launch – Page 4 – NOAA Teacher at Sea Blog

August 3, 2008April 2, 2021

Lisa Hjelm, August 3, 2008

NOAA Teacher at Sea
Lisa Hjelm
Onboard NOAA Ship Rainier
July 28 – 15, 2008

Mission: Hydrographic Survey
Geographical area of cruise: Pavlov Islands, Alaska
Date: August 3, 2008

Lowering a launch using a gravity davit system

Science and Technology Log

This morning I awoke to my first cloudy sky. Although clouds line the horizon, the sky above is blue. The fine weather is holding steady. At 0815 three launches were deployed to continue surveying the deep water, central part of the channel. I watched them head out into open water, but today I am in the survey room observing the Survey Technicians (ST) as they process the multibeam sonar data. At the same time, the ship is underway to a new anchorage on the other side of the end of the world, or more properly, the other side of Inner Iliasik Island. After a full week I have a new perspective on this island and volcano world. I’ve learned the names of our islands, Inner Iliasik and Iliasik. From the launch I am able to orient myself by looking out at the islands, not just by looking at the map. I continue to learn more about navigation charts. Whenever I stop by the Bridge someone points out something new. Today I learned that this area was previously mapped during surveys from 1900 – 1939 and 1940 – 1969. That means that much of it was surveyed with single beam sonar just after World War II. It took twenty summer seasons to cover this area using single beam sonar.

Using modern, multi-beam sonar, NOAA Ship Rainier is the first ship to chart this area, and the survey should be completed by 2009, or less than two years from start of survey to final chart. As the ship transits to its new anchorage we are collecting bottom samples at specified locations along the way. To collect a sample, the ship stops and is maneuvered into position, so the sampler can be safely lowered. A metal container descends on a cable to the seafloor. When it hits bottom a spring loaded scoop closes and collects a bottom sample. The container is winched back to the surface, and the water drained out. Then, we open it up to see what’s inside. Today our samples have been turning up broken shells, sand and shells, pebbles and shells and sticky green mud. After the samples are logged they go right back into the sea. I collected some sand samples to dry out and examine under microscopes with students.

Bottom samples are used to investigate and confirm comments on the existing navigation chart. Examples of chart comments would be sandy, shells (s, sh), black sand (bk s), shoals, rocky, and my personal favorite, smoking volcano. Sample locations are selected to provide representative coverage of the areas that have been mapped, and the data will be used to update the charts. Soon this sample data along with reflectivity data (measured as changes in backscatter of the sound pulse that reflect the hardness of the bottom surface) from the surveys will be used to map the type of seafloor along with the shape of the seafloor. This would be similar to generating a preliminary geologic map of the seafloor. Tomorrow I expect to be back on a launch with a better understanding what goes in to compiling a navigational chart.

Personal Log: Observations from the Fantail

Dinner is at 1700 (5:00 pm) prompt. After dinner people pursue their own activities. Some fish from the fantail. If the weather is calm, the smaller launches are used by fishing parties, and sea kayakers venture out to the islands to explore and hike. As I enjoyed the bright, warm sunlight on the fantail deck, I watched the progress of the hikers, tiny dots progressing steadily up the slope of Inner Iliasik Island. I gazed past the islands at the distant, hazy volcanoes, and spotted an ashy plume! With binoculars it was possible to see that smoke was rising from a small crater atop a conical volcano. Several of us rushed to the bridge to identify the volcano by locating it on the nautical chart. Our best guess, Dutton, which was not listed as presently erupting on the Alaskan Volcano website, http://www.avo.alaska.edu . Volcano watching is an exciting after dinner activity.

August 2, 2008April 2, 2021

Lisa Hjelm, August 2, 2008

NOAA Teacher at Sea
Lisa Hjelm
Onboard NOAA Ship Rainier
July 28 – 15, 2008

Mission: Hydrographic Survey
Geographical area of cruise: Pavlov Islands, Alaska
Date: August 2, 2008

Science and Technology Log

Hydrographic Survey – “Mowing the Ocean”

Science surrounds me. Everywhere I look people are practicing the skills I’ve been teaching for the past twelve years. Today, I am practicing the skills of observation and documentation. The following are my observations of hydrography in action.

Important vocabulary
Hydrographic survey or Hydrography: the measurement and description of the sea bed and coastal area. These data are used to produce navigation charts.

CTD and CTD cast: “CTD” is the abbreviated name for an instrument package that has sensors for measuring the Conductivity, Temperature and Depth of seawater. The instrument is lowered to the bottom. It collects Conductivity, Temperature, Depth and density data for the entire water column. That data is used to make corrections in the hydrographic survey data.

Multibeam sonar: By measuring the time it takes for sound waves sent from a transmitter mounted beneath the launch to bounce back, scientists determine the depth to the seafloor. Multibeam sonar systems provide fanshaped coverage of the seafloor. Because the speed of sound in water is related to conductivity, temperature and depth the CTD data is used with the multibeam sonar data.

The day starts at 0800 (8:00 am) on the fantail (rear, lowermost deck of the ship) with updates, detailed weather forecasts for the areas that will be mapped, and instructions from the Commanding Officer (CO), Executive Officer (XO), and Field Operations Officer (FOO). Then, wearing flotation devices and hardhats, each crew assembles to board the launches. As each launch is lowered, it is stopped even with the deck, and its crew of at least three, two hydrographers and a driver, boards. A cooler and thermoses for lunch are handed over. The launch is lowered into the water on cables and unhooked from the ship. It speeds at about 15 knots to the area to be mapped. The survey begins with a CTD cast. The CTD is lowered to the seafloor to collect data on water conductivity, temperature and depth. It is necessary to conduct a CTD scan every four hours or whenever conditions change. For example, if the launch moves to deeper water or to a different area. That done, the crew engages the multibeam echo sounder system, and at 7 knots per hour, the launch begins collecting data,“mowing the ocean.” In order to completely map the assigned seafloor area, the launch ends up making a pattern very similar to the back and forth pattern made by a lawnmower. This sounds easy enough, but it takes about a year to really learn the job. Each launch needs a three man crew. The Coxswain drives the launch and keeps the towed equipment on the grid line no matter what the seas around are doing.

Driving the launch as we “mow the ocean.”

The two hydrographers take turns scanning and tweaking four computer screens that are monitoring data collection. The towed instruments are collecting real time data that has to be checked and stored. All of this work is conducted in a relatively small boat, in the open ocean. When you add that component, you quickly realize that this is not only exciting science by a true adventure at sea. These crews are highly trained professionals. The launch drivers are senior members of the Deck Crew and are very experienced mariners. So far, I have worked with a ferry driver, a commercial fisherman, and an outward bound instructor. I tried driving the launch for a little while on my first day out. With no experience at all, I found it quite difficult to keep the launch headed along the line. Any deviation of the towed instruments from their prescribed grid path causes missed spots called “holidays.” “Holidays” can be caused by other things as well such as unexpected software crashes or gaps caused when data points have to be removed during processing. For complete survey coverage, the launches must return to remap “holidays.” These are therefore holidays for the equipment not the hydrographers.

Hydrographers have both technical skills and nautical skills. Many of them are officers on the Rainier. They troubleshoot whenever the software malfunctions and fix anything that breaks on the ship during the workday. I looked in the toolbox, and yes, there is duct tape. The launch crew also assists in deploying and retrieving the launches from the ship. This is an exciting and challenging job in an extraordinarily beautiful environment. After the launches return and are recovered, the hydrographers immediately meet to report on the day’s work. Each team leader makes a report and any problems with data logging and equipment are documented and discussed. The Field Operations Officer (FOO) uses this information to plan for the next day. And last but not least, if you’ve read this far, you are wondering how the Teacher at Sea fits into this. Each day the Teacher at Sea becomes more proficient at her tasks. I am provided with training, and my understanding is growing. But, on that first day, my day of “shock and awe,” I spent my time taking pictures, asking questions, investigating my personal flotation device and standing aft (in the back of the boat) to avoid seasickness. Additional time was spent practicing standing steadily and walking around the small boat. In other words, I spent the day “getting my sea legs. “

Personal Log

The second full day at sea we continued our transit to the survey area. Bright sunshine ignited an endless parade of snowy volcanoes. Off the bow, whale spouts dotted the horizon, and puffins bobbed and clumsily took off flashing their orange feet like small flags. At 2100 (9:00 pm), with the day still bright, nearly everyone gathered as the ship dropped anchor in a small bay at what appeared to be the end of the world. Two smooth, lawn-green islands connected by an isthmus marked the boundary. Beyond, on a hazy, distant horizon were the outlines of volcanoes. Behind, loomed the pointed, snowy Pavlof volcanic peaks. Perhaps Robert Frost was right.

SOME say the world will end in fire, Some say in ice. From what I’ve tasted of desire I hold with those who favor fire. – Robert Frost

July 22, 2008April 2, 2021

Gary Ledbetter, July 22, 2008

NOAA Teacher at Sea
Gary Ledbetter
Onboard NOAA Ship Rainier
July 7 – 25, 2008

Mission: Hydrographic Survey
Geographical area of cruise: Pavlov Islands, Alaska
Date: July 22, 2008

Weather from Bridge
Winds W/NW 10-15 building to 20
Partly Sunny, High 55 F
Seas 2-4 feet

NOAA Teacher at Sea, Gary Ledbetter, helps prepare the CTD for a cast.

Science and Technology Log

Navigation

Take a close look at some of the electronic communication and navigation equipment in the picture above. Which one do you think is the most important? Well, it’s probably not in this picture. Depending on who you ask you will get a different answer as to which piece of equipment is the most important. One would think with the advancements in electronics, it would be the GPS, or some other piece of high tech equipment. Although the most important piece is related to some of the high tech equipment, the instrument itself is not even close to being on the list of the latest and greatest technological equipment – it’s the compass; more specifically the gyro compass.

History

Unlike many things we may feel are rather mundane, the gyrocompass has an interesting history. Apparently taking a patent out for something that doesn’t work is not a new phenomenon because the gyrocompass was patented in 1885 (only about 20 years after the end of the Civil War) by Geradus van den Bos…. and yes, it didn’t work! Four years later, Captain Author Krebs designed an electronic gyroscope for use aboard a French submarine. Then, in 1903, Hermann Anschutz-Kaempfre refined the gyrocompass, applied for and also was granted a patent. Five years later, in 1908, Anschutz-Kaempfre, with the help of Elmer Ambrose Sperry did more research on the compass and was granted an additional patent in both Germany and the United States. Then things started to heat up. Sperry, in 1914, tried to sell this gyrocompass to the German Navy and Anschutz-Kaempfre sued Sperry for patent infringement. As happens today, the attorneys got involved and various arguments were presented. Now it even gets more interesting – Albert Einstein got involved. First, Einstein agreed with Sperry and then somewhere during the proceedings, Einstein had a change of heart and jumped on the Anschutz-Kaempfre bandwagon. The bottom line? Anschutz-Kaempfre won in 1915.

A myriad of navigation equipment exists aboard the RAINIER.

So What?

OK, this history is all well and good, but what does a gyrocompass do that any regular compass can’t do? In a nutshell, a gyrocompass finds true north, which is the direction of the Earths rotational axis, not magnetic north – the direction our Boy Scout compass pointed. Another factor of the gyrocompass is that it is not affected by metal such as the ships hull. Put your Boy Scout compass next to a large metal object and see what happens. Also remember one thing: When you tried to find magnetic north with a Boy Scout compass, you had to hold it very, very still. Try reading a regular compass aboard a ship that is not only moving through the water, but is being tossed about by the waves and currents of the ocean. The gyrocompass addresses this concern also. Without going into a lot of detail (and yes there are a lot of details, even about a compass) friction causes torque, which makes the axis of the compass to remain perpendicular. In other words as the ship rolls and pitches, torque makes the axis of the compass to remain perpendicular to the earth. You then have an instrument that can read true north in nearly all weather conditions.

The electronic gyrocompass aboard the RAINIER

Definition

Torque: A turning or twisting force

Personal Log

I was a victim! I was a victim of NOAA! In fact, I was a very, very willing victim! NOAA’s safety record is very high and they conduct numerous safety drills to maintain that record and to insure the safety of all aboard. On July 20^th I was asked if I wanted to play the “victim” in an upcoming safety drill. Of course I jumped at the chance. I was to play an unconscious fire victim with broken bones. After I staged the “accident” the various medical and fire suppression teams came to my rescue. These drills are very serious part of NOAA’s operation and are taken seriously by the crew – but that didn’t mean I didn’t have fun in the process!!

Gary plays the part of the “victim” during a safety drill on the RAINIER.

July 15, 2008April 2, 2021

Gary Ledbetter, July 15, 2008

NOAA Teacher at Sea
Gary Ledbetter
Onboard NOAA Ship Rainier
July 7 – 25, 2008

Mission: Hydrographic Survey
Geographical area of cruise: Pavlov Islands, Alaska
Date: July 15, 2008

Weather from Bridge
Winds SE/E @ 5 knots
Temperature: High 45 degree F
Seas 1-3 feet

Science and Technology Log

Sonar

Sonar, which is short for sound navigation and ranging, is a system that uses sound to communicate, navigate, detect other vessels, and determine the depth of the water. A hydrographic survey ship, such as the RAINIER, extensively uses sonar on their survey boats.

A Very Brief History

Using sound to detect objects is nothing new. In fact man has been using it for hundreds of years. Even before man was using sound, bats use their own form of sonar (more commonly referred to as radar) for navigation. As early as 1490 Leonardo Da Vinci inserted a tube in water, put his ear to the tube and reportedly was able to detect vessels. Not surprisingly, the use of the “echo locate” system was given a big boost following the Titanic disaster of 1912. The British Patent Office gave English meteorologist Lewis Richardson, the world’s first patent for an underwater echo ranging devise within one month of the sinking of the famous ship.

Matt from Earth Resources Technology working on one of the survey launches

Sonar usually plays an important part when we watch World War II war movies depicting the Navy hunting enemy submarines. These depictions were more than just Hollywood. In fact, the British were ahead of the U.S. in sonar technology even prior World War I. In 1916 Canadian physicist Robert Boyle took along with AB Wood, under the direction of the British Board of Invention and Research, produced a prototype for active sound detection in 1917. This was really secret stuff! In fact it was so secret that the word used to describe that early work, called “supersonics”, was changed to ASD’ics. This term eventually morphed into ASDIC. It even gets more interesting. The Admiralty made up a story that ASDIC stood for “Allied Submarine Detection Investigation Committee. Many people today still think that’s what ASDIC means even no committee with this name has even been found in the Admiralty archives.

It seems like we Americans always have to change the name of something, (you history buffs know that Britain had something called the wireless… but we changed it to radio) so we did the same thing with ASDIC. We changed it to SONAR, primarily because it was closely related to RADAR. The name change became official in 1948 with the formation of NATO’s standardization of signals. Thereafter, ASDIC was changed to SONAR for all NATO countries.

The lines you see make up the grid the survey boats follow. The ones scratched out are the ones we have completed.

So Just What Is This Sonar…?

There are two basic types of sonar: Active and Passive. We’ll briefly discuss passive first. Passive listens without transmitting. It is used to determine the absence or the presence of something – primarily in the water. To come directly to the point it is detecting any sound that comes from a remote location. Listening to those sounds helps identify the sound. (Back to Hollywood: remember the scene in nearly any navy warfare movie when the sonar operator of the ship is talking with the captain: “it sounds like a X4IY9, Class H2 Russian sub, Captain). The sound of the sub was not being produced in any form from the ship, but from a remote location – the sub. Now you have an idea of passive sonar.

Active Sonar

Yours truly trying his hand at driving the boat

Active Sonar creates a “ping”. This ping travels through the water until it strikes something; it then bounces back. The bouncing is called reflection, or an echo. The ping is created, normally, electronically. When the ping is transmitted it travels through the water, strikes an object and bounces back (the echo). This time is measured and converted into range (distance) by knowing the speed of sound. Sounds pretty simple, right? Unfortunately numerous variables can affect the time it takes for the echo to return such as salt content (sounds travels faster through salt water than fresh water), the density of the water, and even the temperature of the water. Then there is the “noise”, or other disturbances in the water: fish, seaweed, dirt, trash, etc., that effect an accurate measurement. All of these variables have to be taken into consideration by the survey technicians and scientists.

The survey boats from the RAINIER use different types of sonar. The sonar on the boat I was recently on is called the Reson SeaBat. Instead of simply one “ping”, it produced a swatch of 128 degrees consisting of 256 pings across the ocean floor. It then transmits these pings back to the boat. Think in terms of a triangle, with the top of the triangle being the sonar unit on the boat. The sonar transmits the pings across the ocean floor and sends back numerous signals instead of just one.

Personal Log

Yesterday I was aboard survey boat (called a launch) RA 4. These boats are deployed and retrieved each morning and night. On the ocean each boat follows a predetermined grid across the ocean much like mowing your lawn. Deploying the boats, retrieving the boats, and following the grid looks really simply until you do it yourself, and then you realize how difficult it really is. I guess when you watch experts do something, they make it look easy. The sea was nearly mirror smooth. Although it was cloudy and cool, there was little or no rain or wind. This makes the process much easier as well as more enjoyable. Tim, a NOAA Ensign was operating the onboard computer system that kept track of the sonar readings. I was able to try my hand at driving the boat and operating the computer. I’m not going to talk about how well I did, but as I said before, they make their job look so easy!

July 7, 2008April 2, 2021

Gary Ledbetter, July 7, 2008

NOAA Teacher at Sea
Gary Ledbetter
Onboard NOAA Ship Rainier
July 7 – 25, 2008

Mission: Hydrographic Survey
Geographical area of cruise: Pavlov Islands, Alaska
Date: July 7, 2008

Weather Data from the Bridge
Winds SE/E @ 10 knots
Drizzle, Seas 1-3 feet
Temperature: High 45 degree F.

Background

The Office of Coast Survey (OCS) is a part of the National Oceanic and Atmospheric Administration (NOAA) that conducts hydrographic surveys. In short, they measure the depth and bottom configuration of bodies of water using sonar technology. From these measurements our nation’s nautical charts are developed to assist in safe navigation of the United States waters. Additionally the surveys also locate and publish sea-floor materials that may inhibit safe ocean travel such as pipeline and cables, shipwrecks, and other obstructions. NOAA hydrographic surveys have also been instrumental in locating the wreckage of TWA Flight 800, John F. Kennedy Jr.’s plane, and EgyptAir flight 990. OCS has conducted over 10,600 surveys since it began in the early 1900s. *

Science & Technology Log

If you are like me, you probably thought that sonar was simply aimed at the bottom of the ocean and a graph-like image came back. Well, this is essentially true – but there is a lot more to it than that. Prior to even using that technology, another research tool must be used: The CTD recorder. “CTD” means, Conductivity-Temperature-Depth recorder. This instrument measures either directly or indirectly such factors as temperature, saline, and density.

ENS Junior Officer Christy Schultz preparing to lower the CTD Recorder, which sits in the metal cage in front of her

Although measuring these characteristics are not new (Benjamin Franklin did some of these measurements as far back as the 18^th century), the methods of taking these measurements have drastically changed. The present technology was developed in the 1960’s where the instrument itself is placed in the water it is measuring. The instrument then takes a continuous measurement of conductivity, temperature and depth, which are recorded continuously. These measurements are taken up to 24 times per second. That kind of speed creates a very high-resolution description of the water being tested. When the instrument is measuring conductivity, it is simply discovering how easily electricity passes through the water sample being tested. Since electricity passes through water more easily with a higher salt content; the more easily electricity is passed, the higher the salt content.

The CTD normally uses a thermistor: a platinum thermometer, or a combination of these to measure temperature. The accuracy is quite amazing: greater than 0.005 degrees Celsius. Last, but not least, the CTD measures pressure. This pressure is measured in decibars. Depth and pressure are directly related. In other words, if you are at 340 meters below the surface, the meter will indicate about 350 decibars (dbars). Once all these measurements are taken, they can either be stored in the actual instrument or they can be transferred to a computer when the CTD is withdrawn from the ocean. OK, you may say, this is all well and good, but what does it have to do with mapping the ocean floor (the technicians call this, “mowing the ocean”)? The simple answer: All these conditions affect the speed of sound. Therefore when the sonar “pings” the computer will compensate for variables (temperature, density and salinity); this creates a more accurate reading of the ocean depth at any particular spot. **

Personal Log

I am discovering that hydrographic surveys are both simplistic, and complex. Simplistic in terms that the survey boats simply follow a pre-established grid and collect computerized data. They collect this data by following a pre-determined grid much like someone mowing their lawn. In fact the surveyors call it “mowing the ocean”. However, the interpreting of this data is the job of several engineers and engineer technicians which may take several hours or possibly all night.

*Information obtained from NOAA website, ** Information obtained from the CTD website