Global Positioning System - GPS Satellite Systems
 

I. Global Positioning System

Figure 11: NAVSTAR Insignia. (U.S. Naval Observatory)

Rockwell Collins International manufactured the original NAVSTAR satellites that comprise the current United States GPS system. This system was originally developed by the U.S. Department of Defense with an estimated cost of over $12 billion. The U.S. Navy and the U.S. Air Force combined to form NAVSTAR in 1973, and they launched the first satellite in 1974. Subsequent launchings, with satellites produced by Boeing and Lockheed Martin, have produced the current constellation of 24 operating satellites that became fully operational on December 8, 1993.

The estimated annual cost to operate and maintain this GPS
satellite system is $750 million; however, the economic impact
of this system was estimated to be $6.2 billion in 2000.
(History of GPS)

More information about GPS is explained in the About GPS section.

II. GLONASS

Figure 12: 3 GLONASS orbital planes.
(GPS Information and Observation System)

GLONASS (Global Navigational Satellite System) is a Russian radio-navigation system that operates on similar parameters to the U.S. based GPS. The system was officially declared fully operational on September 24, 1993. It is managed by the Russian Space Forces for the Russian Federation Government.

GLONASS is currently being employed in the fields of:

- Air and naval traffic management
- Geodesy
- Cartography
- Ecological monitoring
- Search and Rescue Coordination

The GLONASS signal is separated into two different transmissions:

1. Standard Precision (SP) - available to all civilian users worldwide.
2. High Precision (HP) - reserved for government or military usage.


The GLONASS constellation:

- Composed of 24 satellites in three orbital planes.
- Orbiting at an altitude of 19100 km.
- Each satellite completes an orbit every 11 hours and 15 minutes.


Control Segment:

- Control locations for the GLONASS system are located entirely within former Soviet Union territory.
- Ground control center located in Moscow with tracking stations located in St. Petersburg, Ternopol, Eniseisk and Komsomolsk-na-Amure.


More information can be found at the Russian Federation Ministry of Defense.

Figure 13: GLONASS Satellite.
(GISCafe.com)

III. GALILEO

GALILEO is the European based radio-navigational system. Designed and produced by the ESA (European Space Agency), it is projected to eventually be co-functional with the U.S. GPS constellation. The European Council unanimously agreed on March 26, 2002, to launch the GALILEO project.

GALILEO is currently being employed in the fields of:

- Public Transport
- Aviation
- Energy
- Civil Engineering
- Agriculture
- Civil Protection


The GALILEO constellation:

- 30 satellites, orbiting at an altitude of nearly 24,000 Kilometers
- Linked to base stations and control stations around the globe


Control Segment:

- Two control centers will be placed on European ground to synchronize clocks,
process signal integrity and handle internal and external data elements.


Figure 14: GALILEO Satellite.
(European Union Directorate-General Energy and Transport)

Unlike the American and Russian GPS systems, GALILEO was designed strictly as a non-military type application for the civilian market. It is expected to have a similar, and at times a higher, degree of precision as the American based GPS; however, GALILEO is said to be more reliable because it includes a "signal integrity" message that immediately informs the user of any errors. Because of the nature of its satellite constellations, GALILEO will allow the user to access positioning data in extreme latitudes of the world. (European Union Directorate-General Energy and Transport)

GALILEO is still very young in terms of its potential realization. This satellite system is expected to be fully functional by 2008. Various goals are currently being set for fully utilizing all of its capabilities, especially with respect to a coexistence with GPS; however, the European Union does intend for this system to reduce its dependence on the currently functioning American GPS system. (Space.com)

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