The Total Solar Irradiance (TSI) Climate Data Record (CDR) measures the spectrally integrated energy input to the top of the Earth's atmosphere at a base mean distance from the Sun (i.e., one Astronomical Unit). The TSI units are Watts per square meter (W m-2). This CDR is constructed using Version 1 of the NASA NOAA LASP (NNL) solar variability models that identify and quantify irradiance change relative to baseline reference Sun conditions at daily, monthly, and yearly intervals.
This CDR applies model coefficients derived from linear regression to proxies of bolometric (i.e., integrated over all wavelengths) change due to facular brightening and sunspot darkening, and compares the results to a composite record of total solar irradiance between 2003 and 2024.
The TSI record is made up of individual measurements made by Total Irradiance Monitor (TIM) instruments on the SOlar Radiation and Climate Experiment (SORCE) mission, the TSI Continuity Transfer Experiment (TCTE), the Total and Spectral Irradiance Sensor (TSIS-1) mission, and the Compact Total Irradiance Monitor (CTIM) flight demonstration. The daily and monthly data records span from 1874 to present, and the yearly data record spans from 1610 to present.
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