Satellite Telemetry FAQs
What is satellite telemetry?
Doppler Effect Satellite tracking, or 'satellite telemetry', involves attaching a tracking device, called a Platform Terminal Transmitter (or PTT) to the high point of a sea turtle's carapace (top shell). Each time the turtle comes to the surface to breathe the PTT sends a message skyward, and when in range of polar-orbiting ARGOS satellites the location of the transmitter is recorded and transmitted to the turtle researcher who applied the tag. There are 10s of thousands of satellite transmitters being used around the world today to monitor wildlife (including sea turtle) movements, fishing vessels, commercial tanker vessels, and ocean currents. Why do we track sea turtles by satellite? Most research of sea turtles has focused on nesting biology, yet turtles spend well over 90% of their lives at sea, foraging, migrating, and mating. As such, there is a huge information gap about sea turtle biology and movements when they are not at nesting beaches. Filling these information gaps can help us better protect sea turtles. We need to learn more about their migratory patterns, and the environmental triggers that lead to different movement patterns, and satellite telemetry is the perfect tool for this type of research. |
How does a satellite transmitter operate?
Every satellite transmitter attached to a loggerhead has two or three metal contact points, called salt-water switches. When the device is underwater, an electric current is able to flow between the metal contact points through the water. This tells the transmitter that it is submerged and thus should not send transmissions. Each occasion that a turtle surfaces to breathe, one or more of the metal contact points comes out of the water and the electric circuit is broken, which indicates to the PTT that the unit is out of the water; at this point tags start transmitting, then cease once the turtle submerges. 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. Fortunately, the Loggerhead STRETCH project comes at a perfect time, as the Argos constellation of satellites will soon move from 7 to 9 operational satellites, which will enhance location accuracy and frequency. The satellite positioning accuracy is organized by the following categories:
Every satellite transmitter attached to a loggerhead has two or three metal contact points, called salt-water switches. When the device is underwater, an electric current is able to flow between the metal contact points through the water. This tells the transmitter that it is submerged and thus should not send transmissions. Each occasion that a turtle surfaces to breathe, one or more of the metal contact points comes out of the water and the electric circuit is broken, which indicates to the PTT that the unit is out of the water; at this point tags start transmitting, then cease once the turtle submerges. 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. Fortunately, the Loggerhead STRETCH project comes at a perfect time, as the Argos constellation of satellites will soon move from 7 to 9 operational satellites, which will enhance location accuracy and frequency. The satellite positioning accuracy is organized by the following categories:
|
Location Class Estimated Accuracy
3 < 150 m 2 150 - 350 m 1 350 - 1000 m 0 > 1000 m A no estimate of location accuracy B no estimate of location accuracy Z invalid locations, no location |
|
What is Argos?
Argos is a satellite-based location and data collection system dedicated to monitoring and protecting the environment. Argos sensors are placed on each of a constellation of Low Earth Orbit (LEO), polar-orbiting satellites. 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). How many loggerheads have been satellite-tracked in the North Pacific? Satellite telemetry research has been ongoing for many years in the Western, Central, and Eastern Pacific Ocean. Tagging programs from universities, non-governmental organizations and government agencies across Japan, Mexico, and the United States have yielded significant information about loggerhead movements at local, regional, and ocean basin scales. |
How much does a satellite transmitter cost?
There are two types of satellite transmitters: those that derive tag location via the Argos satellite constellation and those that locate via the Global Positioning System (GPS) array using Fast-Loc GPS technology. Both approaches ultimately deliver animal locational data via the Argos system. Because of their higher locational resolution, Fast-loc transmitters can cost US$3,500-5,000, with the difference relating to what other sensors beside location are on the device. Argos-only tags, which are much lower in spatial resolution, but perfect for long distance moving loggerheads such as those tracked during the STRETCH project can cost anywhere from US$1400 to US$5000 depending on sensor configuration.
How do you attach a satellite transmitter to a sea turtle?
Satellite transmitters are attached to the carapace of sea turtles using one of several different preferred types of fiberglass resin or epoxy. The shell is cleaned of foreign materials such as algae or epibionts, and tags adhered to the shell at the uppermost portion of the carapace.
How long do satellite transmitters stay on turtles?
Researchers with Loggerhead STRETCH hope that the satellite tags will stay affixed to the turtles’ shells for at least 6 months or more. As these are small, fast-growing turtles, they will tend to shed their transmitters more rapidly than larger, slower-growing turtles. Loggerheads in the North Pacific have been known to have tags stay affixed for more than two years, although the retention time for most turtles is somewhat less.
There are two types of satellite transmitters: those that derive tag location via the Argos satellite constellation and those that locate via the Global Positioning System (GPS) array using Fast-Loc GPS technology. Both approaches ultimately deliver animal locational data via the Argos system. Because of their higher locational resolution, Fast-loc transmitters can cost US$3,500-5,000, with the difference relating to what other sensors beside location are on the device. Argos-only tags, which are much lower in spatial resolution, but perfect for long distance moving loggerheads such as those tracked during the STRETCH project can cost anywhere from US$1400 to US$5000 depending on sensor configuration.
How do you attach a satellite transmitter to a sea turtle?
Satellite transmitters are attached to the carapace of sea turtles using one of several different preferred types of fiberglass resin or epoxy. The shell is cleaned of foreign materials such as algae or epibionts, and tags adhered to the shell at the uppermost portion of the carapace.
How long do satellite transmitters stay on turtles?
Researchers with Loggerhead STRETCH hope that the satellite tags will stay affixed to the turtles’ shells for at least 6 months or more. As these are small, fast-growing turtles, they will tend to shed their transmitters more rapidly than larger, slower-growing turtles. Loggerheads in the North Pacific have been known to have tags stay affixed for more than two years, although the retention time for most turtles is somewhat less.
What is the longest distance that a loggerhead turtle has been satellite tracked?
Individual loggerhead turtles have been tracked for more than 6000 km traversing waters of the Central Pacific. Turtles migrating from Japan to Baja California Mexico have logged more than 10,000 km per turtles, much like the famous loggerhead Adelita that was tracked for 10,400 km between Baja, Mexico and Sendai, Japan. What is the longest duration that an individual loggerhead has been satellite tracked? The longest tracking duration for a loggerhead in the North Pacific is 943 days, which is more than two and a half years!! Does attaching a satellite transmitter hurt the sea turtle? There are several methods to attach a transmitter to a sea turtle, and for hard-shelled turtles, these approaches usually involve the use of braided cloth such as carbon fiber cloth or fiberglass, neoprene (with very small turtles), and fiberglass resin or a fast-set epoxy to adhere these materials to the turtles’ shell.. It is important that the materials used do not produce significant heat during the setting process. Researchers continue to modify and develop new techniques to reduce any impacts to turtles from the attachment process such as damage to its shell or increased likelihood of entanglement. Tagged turtles have shown normal mating, nesting, and foraging patterns, suggesting that the presence of a transmitter does not impact a sea turtle's natural behaviors. |
Oceanography FAQs
What are El Niño and La Niña?
El Niño and La Niña are the warm and cool phases of a recurring climate pattern across the tropical Pacific—the El Niño-Southern Oscillation, or “ENSO” for short. The pattern shifts back and forth irregularly every two to seven years, bringing predictable shifts in ocean surface temperature and disrupting the wind and rainfall patterns across the tropics. These changes have a cascade of global side effects. For the latest forecast visit: https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf What is the California Current? The California Current marine ecosystem is a highly productive coastal ecosystem in the northeastern Pacific Ocean. It is characterized by a seasonal upwelling of cold, nutrient-rich water fuels populations of krill, squid, sardines, and other species that are prey for larger fishes, seabirds, and marine mammals. The ecosystem supports important fisheries and other activities and provides services for the tens of millions of people living along the West Coast. |
What is the North Pacific Transition zone?
The North Pacific Transition Zone is an oceanographic feature of special importance to the biology of many species in the North Pacific Ocean. The North Pacific Transition Zone is a 9000-km wide upper water column oceanographic feature at the boundary between the subtropical gyre on the south and the subarctic gyre on the north. A latitudinal gradient of physical features, including eddies and frontal zones, establishes a highly productive habitat that aggregates prey resources, thereby attracting many species of pelagic predators—including endangered and commercially valuable species. In addition to providing key North Pacific foraging areas, the feature also serves as a migratory corridor for many pelagic species including loggerhead sea turtles.
The North Pacific Transition Zone is an oceanographic feature of special importance to the biology of many species in the North Pacific Ocean. The North Pacific Transition Zone is a 9000-km wide upper water column oceanographic feature at the boundary between the subtropical gyre on the south and the subarctic gyre on the north. A latitudinal gradient of physical features, including eddies and frontal zones, establishes a highly productive habitat that aggregates prey resources, thereby attracting many species of pelagic predators—including endangered and commercially valuable species. In addition to providing key North Pacific foraging areas, the feature also serves as a migratory corridor for many pelagic species including loggerhead sea turtles.
Header photo credit: Paula Olson (NOAA)