Architecture of a Satellite
Minimum Notions Patterns and Designs
Types of Satellites - Satellite History To obtain larger increases in operating capacity with the lowest possible cost, research arises in the communications area. Hence the idea of communications satellites appeared shortly after World War II, due to the combination of two very different technologies (missiles and microwave). The space age began in 1957 launching the first artificial satellite Sputnik I in the former USSR, which was carrying a radio beacon which emits a signal at frequencies 20 and 40 Mhz. this signal could be received by simple receivers throughout the world the first test performing transmission and reception of signals from space.
Characteristics of satellites The most outstanding feature is the diversity of services offered by satellite telecommunication systems, the extensive coverage of the satellites is used to establish long-distance links. Another feature is that the satellites have the ability to collect or distribute signals to and from various locations instead of passing from one point to another.
What is a satellite? It is an electronic repeater located in space, receives signals generated on earth, amplifies and sent back to earth. A satellite is any object that moves or rotates in orbit around another object. For example, the moon is a satellite of the earth, and the earth is a satellite of the sun.
How does a satellite? An amateur radio "A" sends a signal that is received by the satellite. The satellite amplifies and retransmits immediately. The amateur "B" receives and answers. So begins a satellite communication. Communications satellites act as Relay Stations in space. They are used to send messages to another part of the world. These messages can be phone calls, TV boxes, or even Internet connections. Communications satellites are in orbit as EchoStar geosynchronous (GEO = land + synchronous = moving at the same rate). This means that the satellite is always positioned at a point on earth. The land area that can "see" is called satellite footprint.
Types of satellites:
For its orbit:
Or satellites in geostationary orbit. When the orbit is in the equatorial plane of the earth, a distance of about 36000Km (5,6 equivalent to the radius of the earth), and consequently, the orbital period is exactly equal to the period of rotation of the earth (ie, 23 h, and 56s 4 min), known as sidereal day, then we say that the geostationary orbit and the satellite is running through that orbit is a geostationary satellite. These were the starting point for satellite communications, and virtually all satellites used today for corporate communications networks are GEO. The basic applications of these satellites are transmissions are point-to-multipoint and point-to-point.
Ø Satellite Low Earth Orbiting (LEO).LEO satellites are located in low orbit, of 1.500 Km on average, but can be between 200 2000 and Km, the orbital periods are among the 90 and 120 minutes. These low orbits were used in the early days of satellite communications technology as one of the stages to cover to reach the ultimate goal at the time, that was the geostationary satellite, when there were no means to get the necessary launch power to place the satellite in the corresponding high Km 360000 wing geostationary orbit.
For its purpose:
Ø Satellite earth observation.
Ø meteorological satellites.
Ø navigation satellites.
Telecommunications or satellites.
Military and spies or satellites.
Amateur radio or satellites.
Advantages and Disadvantages
Ø immediate and total coverage of large geographic areas, unlike classical terrestrial systems, slow implementation.
Ø Ability to become independent of the distances and natural barriers such as mountains, etc..
Ø The satellite transmissions are subject to propagation delays, are weakened by the rain, snow and sun spots affecting ground stations, also suffer radio interference, microwave and airports.
Ø High cost.
Ø legal problem.
Satellite is central and obligatory network through which pass a set of simultaneous connections. In this sense, may be considered as a nodal point of the network. The main functions of a telecommunications satellite are: Ø To amplify the received carrier signals for transmission on the downlink. Or the change of frequency of the carrier signals to avoid interference problems and satellite consists of a payload and a platform. Or payload consists of the receiving and transmitting antennas, and electronic equipment that supports transmission of information bearing signals. Ø The platform consists of all subsystems which allow the operating payload.