Arrival of the Sequel
In a recent presentation at Auckland University, the Measurement Standards Laboratory of New Zealand (MSL) discussed the redefinition of the International System of Units (SI) and its impact on GPS systems. The event, filmed and edited by Jonathon Potton of Chillbox Creative, was held at Unleash Space, Faculty of Engineering.
At the core of the GPS system's timing mechanism are atomic clocks, specifically Caesium and Rubidium atomic clocks. These clocks, aboard GPS satellites, generate precise time references by measuring the vibrations of atoms—Caesium clocks use the hyperfine transition in Caesium atoms, while Rubidium clocks use Rubidium atoms. Both types produce stable microwave frequencies used to time-stamp signals broadcast by satellites.
GPS positioning is calculated by comparing the time code sent simultaneously from multiple satellites. Any inaccuracy or drift in the clocks causes errors in distance calculation, directly impacting location accuracy. Without atomic clocks, errors would accumulate rapidly and make GPS unusable.
Although extremely precise, satellite clocks still experience drift due to relativistic effects. To counter this, satellite clocks require continual synchronization and periodic corrections by ground control stations using even more accurate atomic clocks.
Advances in Rubidium and Caesium atomic clocks have enabled the current standard of GPS timing accuracy, supporting not only position but also global time synchronization needed for telecommunications, power grids, and other critical infrastructures.
Emerging optical atomic clocks, using Rubidium and other elements, demonstrate the potential for even greater timing precision beyond current microwave-based atomic clocks. This could improve future navigation systems and provide robust alternatives in contested or GPS-denied environments.
The MSL, responsible for keeping the time in New Zealand, produced videos to share the story of metrology development. These videos, published by Referencing Hub media, highlight the crucial role of atomic clocks in GPS systems. New Zealand's time is kept by three atomic clocks at the MSL.
The redefined second, officially defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the unperturbed ground state of the Cs atom, underscores the importance of these clocks. The frequency (Δν) of Caesium atoms in these clocks has a fixed numerical value of 9,192,631,770 Hz, making them incredibly stable and accurate, with an accuracy of 1 second every 30 billion years.
In summary, Caesium and Rubidium atomic clocks aboard GPS satellites serve as the primary timing reference necessary for precise distance measurements that enable the GPS system’s accurate global positioning service. Their unparalleled accuracy, combined with ground-based corrections, underpins the entire GPS infrastructure.
- The redefinition of the International System of Units (SI) has significant implications for various sectors, as it directly impacts the stability and accuracy of Caesium and Rubidium atomic clocks, which are essential for health-and-wellness applications, such as fitness-and-exercise wearables using GPS technology, for measuring distance and time during workouts.
- Updated advancements in atomic clocks, particularly optical clocks using Rubidium and other elements, are poised to revolutionize science, in areas like health-and-wellness (due to improved fitness trackers), as well as technology, by providing higher precision timing that could enhance general-news sectors, like telecommunications and power grids, for more efficient and reliable service.
