P5 - Satellites Flashcards
Where do Communication satellites orbit?
- Communication satellites are put in a quite a high orbit over the equator and orbit once every 24 hours.
- This means that they stay above the same point on the Earth’s surface because it orbits with them.
What is another name for Communication satellites?
• Geostationary or Geosynchronous satellites.
What are Geostationary satellites used for?
- They are ideal for telephone, TV and radio.
- This is because they stay at the same point above the Earth and can transfer signals from one side of the Earth to another in a fraction of a second.
Why are Geostationary satellites not good for checking the weather?
- Geostationary satellites are too high and too stationary to take good weather or spying photos.
- You need low polar orbits, which pass over both poles and are nice and low.
What is a low polar orbit satellites pathway?
• In a low polar orbit, the satellite sweeps over both poles whilst the Earth rotates behind it.
Why do low polar orbit satellites move faster?
• They are much closer to the Earth than geostationary satellites , so the pull of gravity is stronger and they move much faster
How fast do low polar orbit satellites move?
• They are much closer to the Earth than geostationary satellites , so the pull of gravity is stronger and they move much faster They orbit really quickly, often with a period of less than 2 hours.
How do low polar orbit satellites allow the whole surface of the planet to be monitored?
• Each time the satellite comes round it can scan the next bit of the globe, this allows the whole surface to be monitored each day.
What electromagnetic wave is used for communication to and from satellites?
• Microwaves
How are microwaves used for satellite communication?
• For satellite TV and phones, the signal from a transmitter is transmitted into space.
• Where it is picked up by the satellites’s receiver dish orbiting thousands of kilometres above the Earth.
• The satellite transmits the signal back to Earth in a different direction
• Where it is received by a satellite dish on the ground.
OR
• Satellites receiving the signal re-transmit it to other satellites and eventually back down to Earth.
What frequency do microwaves have?
- Microwaves have a very high frequency - over 3,000 MHz ( 3 GHz ).
- Radio-waves a lower frequency than this.
What happens to Microwaves in the atmosphere & why are microwaves able to reach distant parts of the planet?
• Microwaves pass easily through the atmosphere to satellites orbiting the Earth, enabling the signal to reach distant parts of the planet.
What frequencies do low orbit satellites & geostationary satellites use?
• Low orbit satellites use lower frequencies than satellites in higher geostationary orbit ( always above the same point on Earth ).
Why do satellite signals weaken?
• Satellite signals weaken because they travel long distances ( losing intensity and picking up interference ).
Why are digital signals used?
- They are high quality.
* They don’t suffer as much from interference.
