Debbie Stringham, July 10, 2005

NOAA Teacher at Sea
Debbie Stringham
Onboard NOAA Ship Fairweather
July 5 – 15, 2005

Mission: Hydrographic Survey
Geographical Area: North Pacific, Alaska
Date: July 10, 2005

“FISH” Collects sound velocity data while vessel is moving.
“FISH” Collects sound velocity data while vessel is moving.

Weather Data 

Location: Eagle Harbour, Shumagin Islands, AK
Latitude: 55 06.8’ N
Longitude: 160 06.9’ W
Visibility: 10 nm.
True Wind Speed: 16 kts.
True Wind Direction: 340
Sea Wave Height: 1 ft.
Swell Wave Height: none
Swell Wave Direction: none
Sea Water Temperature: 12.0 C
Sea Level Pressure: 1011.5 mb
Sky Description: Partly Cloudy
Dry Bulb Temperature: 15.5 C
Wet Bulb Temperature: 12.5 C

Science and Technology Log 

This morning, I assisted a survey technician entering the bottom sampling data we collected on yesterday’s launch. I also read through training materials about the SeaBat Mutlibeam Survey System and learned  how the system works.

“FISH” winch. Instrument attached collects sound velocity data.
“FISH” winch. Instrument attached collects sound velocity data.

Basically, there are six parts to the system: the multibeam sonar, data acquisitioning software, beacon receiver, SeaBird Water “FISH” winch. Instrument attached collects sound velocity data. Column Profiler, Velocity Probe, and data processing software. When activated, the system generates “pings” that are transmitted through the water column. Those “pings” collide with targets and return echo signals to the receiver. The hydrophones convert the pressure from the echo into an electrical signal. The signal is amplified and the software processes it and displays the information on the computer.

In order to understand SONAR, one must also understand sound. Sound is produced by a vibrating source that causes compression waves which are detectable pressure changes. The speed of the propagation depends on the medium it is traveling through. For instance, sound travels about 390 meters per second in air and 1500 meters per second in water. The velocity of sound in water is dependent on three main factors: salinity, temperature, and pressure.

I interviewed an Ensign on the crew this afternoon about the career paths she had taken to be a part of NOAA. She received her bachelor degree in Marine Studies with an emphasis in marine mammals. She was investigating the Peace Corps and the Navy when she came across NOAA and decided to enroll in their three month officer’s basic training. After three months of studying radar and navigation, she was assigned to the FAIRWEATHER for two years at sea. After her two years are complete, should she decide to continue, she will then be assigned to a three year term in a land-based position. In order to qualify for officer’s training, one needs a bachelor’s degree in any science or engineering related field.

Question of the Day 

What does SONAR stand for?

Answer from Previous Day 

Looking at the nature of the sea floor is important because of implications relating to anchoring, dredging, structure construction, pipeline and cable routing, and fisheries habitat.

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