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Laboratory for Atmospheric and Space Physics


The Sun has both direct and indirect influence on the terrestrial system; and appropriate measurements of both total and spectral solar irradiance provide the requisite understanding of one of the primary climate system variables. SOLSTICE provides precise daily measurements of solar spectral irradiance at ultraviolet wavelengths. Even small variations in the Sun’s radiation at these short wavelengths lead to changes in atmospheric chemistry. Although the ultraviolet radiation from the Sun varies by as much as a factor of 2, its measurement requires access to space since this radiation does not penetrate the atmosphere. Also, the variability of solar ultraviolet radiation over an 11-year solar cycle is a strong function of wavelength, leading to varying requirements for different portions of the ultraviolet spectrum. The SOLSTICE measurements provide coverage from 115 nm to 320 nm with a spectral resolution of 0.1 nm, an absolute accuracy of better than 5%, and a relative accuracy of 0.5% per year.

Table 1: SOLSTICE Properties

Instrument Type Modified Monk-Gilleison spectrometers
Detector Type photomultiplier tubes
Wavelength Range 115 – 310 nm
Resolution 1 nm
Absolute Accuracy 1.2-6%
Relative Accuracy 0.2-2.6%/year
Dimensions (H×W×D) 18.3 × 38.7 × 84.6 (×2) cm
Mass 36.0 kg (total)
Power 33.2 watts (total)
Nominal Data Rate 738 bps (total)
Field-of-View 1.5° × 1.5° (uncalculated) and 0.75° × 0.75° (calculated)