Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Webpage for Optical Technology Division: SIRCUS Facility



Sally S. Bruce, Steven W. Brown, Keith R. Lykke


Spectral irradiance and Radiance Calibrations with Uniform Sources (SIRCUS) is a reference calibration facility that transfers detector based spectral irradiance scales derived from the High Accuracy Cryogenic Radiometer, to broadband filtered detector packages, to transfer-standard spectral irradiance detectors, and to instruments that measure spectral radiance. This facility will be used to realize NIST's illuminance, luminous intensity, radiance temperature, color temperature, and sprectal radiance scales, improving their uncertainties and self-consistency.
Electronic Publication


radiance calibrations, spectral irradiance, uniform sources
Created May 1, 2002, Updated February 17, 2017