Argos satellites:
There are currently 6 Argos satellites in polar orbit at around a height of 850 km. There are also currently 2 data processing centres and 50 terrestrial satellites which receive the information from the polar satellites. In order for an Argos satellite to track the locations of an animal, the animal must first be captured and then have a transmitter attached to it. This can be done in a few different ways, by attaching a harness to the animal, gluing the transmitter to the animal (example: onto the shell of a turtle), and by physically attaching the transmitter (example: through the fin of a shark). These transmitters are now quite small and can be attached to nearly any sized animal, even to an animal as small as a bat or a frog. These transmitters are continuously sending out signals which can be picked up by the Argos satellites which fly overhead. These satellites will continue to pick up signals from this transmitter for approximately 10 minutes, during which the satellite will measure the frequency of the messages that it receives. Due to the Doppler Shift, the changes in frequency that occur as well as with the satellite's speed, position, and original frequency of the transmitter, the position of the transmitter can be calculated. The transmitter will also send any additional information that it has collected, such as temperature changes. The data will then be transmitted to terrestrial receiving stations where the data will then be sent to a processing centre. The location of the animal will then be sent to the researcher through either email, websites, or the researcher can even access the location of the animal through a virtual globe system, such as Google Earth. The only complication arises when a scientist is attempting to track a marine animal through the use of an Argos satellite. This is because the transmitters cannot send signals underwater, so the only way to receive these signals is when the animal surfaces. Due to this inability to transmit there are actually two contact points inside of the transmitter. When salt water flows between these two contact points a current can flow through. When the circuit is complete, the transmitter stops sending out signals. This circuit breaks as the animal surfaces, causing the transmitter to once again send signals to the satellites.
Advantages:
+ Small transmitters cause minimal disruption to the animal
+ Can be used to track most animals
+ Requires only one satellite to track an animal, as opposed to GPS tracking which requires three
+ Simple system
+ Easy access to the data
+ Worldwide satellite coverage
+ New avenues for biological and environmental research
+ Can be used to track most animals
+ Requires only one satellite to track an animal, as opposed to GPS tracking which requires three
+ Simple system
+ Easy access to the data
+ Worldwide satellite coverage
+ New avenues for biological and environmental research
disadvantages:
- Transmitters must sometimes be attached to the animal, which can cause some pain to the animal
- The animals must be captured in order to have a tracking device placed on them
- New data can only be transmitted when a satellite flies overhead
- Does not work as well on marine animals
- Not as accurate as GPS positioning
- The animals must be captured in order to have a tracking device placed on them
- New data can only be transmitted when a satellite flies overhead
- Does not work as well on marine animals
- Not as accurate as GPS positioning
1. Transmitters on animals or objects relay pulses of data
2. Passing satellite collects data and measures signals' frequencies
3. Satellite relays data to terrestrial receiving stations
4. Processing centre processes data and determines positions
5. Researchers view information via email, website or 'virtual globe'
*Taken from http://news.bbc.co.uk/2/hi/technology/6701221.stm
2. Passing satellite collects data and measures signals' frequencies
3. Satellite relays data to terrestrial receiving stations
4. Processing centre processes data and determines positions
5. Researchers view information via email, website or 'virtual globe'
*Taken from http://news.bbc.co.uk/2/hi/technology/6701221.stm