Brief history of GPS

[binh.nv]

Brief history of GPS



1973
Decision to develop a satellite navigation system based on the systems TRANSIT and TIMATION of the U.S. Navy and 621B of the U.S. Air Force.

1974 – 1979
System tests.

1977
First receiver tests are performed even before the first satellites are stationed in orbit. Transmitters installed on the surface of Earth are called Pseudolites (Pseudo satellites).

1978
NAVSTAR (Navigation System with Timing And Ranging), now known as GPS (Global Positioning System), launched by U.S. Department of Defense for military use, with eleven satellites in orbit (1978 – 1985).

1979
Decision to expand the GPS system. Thereupon the resources are considerably shortened and the program is restructured. At first only 18 satellites should be operated.

1980
GPS atomic clocks onboard satellites activated.

1980 – 1982
The financial situation of the project was critical, as the usefulness of the system was questioned again and again by the sponsors.

1982
First GLONASS satellites launched by the Russian Federation Ministry of Defense.

1983
When a civilian airplane of the Korean Airline (Flight 007) was shot down by Soviet fighters after it had gone lost over Soviet territory, GPS was declassified by President Reagan. GPS moved from pure military effort to public project: it was decided to allow the civilian use of the GPS system.

1986
The accident of the space shuttle "Challenger" meant a drawback for the GPS program, as the space shuttles were supposed to transport Block II GPS satellites to their orbits. Finally the operators of the program reverted to the Delta rockets intended for the transportation in the first place.

1988
The number of satellites was again raised to 24, as the functionality was not satisfying with only 18 satellites.

1989
The first Block II satellite was installed and activated.

1990 – 1991
Temporal deactivation of SA (Selective Availability) during the Gulf war. In this period civil receivers were used as not enough military receivers were available. On 1st July 1991 SA was activated again.

1993, 8th December
Initial Operational Capability (IOC) is announced. In the same year it was also definitely decided to authorize the world wide civilian use free of charge.

1994, March
The last Block II satellite completes the satellite constellation.

1995, 17th July
Full constellation of 24 GPS satellites in orbit. Full Operational Capability (FOC) is announced.

1996
U.S. President Clinton authorizes SA (Selective Availability) to be phased out to provide civilians worldwide with greater GPS accuracy.

2000, 2nd May 04 UTC
SA (Selective Availability) phased out as a result of the 1996 executive order by U.S. President Clinton. Civilians could now achieve 10 – 15 meters accuracy, compared to the previously available 100 meters accuracy. This was a major win for the GPS consumers (and the GPS industry).

2004, 20th March
Launch of the 50th GPS satellite.

2005, 25th September
Lauch of the first IIR-M GPS satellite. This new type supported the new military M-signal and the second civil signal L2C.

2007, end of year
Five IIR-M GPS satellites in space adding extra navigation signals for both civil and military users.

Links to more detailed history of GPS:
http://www.rand.org/pubs/monograph_repor....appb.pdf, pages 24 (260) – 30 (266).
http://support.radioshack.com/support_tu...mline.htm.
At the end of http://www.astronautix.com/project/navstar.htm.

(http://home.online.no/~sigurdhu/GPS_history.htm)