The synchronisation of systems is one of the major issues in critical infrastructures and the digital economy: our societies rely on a Universal Coordinated Time (UTC), calculated by the Bureau International des Poids et Mesures, which has become crucial with industrialisation, globalisation of the economy and the digitalisation/digitalisation of our societies.

The Paris Observatory is the institution designated by decree to elaborate the local value of Universal Time Coordinated, the basis of the French legal time, and to make it available to our Nation. The basis of the French legal time is the realisation of the universal time coordinated by the LNE-SYRTE, and is noted UTC(OP). The National Time References (RNT) service of the LNE-SYRTE of Paris Observatory is in charge of these missions.

UTC(OP) is permanently compared with the national realizations in the world. UTC(OP) is a remarkably stable time scale, driven by some of the best and most operational clocks in the world. UTC(OP) is also one of the 3 best realizations of Universal Time Coordinated.

The SYRTE (Observatoire de Paris and Paris Sciences et Lettres, CNRS, Sorbonne University and Laboratoire National d’Essais) continues to make UTC(OP) available and disseminates legal time by different means, which meet the needs of a very large number of users:

• by NTP (Network Time Protocol, free service, about 1 million requests per hour);
• by receiving a time signal transmitted on long wave (162 kHz): ALS162 (free, 200,000 clocks);
• by receiving satellite signals, in particular GNSS systems such as the American GPS and the European systems GALILEO and EGNOS;
• by using a service operated by a third party
• by calibration

For users for whom timing accuracy is important, they can, in particular, depending on their performance needs:

1. exploit the web page https://heurelegalefrancaise.fr/ and analyse the desynchronisation information between their equipment and our NTP servers;
2. Exploit the signal of the ALS162 long wave transmitter, using a receiver and a suitable method. The ALS162 signal includes a time code generated from clocks located at the transmitter, connected by satellite link to UTC(OP);
3. Use the SCPTime service to disseminate time via the Internet. The primary production servers are hosted at Paris Observatory and directly referenced on UTC(OP);
4. Use a COFRAC accredited laboratory for time frequency;
5. For the users of GNSS signals, we provide them with our monitoring data with respect to UTC(OP) of the time scales disseminated by GNSS and carry out relative calibrations of stations for laboratories and industrialists specialized in time-frequency. SYRTE has developed a connection software available on its website to facilitate these scientific uses.

The laboratory is also a major player in the generation of the international time scale UTC computed by the BIPM by providing data from its clock ensemble, and in particular the primary frequency standards developed in the laboratory, which achieve frequency accuracy in the range 1E-16.

UTC(OP) is one of the 5 time scales generated in a European metrology laboratory used to drive the time reference of the European satellite positioning system GALILEO. UTC(OP) is the only real time realisation of UTC broadcast by the EGNOS system.

The laboratory also conducts world-class research activities on the development of new generation clocks operating in the optical domain and on the improvement of time and frequency reference dissemination means, by satellite on a global scale and by optical fibre on a continental scale.

To get the legal time by NTP:
https://heurelegalefrancaise.fr/

For more information:
https://syrte.obspm.fr/spip/services/ref-temps/
https://syrte.obspm.fr/spip/services/ref-temps/article/deux-references-de-temps-sont-produites-et-diffusees-par-le-service-des-rnt
https://syrte.obspm.fr/spip/services/ref-temps/article/donnees-rnt