<p>The GOES-R series of satellites includes a redesigned instrument for solar spectral irradiance: the Extreme ultraviolet and X-ray Irradiance Sensor (EXIS).&#160; Our team will be using a high-cadence broadband visible light diode to construct a proxy for Total Solar Irradiance (TSI).&#160; This will have two advantages over the existing TSI measurements:&#160; measurements are taken at 4 Hz, so the cadence of our TSI proxy is likely faster than any existing applications, and the observations are taken from geostationary orbit, so the time series of measurements is virtually uninterrupted.&#160; Calibration of the diode measurements will still rely on the standard TSI composites.&#160;&#160;</p><p>The other measurement from EXIS that will be used is the Magnesium II core-to-wing ratio.&#160; The MgII index is a proxy for chromospheric activity, and is measured by EXIS every 3 seconds.&#160; The combination of the two proxies can be used to generate a model of the full solar spectrum similar to the NRLSSI2 empirical model.</p><p>We are in the first year of a three-year grant to develop the TSI proxy and the SSI model, so only very preliminary findings will be discussed in this presentation.</p>