History of GPS

Posted on 21. Jul, 2011 by admin in Uncategorized

History

In 1957 , the Soviet Union launched the space satellite Sputnik I , which was monitored by observing the Doppler shift of the signal transmitted. Because of this, we began to think that, similarly, the position of an observer could be established by studying the Doppler frequency of a signal transmitted by a satellite whose orbit was determined precisely.

The U.S. Navy quickly applied this technology to provide navigation systems for their fleets of observations to date and accurate positions. Thus arose the systemTRANSIT , which became operational in 1964 , and by 1967 was available also for commercial use.

The position updates, then, were available every 40 minutes and should remain almost static observer to obtain adequate information.

Later in that decade and through the development of atomic clocks, we designed a constellation of satellites, each carrying one of these watches and being all synchronized based on a reference of time.

In 1973 we combined the programs of the Navy and the Air Force United States (the latter consisting of a transmission technique that provided accurate data encoded using a signal modulated with a PRN code (Pseudo-Random Noise: pseudo noise -random), in what became known as Navigation Technology Program (navigation technology), later renamed as NAVSTAR GPS.

Between 1978 and 1985 were developed and released eleven satellites NAVSTAR experimental prototype, the following generations of satellites to complete the current constellation, which is said to “initial operational capability” in December 1993 and with “full operational capability “in April 1995 .

In 2009 , this country offered the service standard for determining the position to support the needs of the ICAO , and she accepted the offer.

[ edit ]Technical features and benefits

 

Satellite operator controlling the NAVSTAR-GPS, Schriever Air Force Base.

 

Launch of satellites for the NAVSTAR-GPS by a Delta rocket.

The Global Navigation Satellite component:

• Satellite System : It consists of 24 units with synchronized paths to cover the entire surface of the globe. More specifically, distributed in 6 orbital planes of four satellites each. The electrical energy required to operate the acquired from two composite panels of solar cells attached to its sides.
• Ground stations : send control information to control the satellite orbits and perform maintenance on the entire constellation.
• Receiving terminals : Indicate the position you are, also known as GPS units, are that we purchased at specialty stores.

[ edit ]Space segment

• Satellites in the constellation: 24 (4 × 6 orbits)
  • Altitude: 26,580 m
  • Period: 11 h 58 min (12 hours sidereal )
  • Tilt: 55 degrees (relative to the Earth Ecuador).
  • Shelf Life: 7.5 years
• Control segment (ground station)
  • Main Station: 1
  • Ground antenna: 4
  • Monitoring station (tracking): 5
• RF Signal
  • Carrier frequency:
    • Civil – 1575.42 MHz (L1). Use the coarse acquisition code (C / A).
    • Military – 1227.60 MHz (L2). Use the Precision Code (P) encryption.
      • Level of signal strength: -160 dBW (surface soil).
      • Polarization: circular clockwise.
• Correctness
  • Location: officially stated approximately 15 m (95% of time). In reality a portable GPS 12 parallel channel single frequency provides an accuracy of 2.5 to 3 meters in more than 95% of the time. With WAAS / EGNOS / MSAS enabled, the accuracy rises from 1 to 2 meters.
  • Time: 1 ns
• Coverage: global
• User Capacity: Unlimited
• Coordinate system:
  • World Geodetic System 1984 ( WGS84 ).
  • Earth-centered, fixed.
• Integrity: notification time of 15 minutes or more. Not enough for civil aviation.
• Availability: 24 satellites (70%) and 21 satellites (98%). It is not enough as the primary means of navigation.