Evaluation of Dependencies of Critical Infrastructure Timing Systems on the Global Positioning System (GPS) [open pdf - 5MB]
From the Abstract: "Accurate and reliable time signals are an essential part of critical infrastructure systems in the United States. Because these systems often cannot function properly without accurate time signals, timing system failures can have serious consequences, with the potential implications including economic loss, reduced safety and security, and loss of human life. The primary time synchronization sources for these systems are signals broadcast by Global Positioning System (GPS) satellites, which has understandably led to concerns about our dependency on GPS timing. This report provides an overview of how timing systems work and defines some basic terminology and specifications. It then discusses the regulatory timing requirements and GPS timing dependencies of United States critical infrastructure systems operating in the financial, telecommunications, and electric power sectors."
NIST Technical Note 2189; National Institute of Standards and Technology Technical Note 2189
National Institute of Standards and Technology: https://www.nist.gov/