Passive TWSTFT method for increased robustness in UTC (SP)

Purpose and goal

The project has developed a method for calculating the real-time orbit parameters for the geostationary satellite used. From the necessary data published by the active metrological network it is now possible to determine the satellite´s instantaneous 3D position and an interpolating orbit model within the acceptable error margins with typical errors of one meter. For a given user-position such uncertainty enables us to calculate a distance correction and implement a one-way (passive) time transfer with a method specific error margin of some nanoseconds.

Expected results and effects

The project has developed a satellite orbit determination method that with high accuracy can be used to determine the length of the instantaneous signal path from any geographical point to the geostationary satellite, thus supporting a differential time transfer with typically few nanoseconds error margin. We expect the method to be used to complement GNSS time distribution to increase the robustness of national time-keeping.

Planned approach and implementation

The project was mainly carried out by two employees between autumn 2016 and summer 2017, as well as a follow-up at the end of 2017. We expect further efforts during preparation and presentation of the project under EFTF2018. The project primarily required knowledge in space geodetic computation methods, estimation techniques and metrology. Additional skills in the time and frequency group, like IP networking, have been utilized and we can see that the group´s capacity has been used well.