Abstract
The final version (V.19) of the total solar irradiance data from the SOlar Radiation and Climate Experiment (SORCE) Total Irradiance Monitor has been released. This version includes all calibrations updated to the end of the mission and provides irradiance data from 25 February 2003 through 25 February 2020. These final calibrations are presented along with the resulting final data products. An overview of the on-orbit operations timeline is provided as well as the associated changes in the time-dependent uncertainties. Scientific highlights from the instrument are also presented. These include the establishment of a new, lower TSI value; accuracy improvements to other TSI instruments via a new calibration facility; the lowest on-orbit noise (for high sensitivity to solar variability) of any TSI instrument; the best inherent stability of any on-orbit TSI instrument; a lengthy (17-year) measurement record benefitting from these stable, low-noise measurements; the first reported detection of a solar flare in TSI; and observations of two Venus transits and four Mercury transits.
Highlights
The total solar irradiance (TSI) is the spatially and spectrally integrated radiant energy from the Sun at a distance of one astronomical unit
While still employing the same fundamental concepts of electrical substitution radiometry as all other TSI instruments, the Total Irradiance Monitor (TIM) onboard the Solar Radiation and Climate Experiment (SORCE) mission (Rottman, 2005) introduced several new instrument improvements described by Kopp and Lawrence (2005) and briefly summarized here: i) This was the first instrument to place the precision aperture, which accurately determines the area over which the incident sunlight is collected, at the front of the instrument instead of deep inside, reducing scatter
The final mission values for these are applied in V.19 data and described below
Summary
The total solar irradiance (TSI) is the spatially and spectrally integrated radiant energy from the Sun at a distance of one astronomical unit. While still employing the same fundamental concepts of electrical substitution radiometry as all other TSI instruments, the Total Irradiance Monitor (TIM) onboard the Solar Radiation and Climate Experiment (SORCE) mission (Rottman, 2005) introduced several new instrument improvements described by Kopp and Lawrence (2005) and briefly summarized here: i) This was the first instrument to place the precision aperture, which accurately determines the area over which the incident sunlight is collected, at the front of the instrument instead of deep inside, reducing scatter. Most notable is the TIM’s establishment of the now-accepted, lower TSI value than that measured prior to the SORCE launch (Kopp, Lawrence, and Rottman, 2005; Kopp and Lean, 2011) This value is the IAU-accepted solar-irradiance value (Prša et al, 2016) and has helped reduce differences between measured incoming and outgoing radiation (Loeb et al, 2012; L’Ecuyer et al, 2015; Loeb and NCAR Staff, 2018) to better understand the Earth’s radiation imbalance. Details of the instrument design and functionality are not described; for those, see Kopp and Lawrence (2005) and Kopp, Heuerman, and Lawrence (2005)
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