Design and Ground Test of the NTS-1 Frequency Standard System.

The NRL TIMATION III satellite, redesignated as GPS Navigation Technology Satellite I NTS-1 was successfully placed into a medium altitude orbit, 7,300 mi, on July 14, 1974. One of the major experiments performed with the satellite is the investigation of the space-environment performance of two rubidium controlled frequency standards and a specially developed quartz oscillator. System design, ground testing, and flight qualification modifications were performed at NRL. This included modifying commercial-quality rubidium standards to levels acceptable to the flight environment the design and construction of power control, RF switching, and remote digital tuning circuits and ground testing the candidate frequency standards in terms of short-term stability Allen Variance, aging, warmup, tuning characteristics, DC power consumption and environmental effects due to vacuum, radiation, vibration, and temperature.