Spaceborne Relative Radiometer: Instrument Design and Pre-Flight Test

In order to simultaneously determine the values of total solar irradiance (TSI) and Earth’s radiation at top atmosphere (TOA) on board Fengyun-3F satellite, a spaceborne relative radiometer (SRR) was developed. It adopts dual-channel structure, including channel (SR) with an unobstructed field view (FOV) 1.5° Earth (ER) wide (WFOV) 95.3° diameter about 1900 km ground. Before launch, both SR ER were calibrated. The SR, installed inner frame tracker SIM-II (solar monitor-II), is used observe rapid changes in radiance SIAR absolute radiometer), electrical-substitution radiometer, orbit. mounted U-shaped tracker, directly pointing nadir direction. Additionally, dark space observation mode on-orbit background noise lunar for calibration. this article, instrument design working principle SRR first introduced, analysis measurement model ER, WFOV SRR, focused on. Finally, ground test results are introduced.