RELATIVISTIC EFFECTS ON SV CLOCKS DUE TO ORBIT CHANGES, AND DUE TO EARTH'S OBLATENESS

摘要

Improvements in GPS motivate attention to some small relativistic effects which have long been known, but have previously been too small to be explicitly considered. For SV clocks, these include frequency changes due to orbit adjustments, and effects due to the earth's oblateness. For example between 25 July and 10 October 2000, SV43 occupied a transfer orbit while it was moved from slot F5 to slot F3. The fractional frequency change associated with a change da in the semi-major axis a (in meters) can be estimated as 9.429×10~(-18)da. This yields a prediction of -1.77×10~(-13) for the fractional frequency change of the SV43 clock which occurred 25 July 2000. This relativistic effect has been pointed out and measured by Epstein, Fine, and Stoll [4]. On October 10, 2000 the fractional frequency change should have been +1.75×10~(-13). Also, the earth's oblateness causes a periodic fractional frequency shift with period of almost 6 hours and amplitude 0.695×10~(-14). These effects will be discussed with the help of Lagrange's planetary perturbation equations.