Following the successful launch and return of its recoverable experimental spaceplane, China launched another remote sensing satellite on September 7, 2020, from the Taiyuan Satellite Launch Center. Launch of the Gaofen-11 (02) took place at 05:57 UTC from the LC9 Launch Complex using the Long March-4B – Chang Zheng-4B – Y46 rocket.
The second Gaofen-11 satellite is, according to official news sources, an optical remote sensing satellite with a ground image resolution up to the sub-meter level.
It will be mainly used in land census, urban planning, land rights, road network design, crop estimation, and disaster prevention and mitigation, and other fields. It can also provide information security for the “Belt and Road” construction and other major national strategic implementation and national defense modernization to provide information security.
To meet the requirements of the satellite protection and security, the rocket was equipped with a four-meter diameter reactive payload shroud and used high-altitude wind passive load reduction technology. With this technology, the additional loads caused by high-altitude wind were reduced, enhancing the rocket’s ability to adapt to the wind field. At the same time, this model, for the first time, added a wireless environmental monitoring system, which simplifies the detection of the temperature and humidity environment in the satellite fairing in the launch area.
Gaofen (“High Resolution”) is a series of civilian Earth observation satellites developed and launched for the state-sponsored program China High-definition Earth Observation System (CHEOS).
In May 2010, China officially initiated the development of the CHEOS system, which is established as one of the major national science and technology projects.
The Earth Observation System and Data Center of China National Space Administration (EOSDC-CNSA) is responsible for organizing the construction of the CHEOS that is a near-real-time, all-weather, global surveillance network consisting of the satellite, stratosphere airships, and aerial observation platforms.
The Earth Observation System and Data Center, China National Space Administration was established in March 2010.
The Center is principally responsible for organizing and implementing as well as managing CHEOS. It is also accountable for EO application services, commercial development, technology consultant, and international cooperation.
By following an arrangement of integral observation from space, air, and ground, the CHEOS is developing a space-based system, near-space system, aerial system, ground system, and application system.
This is to create Earth observation at a high temporal, spatial, and spectral resolution, which is making good progress.
The feasibility study of the CZ-4 Chang Zheng-4 began in 1982 based on the FB-1 Feng Bao-1 launch vehicle. Engineering development was initiated in the following year. Initially, the Chang Zheng-4 served as a backup launch vehicle for Chang Zheng-3 to launch China’s communications satellites.
After the successful launch of China’s first DFH-2 communications satellites by Chang Zheng-3, the primary mission of the Chang Zheng-4 was shifted to launch sun-synchronous orbit meteorological satellites. On the other hand, the Chang Zheng-4B launch vehicle was first introduced in May 1999 and also developed by the Shanghai Academy of Space Flight Technology (SAST), based on the Chang Zheng-4.
The rocket is capable of launching a 2,800 kg satellite into low Earth orbit, developing 2,971 kN at launch. With a mass of 248,470 kg, the CZ-4B is 45.58 meters long and has a diameter of 3.35 meters.
SAST began to develop the Chang Zheng-4B in February 1989. Originally, it was scheduled to be commissioned in 1997, but the first launch didn’t take place until late 1999. The modifications introduced on the Chang Zheng-4B included a larger satellite fairing and the replacement of the original mechanical-electrical control on the Chang Zheng-4 with electronic control.
Other modifications were improved telemetry, tracking, control, and self-destruction systems with smaller size and lighter weight, a revised nozzle design in the second stage for better high-altitude performance. Additional advanced included a propellant management system for the second stage to reduce the spare propellant amount, thus increasing the vehicle’s payload capability and a propellant jettison system on the third-stage.
The first stage has a 24.65-meter length with a 3.35-meter diameter, consuming 183,340 kg of N2O4/UDMH (gross mass of the first stage is 193.330 kg). The vehicle is equipped with a YF-21B engine capable of a ground thrust of 2,971 kN and a ground specific impulse of 2,550 Ns/kg. The second stage has a 10.40-meter length with a 3.35-meter diameter and 38,326 kg, consuming 35,374 kg of N2O4/UDMH.
The vehicle is equipped with a YF-22B main engine capable of a vacuum thrust of 742 kN and four YF-23B vernier engines with a vacuum thrust of 47.1 kN (specific impulses of 2,922 Ns/kg and 2,834 Ns/kg, respectively).
The third stage has a 4.93-meter length with a 2.9-meter diameter, consuming 12,814 kg of N2O4/UDMH. Having a gross mass of 14,560 kg, it is equipped with a YF-40 engine capable of a vacuum thrust of 100.8 kN and a specific impulse in a vacuum of 2,971 Ns/kg.
Situated in the Kelan County in the northwest part of the Shanxi Province, the Taiyuan Satellite Launch Center (TSLC) is also known by the Wuzhai designation. It is used mainly for polar launches (meteorological, Earth resources, and scientific satellites).
The launch center has two single-pad launch complexes, a technical area for rocket and spacecraft preparations, a communications center, a mission command and control center, and a space tracking center.
The stages of the rocket are transported to the launch center by railway and offloaded at a transit station south of the launch complex. They were then transported by road to the technical area for checkout procedures.
The launch vehicles were assembled on the launch pad by using a crane at the top of the umbilical tower to hoist each stage of the vehicle in place. Satellites were airlifted to the Taiyuan Wusu Airport about 300km away and then transported to the center by road.
The TT&C Centre, also known as Lüliang Command Post, is headquartered in the city of Taiyuan. It has four subordinate radar tracking stations in Yangqu (Shanxi), Lishi (Shanxi), Yulin (Shaanxi), and Hancheng (Shaanxi).