China has launched a second Gaofen 3C-band satellite to remote sensing and earth observation. The launch was conducted on November 22 at 23: 45 UTC from launch pad SLS-2 (South Launch Site-2) of the Jiuquan Satellite Launch Center (JSLC).
The Gaofen-3 satellites are based on the CS-L3000B bus, built for a lifetime of up to eight years. They have a Synthetic Perturber Radar (SAR), a data transmission system, and use Control Moment Gyros for space orientation.
The Gaofen 3 series is built and developed at the China Academy of Space Technology, which is part of China Aerospace Science and Technology Corporation. They are China’s main spacecraft development and production center and participated in the launch of Dong Fang Hong I, the first artificial satellite.
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.
Video including some pre-dawn drone views: pic.twitter.com/GuPv2XzbIL
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To oversee and execute the program, the Earth Observation System and Data Center – China National Space Administration (EOSDC-CNSA) was founded. It is part the “One Belt One Road” regional development project by the Chinese government. It provides environmental and geographical mapping, as well as prevention and observation of disasters.
Gaofen 3-02 will work with the original Gaofen-3 satellite, launched in August 2016 to a 735×747 km Sun-synchronous orbit, and will focus on ocean observation with an image resolution of one meter.
The first launch of a Gaofen (“high resolution”) happened in April 2013 on a Chang Zheng 2D. After that, 22 more Gaofen satellites entered service, with the latest installment being the Gaofen-5-02 mission in September 2021.
The vehicle used for this mission was Chang Zheng 4C. Long March 4C is the international name. It is 45.8 meters tall with a diameter of 3. 35 meters and a liftoff mass of about 250,000 kg — with the majority of this being the first stage.
The Chang Zheng 4C (CZ-4C) is mainly used for low Earth orbit (LEO) and Sun-synchronous orbit (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.
The rocket has launched 37 times, including this mission, of which 35 were a success. The last failure occurred in May 2019 after the second stage underperformed for an unknown reason resulting in the loss of the Weixing-33 satellite. One year later, the satellite was repaired.
The first stage of the CZ-4C stands 27. 91 meters tall and has a liftoff mass of 182,000 kg. It is powered by four YF-21C engines which run on dinitrogen tetroxide and unsymmetrical dimethylhydrazine. This combination was also used to power the Dongfeng 5 missiles.
The engines provide a liftoff thrust of 2,961.6 kN and a specific impulse of 260 seconds. The four engines are an updated version of the YF-21, which originally flew on the Chang Zheng 2A. The engines can be used on the Chang Zheng 2, 3 and 4.
The second stage, with a length of 10.9 meters and the same diameter, uses a single YF-22C engine that produces a thrust of 742. 04 kN along the four YF-23C vernier engines to steer the second stage on its way to orbit. In this configuration, the whole set of engines is called the YF-24C. It runs on the same fuel as the first stage.
The last stage has a smaller diameter of only 2.9 meters and a length of 14. 79 meters. Its one YF-40 gas generator engine runs on the same fuel combination as the first two stages, but with a thrust of 100 kN and a specific impulse of 412 seconds, it is used to place payloads into the desired orbit.
The rocket flew from the JSLC, which was first opened in 1958. It was named after Jiuquan, Gansu Province. It can be used to launch a variety of vehicles. It has three launch areas and six pads. Currently, the center supports launch capabilities for the CZ-2C/2D/4B, the CZ-4C, and CZ-11.
While the Wenchang Spacecraft Launch Site is closer to the coast so launches don’t potentially endanger populated regions, the Jiuquan launch complex is inland. The rocket’s flight path can pose a danger to villages if there are any falling stages.
Overall, this mission was the 45th Chinese launch in 2021, with two more planned this week in the Ceres-1 mission on November 24 and a Chang Zheng 3B/E launch on November 26.
(Lead image: A Chang Zheng 4C lifts off with Gaofen 3-02)