A resilient architecture for the realization and distribution of coordinated universal time to critical infrastructure systems in the United States :

The Time and Frequency Division of the National Institute of Standards and Technology (NIST), an agency of the United States Department of Commerce (DOC), was tasked with fulfilling Section 4, Part (i) of the Position, Navigation and Timing (PNT) Executive Order that was signed by the President on February 12, 2020. The Executive Order states that Within 180 days of the date of this order, the Secretary of Commerce shall make available a GNSS-independent source of Coordinated Universal Time, to support the needs of critical infrastructure owners and operators, for the public and private sectors to access. Although the Executive Order does not specifically provide an accuracy requirement, this report assumes an accuracy requirement of 1 ?s with respect to Coordinated Universal Time (UTC). This specification is assumed because numerous critical infrastructure timing systems in the United States are now heavily dependent on signals received from the Global Positioning System (GPS) satellites that routinely provide sub-microsecond accuracy, and other UTC sources that deliver time at comparable accuracy levels are needed to alleviate or reduce these dependencies. This report was written to describe, propose, and recommend technical methods that NIST has already implemented, or can potentially implement, to fulfill Section 4, Part (i) of the PNT Executive Order.