Solar Irradiance at Solar Minima

Solar spectral irradiance (SSI) and total solar irradiance (TSI) have been measured from space over the last few minima. We will report on the irradiance levels during the WHPI campaigns, and compare them to the irradiance levels during the WHI (2008) and WSM (1996) periods. Comparing space-based observations over on decadal timescales requires careful understanding of instrument calibration and uncertainties. We will include such details and assess if there is a statistically significant trend in SSI as a function of wavelength for the three minima.