Changes

===Geosynchronous orbit===

===Geosynchronous orbit===

In some cases, satellites are placed in a high earth orbit (at an altitude of about 22,000 miles), where they orbit over the equator.  They are placed in a precise orbit, so that they remain stationary, relative the the earth's surface.  These satellite are capable of communicating with devices over an enormous area, and this capability remains persistent, since it orbits at the perfect speed.  Since these satellites can service such a large area, they are usually quite sizable and capable to service the requirements of all satellite phones in this area. In most cases, only three four of these satellites are required to provide service to satellite phones around most of the world.<ref>http://electronics.howstuffworks.com/gadgets/travel/satellite-phone1.htm</ref>

In some cases, satellites are placed in a high earth orbit (at an altitude of about 22,000 miles), where they orbit over the equator.  They are placed in a precise orbit, so that they remain stationary, relative the earth's surface.  These satellite are capable of communicating with devices over an enormous area, and this capability remains persistent, since it orbits at the perfect speed.  Since these satellites can service such a large area, they are usually quite sizable and capable to service the requirements of all satellite phones in this area. In most cases, only three four of these satellites are required to provide service to satellite phones around most of the world.<ref>http://electronics.howstuffworks.com/gadgets/travel/satellite-phone1.htm</ref>

===Low earth orbit===

===Low earth orbit===

==Network comparison==

==Network comparison==

Low-earth orbit satellites, although less economical, generally offer better service.  Rather than the radio signals needing to travel between a temperate or arctic zone and a satellite 22,000 miles above the equator, the signals must only travel between a nearer satellite which is about 17,000 miles above (which only takes about 50 milliseconds).  Additionally, LEO networks require less transmission power, which enables the phone batteries to power their devices longer per charge than their counterparts. This also means that relatively small antennas may be used with LEO networks. This means that these phones can be constructed with a size roughly equal to [[smartphone]]s.<ref name="howstuffworks 3">http://electronics.howstuffworks.com/gadgets/travel/satellite-phone2.htm</ref> <br />

Low-earth orbit satellites, although less economical, generally offer better service.  Rather than the radio signals needing to travel between a temperate or arctic zone and a satellite 22,000 miles above the equator, the signals must only travel between a nearer satellite which is about 17,000 miles above (which only takes about 50 milliseconds).  Additionally, LEO networks require less transmission power, which enables the phone batteries to power their devices longer per charge than their counterparts. This also means that relatively small antennas may be used with LEO networks. This means that these phones can be constructed with a size roughly equal to [[smartphone]]s.<ref name="howstuffworks 3">http://electronics.howstuffworks.com/gadgets/travel/satellite-phone2.htm</ref> <br />

However, LEO networks use smaller, less powerful satellites, since each one has fewer requirements.  They can only communicate at a rate of 9,600 bits per second, much slower than geosynchronous systems. Although much larger antennas are required for geosynchronous systems, they can communicate at a much greater rate, since each satellite is much more powerful.<ref name="howstuffworks 3">http://electronics.howstuffworks.com/gadgets/travel/satellite-phone2.htm</ref>

However, LEO networks use smaller, less powerful satellites, since each one has fewer requirements.  They can only communicate at a rate of 9,600 bits per second, much slower than geosynchronous systems. Although much larger antennas are required for geosynchronous systems, they can communicate at a much greater rate, since each satellite is much more powerful.<ref name="howstuffworks 3"/>

==Politics==

==Politics==

==Disadvantages==

==Disadvantages==

The development, deployment, and maintenance of a satellite phone network is much more costly than that of a traditional cellular phone network.  This means that satellite phone service is more expensive than its ground-based counterpart.  Also, satellites have limited data transfer rates.  Data speeds depend largely on the kind of satellite network used (either high or low orbit), but in general, only voice and text messaging is available, often at a cost of one dollar or more.  If users want Internet access on their phones, they will be much better off with a land-based system.<br />

The development, deployment, and maintenance of a satellite phone network is much more costly than that of a traditional cellular phone network.  This means that satellite phone service is more expensive than its ground-based counterpart.  Also, satellites have limited data transfer rates.  Data speeds depend largely on the kind of satellite network used (either high or low orbit), but in general, only voice and text messaging is available, often at a cost of one dollar or more.  If users want Internet access on their phones, they will be much better off with a land-based system.<br />

Another disadvantage of satellite phones is the signal communication delay.  If using a low-earth orbit satellite system, this delay is quite short (50 milliseconds<ref name="howstuffworks 3">http://electronics.howstuffworks.com/gadgets/travel/satellite-phone2.htm</ref>), but if using a high-earth orbit system, this delay is much longer. The phone size is another concern, since they need stronger transceivers than traditional cellular phones.  If using a LEO network, this is not much of a problem, since functionality is sacrificed in order to maintain a pock-sized device.  However, HEO (geosynchronous) system phones much be larger.<br />

Another disadvantage of satellite phones is the signal communication delay.  If using a low-earth orbit satellite system, this delay is quite short (50 milliseconds<ref name="howstuffworks 3"/>), but if using a high-earth orbit system, this delay is much longer. The phone size is another concern, since they need stronger transceivers than traditional cellular phones.  If using a LEO network, this is not much of a problem, since functionality is sacrificed in order to maintain a pock-sized device.  However, HEO (geosynchronous) system phones much be larger.<br />

Perhaps one of the greatest disadvantages is that satellite phones must be in line-of-sight of the servicing satellite. While in some areas this may be as simple as stepping out a building, it can be a problem in wooded and mountainous areas.<ref name="howstuffworks 3">http://electronics.howstuffworks.com/gadgets/travel/satellite-phone2.htm</ref>  If HEO satellites are used, it can be nearly impossible to get this line-of-site connection—in many cases, the satellite will be perpetually blocked.  LEO systems can work better in such circumstances, since the satellites continue to move.  Even if they are sometimes blocked, satellites will usually pass within range from time-to-time.  This means that in such areas, sporadic service is often available. While intermittent service is better than none, it can be inconvenient.

Perhaps one of the greatest disadvantages is that satellite phones must be in line-of-sight of the servicing satellite. While in some areas this may be as simple as stepping out a building, it can be a problem in wooded and mountainous areas.<ref name="howstuffworks 3"/>  If HEO satellites are used, it can be nearly impossible to get this line-of-site connection—in many cases, the satellite will be perpetually blocked.  LEO systems can work better in such circumstances, since the satellites continue to move.  Even if they are sometimes blocked, satellites will usually pass within range from time-to-time.  This means that in such areas, sporadic service is often available. While intermittent service is better than none, it can be inconvenient.

Yet another disadvantage of Satellite phones is that certain acts of nature can interfere with communication.  Solar flares and other natural events can disrupt such sensitive systems.<ref name="Howstuffworks 4">http://electronics.howstuffworks.com/gadgets/travel/satellite-phone3.htm</ref>

Yet another disadvantage of Satellite phones is that certain acts of nature can interfere with communication.  Solar flares and other natural events can disrupt such sensitive systems.<ref name="Howstuffworks 4"/>

==Dual-mode sat phones==

==Dual-mode sat phones==