GPS History, Dates & Timeline
- summary of the GPS history detailing how the GPS system came into being with major milestone dates or timeline.
The GPS history shows how the system required many other related developments to take place to enable, what is a very sophisticated technology to become reality.
There are many significant GPS dates of significant satellite launches as well as other developments that took place before the overall system could become reality.
The accuracy of GPS systems available nowadays is taken for granted - it is is everyday use by all people in consumer devices as well as professional and military devices.
Navigation history before GPS
Before GPS became available a variety of systems were used, but none gave the same accuracy, especially on a global basis. Compasses using the Earth's magnetic field, as well as more localised systems such as LORAN and the Decca navigator system using hyperbolic patterns generated by three base stations were some of the main systems used. Aircraft also used systems such as TACAN.
Ideas for a satellite based global positioning system were based around some of the first satellite and space missions. With Sputnik in 1957 and the following American satellites the first steps towards a GPS system were set.
Using some of these early satellites, some the effects that would need to be incorporated into any future systems were able to be noted and investigated. One important point was the Doppler effect where the speed of the satellite relative to the ground station caused a perceived shift in frequency of the carrier.
First satellite navigation systems
One of the major limitations of ground based navigation systems was the fact that they were limited in range. Only magnetic and stellar based systems were global and these did not possess the accuracy or the convenience of use needed for many modern navigational requirements. Omega was a system using very low radio frequencies that became operational around 1971, and although global, it only provided navigation with an accuracy to within about 6km.
After the launch of the first satellites it did not take long before work started on some satellite based navigational systems. In 1960 a system called TRANSIT was tested by the US Navy. This satellite based navigation system used five satellites and was able to provide a fix about once every hour. The first satellite, TRANSIT IB was launched on 13th April 1960.
Later this year, Dr Ivan Getting and Dr Shep Arikin of Raytheon proposed a radio-navigation system called MOSAIC (Mobile System for Accurate ICBM Control) to the U.S. Air Force.
A further development took place when a project named Project 57 was initiated to investigate areas where space systems could be used to aid national security.
One of the next major developments was another US Navy system called Timation. This proved the ability to put very high accuracy clocks into space - a key element of GPS. In 1967, as part of this programme, an atomic clock was launched into space. However the three US forces were each pursuing their own development programmes and this slowed the rate of development as three separate programmes were being run in parallel.
Impetus from the cold war
In order to develop a global positioning navigation system, it was realised that a huge amount of investment would be required. This could not normally be justified for commercial, or domestic use. Instead the impetus came from a military need.
During the Cold War, there was a significant threat from nuclear attack, and credible and effective deterrent was needed. Not only did the possible launch carriers (submarines, aircraft and vehicles) need very accurate positioning, but the possibility of cruise missiles using a global positioning system was also considered.
The first concrete steps towards the future global positioning system took place during a meeting in 1973 between heads of the US military. They discussed the creation of a Defense Navigation Satellite System, DNSS. Later that year, the programme was named Navstar, and the overall system was called Navstar Global Positioning System, or Navstar GPS, or just GPS.
GPS development and launch
Once the decision had been made to develop GPS, a colossal amount of development was required.
The development of GPS included a launch programme of 10 satellites known as Block I satellites. This started in 1978, although the initial launch suffered a failure and the satellite was lost. This launch programme lasted until 1985, when on 9th October the last Block I satellite was launched.
The first production satellite, Block II, was launched in 1989, and the 24th satellite was launched in 1994. Block II consisted of a total of 28 satellites as this allowed for spares to be in place for any failures that might occur. The final Block II satellite was launched in 1997.
Finally, in December 1990, the Navstar system became operational, although not all the satellites had been launched by this time..
|GPS Satellite Launch Timeline|
|Satellite Block||Launch Period||Successful Launches||Failures|
|I||1978 - 1985||10||1|
|II||1989 - 1990||9||0|
|IIA||1990 - 1997||19||0|
|IIR||1997 - 2004||12||1|
|IIR-M||2005 - 2009||8||0|
|IIF||2010 - 2011||1 (11 in prep)||N/A|
|IIIA||2014 onwards||12 planned||N/A|
Civilian use for GPS
A defining occurrence for GPS occurred when Korean Flight 007 wandered off its course, flying over the highly sensitive Russian area around Sakhalin Island where it was shot down with the death of all 269 passengers on board. As a result, President Reagan ordered that GPS should be made freely available for civilian use once it was sufficiently developed.
The version of GPS available for civilian use was downgraded using what was termed Selective Availability, SA. The full accuracy was reserved for military use. President Bill Clinton ordered that Selective Availability should be turned off at midnight on 1st May 2000. The USA protected their advantage because they could deny service to potential adversaries on a regional basis.
GPS dates / timeline
There are a number of significant GPS dates within the overall GPS timeline:
|1960||The first navigation satellite TRANSIT IB is launched.|
|1972||USAF conducted development flights with experimental navigational receivers of the form that could be used with a satellite based navigational system|
|1978||After an initial launch failure, the first of the Block I development satellites is launched.|
|1983||US Air Force signs a $1.2 billion for the production build, Block II satellites.|
|1985||On 9th October, the last of the Block I satellites is launched.|
|1989||First production, Block II GPS satellite launched|
|1990||Navstar GPS becomes operational.|
|1994||24th Block II is satellite launched|
|1995||In April, Full Operational Capability status of the system is reached signifying availability of the Precise Positioning Service, PPS.|
|1998||United States Vice President Al Gore announced plans to upgrade GPS with two new civilian signals to provide enhanced accuracy.|
GPS history and the future
GPS is now well established, and competitor systems are being developed, but GPS is by far the leading light in terms of global satellite navigation systems. In addition to this GPS technology itself is being further developed to enable to meet the growing requirements of the different users.
By Ian Poole
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