Module 2 : Global Positioning System
 Lecture 4 : Basic GPS
  Examples of U.S. Satellite Navigation Systems
U.S. Satellite Navigation Systems
Satellite navigation system
Developed by
Number of satellites
Satellites launched
TRANSIT John Hopkins Applied Physics Laboratory by Dr. Richard Kirschner in 1960s
7
Launched in 1960, available to civilian users in 1967.
TIMATION Naval Research Laboratory (NRL)
2
1967
SECOR U.S. Army satellite navigation
13
1964 and 1969
NAVSTAR Joint Program Office (JPO) under DoD
Block I- 11Block II/IIA- 28Block IIR- 21
 1973
 
Brief description of Satellite Navigation Systems
Transit
  • The first US Navy operational satellite navigation system, also known as NAVSAT (Navy Navigation Satellite System), was based on the Doppler effect.
  • Purpose
    • Locating  - Ballistic missile and submarines
    • Navigation - Sea and air traffic
    • Surveying - Hydrographic and geodetic
  • Launched on April 13, 1960
    • 51° inclination in low polar orbits.
    • Altitude of 600 nautical miles (1100 km altitude).
    • Apogee-745 and a perigee of 373 km.
    • Orbital period of about 106 minutes.
  • The satellites broadcast ephemeris information (position and velocity information of satellites) continuously on 150 and 400 MHz.
  • OSCAR and NOVA satellites used in the system.
  • The final constellation consisted of six satellites, three Ground control stations (GCS) and receivers (i.e., the system's users).
  • Limitation of Transit
    • Inherently two dimensional system
    • Velocity sensitive
    • Limited coverage, unavailability periods of 35-100 min.
  • The Transit Program terminated navigation service on December 31, 1996 .
Timation
  • Developed in 1972 by the Naval Research Laboratory (NRL) and kept into a 70° inclination circular orbit at and altitude of 900 km.
  • Timation satellites intended to provide transfer of time and frequency.
  • The original satellite flew with
    • Stable quartz crystal oscillators.
    • Later models had first space-borne atomic clocks.
  • Timation program was later merged with the Transit and GPS Programs.
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