Introduction to Earth Observation Images and Preprocessing Operational Issues of KARI's Geostationary Satellites

The geostationary satellites operated by the Korea Aerospace Research Institute (KARI), known as the Cheonlian satellite series, include three satellites dedicated to Earth observation missions. Cheonlian 1 (Communication Ocean and Meteorological Satellite; COMS), with a decade-long operation, utilized two onboard instruments (MI, GOCI) for Earth observation missions, accumulating approximately 600,000 images over 10 years. The Earth observation images from Cheonlian 1 can be obtained free of charge through Korean data utilization organizations (National Meteorological Satellite Center, Korea Ocean Satellite Center). The KARI ground station holds complete data related to satellite control and operation, including the Earth observation images from Cheonlian 1. After completing its Earth observation mission, Cheonlian 1 is currently operating only its communication payload. The plan is to continue operations until the launch of Cheonlian 3 in 2027, which will take over communication payload duties. Cheonlian 2A (Geo-KOMPSAT-2A; GK-2A), launched in December 2018, succeeded Cheonlian 1 in meteorological payload Earth observation tasks. Equipped with the Advanced Meteorological Imager (AMI), developed by HARRIS, Cheonlian 2A observes the globe with 16 optical bands, focusing on the Korean Peninsula. Real-time distribution of global observation images in UHRIT, HRIT, and LRIT formats is available. Cheonlian 2B (Geo-KOMPSAT-2B; GK-2B), operated since February 2020, simultaneously operates GOCI-Ⅱ and GEMS instruments for Earth observation missions. These two instruments observe only during daytime unlike meteorological payload. GOCI-Ⅱ performs Earth observation missions with a more diverse set of optical bands compared to GOCI on Cheonlian 1. Utilizing hyperspectral sensors, GEMS observes the Earth in five different areas, enabling more accurate observation of atmospheric characteristics such as aerosols. This paper provides a detailed overview of the observation areas, data types, and validation materials of Earth observation images from KARI's geostationary satellites. Additionally, it will be introduced operational issues related to Earth observation image preprocessing system of currently operational Cheonlian 2A/2B satellites. Operational issues of image preprocessing systems include various events such as failure of image reception due to environmental factors such as Sun and radio interference. Image processing failures, such as software errors, are also part of these problems. We also discuss payload anomalies that occurred during the post-launch stabilization phase. KARI is committed to continuous research and development for the stable operation of geostationary satellites, thereby ensuring the best performance for Earth observation missions.