An official website of the United States government
Here’s how you know
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.
We are developing a comprehensive next-generation greenhouse gas (GHG) calibration system capable of extending SI traceability to global satellite remote
The very best atomic clocks today are known as optical clocks, because their timebase resides at a very high frequency (~10 15 Hz), corresponding to the optical