What is Sputnik? What is an artificial satellite? How do satellites impact our everyday lives? How many satellites are necessary to accurately find our location on the globe? Impact of this question views around the world. An object in GEO has an orbital period equal to Earth's rotational period, so to ground observers it appears motionless at a fixed position in the sky. Satellites in GEO allow permanent communication links to be established by transmitting radio-frequency signals from fixed antennas.
These signals are not very different from the signals that are used to broadcast terrestrial television, but usually have a frequency 3—50 times higher.
The signal is received by the satellite, amplified and transmitted back to Earth, allowing communications between points thousands of kilometres apart.
A particular property that makes geostationary satellites extremely attractive is their capacity to broadcast. The re-transmitted signal can be picked up by antennas anywhere in the satellite's coverage area. If the Forum is to be a success, the ITU Membership will need to focus on the broad policy and regulatory issues which are raised by GMPCS, which are for the most part technology independent.
Geostationary GSO satellites occupy an orbital position 36, km above the earth, and remain in a stationary position relative to the Earth itself. The world's major existing telecommunications and broadcasting satellites fall into this category. Non-geostationary NGSO satellites occupy a range of orbital positions LEO satellites are located between km-1,km from the Earth, MEO satellites are located at 10,km from the Earth , and do not maintain a stationary position, but instead move in relation to the Earth's surface.
Many of the new proposed 'global mobile phone' services will be provided by this type of satellite. A ' MEO ' is a non-geostationary satellite which operates in Medium Earth Orbit, again providing mobile telephony services. These satellites have also been proposed to be used as part of new global mobile telephone systems.
Many contributions to the WTPF have recommended a broad approach to the concept of Global Mobile Personal Communications by Satellite, in order to fully address the important issues. If your radio spectrum holdings are not large then you will not be able to support very many high data connections at all.
If you have many small flying satellites you need to split the use of this spectrum between them, further reducing how many higher data connections a single small satellite can provide. When you combine access to a large amount of radio spectrum with a large, single geostationary satellite you have far more ability to increase the number of higher data rate connections you can deliver simultaneously.
Governments often have to move at short notice to solve a problem in a particular location and need to be assured their access to a connection in this location is available, capable and reliable. If you only have limited spectrum this availability, capability and reliability requirements can be a real problem.
The satellites also have the ability to move resources within themselves to suit the current situation. If a significant event happens, resulting in greater customer connectivity needs in a given location, we can move resources on the satellite from less busy beams into the beam or beams covering the event.
A typical low orbit satellite is only overhead at any given location on earth for around seven minutes and can only provide the given resource available on that satellite in that one location for seven minutes before having to hand over to one of its fellow satellites in the constellation. If too many users are in that one location they could quickly exceed the number of higher data rate channels available from any of the small satellites and any additional users will not be able to get a connection.
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