Thomas Savage: Which radars are used on the bridge? August 6, 2018

NOAA Teacher at Sea

Tom Savage

NOAA Ship Fairweather

August 6 – 23, 2018


Mission: Arctic Access Hydrographic Survey

Geographic Area of Cruise: Point Hope, northwest Alaska

Date: August 6, 2018

Weather data from the Bridge

Wind speed 14 knots
Visibility: 5 nautical  miles
Barometer: 1007.5 mB
Temp:  8.5 C     47 F
Cloud Height: 10,000 ft
Type: Alto Stratus
Sea Height 2 feet

Science and Technology 

The focus of the NOAA ship Fairweather is to generate and update existing maps of the ocean floor called hydrography. The ship is outfitted with state of the art mapping equipment which uses single and multibeam sonar in capturing the physical topography of the ocean floor (more on this in a future blog).  The region we are mapping is located off the coast of Point Hope in north west Alaska.  It takes an amazing amount of technology especially navigational tools located in the bridge to navigate the ship within this challenging region called the Chukchi Sea.  There are two types of radar on the bridge used to navigate the ship using different radio frequencies, the X band and S band.

The X Band radar generates radio waves with 3 cm and 9 GHz, respectively. The radar is positioned high above the bridge and has the ability to pick up ships up to 40 miles in the distance. During the best weather conditions, officers on the bridge can see the horizon at a distance of 6 miles with the highest powered binoculars and make out other vessels out to about 14 miles. This radar extends the visual range of officers especially identifying ships that are not visible through the use of binoculars. This radar is useful for detecting smaller objects such as small boats in the vicinity of the ship, due to its ability to better resolve smaller objects.

The S Band radar generates radio waves with 9cm and 3 GHz … for context, a microwave oven operates at around 2.5 GHz; a car radio receives at 0.1 GHz (though most people think in MHz… e.g. “You’re listening to The Mountain on 105.9 (MHz)”… the lower frequency of the radio means it’s even less affected by rain and can travel even farther – both good things if you’re running a radio station). This type sound wave have longer distances between each crest. As a result, the sound wave can better track larger objects than the X band and objects at greater distances. In addition, this radar can be used to detect ships through walls of rain. This radar is used by weather forecasters to track types of precipitation, direction and severity and to identify possible rotations that could develop tornado. Another unique property of this radar is its ability to track precipitation on the other side of mountains. In this region of Point Hope, the Brooks Range is visible to the east and knowing the precipitation and direction is important for planning ship operations.


X Band Radar

Ensign Tennyson operating the X Band Radar

Another vital role of these radars is to track current position of the ship when anchored. By using four known coordinates of physical objects on land, in our case, the Brooks Range, located to our east, and known peninsulas are targeted. Officers will use the alidade (and compass rose) located outside the bridge to get their bearings and confirm the ships geographic coordinates. This information reveals whether the ship’s anchor is being dragged.


Ensign Tennyson operating an alidade


Geography – Point Hope is located just above the Arctic Circle; why is NOAA mapping this region?  The sea ice in this region of Point Hope continues to disappear as a reflection of increased global temperatures. This has generated an opportunity for merchant ships to sail north of Canada instead of using the Panama Canal. The mapping of the ocean floor will provide mariners accurate maps resulting in safer passage.

Personal Log

My journey began at 6 am as my plane from the Asheville airport departed. Traveling over Alaska viewing the Rockies and glaciers from the window has been inspiring and reveals how big Alaska really is.  As soon as I landed in Nome, Alaska, around 1 am eastern time, I was reminded again how important it is to be flexible when participating in any NOAA research. After meeting up with the junior officer at the airport, he informed me that the ship is leaving in two hours due to an approaching storm. Scientists conducting research on board a ship at sea are always at the mercy of mother nature. Everyone on board NOAA’s hydrographic ship Fairweather has been exceptionally welcoming and nice which made my transition to life at sea smooth. The tradition of excellent food on board NOAA ships continues!!

Flying out of Asheville

Flying out of Asheville


I am looking forward to learning as much as I can during this three week adventure and bring back inspiring lessons and labs to the classroom. It is always my hope and vision to provide real world science in action to excite and encourage our students to explore and possible explore careers in science.

Until next time, happy sailing !

~ Tom





Heather O’Connell: Voyage through the Inside Passage, June 9, 2018

NOAA Teacher at Sea

Heather O’Connell

NOAA Ship Rainier

June 7 – 21, 2018

Mission: Hydrographic Survey

Geographic Area of Cruise: Seattle, Washington to Southeast, Alaska

Date: 6/9/18

Weather Data from the Bridge:

Latitude and Longitude : 49°49.7’ N, 124 °56.8’ W, Sky Condition: Overcast , Visibility: 10+ nautical miles, Wind Speed: 5 knots, Air Temperature: 12.2°C

Science and Technology Log

Today while in transit through the Inside Passage, I learned to mark the position of the vessel from the pilot house, or Bridge of the ship, using three different methods thanks to Junior Officer Airlie Pickett. Utilizing this triangulation of data ensures accuracy in the placement of the ship on the two dimensional chart located on the port side of the bridge. This process must be completed every fifteen minutes when the ship is in motion close to small landmasses or every thirty minutes when further from land.

The first method involves choosing three different landmarks and recording the angular measurement to the body using alidades. Alidades are located on the port and starboard sides directly outside of the Bridge. When looking at your landmark, it is important to choose the easternmost or westernmost side of the body with a more prominent feature. When viewing the landmass through the alidade, there will be a bearing of the object in relation to the bridge. Once you have the measurements, use the north lines on the map as the zero degree of the protractor and mark a line with the proper angular measurement from the landmass. Repeat this process for the other two locations. Then, draw a circle within the triangle formed from the three intersecting lines along with the time to mark the placement of the ship.

Alidade on the port side of ship

Alidade on the port side of ship

Another way to mark the placement of the vessel visually is to look at the radar for three known landmarks. Record the distance to each landmark. One nautical mile equals one minute of latitude. Longitude cannot be used for distance since these values change as you approach the poles of the Earth. Use a compass to mark the appropriate distance from the scale on the perimeter of the map. Then, draw an arc with the compass from the landmass. Repeat this process for both of the other landmarks. The three arcs intersect at the current location of the vessel and should be marked with a circle and the time.

Protractor and compass

Protractor and compass used to mark the course of the ship on the chart.

The two visual methods for marking the placement of the vessel are used in conjunction with an electronic fix. The digital latitude and longitude recording  from the G.P.S, or Global Positioning System, provides the third check. This data is recorded and then charted using the latitude and longitude marks on the perimeter of the chart.

Another responsibility of the navigator is to mark on the nautical chart the approximate location of the ship moving forward. This is called D.R, or dead reckon, and it shows where you would be if you were to continue on coarse at the current speed for up to two hours.

Personal Log

As we approached the Inside Passage, a feeling of peace and serenity came over me as I viewed snow capped mountains beyond islands with endless evergreen trees. The feelings of the navigators may be different since this is a treacherous journey to traverse, although it is preferred to the open sea. The Inside Passage proves to be a great learning opportunity for new junior officers without much navigation experience. However, due to the weather issues and narrow passages, the Commanding Officer, Senior Watch Officer and Officer of the Deck have extended experience navigating the Inside Passage.

The strong currents at Seymour Narrows in British Columbia can make this voyage dangerous. This was taken into consideration and we crossed them during slack tide, the time between high and low tide, with a current of only about two knots. Tides can get as high as 15 knots during maximum ebb and flood tides. The visible circular tides, or eddies, are created from the current coming off of Vancouver Island being forced into a narrow channel. As Senior Survey Technician Jackson shared, the Seymour Narrows once had Ripple Rock, a two peak mountain, that caused several shipwrecks and was home to the largest non-nuclear explosion in North America in 1958.

Inside Passage by Seymour Narrows

Inside Passage by Seymour Narrows

As we entered the Inside Passage, islands covered in Western red cedar, Sitka spruce and Western hemlock provided the beautiful green amongst the spectacular ocean and sky blue. These colors paint the canvas indicative of the Pacific Northwest that make my soul feel at home. The cloud covered sky could be seen in every direction. We saw moon jellyfish floating by from the flying bridge and later a group of porpoises jumping up out of the water. The watch from the deck crew would spot lighthouses and fishing boats with binoculars well before anyone with a naked eye. I observed the approaching sunset from the bow of the ship and felt gratitude for the day.

Approaching sunset in Inner Passage

Inner Passage Sunset

Did You Know?

There are two different types of radar on the Bridge. S Band radar sends out pulses between 4 and 8 centimeters at 2-4 GHz and can go over longer distances. This is helpful to determine what is happening far from the boat. The X Band radar sends out smaller pulses of 2.5 -4 cm at 8-12 GHertz and can create a clear image of what is occurring close to the boat. Both radar systems provide useful information and must be used in conjunction with one another to have an understanding of what is happening near and far from the ship.

Source –

Beverly Owens: Science on Board NOAA Ship Henry Bigelow, June 18, 2013

NOAA Teacher at Sea
Beverly Owens
Aboard NOAA Ship Henry B. Bigelow
June 10 – 24, 2013

Mission:  Deep-Sea Corals and Benthic Habitat: Ground-Truthing and Exploration in Deepwater Canyons off the Northeastern Coast of the U.S.
Geographical Area: Western North Atlantic
Date: June 18, 2013

Weather Data from the Bridge:
Air temperature: 13.50 oC (56.3 oF)
Wind Speed: 20.05 knots (23.07mph)

Science and Technology Log

Teacher at Sea Beverly Owens, and Dewey the Dragon at the Helm

Teacher at Sea Beverly Owens, and Dewey the Dragon at the Helm

On a research vessel such as NOAA Ship Henry B. Bigelow, does the ship support the science? Or are the ship’s activities separate from those of the Science Crew?  I didn’t realize how much the Ship’s Crew and the Science Crew worked hand-in-hand until I toured the Bridge.

First off, the ship is what’s known as an FSV. What does FSV stand for? FSV stands for Fisheries Survey Vessel. The primary responsibility of the Henry B. Bigelow is to study and monitor the marine fisheries stocks throughout New England (the Northeastern section of the United States). There are many scientific instruments aboard the Henry B. Bigelow that allow crew members and visiting science teams to do this and other work.

The ship has multiple labs that can be used for many purposes. The acoustics lab has many computers and can be used for modeling data collected from multibeam sonar equipment.  The chemistry lab is equipped with plentiful workspace, an eyewash, emergency shower, and fume hood. Our TowCam operations are being run from the dry lab. This space has nine computers displaying multiple data sets. We have occupied the counter space with an additional eight personal laptops; all used for different purposes such as examining TowCam images or inputting habitat data. The wet lab is where the collection sorting, and filtering take place. It is used during fisheries expeditions to process and examine groundfish.  During our research expedition, the wet lab is used mostly for staging TowCam operations. We also process sediment and water samples that were collected from the seafloor.  Sediment is collected using a vacuum-like apparatus called a slurp pump; water is collected in a Niskin bottle.  The sediment is sieved and any animals are saved for later examination.  Water samples are also filtered there, to remove particulate matter that will be used to determine the amount of food in the water column.

Walking around the ship, I noticed a psychrometer set, which is used to monitor relative humidity, or moisture content in the air. There is also a fluorometer, which measures light emitted from chlorophyll in photosynthetic organisms like algae or phytoplankton. The CTD system measures physical properties of the ocean water including conductivity/salinity, temperature, and depth. Additionally, the ship has a thermosalinograph (therm = heat, salin = salt, graph = write). Saltwater is taken into the ship and directed toward this instrument, which records the sea surface salinity and sea surface temperature.

The crew of the Henry B. Bigelow not only supports the research efforts of the science team but is also actively involved in conducting scientific research. Their instrumentation, knowledge, and team work enable them to protect and monitor the western North Atlantic waters and its living marine resources.

 Personal Log

Dragon on the Bridge

Dewey the Dragon is plotting the course.

Dewey the Dragon, all the way from Crest Middle School, enjoyed getting a tour of the Bridge. Dewey the Dragon learned how to steer the ship, read charts, and monitor activity using devices such as the alidade. Thanks to Ensigns Katie Doster and Aras Zygas for showing us around.

Did You Know?

Teacher at Sea, Beverly Owens, using the Alidade on the FSV Henry B. Bigelow

Teacher at Sea, Beverly Owens, using the Alidade on the FSV Henry B. Bigelow

The alidade is a device that allows people on the ship to sight far away objects, such as land. The person on the ship spots three separate points on land uses these sighting to determine the location of the ship. Alidades can also be used as a tool when making and verifying maritime charts.

Mary Cook, December 18, 2004

NOAA Teacher at Sea
Mary Cook
Onboard NOAA Ship Ronald H. Brown
December 5, 2004 – January 7, 2005

Mission: Climate Prediction for the Americas
Geographical Area: Chilean Coast
Date: December 18, 2004

Location: Latitude 22°16.32’S, Longitude 86°10.94’W
Time: 8:30 am

Weather Data from the Bridge
Air Temperature (Celsius) 19.46
Water Temperature (Celsius) 19.81
Relative Humidity (percent) 69.46
Air Pressure (millibars) 1016.99
Wind Direction (degrees) 123.54
Wind Speed (knots) 15.73
Wind Speed (meters/sec) 7.20
Sunrise 07:57
Sunset 21:27 (9:27 pm)

Question of the Day

What does a psychrometer measure?

Positive Quote of the Day

For where your treasure is, there will your heart be also. Jesus Christ

Science and Technology Log

Today Diane and I journeyed up to the bridge struggling against the strong winds and the lurching of the ship. We interviewed Ensign Silas Ayers and “Pirate” Jim Melton. Silas gave us instruction on ship safety and navigation. He said the two most important things in navigation are: don’t hit anything and don’t run aground. Silas showed us how they plot the ship’s course on a map/chart and all the navigational instrumentation. The RONALD H. BROWN has radar that ranges up to 96 miles but it is set for 24 miles at this time. The radar is used to detect other ships that might be in our path. He also showed us the autopilot computer and controls. They can set the coordinates and the ship will drive itself!!! Of course someone has to stay on the bridge at all times, because as everyone knows computers have glitches that could cause a malfunction. That could be a disaster. Something that I find fascinating is that this ship can hover in one place! It’s officially called dynamic auto positioning. They set all the thrusters at a specific setting and the ship stays in one place. He then explained the ship’s lights. The ship has a red light on the port side and a green light on the starboard side. These lights reveal our ship’s location to other ships and enable them to ascertain our heading by watching the movement of our lights.

There’s another series of light signals that communicate the ship’s condition. For example, when we hover to do a CTD cast, the ship displays a set of red/white/red lights that tell other ships we are unable to make quick maneuvers. There’s also a set of lights that means man overboard. Another cool thing on the bridge was the spinning window. Yep. I said spinning window. It wasn’t spinning today but it can spin. (I hope they weren’t pulling my leg.) The purpose of the spinning window is to reduce ice buildup on the glass.

“ Pirate” Jim Melton shared with us the lookout duties. He keeps a watch that scans the horizon constantly. Jim uses an alidade. An alidade is a telescopic instrument that has a special swiveling balance that can compensate when the ship rolls, pitches, or yaws.

I looked through the alidade and saw a line across my field of vision. Jim said that they use that line as a reference point and they can determine the size of the ocean swells. Everyone working on the bridge must also report the complete weather data to NOAA every hour.

Before we finished, I sat in the captain’s chair and scanned the horizon for whales and other ships at sea!

Late this afternoon, Diane and I continued working on the children’s book. Bruce Cowden, the illustrator, is producing artwork faster than we’re writing the story! So we’re feverishly trying to catch up. It’s fun writing with Diane. She has a bright mind and she has a genuine excitement for atmospheric and oceanic science.

Tonight at “6:00 Science on the Fantail”, we interviewed meteorologist Dan Wolfe of the Environmental Technologies Laboratory in Boulder, Colorado and Frank Bradley physicist/ meteorologist of Australia’s Commonwealth Scientific and Industrial Research Organization. They have been studying clouds, precipitation and humidity, as well as launching radiosondes (weather balloons) 4-6 times a day. Dan explained how the radiosondes work. The instrument package records temperature, pressure, and humidity as the helium-filled balloon ascends into the sky. The radiosondes have a GPS antenna that transmits its location and another transmitter that communicates the data being collected back to the computer in the lab. All of this information is compiled to help develop a “picture” of the atmosphere in this region which has never been thoroughly studied. This information can then be used in making models for more accurate weather prediction.

Frank Bradley shared with us his work which has been in collaboration with Dr. Bob Weller and Dr. Chris Fairall for the past 20 years. Frank showed us the somewhat “old fashioned” Assman psychrometer that he uses to take the wet bulb and dry bulb temperature readings several times a day. A psychrometer’s temperature readings can be used to determine relative humidity. Frank says that he uses this low-tech instrument because nothing can go wrong. This psychrometer’s readings are then used as a validation of the high tech instruments on board. Frank said that he has studied air-sea interaction, the interface of the ocean and the atmosphere, for many years and considers it a very important area for developing better models to predict the weather.

Personal Log

Wow! I really liked the bridge! It is cool. I don’t know why they wouldn’t let me drive the ship. I mean, come on, we’re out in the middle of the biggest ocean on Earth. What could I run into? And there’s no ground in sight. Actually, there’s nothing in sight. So I’d be satisfying the two most important rules of ship navigation and safety: don’t hit anything and don’t run aground. It seems though, that I remember something about needing a license to drive. I’m not sure.

While on the bridge, I saw that our planned course will take us right by the San Felix islands. It’ll be the first land I’ve seen since December 5! I wonder what that will feel like?

As we near the end of the cruise and it seems almost all the work is done, everyone is reading guidebooks about Valparaiso and planning some excursions. Even though I’m not ready to get off the ship, I am feeling a little excited about seeing a new place. I just love to go to new places and I’ve heard that Valparaiso is one of Chile’s most beautiful cities. Diane and I are deciding what to do during our two days there. One day we want to see the city and another day we want to drive toward the Andes Mountains and get glimpse of Aconcagua, the highest mountain in all of the Americas!

Yeah! Another adventure awaits!

Until tomorrow,