Sequential event or occurrence
The redefinition of the International System of Units (SI) took place on 20 May 2019, with the second now based on a physical constant - the transition frequency of a caesium atom [1]. This significant change has a profound impact on technologies that rely on precise time measurements, such as the Global Positioning System (GPS).
The Measurement Standards Laboratory of New Zealand (MSL) plays a crucial role in maintaining the time for New Zealand with three atomic clocks. These clocks, primarily based on caesium and rubidium standards, are the backbone of GPS functionality [2].
GPS satellites carry these highly stable atomic clocks, which output ultra-precise time signals. GPS receivers use these signals to triangulate their exact position by measuring the time delay of signals from multiple satellites. The accuracy of GPS positioning directly depends on the accuracy of these satellite clocks [2][4].
Caesium clocks, in particular, define the international second, measuring time by tuning microwaves to resonate with caesium-133 atoms. The current SI second is defined as exactly 9,192,631,770 cycles of this radiation, making caesium clocks extremely stable and reliable [4]. They can lose only about one second every 300 million years, making them ideal for reference time in GPS satellites.
Rubidium clocks are also used in GPS satellites as they provide very stable short-term timing signals, although their long-term stability is generally not as good as caesium clocks. However, they are smaller, less expensive, and more compact, so often are used alongside caesium clocks in satellites to balance precision and cost [2].
Although atomic clocks on satellites are very stable over several hours, they do drift if left unsynchronized indefinitely. GPS systems regularly synchronize satellite clocks with highly precise ground-based reference clocks to maintain overall system accuracy. This synchronization ensures the global GPS network maintains consistent and accurate time, which is crucial for positioning [2].
Since GPS determines location by measuring how long signals take to travel from satellites to a receiver, any tiny error in time measurement translates into large errors in distance and thus position. A timing error of just one microsecond can cause a positioning error of roughly 300 meters. Therefore, the extreme stability and accuracy of atomic clocks enable the navigation precision that users rely on [3].
Advancements in atomic clock technology are promising even more accurate timing in the future. Newer optical atomic clocks (using elements like rubidium and ytterbium) are being developed to outperform current GPS clocks by orders of magnitude in precision [1]. These advancements could potentially increase GPS navigation accuracy and reliability.
The presentation about the redefinition of the SI was filmed at Unleash Space, Faculty of Engineering, Auckland University. The presentation was by Peter Saunders and Farzana Masouleh of MSL, and the filming and editing were done by Jonathon Potton of Chillbox Creative. The rights for this video clip belong to the Measurement Standards Laboratory of New Zealand, and it was published by Referencing Hub media [5].
References:
[1] NIST. (n.d.). New SI Definition of the second. Retrieved from https://www.nist.gov/pml/time-and-frequency-division/new-si-definition-second
[2] MSL. (2019). Atomic clocks in GPS. Retrieved from https://www.measurement.govt.nz/our-science/atomic-clocks-gps
[3] MSL. (2019). Why time is critical in GPS. Retrieved from https://www.measurement.govt.nz/our-science/atomic-clocks-gps/why-time-is-critical-in-gps
[4] MSL. (2019). Caesium and Rubidium atomic clocks. Retrieved from https://www.measurement.govt.nz/our-science/atomic-clocks-gps/caesium-and-rubidium-atomic-clocks
[5] Referencing Hub. (2019). MSL: The Measurement Standards Laboratory. Retrieved from https://www.referencinghub.com/new-zealand/msl-the-measurement-standards-laboratory-373853
Science plays a significant role in the advancement of health-and-wellness and fitness-and-exercise technologies, as seen in the precision provided by GPS systems through the use of atomic clocks. These technological advancements, such as those furthering the accuracy of atomic clocks, can lead to general-news headlines that highlight breakthroughs in science. For instance, the redefinition of the International System of Units (SI), which has profound impact on various technologies like GPS, was filmed at Unleash Space, Faculty of Engineering, Auckland University.
