A Guide to the Global Positioning System (GPS)

GPS Timeline

1959	The first operational satellite-based navigation system TRANSIT is developed by the John Hopkins Applied Physics Laboratory (APL). Even though this was developed for use by the submarine fleet of the U.S. Navy, this technology became useful for GPS. The first TRANSIT navigation satellite (TRANSIT 1A) is launched but it fails to make orbit.

1960	In response to a U.S. Air Force requirement for a guidance system to be used with ICBM (Minuteman missiles) that are made mobile by traveling on the railroad system, Raytheon Corporation suggests a radionavigation system called MOSAIC (Mobile System for Accurate ICBM Control). The first navigation satellite (TRANSIT 1B) is launched for the U.S. Navy and operates for three months.

1961	MOSAIC, the 3D (longitude, latitude, altitude) time-difference-of-arrival system idea is abandoned when the Mobile Minuteman program is canceled. The first satellite (TRANSIT 4A) using a SNAP (Systems for Nuclear Auxiliary Power) nuclear generator for a power supply is launched.

1962	TRANSIT 5A is launched and the system is declared operational.

1963	The Aerospace Corporation begins a study on using a space system as the basis for a navigation system that uses vehicles rapidly moving is 3D. This idea leads directly to the concept of GPS. The U.S. Air Force begins to support the Aerospace study with system 621B.

1964	A U.S. Army navigation and positioning satellite, SECOR 1, is launched. SECOR stands for Sequential Correlation of Range A U.S. Navy satellite system, Timation is developed at the Naval Research Lab (NRL) to advance the development of high-stability clocks, time-transfer capability and 2D navigation. This is an important foundation for GPS.

1965	SECOR satellites 2, 3, 4 and 5 are launched.

1966	SECOR satellites 6, 7 and 8 are launched.

1967	The TRANSIT system is made available to the civilian community. The first Timation satellite, TIMATION-1, is launched.

1968	NAVSEG (Navigation Satellite Executive Committee) is established by the DoD to coordinate the efforts of the different satellite navigation groups.

1969	TIMATION-2 is launched.

1971	The L2 frequency is added to the 621B concept in order to accommodate corrections for changes in the ionosphere.

1973	The Deputy Secretary of Defense consolidates the U.S. Navy Timation and the Air Force System 621B 3D navigation system known as the DNSS (Defense Navigation Satellite System). The Air Force is made the program manager. DNSS later becomes NAVSTAR. The JPO (Joint Program Office) is to develop the new program with all military services particpating. The first DNSS system presented to DSARC (Defense System Acquisition and Review Council) is not approved. Packaged as Air Force's 621B system it did not represent a joint program. Later a new system is presented to DSARC and approved. This system consists of twenty-four satellites placed in twelve hour inclined orbits and is Phase I of the GPS program NAVSTAR.

1974	Rockwell International is selected to be the satellite contractor for GPS. A refurbished Timation satellite built by the NR is launched and is the first NAVSTAR NTS-1 (Navigation Technology Satellite 1)satellite. It carries the first atomic clocks into space.

1977	In Yuma, Arizona, testing of user equipment is carried out before any satellites are in place. Solar powered ground transmitters are set up in such a way to represent GPS satellites and broadcast signals that are similar to signals transmitted by GPS satellites. Although on the ground they provided a geometry similar to that of GPS satellites.

1978	NAVSTAR satellites 1, 2, 3 and 4 are launched.

1979	The JPO is able to proceed with full scale development of GPS now that the basic components are in place.

1980	NAVSTAR satellites 5 and 6 are launched. NAVSTAR 5 is the first satellite to have aboard an Integrated Operational Nuclear Detonation Detection System (IONDS). This detects and monitors nuclear explosions worldwide using bhangmeter sensors and GPS location data.

1981	NAVSTAR 7 is lost due to launch failure.

1982	Due to budget cuts the DoD approves the reduction of twenty-four satellites to eighteen in the GPS satellite constellation.

1983	The first satellite NAVSTAR 8 to carry the newer NDS (Nuclear Detonation Detection System) is launched. Following the Soviet shooting down of a Korean Airliner, President Reagan offers to make GPS available free to charge to civilian aircraft when it becomes available.

1984	NAVSTAR satellites 9 and 10 are launched. Due to the decision by the NOAA (National Oceanic and Atmospheric Administration) to allow the use of GPS data, even though the GPS system is still in development, surveying is the first commercial GPS market to take off. To compensate for the limited number of satellites available at this stage of development, surveyors make use of GPS enhancement techniques that include differential GPS and carrier phase tracking.

1985	The last of the Block 1 satellites NAVSTAR 11 is launched. The JPO awards the first UE (user equipment) contract for airborne, shipboard, manpack (portable) and vehicle use.

1986	The space shuttle Challenger explodes shortly after launch. The space shuttle is the only planned launch vehicle for GPS satellites at this time. This loss causes a delay of two years in the scheduled launch of the second generation, Block II, GPS satellites.

1988	Expansion of the GPS constellation to twenty-one satellites plus three operational spares is announced by the Secretary of the Air Force.

1989	A Delta II booster at Caper Canaveral AFS, Florida, launches the first of twenty-eight Block II GPS satellites, NAVSTAR 13, 14, 16, 17 and 19. Responsibility is assumed by the U.S. Coast Guard as the lead agency in the Department of Transportation for being the civilian point of contact for NAVSTAR information.

1990	NAVSTAR satellites 15, 18, 20, 21 and 23 are launched. The DoD activates Selective Availability. This is an variable error that deliberately degrades GPS navigation accuracy to those who do not have filter.

1991	NAVSTAR satellite 24 is launched. The United States offers to make GPS SPS (standard positioning service) available to the international community with no direct user charges for a minimum of ten years beginning in 1993.

1992	NAVSTAR satellites 25, 26, 27, 28, 29 and 32 are launched. The United States extends the 1991 offer of SPS to the world for the forseeable future to provide a minimum of six years advance notice of termination of GPS operations or SPS elimination.

1993	NAVSTAR satellites 22, 31, 34, 35, 37 and 39 are launched. The FAA (Federal Aviation Adminstration) approves the use of GPS by civilian users. Initial Operational Capability of GPS is formally declared by the Secretary of Defense. This signifies that GPS is no longer a developmental system now that twenty-four satellites are in orbit.

1994	NAVSTAR satellite 36 is launched. The FAA announces that the GPS system is now operational and is an integrated part of the U.S. air traffic control system. FAA Administrator David Hinson announces the development and installation of the WAAS (Wide-Area Augmentation System). This will improve the integrity and availability for civil users in all phases of flight. The contract is awarded to Wilcox Electric at a projected cost of 400 to 500 million dollars. The Department of Transportation Positioning / Navigation Executive Committee is formed to provide a cross-agency forum for making GPS policy.

1996	NAVSTAR satellite 33 is launched. The Transit satellite system stops operation as called for in the 1994 Federal Radionavigation Plan. White House announces that a higher level GPS accuracy will be available to everyone.

1997	The DoD and U.S. Department of Transportation issue a press release that states that civil users will have uninterrupted access to the carrier phase portion of the L2 signal (military only). Also that the next block of NAVSTAR satellites will include the capability to deploy a second civilian frequency.