Metsähovi connected to the official time of Finland

The Metsähovi Geodetic Research Station of the Finnish Geospatial Research Institute at the National Land Survey of Finland and the Aalto University Metsähovi Radio Observatory were connected to the official time of Finland, UTC(MIKE).

Anders Wallin (VTT) working on the time transfer equipment in Metsähovi
Foto: Jyri Näränen / National Land Survey of Finland
Anders Wallin (VTT) working on the time transfer equipment in Metsähovi.

The time transfer to Metsähovi, Kirkkonummi, occurs from the UTC-laboratory at VTT MIKES Metrology in Otaniemi via optical fibre using the White Rabbit protocol. VTT MIKES Metrology has been an early adopter of the White Rabbit technology for time transfer across long distances. White Rabbit was developed at CERN, the European Organization for Nuclear Research.

– The link between Metsähovi and the official time of Finland maintained by VTT MIKES was built in early summer and we have studied its functioning and stability during the summer, says Research Manager Jyri Näränen, manager of the Metsähovi Geodetic Research Station.

– The measurements show, for example, how the travel time of light each way in a 50-kilometre fibre optic cable varies by approx. 7 nanoseconds within a 24-hour period as temperature changes affect the properties of the fibre optic cable, particularly its length.

The uncertainty of time transfer is expected to be 100 ps or better. The precision of frequency transfer is currently approx. 15 digits.

Supports geodetic measurements

The time transfer supports geodetic measurements at Metsähovi. The geodetic radio telescope system currently being built requires precise time and frequency information to base measurements on. The new link, together with the atomic clocks of the Metsähovi Radio Observatory also improve the time and frequency precision for all other measurements undertaken at Metsähovi.

Through the time transfer link, Finland's official time can be connected to international geodetic networks, such as global navigation satellite systems (GNSS). At the same time, the Metsähovi Radio Observatory's atomic clocks can be used to support Finland's official time.

The project is a part of the G-EPOS consortium financed by the Academy of Finland's FIRI financing. The time transfer was implemented in cooperation between the Finnish Geospatial Research Institute at the National Land Survey, VTT MIKES, Aalto Universty and CSC-IT Center for Science.

More information

Research Manager Jyri Näränen, +358 50 435 7258, firstname.lastname@nls.fi

Academy of Finland Research Fellow Thomas Fordell , +358 50 443 4218, firstname.lastname@vtt.fi