WASHINGTON, DC -
The launch of the TIMATION satellite on May 31, 1967 proved that a system using a passive ranging technique, combined with highly accurate atomic clocks, could provide the basis for a new and revolutionary navigation system, providing longitude, latitude, and altitude around the globe.
Before the era of artificial satellites, the accuracy of navigation had not improved much beyond that available from celestial techniques. With the introduction of satellite navigation systems, a new order of magnitude of accuracy became possible.
A vision of NRL research physicist, Roger Easton, TIMATION, short for 'time navigation,' introduced continuous navigation fixes from satellites in low Earth orbit (LEO).
In the TIMATION system, a satellite contains a stable oscillator that controls its transmissions. Navigators receive these transmissions and compare with outputs from their own ship-based oscillator. If both oscillators are suitably synchronized, satellite range and position can be determined and the navigator can then use celestial-navigation
techniques to determine the position of their ship.
To authenticate proof of concept, NRL-operated experimental space-surveillance stations
in south Texas were used to calibrate the satellite oscillator and preliminary "looks" at the orbital data revealed that the satellite's positions could be predicted well enough to provide navigation fixes accurate to within a few tenths of a mile.
Through the development and deployment of three additional experimental satellites: TIMATION II in 1969; Navigation Technology Satellite (NTS-I) in 1974; and the first satellite to fly a rubidium atomic frequency standard in a 12-hour GPS orbit, NTS-2, in 1977; and the first satellite to fly a cesium atomic frequency standard. Easton had unequivocally proven the practicality of using satellite-based atomic clocks for precision global navigation.
Using time measurements from NTS-2, Easton was able to verify Einstein's theory of relativity, affirming the need for a relativistic offset correction that remains in use today by every satellite in our modern day GPS constellation.
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