A Long-Term Comparison of GPS Carrierphase Frequency Transfer and Two-Way Satellite Time/Frequency Transfer
Abstract
GPS carrier-phase frequency transfer (GPSCPFT) and two-way satellite time and frequency transfer (TWSTFT) were performed along three transatlantic links over the 6-month period 29 January 31 July 2006. The GPSCPFT and TWSTFT results were subtracted in order to estimate the combined uncertainty of the methods. The frequency values obtained from GPSCPFT and TWSTFT agreed at 1.8 to 3.8 10(exp-16) RMS for averaging times of 30 d, with no single value of gammaGPSCPFT gammaTWSTFT exceeding 5.5 10(exp-16). These RMS frequency-accuracy values were equal to or less than the frequency-stability values sigma gamma(GPSCPFT) gamma(TWSTFT) (tau) (or TheoBR (tau)) computed for the corresponding averaging times; in general, no frequency bias between GPSCPFT and TWSTFT was observed. The transfer noise of the links varied with time of year, which was especially noticeable in the gammaGPSCPFT gammaTWSTFT values obtained for 10-15 d averaging times: gammaGPSCPFT gammaTWSTFT (10 d) sometimes became as large as 2 10(exp-15). It is not yet clear what caused these variations. RMS (gammaGPSCPFT gammaTWSTFT, 10 d) ranged from 0.7 to 1.1 10(exp-15), with these RMS values approximately equal to sigma gamma(GPSCPFT) gamma(TWSTFT) (tau = 10 d, 21 h). Day-boundary discontinuities were not removed or otherwise circumvented in this experiment; we hope to reduce the uncertainty at shorter averaging times (e.g., 10 d) through better management of these discontinuities, along with improved understanding of the seasonal components.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 2007
- Accession Number
- ADA473920
Entities
People
- Christine Hackman
- Judah Levine
- Thomas E. Parker
Organizations
- JILA