22 Nov 2021: China launched a CZ-4C (Long March 4C) containing the second Gaofen (“high resolution”) 3 from Jiuquan Satellite Launch Center (JSLC) pad SL-2 (South Launch Site 2). The Gaofen-3 is a C-band radar imaging satellite, used for remote sensing and Earth observation.
– The Gaofen-3 satellites are based on the CS-L3000B bus, built for a lifetime of up to 8 years. They are equipped with a Synthetic Aperture Radar (SAR), a data transmission system, and utilize Control Moment Gyros (CMGs) for orientation in space.
– This satellite is part of the Chinese High-resolution Earth Observation System (CHEOS) program, which was proposed in 2006 and initiated in 2010 with the goal to improve and update China’s Earth observation system.
– It is part of the Chinese government’s “One belt one road” regional development project and provides geographical and environmental mapping as well as disaster observation and prevention.
– Gaofen 3-02 will work with the original Gaofen-3 satellite, launched in Aug 2016 to a 735×747 km Sun-synchronous orbit (SSO), and focus on ocean observation with an image resolution of one meter.
– Sun-synchronous orbit (SSO) is a special type of orbit which nearly passes over the planet’s poles. Each time the satellite passes over any location on Earth, it is always the same local solar time.
– The satellite was developed by the China Academy of Space Technology (CAST) and features upgrades over the first Gaofen-3, including optimized imaging, improved ship-positioning technology and real-time onboard processing that makes imagery available much faster than transmitting raw data does.
– The Chang Zheng 4C (CZ-4C) is mainly used for low Earth orbit (LEO) and SSO missions, like this particular one. It can lift 4,200 kg to LEO and 2,800 kg to SSO. The launch mass of this payload is reported to be about 2,779 kg.