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An electronic optical camera is installed in the earth observation satellite, which takes pictures of the ground objects in the visible spectrum range that can be seen with the naked eye.
Based on the technology acquired from the development of Korea Multi-Purpose Satellites Arirang 1 and 2, KARI independently developed the world-class electro-optical payloads AEISS (Advanced Earth Imaging Sensor System) and AEISS-A (Advanced Earth Imaging Sensor System-A). AEISS and AEISS-A were installed in Arirang 3 and 3A, respectively.
The AEISS accommodated on Arirang 3 is a 70cm resolution optical camera, which means that it can make the image of each people on the ground into a dot which can be distinguished from adjacent ones and accurately identify small cars moving on the ground while the satellite flies at 7km/s at an altitude of around 700km, which is roughly the distance between Pyeongyang and Jeju Island. For a commercial purpose observation satellite, this performance is among the world's top 5.
With the exception of the part manufacturing, AEISS was developed by KARI from its design to the assembly, alignment, and testing, as well as the final verification test in the space environment.
Since a high performance camera like AEISS can be hardly developed through technology transfer or joint development, it is a technology that must be thoroughly acquired in house for the successive development and improvement of the high-performance earth observation satellites.
The development process is also very complicated. First of all, ultra-precision technology to the level of 1/5000 of a human hair is needed for the assembly of an optical system mainly consists of the reflectors and the structures. Moreover, even micro-vibrations generated by a human or vehicle near the building can cause a measurement error. This ultrasensitive instrument must be operated for 3~7 years under vacuum conditions and temperature difference of more than 100°C after withstanding a launch environment which gives shocks tens of times of gravity. That is why only a few counties such as the US, and France have been able to develop the state-of-the-art satellites with the electro-optical cameras like AEISS.
AEISS-A is a sister model of AEISS developed by KARI. Its optical resolution is 55cm, and it includes an IR channel to enable nighttime photography and heat sensing. To achieve this, the electronic module of AEISS was upgraded, and the IR channel developed in Korea was added to it. The higher resolution was obtained by solving the problems related to the shorter integration time and undesirable noise signals caused by lowering the altitude from 685km to 528km.