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Satellite Tracking

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Frequently Asked Questions

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Ask our experts a question! Do you have a question about sea turtles and satellite telemetry that you want answered? Submit your question to our sea turtle scientists.

Most Frequently Asked Question:

Why did animal X stop transmitting?

1. What is satellite telemetry?

Doppler EffectSatellite tracking, or 'satellite telemetry', involves attaching a special piece of tracking equipment, called a Platform Terminal Transmitter (or PTT) to a sea turtle's carapace (shell). The PTT sends a message to a satellite each time the turtle comes to the surface to breathe. We then receive messages via the satellite regarding the location of the turtle and plot them onto a map. There are thousands of satellite transmitters being used around the world today to monitor ocean circulation, natural hazards, water resources, polar currents, fishing vessels, shipping and offshore oil and wildlife such as albatrosses, whales, polar bears and of course, sea turtles!

2. How does satellite telemetry work?

Every satellite transmitter attached to a sea turtle has two metal contact points, called a salt-water switch. When the satellite transmitter is underwater, an electric current is able to flow between the metal contact points through the water. This tells the transmitter that is is under water so it should not send transmissions to the satellites. Every time the turtle surfaces to breathe, one or more of the metal contact points comes out of the water and the electric circuit can no longer run between the contact points. This tells the PTT that it is out of the water and to start transmitting to NOAA satellites. Argos receivers are carried on board NOAA polar orbiting environmental satellites providing full global coverage. The location of the transmitter is calculated and accuracy is determined as one of 5 different classes called location classes. Accuracy of individual locations received from the Argos system vary depending on the number of messages received from the transmitter, environmental conditions and relative positions of the transmitter and satellites.

Location Class Estimated Accuracy
< 150 m
150 - 350 m
350 - 1000 m
> 1000 m
no estimate of location accuracy
no estimate of location accuracy
invalid locations


3. Who is Argos?

Argos is a satellite-based location and data collection system dedicated to monitoring and protecting the environment. Argos has been operating since 1978 and was initiated under an agreement by NOAA (the National Oceanic and Atmospheric Administration, USA), NASA (National Aeronautics and Space Administration, USA) and CNES (the French Space Agency). See for more information.

4. Who is NOAA?

NOAA is the National Oceanic and Atmospheric Administration for the government of the United States. Its mission is to: “…understand and predict changes in the Earth's environment and conserve and manage coastal and marine resources…” See for more information.

5. Why do you do satellite telemetry?

Sea turtles are migratory animals, which means that they feed and live in one place and swim many thousands of miles to another place where they breed and lay their eggs. Of the 7 species of sea turtles, 6 are listed as either Critically Endangered or Endangered on the IUCN Red List of Threatened Species. The 7th, the Flatback, is listed as “Data Deficient,” meaning that insufficient information exists to assess risk of extinction. Many populations of sea turtles around the world are thought to be declining. In order to protect these animals, we need to find out where they live. Since sea turtles nest on land, most sea turtle nesting beaches are identified and well studied. However, after turtles leave the nesting beaches and swim away, we have little idea where they go. The only way right now that we can track a sea turtle in the open ocean is to attach a transmitter and wait for uplinks to be received when the turtle swims to new locations. If we can find out where the turtles migrate to, we can help to reduce the threats both at that location and along the migratory pathway to get there.

6. What does a satellite transmitter look like?

Telonics ST-18A satellite transmitter is a small oblong shape box with an antenna that comes out of one end. Transmitters come in a variety of colours and sizes. The pictures at right show two kinds of satellite transmitters: the first one is a Telonics ST-18, which transmits location information only. The second transmitter (below) is a Telonics ST-14, which transmits and records location and dive information such as dive depth, duration and profile. A third transmitter commonly used for sea turtle tracking (not shown) is a Sirtrack KiwiSat 101 which transmits location information. Visit the Sea Turtle Tagging section of for more details.

7. How big is a satellite transmitter?

Telonics ST-14The Telonics ST-18 measures 12 by 5 cm and weighs approximately 200g. The Telonics ST-14 transmitter is larger at 16 by 10 cm and weighs approximately 750g. The Sirtrack Kiwisat 101 and is approximately 18 by 6 cm. Visit the Sea Turtle Tagging section of for more details.

8. What is a PTT?

A Platform Terminal Transmitter (PTT) is a small satellite transmitter attached to a sea turtle in order to monitor its movements.

9. How do you attach a satellite transmitter?

A satellite transmitter is a sophisticated and expensive piece of equipment and has to stay attached to a sea turtle for a year or more. Therefore, it has to be attached very well. There are several methods for attaching satellite transmitters and this project uses the most common and successful method, gluing the transmitter to the turtle's shell using marine epoxy (a kind of very strong glue). To ensure the transmitter sticks very well to the turtle's carapace, you must first prepare the turtle's carapace and ensure rough areas are smoothed flat and that all grease is removed. First, we use a knife to remove any barnacles or fouling organisms that might come off later, followed by rough and then fine grade sand paper. When the surface of the carapace has been lightly scored we scrub and wash it to remove all sanding dust and grease so that the glue can stick very well. Finally we wipe the carapace with a chemical called acetone to remove the last traces of all grease. Now we are ready to apply the epoxy which is pasted over a large area in the front half of the turtles' carapace (see diagram 1). The transmitter is then pressed into place on the second central (vertebral) scute (see diagram 2) and the epoxy will start to dry. Sometimes 2 small wooden blocks are pressed into the epoxy in front of the PTT to protect it from damage in case the turtle scrapes her shell against a rock ledge underwater. Another tube of epoxy is mixed up and spread over the top of the PTT and the surrounding area. The epoxy will be dry in about 30 minutes after which time the turtle can be released to crawl back to the ocean.

10. How long does it stay on for?

If the carapace is well prepared and the transmitter attached very securely, it may be reasonable to expect a PTT to remain attached to a sea turtle for at least a year.

11. How much does a satellite transmitter cost?

Satellite transmitters cost between 2000 and 4000 USD, depending on the model and functions that each PTT performs. The total cost of the satellite transmitters can be between 3000 and 5000 USD, as you also have to pay for time spent communicating with the satellites.

12. Why is it so expensive?

Satellite telemetry is the most sophisticated technology available to sea turtle research and the equipment reflects this. Each transmitter has to be individually programmed and set up for each project. Once you have the transmitter itself, you will be required to pay time for the satellite that your location and or dive information is sent to.

13. Does it hurt the turtle?

No. A satellite transmitter is a small device that has been designed to be flat and cause as little disturbance to the swimming sea turtle as possible. The Sirtrack transmitter is even hydro-dynamically shaped to cause less drag. The turtle will quickly get used to the transmitter attached to her shell. The attachment process is also harmless to the sea turtle. Normal marine epoxy sets exothermically, which means that is gives off heat as it sets. Turtle researchers use a special epoxy that does not give off as much heat as it sets, and therefore does not cause the turtle any discomfort.

14. Where do you think the turtles are going to go?

The Bald Head Island Project: The nesting sea turtles of North Carolina have never been tracked before and therefore migratory routes are unknown and this study will be very significant. However, the turtles of North Carolina belong to a large genetic group of turtles that are found nesting from the north of Florida (Daytona beach and north) up to Cape Lookout, North Carolina. Some loggerhead turtles from the beaches of South Carolina and Georgia have been tracked by satellite, and we can try to predict the movements of the turtles migrating from North Carolina using these studies. So far we will be expecting the turtles to feed on the coasts of North and South Carolina possibly north to Virginia and beyond and then to move out to the open ocean as temperatures drop in the fall.

The Cayman Islands Project: Cayman green and loggerhead turtles are also being tracked for the first time this summer. We know that turtles can migrate hundreds or thousands of kilometres between nesting beaches and foraging grounds, but the destinations of Shelby, Myles, and Samia are still mysterious. As we follow their journeys, we can map migration routes and identify foraging grounds used by vulnerable Cayman Islands sea turtle nesting populations.

15. How do you know where they are?

The locations of the turtle are automatically plotted onto maps so that we can see where the turtle has been. To see the latest locations of sea turtles that were satellite tracked on, click here.

16. How fast do the turtles swim?

Although sea turtles have been reported swimming in bursts of speed up to 30mph, it is likely that the turtles moving in this project are swimming at average speeds of 4-5 mph. That is the equivalent to a fast walking pace for a human. Of course, now that these turtles have finished nesting, they will be stopping along the way to feed!

17. Why are sea turtles endangered?

For millions of years, sea turtles were abundant in marine ecosystems across the world. Today, the numbers of sea turtles in different populations appear to have been reduced relative to historical levels. Human actions can threaten sea turtles during all stages of their lives. For instance, nesting habitat is often lost to beach development as lights, erosion, seawalls and other structures can prevent turtles from nesting. In many countries, nesting turtles are killed for meat, and turtle eggs are taken and eaten. Hatchlings can be killed by lights near the beach, because baby turtles crawl toward lights on land instead of toward the natural light of open horizon. As juveniles and adults, sea turtles are threatened by directed hunting at sea, by incidental capture in commercial fishing nets or long-lines, by disease and marine pollution. Using satellite tracking of sea turtles, we can increase our knowledge about the habitats turtles need to maintain healthy populations and the threats they face.

18. What is the status of sea turtles in the Cayman Islands?

Despite an immense historical population size, recent surveys by the Department of Environment reveal that only a few dozen nesting green and loggerhead turtles remain in the Cayman Islands. Loss of any turtles represents an enormous loss in genetic diversity, disease resistance, and potential to recover to a healthy population size. Any additional population reduction could push our precariously small populations over the brink of extinction.

Against all odds, extremely rare animals have been protected, though others have been lost forever despite efforts to save them. Regaining viable nesting populations represents one of our most critical conservation challenges in the Cayman Islands. Sea turtles represent a central part of Caymanian heritage, and with the enthusiasm and commitment of the community, we could protect our fragile populations for future generations.

19. I see lots of turtles in the Cayman Islands: How can they be in trouble?

We have both young and full-grown turtles in the Cayman Islands. Most people see juvenile hawksbill turtles when they dive, boat, or fish here. These young turtles are not part of our nesting population - they will migrate elsewhere to nest. Turtles that nest on our beaches are much bigger and are almost exclusively green and loggerhead turtles, not young hawksbills. A full-grown green turtle weighs about 300 pounds and is over 3 feet long! There are only a few of these large turtles left in the Cayman Islands.

It is important to protect both juvenile and mature turtles in the Cayman Islands. Because few turtles survive to adulthood, large populations of juveniles are necessary to support even small breeding populations. Young turtles seen while diving, snorkelling, and boating delight our children and draw visitors to our islands hoping for the chance to see these charismatic creatures, while our nesting population represents a living remembrance of our rich cultural heritage.

20. Why are sea turtles worth saving?

We are still learning about the importance of sea turtles in the environment but it is thought that they play many important ecological roles. The shells of loggerhead turtles provide habitat for dozens of species including the Columbus crab and might be very important for the survival of these crabs. Green turtles grazing on seagrass may help to maintain the health of the grass bed. Hawksbill turtles are believed to be keystone species in coral reef environments, grazing on encrusting sponges and preventing them from out-competing slow growing corals. This maintains species diversity and the natural balance of fragile reef systems. All those who have witnessed a mother sea turtle laying her eggs or seeing turtle hatchlings dashing from their nest to the sea will have been moved by the experience. We will have seen one of the few examples in nature where such a large wild animal can be observed so close up or at such vulnerable time in it's life cycle. Perhaps the most important reason is that the sea turtles have been living on earth in their current form since the age of the dinosaurs. It is only recently that they have become endangered by the actions of humans.

21. Where can I find pictures of the project?

See our image library:

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