What is satellite telemetry?

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Satellite tracking, or 'satellite telemetry', involves attaching a special piece of tracking equipment, called a Platform Terminal Transmitter (or PTT) to a seal. The PTT sends a message to a satellite each time the seal comes to the surface to breathe. We then receive messages via the satellite regarding the location of the seal 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, seals!

How does satellite telemetry work?

Every satellite transmitter attached to a seal 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 seal 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
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

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 www.argos-system.org for more information.

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 www.noaa.gov for more information.