degrees Fahrenheit, which is about 12 degrees colder than your core body temperature. In the event that you would have to abandon ship that 12 degree difference would eventually take its toll on you and you could become hypothermic. We do drills like this on a weekly basis to keep our skills sharp. Hopefully we never need them!

A view like this never gets old
In just a few hours I will begin my first shift on deck collecting data for a stock assessment. I am both excited and nervous. Nervous in the sense of not knowing what to expect, but I cannot wait to get started. While I have loved the downtime to learn the ways of the ship and get to know the crew, I know that it will not last. This type of work is going to be very new to me, and the hours very long. While it is most certainly intimidating, I cannot wait to begin this very important scientific work.

Did You Know?

The deepest part of the Gulf of Mexico is an area known as the Sigsbee Deep. At its deepest, it is more than 12,000 feet! At more than 300 miles long, it is commonly referred to as the “Grand Canyon under the sea”. (Source-Encyclopedia Britannica)



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