The performance of the Advanced Geosynchronous Radiation Imager (AGRI) onboard the Fengyun-4 (FY-4) satellite was evaluated. The results showed that its performance has approached the international advanced level of similar instruments. A wavelet filter was designed to filter the striping noises of the AGRI, which come from the inconsistency of the spectrum and thus varies with the observed target. The non-uniformity of the whole image was evaluated by weighting the probability variance of its count values. After filtering, the infrared image of the AGRI had a uniform visual effect on a single channel, and the pattern noise was reduced to below 0.2 K, which ensures the uniformity of products such as cloud detection and sea temperature that use the infrared splitting window channels. Furthermore, the AGRI carries the surface source blackbody as the on-orbit radiation calibration benchmark and rotates the north-south scanning mirror to point to the blackbody to obtain the blackbody observation data in each infrared band. In the current mode, the infrared calibration is performed every 15 minutes. The long-term evaluation results showed that the radiation calibration accuracy of the infrared channels of the AGRI was better than 0.5 K, and some of the channels reached 0.2 K. In addition, the long-term monitoring of the sensitivity and radiative cooling of the AGRI has shown the on-orbit variation of the instrument, which provides a reference for the development of the subsequent instrument.
As a main element of China second generation of geostationary meteorological satellite Fengyun 4B (FY-4B), which was launched on Jun. 03, 2021, the Geostationary High-speed Imager (GHI) is the first round the clock high-frequency imaging instrument working on the international geo-stationary orbit. It can continuously observant and imagine for 2000km×2000km regions with spatial resolution up to 250m in 1 minute interval. The challenge of GHI thermal design was that the sun intrusion of the optic system would induce destabilization of the internal temperature field. It conflicted with the target of the GHI thermal system, which should ensure small temperature difference between two sides of scanner shrouds (less than 3K), the low temperature gradient of optical mounting platform (less than 2K), and high precision temperature control (±0.1K) of blackbody. This paper described the control strategy and requirements of the GHI thermal system, which successfully performs all phases of the mission. The on-orbit data showed that the instrument maintained a stable internal thermal environment when optical system exposed to external heat flux disturbances in mid-night.
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