Introduction
The Total Irradiance Monitor (TIM) was launched in 
January 2003 on the NASA Earth Observing System (EOS) SOlar Radiation
and Climate Experiment (SORCE). The TIM measures the total solar irradiance (TSI),
the integrated solar radiation incident at the top of the Earth's atmosphere.
The TIM continues this climate record, which began in 1978 and is used to
determine the sensitivity of the Earth's climate
to the natural effects of solar forcing.
The TIM TSI measurements monitor changes in incident sunlight to the Earth's atmosphere via an ambient temperature active cavity radiometer. Using state-of-the-art technologies in its Electrical Substitution Radiometers (ESRs) and taking full advantage of new materials and modern electronics, the TIM measures TSI to an estimated absolute accuracy of 350 ppm (0.035%). Relative changes in solar irradiance are measured to less than 10 ppm/yr (0.001%/yr), allowing determination of possible long-term varations in the Sun's output.
TIM TSI plot for the last 3 months
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