question: How do home satellite systems never lose connection to the satellite they communicate with? Does the satellite orbit the earth at the same rate it spins? Or are there multiple satellites that transfer the signal as they go by?
comment: Most satellites used for things like satellite TV are in geostationary orbit. They are over the equator and they go around the earth at the same rotational speed and in the same direction that the earth rotates, so they remain over the same "spot" of ground.
passages: Only downlinks from the satellite are affected, uplinks from the Earth are normally not, as the planet "shades" the Earth station when viewed from the satellite. Satellites in geosynchronous orbit are irregularly affected based on their inclination. Reception from satellites in other orbits are frequently but only momentarily affected by this, and by their nature the same signal is usually repeated or relayed on another satellite, if a tracking dish is used at all. Satellite radio and other services like GPS are not affected, as they use no receiving dish, and therefore do not concentrate the interference. (GPS and certain satellite radio systems use non-geosynchronous satellites.)
   The eight identical spacecraft use absolute timing obtained from GPS Satellites to maintain a schedule. Each day, one satellite acts as a Captain and the rest act as Lieutenants. Each spacecraft is able to act as a Captain, and the role of Captain rotates through the constellation each 25-hour period. Lieutenants only communicate with the Captain, and the Captain is responsible for downlinking to an earth station.
  
  Section::::Mission.:Lifetime.
  
  NASA has estimated a 60-day mission lifetime, at which time the satellites will drift apart beyond the 100–120 km estimated range of the cross link and no longer be able to network.
  
  Section::::Mission.:Orbit.
   BULLET::::- Command and Control subsystem, which maintains communications with ground control stations. The ground control Earth stations monitor the satellite performance and control its functionality during various phases of its life-cycle.
  
  The bandwidth available from a satellite depends upon the number of transponders provided by the satellite. Each service (TV, Voice, Internet, radio) requires a different amount of bandwidth for transmission. This is typically known as link budgeting and a network simulator can be used to arrive at the exact value.
  
  Section::::Frequency Allocation for satellite systems.
   A communications satellite is an example of an active repeater that does change frequency. Communications satellites, in most cases, are in geosynchronous orbit at an altitude of 22,300 miles (35,000 km) above the Equator.
  
  Section::::Means of achieving non-line-of-sight transmission.:Groundwave propagation.
   Geostationary satellites also carry international telephone traffic but they are being replaced by fiber optic cables in heavily populated areas and along the coasts of less developed regions, because of the greater bandwidth available and lower latency, due to the inherent disconcerting delay in communicating via a satellite in such a high orbit. It takes electromagnetic waves about a quarter of a second to travel from one end to the other end of the link. Thus, two parties talking via satellite are subject to about a half second delay in a round-trip message/response sequence.
   Instead of being de-orbited, most satellites are either left in their current orbit or moved to a graveyard orbit. As of 2002, the FCC requires all geostationary satellites to commit to moving to a graveyard orbit at the end of their operational life prior to launch. In cases of uncontrolled de-orbiting, the major variable is the solar flux, and the minor variables the components and form factors of the satellite itself, and the gravitational perturbations generated by the Sun and the Moon (as well as those exercised by large mountain ranges, whether above or below sea level). The nominal breakup altitude due to aerodynamic forces and temperatures is 78 km, with a range between 72 and 84 km. Solar panels, however, are destroyed before any other component at altitudes between 90 and 95 km.
   Typically a completely clear line of sight between the dish and the satellite is required for the system to work optimally. In addition to the signal being susceptible to absorption and scattering by moisture, the signal is similarly impacted by the presence of trees and other vegetation in the path of the signal. As the radio frequency decreases, to below 900 MHz, penetration through vegetation increases, but most satellite communications operate above 2 GHz making them sensitive to even minor obstructions such as tree foliage. A dish installation in the winter must factor in plant foliage growth that will appear in the spring and summer.
   Although many populated land locations on the planet now have terrestrial communications facilities (microwave, fiber-optic), even undersea, with more than sufficient capacity, telephone and Internet access is still available only via satellite in many places in Africa, Latin America, and Asia, as well as isolated locations that have no terrestrial facilities, such as Canada's Arctic islands, Antarctica, the far reaches of Alaska and Greenland, and ships at sea.
  
  Section::::Uses.
  
  Most commercial communications satellites, broadcast satellites and SBAS satellites operate in geostationary orbits.
  
  Section::::Uses.:Communications.
   Section::::Characteristics of the SHF frequency band.:Rain resilience.
  
  X band is below those frequencies which are severely affected by Rain Fade, therefore X band provides extremely good rain resilience unlike higher frequencies such as Ku or Ka which are also used for satellite communication. This allows extremely high link availability, in some cases as high as 99.9%
  
  Section::::Characteristics of the SHF frequency band.:4° separation between satellites.
  
  X band satellites typically have at least 4° separation between satellites, therefore there is less chance of adjacent satellite interference (ASI) and higher power density carriers allowed.
   As satellites in MEO and LEO orbit the Earth faster, they do not remain visible in the sky to a fixed point on Earth continually like a geostationary satellite, but appear to a ground observer to cross the sky and "set" when they go behind the Earth. Therefore, to provide continuous communications capability with these lower orbits requires a larger number of satellites, so one will always be in the sky for transmission of communication signals. However, due to their relatively small distance to the Earth their signals are stronger.
  
  Section::::Satellite orbits.:Low Earth orbit (LEO).
   A solar transit (also called a solar outage, sometimes solar fade, sun outage, or sun fade) also occurs to communications satellites, which pass in front of the Sun for several minutes each day for several days straight for a period in the months around the equinoxes, the exact dates depending on where the satellite is in the sky relative to its earth station. Because the Sun also produces a great deal of microwave radiation in addition to sunlight, it overwhelms the microwave radio s coming from the satellite's transponders. This enormous electromagnetic interference causes interruptions in fixed satellite services that use satellite dishes, including TV networks and radio networks, as well as VSAT and DBS. 
   Modulated carriers can be dynamically altered in response to rain problems or other link impairments using a process called adaptive coding and modulation, or "ACM". ACM allows the bit rates to be increased substantially during normal clear sky conditions, increasing the number of bits per Hz transmitted, and thus reducing overall cost per bit. Adaptive coding requires some sort of a return or feedback channel which can be via any available means, satellite or terrestrial.
  
  Section::::Challenges and limitations.:Line of sight.
   Often, nonstandard IP stacks are used to address the latency and asymmetry problems of the satellite connection. As with one-way receive systems, data sent over the satellite link is generally also encrypted, as otherwise it would be accessible to anyone with a satellite receiver.
   Satellite communications are affected by moisture and various forms of precipitation (such as rain or snow) in the signal path between end users or ground stations and the satellite being utilized. This interference with the signal is known as "rain fade". The effects are less pronounced on the lower frequency 'L' and 'C' bands, but can become quite severe on the higher frequency 'Ku' and 'Ka' band. For satellite Internet services in tropical areas with heavy rain, use of the C band (4/6 GHz) with a circular polarisation satellite is popular. Satellite communications on the K band (19/29 GHz) can use special techniques such as large "rain margins", "adaptive uplink power control" and "reduced bit rates" during precipitation.
   Like LEOs, these satellites do not maintain a stationary distance from the earth. This is in contrast to the geostationary orbit, where satellites are always from the earth.
  
  Typically the orbit of a medium earth orbit satellite is about above earth. In various patterns, these satellites make the trip around earth in anywhere from 2 to 8 hours.
  
  Section::::Satellite orbits.:Medium Earth orbit (MEO).:Example.
   One should thoroughly test the functionality of live interactive access to a distant computer—such as virtual private networks. Many TCP protocols were not designed to work in high-latency environments.
  
  Section::::Challenges and limitations.:Signal latency.:Medium and Low Earth Orbits.
  
  Medium Earth orbit (MEO) and low Earth orbit (LEO) satellite constellations do not have such great delays, as the satellites are closer to the ground. For example:
   Section::::Network links.:Wireless technologies.
  
  BULLET::::- "Terrestrial microwave" – Terrestrial microwave communication uses Earth-based transmitters and receivers resembling satellite dishes. Terrestrial microwaves are in the low gigahertz range, which limits all communications to line-of-sight. Relay stations are spaced approximately apart.
  
  BULLET::::- "Communications satellites" – Satellites communicate via microwave radio waves, which are not deflected by the Earth's atmosphere. The satellites are stationed in space, typically in geosynchronous orbit above the equator. These Earth-orbiting systems are capable of receiving and relaying voice, data, and TV signals.
   The exact days and times of solar transit outages, for each satellite and for each receiving point (Earth station) on the Earth, are available at various websites. For broadcast networks, the network feed must be pre-recorded, replaced with local programming, fed via another satellite in a different orbital position, or fed via another method entirely during these times. 
   Satellites in geostationary orbits are far enough away from Earth that communication latency becomes significant — about a quarter of a second for a trip from one ground-based transmitter to the satellite and back to another ground-based transmitter; close to half a second for two-way communication from one Earth station to another and then back to the first. Low Earth orbit is sometimes used to cut this delay, at the expense of more complicated satellite tracking on the ground and requiring more satellites in the satellite constellation to ensure continuous coverage.
  
  Section::::Audio latency.
   There are two major classes of communications satellites, "passive" and "active". Passive satellites only reflect the signal coming from the source, toward the direction of the receiver. With passive satellites, the reflected signal is not amplified at the satellite, and only a very small amount of the transmitted energy actually reaches the receiver. Since the satellite is so far above Earth, the radio signal is attenuated due to free-space path loss, so the signal received on Earth is very, very weak. Active satellites, on the other hand, amplify the received signal before retransmitting it to the receiver on the ground. Passive satellites were the first communications satellites, but are little used now.
   Satellite Internet generally relies on three primary components: a satellite, typically in geostationary orbit (sometimes referred to as a geosynchronous Earth orbit, or GEO), a number of ground stations known as gateways that relay Internet data to and from the satellite via radio waves (microwave), and a small antenna at the subscriber's location, often a VSAT (very-small-aperture terminal) dish antenna with a transceiver. Other components of a satellite Internet system include a modem at the user end which links the user's network with the transceiver, and a centralized network operations center (NOC) for monitoring the entire system. Working in concert with a broadband gateway, the satellite operates a Star network topology where all network communication passes through the network's hub processor, which is at the center of the star. With this configuration, the number of remote VSATs that can be connected to the hub is virtually limitless.
   While most clocks are synchronized to Coordinated Universal Time (UTC), the atomic clocks on the satellites are set to "GPS time". The difference is that GPS time is not corrected to match the rotation of the Earth, so it does not contain leap seconds or other corrections which are periodically added to UTC. GPS time was set to match Coordinated Universal Time (UTC) in 1980, but has since diverged. The lack of corrections means that GPS time remains at a constant offset with International Atomic Time (TAI) (TAI - GPS = 19 seconds). Periodic corrections are performed on the on-board clocks to correct relativistic effects and keep them synchronized with ground clocks.
   When they run out of thruster fuel and are no longer able to stay in their allocated orbital position geostationary satellites are generally retired. The transponders and other onboard systems often outlive the thruster fuel and, by stopping N–S station keeping, some satellites can continue to be used in inclined orbits (where the orbital track appears to follow a figure-eight loop centred on the equator), or else be elevated to a "graveyard" disposal orbit. This process is becoming increasingly regulated and satellites they must have a 90% chance of moving over 200km above the getostationary belt at end of life.
   Compared to ground-based communication, all geostationary satellite communications experience higher latency due to the signal having to travel  to a satellite in geostationary orbit and back to Earth again. Even at the speed of light (about 300,000 km/s or 186,000 miles per second), this delay can appear significant. If all other signaling delays could be eliminated, it still takes a radio signal about 250 milliseconds (ms), or about a quarter of a second, to travel to the satellite and back to the ground. The absolute minimum total amount of delay varies, due to the satellite staying in one place in the sky, while ground-based users can be directly below (with a roundtrip latency of 239.6 ms), or far to the side of the planet near the horizon (with a roundtrip latency of 279.0 ms).
   Section::::Challenges and limitations.:Fresnel zone.
  
  Even if there is a direct line of sight between the transmitting and receiving antenna, reflections from objects near the path of the signal can decrease apparent signal power through phase cancellations. Whether and how much signal is lost from a reflection is determined by the location of the object in the Fresnel zone of the antennas.
  
  Section::::Two-way satellite-only communication.
  
presuppositions: Satellites orbit the Earth faster than the Earth spins.
corrections: Satellites used for TV go around the Earth at the same rotational speed, remaining over the same spot of ground.
raw_presuppositions: Satellites orbit the Earth faster than the Earth spins. Satellites orbit the Earth faster than it spins.
raw_corrections: Satellites used for TV go around the Earth at the same rotational speed, remaining over the same spot of ground. Satellites used for TV are in geostationary orbit, where they go around the earth at the same rotational speed, so it remains over the same spot of ground.