Stability Analysis of the Cesium Frequency Standard on Board Navigation Technology Satellite 2 (NTS-2).

NTS-2 was successfully launched on June 23, 1977, and maneuvered into a preassigned constellation position as part of the Phase I demonstration for NAVSTAR GPS. NTS-2 carried two cesium frequency standards. Precise timing signals, derived from one of the cesium frequency standards, were continuously transmitted. Time differences were then measured by the NTS ground stations. The NTS-2 time differences were used to fit an orbit to the observations over a typical 6-day span. Clock offsets were then obtained using the reference orbit and other measured parameters these clock offsets were then used to estimate the cesium frequency stability. Estimates of frequency stability have been obtained for one of the two cesium frequency standards for sample times of from 1 to 9 days. Analysis of the results indicates a white frequency noise of 0.00000000011 divided by the square root of the sample time in days for sample times of 1 to 5 days with a flicker floor of 0.00000000000017 for sample times from 5 to 9 days. For sample times of 10 days or longer an attempt was made to check for cesium aging with respect to the Universal Time Coordinated of Master Clock 1 at the United States Naval Observatory. The value for aging was not significantly different from zero that is, no cesium aging was found.