GPS NAVSTAR-4 and NTS-2 Long Term Frequency Stability and Time Transfer Analysis.
Abstract
Since the launch of the first Navigation Technology Satellite (NTS) in 1974, international time-transfer experiments have been performed as part of the concept validation phase of the Global Positioning System (GPS). Time-transfer results from both NTS-1 and NTS-2 are presented, including recent measurements from receivers located in South America, Germany, Japan, and the United States. A time link to the DOD Master clock allows submicrosecond intercomparison of UTS (USNO, MC1) with clocks in the respective countries via the NTS link. Work is progressing toward a retrofit conversion of existing NTS receivers (located at NASA and foreign observatories) into GPS time-transfer receivers. Initial results are presented on the long-term rubidium frequency stability as measured from the GPS NAVSTAR-4 space vehicle (SV). Analysis has been performed for sample times varying from 1 to 10 days. Using a 154-day data span starting on day 36, 1979, data was collected from the four GPS monitor stations located at Vandenberg, Guam, Alaska, and Hawaii. A time domain estimate for the NAVSTAR-4 SV clock off-set is obtained for each SV pass over the GPS monitor sites, using a smoothed reference ephemeris, with corrections for ionospheric delay, tropospheric delay, earth rotation, and relativistic effects. Conversion from the time domain to the frequency domain is made using the two-sample Allan Variance; sigma-tau plots are used to identify the noise processes. Estimates of flicker and white frequency noise for the NAVSTAR-4 rubidium frequency standard are obtained.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 30, 1980
- Accession Number
- ADA088092
Entities
People
- J. A. Buisson
- M. M. Largay
- O. J. Oaks
- S. B. Stebbins
- T. B. Mccaskill
Organizations
- United States Naval Research Laboratory