NOTICE: Due to a lapse in annual appropriations, most of this website is not being updated. Learn more.
Form submissions will still be accepted but will not receive responses at this time. Sections of this site for programs using non-appropriated funds (such as NVLAP) or those that are excepted from the shutdown (such as CHIPS and NVD) will continue to be updated.
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.
This document describes the process of the realization, the maintenance and the dissemination of the spectral irradiance scale and its accompanying uncertainties at the National Institute of Standards and Technology. It describes the measurement procedures for the realization of the scale and the uncertainties of the detector-based spectral irradiance scale. During the realization process, the spectral irradiances are ultimately made Système International d'Unités (SI) traceable to the unit of electrical power through the electrical-substitution cryogenic radiometer and the unit of length through the aperture area and the distance measurements. This document also contains a representative calibration report and values for the NIST-disseminated spectral irradiance standards along with the irradiance calibration procedures manual.
Yoon, H.
and Gibson, C.
(2011),
SP250 Spectral Irradiance Calibrations, Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD, [online], https://doi.org/10.6028/NIST.SP.250-89
(Accessed October 10, 2025)