The Fengyun-3E/Joint Total Solar Irradiance Absolute Radiometer: Instrument Design, Characterization, and Calibration

Solar Irradiance Variability Monitor for the Galileo Solar Space Telescope Mission: Concept and Challenges

“…The radiometers' cross-calibrations and overlapping observations between the different instruments are essential to the TSI reconstruction. JTSIM includes two instruments, digital absolute radiometer (DARA) and the solar irradiance absolute radiometer (SIAR), on the same pointing system to monitor TSI at the same time in orbit for 8 years [72]. These observations can provide important information on each instrument's stability.…”

“…The relation between electrical and optical power only has been guaranteed by the careful design of the critical components and each component's characterization and proper radiometer calibration. In order to measure the TSI, the characterization include analysis such as non-equivalence, cavity absorptance, radiation from background space, diffraction-losses, the Earth-Sun distance coefficient, Doppler-effect coefficient, for correction factor [72,73].…”

“…In practice, the blackbody absorbers are cavities to improve the absorption of solar radiation. Commonly, the cavities are made of silver to increase thermal diffusivity along the cone [72][73][74][75]. ACRIM prevented heat transfer to the environment by aluminized Kapton shields [74], while TIM, CLARA, and JTSIM plated gold outside to minimize the radiative losses.…”

“…The effects of non-equivalence are minimized using high conductive material cavities, thin walls, a meticulous combination of electric and radiant heating, and ensuring the excellent connection of the interfaces, guaranteeing long periods of operation. In practice, the ultrasonic welding technique used in the DARA detector is an option implemented to connect cavity and heat link interfaces manufactured in one aluminum piece with the heat sink [72,75].…”

Preface to Monitoring the Earth Radiation Budget and Its Implication to Climate Simulations: Recent Advances and Discussions

“…Among them the Variability of Irradiance and Gravity Oscillations (VIRGO) on the mission Solar and Heliospheric Observatory (SOHO), which started in 1996 and is still operational (Finsterle et al, 2021;Fröhlich et al, 1997), and the experiments Precision Monitoring of Solar Variability (PREMOS) on the PICARD satellite (2010-2014) (Schmutz et al, 2013). Recent missions include TSIS-1/TIM (2018 to present) (Kopp, 2016), the Compact Lightweight Absolute RAdiometer (CLARA) (Finsterle et al, 2014;Walter et al, 2017Walter et al, , 2020 onboard the Norwegian NorSat-1 microsatellite (2018 to present) and the Davos Absolute Radiometer (DARA) embedded on the Fengyun 3E (FY-3E) spacecraft launched the fourth of July 2021, part of the Joint Total Solar Irradiance Monitor (JTSIM) built by the Changchun Institute of Optics, Fine Mechanics and Physics Chinese Academy of Sciences in Changchun, China (Song et al, 2021). Later in 2024, another DARA instrument will be launched on the PROBA-3 mission operated by the European Space Agency (Montillet et al, 2023).…”