calibration – Page 2 – NOAA Teacher at Sea Blog

July 29, 2017August 15, 2017

Samantha Adams: Day 6 – Testing… 1 – 2 – 3, July 29, 2017

NOAA Teacher at Sea

Samantha Adams

Aboard NOAA Ship Hi’ialakai

July 25 – August 3, 2017

Mission: Woods Hole Oceanographic Institution (WHOI) Hawaii Ocean Time-series Station deployment (WHOTS-14)

Geographic Area of Cruise: Hawaii, Pacific Ocean

Date: Saturday, 29 July 2017

Weather Data from the Bridge:

Latitude & Longitude: 22^o45’N, 157^o56’W. Ship speed: 1.3 knots. Air temperature: 27.8^oC. Sea temperature: 27.0^oC. Humidity: 72%.Wind speed: 14 knots. Wind direction: 107 degrees. Sky cover: Few.

Science and Technology Log:

The most difficult part of Thursday’s buoy deployment was making sure the anchor was dropped on target. Throughout the day, shifting winds and currents kept pushing the ship away from the anchor’s target location. There was constant communication between the ship’s crew and the science team, correcting for this, but while everyone thought we were close when the anchor was dropped, nobody knew for sure until the anchor’s actual location had been surveyed.

blog.4.Day6.image1 — Triangulation of the WHOTS-14 buoy’s anchor location. Look at how close the ‘Anchor at Depth’ location is to the ‘Target’ location — only 177.7 meters apart! Also notice that all three circles intersect at one point, meaning that the triangulated location of the anchor is quite accurate.

To survey the anchor site, the ship “pinged” (sent a signal to) the acoustic releases on the buoy’s mooring line from three separate locations around the area where the anchor was dropped. This determines the distance from the ship to the anchor — or, more accurately, the distance from the ship to the acoustic releases. When all three distances are plotted (see the map above), the exact location of the buoy’s anchor can be determined. Success! The buoy’s anchor is 177.7 meters away from the target location — closer to the intended target than any other WHOTS deployment has gotten.

After deployment on Thursday, and all day Friday, the Hi’ialakai stayed “on station” about a quarter of a nautical mile downwind of the WHOTS-14 buoy, in order to verify that the instruments on the buoy were making accurate measurements. Because both meteorological and oceanographic measurements are being made, the buoy’s data must be verified by two different methods.

Weather data from the buoy (air temperature, relative humidity, wind speed, etc.) is verified using measurements from the Hi’ialakai’s own weather station and a separate set of instruments from NOAA’s Environmental Sciences Research Laboratory. This process is relatively simple, only requiring a few quick mouse clicks (to download the data), a flashdrive (to transfer the data), and a “please” and “thank you”.

blog.4.Day6.image2 — July 28, 2017, 5:58PM HAST. Preparing the rosette for a CDT cast. Notice that the grey sampling bottles are open. If you look closely, you can see clear plastic “wire” running from the top of the sampling bottles to the center of the rosette. The wires are fastened on hooks which, when triggered by the computer in the lab, flip up, releasing the wire and closing the sampling bottle.

Salinity, temperature and depth measurements (from the MicroCats on the mooring line), on the other hand, are much more difficult to verify. In order to get the necessary “in situ” oceanographic data (from measurements made close to the buoy), the water must be sampled directly. This is done buy doing something called a CTD cast — in this case, a specific type called a yo-yo.

The contraption in the picture to the left is called a rosette. It consists of a PCV pipe frame, several grey sampling bottles around the outside of the frame, and multiple sets of instruments in the center (one primary and one backup) for each measurement being made.

blog.4.Day6.image3 — July 28, 2017, 6:21PM HAST. On station at WHOTS-14, about halfway through a CDT cast (which typically take an hour). The cable that raises and lowers the rosette is running through the pulley in the upper right hand corner of the photo. The buoy is just visible in the distance, under the yellow arm.

The rosette is hooked to a stainless steel cable, hoisted over the side of the ship, and lowered into the water. Cable is cast (run out) until the rosette reaches a certain depth — which can be anything, really, depending on what measurements need to be made. For most of the verification measurements, this depth has been 250 meters. Then, the rosette is hauled up to the surface. And lowered back down. And raised up to the surface. And lowered back down. It’s easy to see why it’s called a yo-yo! (CDT casts that go deeper — thousands of meters instead of hundreds — only go down and up once.)

For the verification process, the rosette is raised and lowered five times, with the instruments continuously measuring temperature, salinity and depth. On the final trip back to the surface, the sampling bottles are closed remotely, one at a time, at specific depths, by a computer in the ship’s lab. (The sampling depths are determined during the cast, by identifying points of interest in the data. Typically, water is sampled at the lowest point of the cast and five meters below the surface, as well as where the salinity and oxygen content of the water is at its lowest.) Then, the rosette is hauled back on board, and water from the sampling bottles is emptied into smaller glass bottles, to be taken back to shore and more closely analyzed.

On this research cruise, the yo-yos are being done by scientists and student researchers from the University of Hawaii, who routinely work at the ALOHA site (where the WHOTS buoys are anchored). The yoyos are done at regular intervals throughout the day, with the first cast beginning at about 6AM HAST and the final one wrapping up at about midnight.

blog.4.Day6.image4 — July 29, 2017, 9:43AM HAST. On station at WHOTS-13. One CDT cast has already been completed; another is scheduled to begin in about 15 minutes.

After the final yo-yo was complete at the WHOTS-14 buoy early Saturday morning, the Hi’ialakai traveled to the WHOTS-13 buoy. Today and tomorrow (Sunday), more in situ meteorological and oceanographic verification measurements will be made at the WHOTS-13 site. All of this — the meteorological measurements, the yo-yos, the days rocking back and forth on the ocean swell — must happen in order to make sure that the data being recorded is consistent from one buoy to the next. If this is the case, then it’s a good bet that any trends or changes in the data are real — caused by the environmental conditions — rather than differences in the instruments themselves.

Personal Log:

blog.4.Day6.image5 — The *Hi’ialakai*’s dry lab. Everyone is wearing either a sweatshirt or a jacket… are we sure this is Hawaii?

Most of the science team’s time is divided between the Hi’ialakai’s deck and the labs (there are two; one wet, and one dry). The wet lab contains stainless steel sinks, countertops, and an industrial freezer; on research cruises that focus on marine biology, samples can be stored there. Since the only samples being collected on this cruise are water, which don’t need to be frozen, the freezer was turned off before we left port, and turned into additional storage space. The dry lab (shown in the picture above) is essentially open office space, in use nearly 24 hours a day. The labs, like most living areas on the ship, are quite well air conditioned. It may be hot and humid outside, but inside, hoodies and hot coffee are both at a premium!

Did You Know?

The acronym “CTD” stands for conductivity, temperature and depth. But the MicroCats on the buoy mooring lines and the CTD casts are supposed to measure salinity, temperature and depth… so where does conductivity come in? It turns out that the salinity of the water can’t be measured directly — but conductivity of the water can.

When salt is dissolved into water, it breaks into ions, which have positive and negative charges. In order to determine salinity, an instrument measuring conductivity will pass a small electrical current between two electrodes (conductors), and the voltage on either side of the electrodes is measured. Ions facilitate the flow of the electrical current through the water. Therefore conductivity, with the temperature of the water taken into account, can be used to determine the salinity.

June 15, 2017

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: noaa.gov

IMG_4317[1] — 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.

IMG_4131[1] — Diagram of calibration set up (Noaa.gov)

Calibration sphere (Noaa.gov)

Downrigger system (Noaa.gov)

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.

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.

IMG_4232[1] — Stairs from the bottom deck up to the crew’s lounge

IMG_4095[1] — 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!

FBNH3430[1] — 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)

August 9, 2013March 12, 2021

Julia Harvey: Calibration in Sea-Otterless Sea Otter Bay, August 7, 2013

NOAA Teacher at Sea
Julia Harvey
Aboard NOAA Ship Oscar Dyson (NOAA Ship Tracker)
July 22 – August 10, 2013

Mission: Walleye Pollock Survey
Geographical Area of Cruise: Gulf of Alaska
Date: 8/7/13

Weather Data from the Bridge (as of 21:00 Alaska Time):
Wind Speed: 10.42 knots
Temperature: 13.6 C
Humidity: 83%
Barometric Pressure: 1012.4 mb

Current Weather: A high pressure system is building in the east and the swells will increase to 8 ft tonight.

Science and Technology Log:

Before I begin, I must thank Paul for educating me on the calibration process. Because calibration occurred during the day shift, I was not awake for some of it.

The EK60 is a critical instrument for the pollock survey. The calculations from the acoustic backscatter are what determines when and where the scientists will fish. Also these measurements of backscatter are what are used, along with the estimates of size and species composition from the trawling, to estimate fish biomass in this survey. If the instruments are not calibrated then the data collected would possibly be unreliable.

Calibration of the transducers is done twice during the summer survey. It was done before leg one in June, which began out of Dutch Harbor, and again now near Yakutat as we end leg three and wrap up the 2013 survey.

As we entered Monti Bay last night, Paul observed lots of fish in the echosounder. This could pose a problem during calibrations. The backscatter from the fish would interfere with the returns from the spheres. Fortunately fish tend to migrate lower in the water column during the day when calibrations were scheduled.

This morning the Oscar Dyson moved from Monti Bay, where we stopped last night, into Sea Otter Bay and anchored up. The boat needs to be as still as possible for the calibrations to be successful.

Monti and Sea Otter Bays Map by GoogleEarth — Monti and Sea Otter Bays
Map by GoogleEarth

Calibration involves using small metal spheres made either of copper or tungsten carbide.

Chief Scientist Patrick Ressler with a tungsten carbide sphere

Copper sphere photo courtesy Richard Chewning (TAS) — Copper sphere
photo courtesy Richard Chewning (TAS)

The spheres are placed in the water under transducers. The sphere is attached to the boat in three places so that the sphere can be adjusted for depth and location. The sphere is moved throughout the beam area and pings are reflected. This backscatter (return) is recorded. The scientists know what the strength of the echo should be for this known metal. If there is a significant difference, then data will need to be processed for this difference.

The 38 khz transducer is the important one for identifying pollock. A tungsten carbide sphere was used for its calibration. Below shows the backscatter during calibration, an excellent backscatter plot.

The return for this sphere was expected to be -42.2 decibels at the temperature, salinity and depth of the calibration The actual return was -42.6 decibels. This was good news for the scientists. This difference was deemed to be insignificant.

Personal Log:

Calibration took all of the day and we finally departed at 4:30 pm. The views were breathtaking. My camera doesn’t do it justice. Paul and Darin got some truly magnificent shots.

As we left Yakutat Bay, I finally saw a handful of sea otters. They were never close enough for a good shot. They would also dive when we would get close. As we were leaving, we were able to approach Hubbard Glacier, another breathtaking sight. Despite the chill in the air, we stayed on top getting picture after picture. I think hundreds of photos were snapped this evening.

Location of Hubbard Glacier. Map from brentonwhite.com

Many came out in the cool air to check out Hubbard Glacier

Lots of ice from the glacier as we neared

Nearby Hubbard Glacier with no snow or ice — Near Hubbard Glacier

Did You Know?

According to the National Park Service, Hubbard Glacier is the largest tidewater glacier in North America. At the terminal face it is 600 feet tall. This terminal face that we saw was about 450 years old. Amazing!

Staci DeSchryver: Don’t Hate, Just Calibrate! August 9, 2011

NOAA Teacher at Sea
Staci DeSchryver
Onboard NOAA Ship Oscar Dyson
July 26 – August 12, 2011

Mission: Pollock Survey
Geographical Area of Cruise: Gulf of Alaska
Location: Barnabas Strait 57 deg 22.630 N, 152 deg 24.910W
Heading: 67.8 deg
Date: August 9, 2011

Weather Data From the Bridge
Partly Cloudy Skies
Temp: 13.5 deg
Dewpoint: 6 deg
Barometric Pressure: 1020 mb, falling, then steady
Wind: 240 deg at 12kts
Seas: Calm
stn model 08.11

Science and Technology Log

The start of my first official shift onboard the Oscar Dyson was an interesting one! We had lost some time (11 days) to some complications, so our cruise goals shifted a bit from the original plan. We had to focus on the most important aspects of the mission, and sacrifice carefully, as it wasn’t plausible to complete the entire mission in the time allotted. One of the major steps for completing the season was to do what is known as a calibration. In order to save time, we did the calibration on my first night out on the job!

Calibrations are typically done during the daytime because the fish are curious little beasts. During the day, they move lower in the water column, and therefore do not interfere with the calibration of the system, mainly because they are so far away they are oblivious to it. At night, however, they party at a shallower depth, and sometimes their acoustic signatures can mar the data collected during a calibration. It is critical to the scientists that they calibrate the acoustic system accurately, and if there is a school of fish swarming the calibration tools, well, it’s a big ‘ole mess. Given that we are on a shortened time schedule, it made practical sense to conduct the calibration overnight.

Marshmallow has been very helpful on the trip. Here he is counting krill. I don't have the heart to inform him that these krill have already been counted.

Why do we calibrate the acoustic transducer? Think of it like this. Have you ever baked cookies before and followed the directions to the letter, only to have them come out of the oven like crispy critters or balls of goo? Or, let’s say, you have a favorite recipe you use all the time, and you gave the recipe to a friend who makes the same cookies the same way, yet complains that they are overcooked? Well, one of the reasons that the recipe may have not turned out was because either your oven, or your friend’s oven was not properly calibrated. Let’s say, for example, the recipe calls to bake the cookies at 350 degrees for 15 minutes.

If you turn the dial to 350 degrees, it is reasonable to expect that the oven is, in fact, 350 degrees. But there is an equal possibility that the oven is actually only 325, or maybe even 400 degrees. How would you double check to see if your instrument is off its mark? One solution is to heat the oven to 350, and use a meat or candy thermometer that you know has an accurate readout and then put the thermometer in the oven. If the candy thermometer reads out at 350, you can be certain that your oven really is 350 when you turn it on. If the candy thermometer reads out at 375, then you can be certain there’s an error in the readout of your instrument. Calibration corrects for those errors.

Here you see Cat and I showing off the downrigger - the piece of equipment that holds the calibration spheres under the ship.

Calibration on this survey is important because scientists use information from the acoustic transducer to determine the types and abundance of organisms in the water column. If the instrument they use to make these predictions is off in any way, then all of the data they collect could be determined to be insufficient or unreliable. Calibration also ensures that acoustic measurements (and survey results) are comparable between different cruises, locations, and times.

Calibration is done much in the same way as an oven is calibrated. We take an object that has a known and reliable return rate on the acoustic transducer, and hang it below the ship. Then, the scientists will “ping” acoustic soundings off of the object and see how well the return matches up with the known return rate. If it’s off, then they can “tune” the transducers, much like a guitar is tuned.

downriggers ii — Here, the chief scientist, Chris Wilson, double checks our superior downrigging work!

It is only necessary to calibrate the transducers twice per survey – once at the beginning of the survey (one was done in June) and one at the end of the survey (which was now). When the transducer is calibrating, the ship must be as close to stationary as possible. This is why the lead scientist chose to do the calibration at night – we can’t calibrate and conduct assessment surveys at the same time. Therefore, it’s a one-pony show when the transducer is calibrating. Almost all other scientific field work ceases while the calibration is completed.

There are two materials used for calibration for this particular transducer on the Oscar Dyson. The first is Tungsten Carbide, and the second is pure Copper. These small, spherical objects are quite cleverly hung below the ship off of three downriggers attached to the port and starboard rails. In order to hang the spheres, the strings on either side of the ship must connect. In a sense, we ask the Dyson to “jump rope” to get the calibration sphere underneath the ship in the correct position.

Calibration takes about six to eight hours to complete. I got to help with setting the downriggers up, changing out the calibration spheres, and breaking down the equipment. As it turns out, the transducer only needed minor adjustments this time, which is pretty typical for the ship. However, it’s important to double check so that if there is a problem, it can be detected early and corrected.

Personal Log

Today, the chief engineer of the ship, Jeff, gave us a tour of the engine room. Holy cow, was that impressive! I don’t know what I was thinking when I thought that the guts of this beast were contained in one small room. They most decidedly are not. There are two whole decks below the lowest level I know of – and they are filled with all kinds of interesting equipment. We got to see all of the engines (there are 4 diesel generators), where the water is purified for consumption, and all of the internal components of the winch system that lowers and raises our fishing nets. As if that weren’t enough, we popped open a floor hatch, climbed down the ladder two flights, and got to stand right on the “skin” of the boat. Translation: The only thing separating my feet and the big blue sea was a thin little piece of metal. It was so cool. The ship is designed to be “acoustically silent” – like a stealth fighter, except they don’t call it stealth and we aren’t fighting enemies – we are hunting fish. Because of this, many of the larger pieces of equipment are hoisted up on platforms that silence their working parts. The ship has diesel-electric propulsion.

engine rm — Here is just ONE of the four massive engines on the ship!

This means that there are four diesel generators that make electricity, which then gets split into two different forms – one type is for propulsion, and the other is for our lights and other conveniences. It sounds really complicated, and much of what the engineers do on board is quite complicated, but everything onboard is smartly labeled to help the engineers get the job done. I also learned today what the funny numbers on all of the passage doors mean. See the caption for a description.

Here is one of the door signs on the ship, which act like a "you are here" sign on a map. The first number tells us what floor we are on. The second number tells us what area of the ship we are in. The third number tells us whether we are port, starboard, or in the center of the ship.

One thing that Cat and I were discussing this morning while searching through binoculars in Alitak Bay for interesting woodland creatures was that we can go pretty much wherever we want to go on this ship. Everyone who works and lives here is so friendly and welcoming. They answer any of our questions (even the silly ones) and they all have such cool life stories. What’s better is that everyone is willing to share what they’ve learned, experiences they’ve had, and accomplishments they’ve achieved to make it here. I am aboard a utopian city bursting with genuine people who love what they do. Now, please understand that it’s not that I ever expected the opposite for even a single second. The science and technology is definitely neat, but the people who live and work here are what is making this trip a once-in-a-lifetime experience.

Do you know….

Your Ship Superstitions?

1. Bananas on a boat are considered bad luck.

2. Black luggage for sailors is considered bad luck.

3. One should never whistle – especially on the bridge or in the wheelhouse – you may whistle up a storm.

4. To see a black cat before boarding is good luck.

5. Dolphins swimming along the ship are good luck.

6. Never sail on Friday – it’s unlucky.

7. Never sail on the first Monday in April – also unlucky.

8. Never say the word “Drown” on a ship, as it encourages the act.

9. Sailors should avoid flat-footed people – they are bad luck.

10. Never step onboard a ship with your left foot first.

June 24, 2006March 19, 2021

Diana Griffiths, June 24, 2006

NOAA Teacher at Sea
Diana Griffiths
Onboard UNOLS Ship Roger Revelle
June 22 – June 30, 2006

Mission: Hawaiian Ocean Timeseries (WHOTS)
Geographical Area: Hawaiian Pacific
Date: June 24, 2006

Weather Data from Bridge
Visibility: 10 miles to less than 25 miles
Wind direction: 065°
Wind speed: 06 knots
Sea wave height: small
Swell wave height: 4-6 feet
Sea level pressure: 1014.5 millibars
Cloud cover: 3, type: stratocumulus and cumulus

Buoy Technician, Sean Whelan, contacting the Acoustic Releases on WHOTS-2.

Science and Technology Log

Today was very busy because it was the day that WHOTS-2 mooring, which has been sitting out in the ocean for almost a year, was recovered. At around 6:30 a.m., Sean Whelan, the buoy technician, tried to contact the Acoustic Release. (The Acoustic Release is the device that attaches the mooring to the anchor. When it receives the appropriate signal, it disengages from the anchor, freeing the mooring for recovery. There are actually two releases on WHOTS2.) He does this by sending a sound wave at 12 KHz down through the ocean via a transmitter, and when the release “hears” the signal, it returns a frequency at 11 KHz. The attempt failed, so the ship moved closer to the anchor site and the test was repeated. This time it was successful. Based on the amount of time it takes the acoustic signal to return, the transmitter calculates a “slant range” which is the distance from the ship to the anchor. Because the ship is not directly over the anchor, this slant range creates the hypotenuse of a right triangle. Another side of the triangle is the depth of the ocean directly below the ship. Once these two distances are known, the horizontal position of the ship from the anchor can easily be calculated using the Pythagorean theorem.

Recovery of WHOTS-2 buoy aboard the R/V REVELLE.

After breakfast, the buoy recovery began. A small boat was lowered from the ship and driven over to the buoy, as the ship was steamed right near the buoy. A signal was sent down to activate the Acoustic Releases. Ropes were attached from the buoy through a pulley across the A-frame, located on the stern of the ship, to a large winch. With Jeff Lord leading the maneuvering of the 3750-pound buoy, it was disengaged from the mooring and placed safely on deck. This was a bit of a tense moment, but Jeff did a wonderful job of remaining calm and directing each person involved to maneuver their equipment to effectively place the buoy. Once the buoy was recovered and moved to the side of the deck, each instrument on the mooring was recovered. The first to appear was a VMCM, (Vector Measuring Current Meter) located just 10 meters below the buoy.

Jeff Lord, engineering technician, directing the recovery of a Vector Measuring Current Meter (VMCM).

Then two microCATs were pulled up, located 15 and 25 meters below the buoy, followed by a second VMCM. This was followed by a series of eleven microCATs located five or ten meters apart, an RDI ADCP (Acoustic Doppler Current Profiler), and two more microCATs. As each instrument was recovered, the time it was removed from the water was recorded and its serial number was checked against the mooring deployment log. Each instrument was photographed, cleaned off and sent to Jeff Snyder, an electronic technician, for data upload. Each of these instruments has been collecting and storing data at the rate of approximately a reading per minute for a year (this value varies depending on the instrument) and this data now needs to be collected. Jeff placed the instruments in a saltwater bath to simulate the ocean environment and connected each instrument to a computer by way of a USB serial adaptor port. The data from each instrument took approximately three hours to upload. Tomorrow, these instruments will be returned to the ocean alongside a CTD in order to compare their current data collection with that of a calibrated instrument.

Once all of the instruments were recovered, over 4000 feet of wire, nylon rope, and polypropylene rope were drawn up using a winch and a capstan. Polypropylene rope is used near the end of the mooring because it floats to the surface. The last portion of the mooring recovered was the floatation. This consisted of eighty glass balls chained together and individually encased in plastic. The glass balls, filled with air, float the end of the mooring to the surface when the Acoustic Releases disengage from the anchor. It takes them about 40 minutes to reach the surface. Recovering the glass balls was tricky because they are heavy and entangled in one another. Once on deck they were separated and placed in large metal bins. After dinner, a power washer was used to clean the buoy (it is a favorite resting place for seagulls and barnacles) and the cages encasing some of the instruments. The deck was cleaned and organized to prepare for tomorrow.

Recovery of mooring floatation on WHOTS-2, consisting of 80 glass balls encased in plastic.

Personal Log

The theme that keeps going through my mind during this trip and today especially, is how much of a cooperative effort this research requires. It begins with the coordination between Dr. Weller and Dr. Lukas to simultaneously collect atmospheric data using the buoy and subsurface data with the mooring instruments. In addition, Dr. Frank Bradley, an Honorary Fellow at the CSIRO Land and Water in Australia, is on the cruise working to create a manual set of data points for relative humidity using an Assman psychrometer to further check the relative humidity data produced on the buoy. Within the science teams, coordination has to occur at all stages, from the collection of data to its analysis. This was very evident in physical form today with numerous people on deck throughout the day working to retrieve the mooring, fix machinery as it broke down (the winch stopped twice), and clean the instruments. In the labs, others were working to upload data and configure computer programs to coordinate all of the data. In addition to all of this is the quiet presence of the ship’s crew who are going about their duties to be sure that the ship is running smoothly. Several of the crew did take a break today just after the instruments were collected in order to put out fishing lines! They caught numerous tuna and beautiful Mahi Mahi that the cook deliciously prepared for dinner.