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Laboratory for Atmospheric and Space Physics

NIST Hosts TIM Optical Power Measurements

December 1, 2006

Since the launch of SORCE in early 2003, the Total Irradiance Monitor (TIM) has been measuring total solar irradiance (TSI) values approximately 0.34% lower than the other currently flying TSI instruments ERBE, VIRGO, and ACRIM3. Recent optical power measurements of the ground-based SORCE/TIM Witness Unit at NIST do not indicate that the TIM is measuring erroneously low by this amount. Such collaborations with NIST throughout the SORCE mission have been extremely valuable to TIM calibrations and uncertainties. (Read more in December 2006 newsletter.)


The NIST laser and optics provide a stable, highpower illumination source for the TIM.

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