SURF [Synchrotron Ultraviolet Radiation Facility] provides critical calibration for NASA. .

In September 2002, a group from the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado performed the final pre-flight calibration of the EOS SORCE (SOLar Radiation and Climate Experiment) SOLSTICE (SOLar STellar Irradiance Comparison Experiment) A instrument. The calibration was carried out on the NASA-supported spectrometer calibration beam line at the NIST Synchrotron Ultraviolet Radiation Facility (SURF III). This beam line provides a well-characterized source of structureless continuum radiation from 2 nm to 400 nm with a relative uncertainty of 1 % or better.

This version of SOLSTICE is a component of the SORCE satellite that was launched on a Pegasus XL launch vehicle on Jan. 25, 2003. SORCE is a key component of NASA's Earth Observing System (EOS) program and will carry four instruments to measure the solar radiation incident at the top of the Earth's atmosphere (640 km altitude). SOLSTICE consists of a pair of identical spectrometers that will measure spectral irradiance from 115 nm to 300 nm with a resolution of 0.2 nm, and with an absolute uncertainty of better than 5 % and a relative uncertainty of better than 1 %.

Solar ultraviolet radiation at wavelengths below 300 nm is totally absorbed by the Earth's atmosphere. It is the major energy source in the stratosphere and thermosphere and thus determines the upper atmosphere's temperature, structure, composition, and dynamics. Even small variations in the sun's radiation at these short wavelengths lead to significant changes in atmospheric chemistry. SORCE will accurately monitor both the total solar irradiance and its spectral dependence over a period of at least 5 years.

CONTACT: Mitchell Furst, [phone]; [e-mail].