History of GPS

  The U.S. Navy made the first non-GSP satellite system for use of updating the position of U.S. submarines and to reset their inertial navigation system. The system only had five satellites and intervals of 100 mins before the next satellite would come within range. These satellites used measurements of Doppler shift in their signals broadcast. The process took between ten and fifteen minutes. To have a good reading the object that it was tracking had to be stationary or moving slowly. The satellites had to be in a well defined orbit around earth for the reading to be accurate.
  In 1973 the Department of Defense (DOD) approved the basic architecture of the GPS satellite system. Then after five years the first beta satellite was launched in 1978. These were referred to as the 11 Block I beta satellites and were launched between 1978 to 1985. Currently there are three different types of fully functional satellites that currently make the GPS constellation. The first series of these satellites were the block II satellites. They were launched from February of 1989 to October of 1990. These satellites made by Rockwell International. They have four atomic clocks and have a life spawn of 7.3 years. The second series of satellites were the block IIA. These are a step up from Block II because they can run 180 days without contact from Control Segment instead of 14 days. Block IIA also had quit a big down fall do to the fact that the longer they don't have contact from Control Segment, the more the accuracy will degrade. These satellites were launched from 1990 to 1997. The last satellites in the series are called the Block IIR satellites. Lockheed Martin makes these satellites to replace the old satellites that don't work any more. Block IIR have fixed the downfall of the Block IIA satellites. It has the ability to be launched into any of to required GPS orbits at any time with a 60 day advanced notice. It can provide at least 14 days of operation without any contact from Control Segment. They also can run 180 days in autonav mode without their accuracy degrading. The Block IIR costs 33 percent less then the other satellites even with all these improvements.   In 1995 the system was declared operational. The cost was around 10 billion dollars and has cost 250 to 500 million a year to maintain. The main purpose of the system is primarily for the U.S. military to provide precise estimates of position, velocity, and time. Civil use was only a second objective of making the system.
  GPS has found many ways to be used by military and civilians. Using lessons learned from Operation Desert Shield and Desert Storm, GPS is being integrated into the modern battlefield. Air controllers, pilots, tank drivers, and ground troops all use GPS to keep track of the battle and know were they are at so they don't get hit by friendly fire. Some civil fields are land transportation, civil aviation, maritime commerce, surveying, mapping, construction, mining, agriculture, earth science, telecommunication, and recreational activities. GPS is starting to become an every day part of our lives. It is estimated by the U.S. Department of Commerce that sales worldwide will reach 8 billion by 2000 and 16 billion by 2003.