Investigation of Instabilities in Two-Way Time Transfer

Abstract

The U.S. Naval Observatory (USNO) and the National Institute of Standards and Technology (NIST) have begun an investigation of the instabilities in Two-Way Satellite Time and Frequency Transfer (TWSTFT). Initial results of these tests show that the time deviation (TDEV) is typically at or below 100 ps for averaging times ranging from 10 to 104 seconds. Beyond 104 seconds we see the presence of a diurnal instability that peaks at about 400 ps. The magnitude of this diurnal appears to be dependent on the earth station equipment being used and is most likely related to environmental factors. A comparison of two-way with GPS common view and GPS carrier phase is also made along with a comparative stability analysis. This program is partially supported by the Interagency GPS Executive Board (IGEB).