China has launched a new remote sensing satellite on Tuesday, with Gaofen-11 departing from LC9 at the Taiyuan Satellite Launch Center on a Long March-4B – Chang Zheng-4B – rocket. The Launch took place at 03:00 UTC.
Previously unannounced, the new satellite, Gaofen-11, is described as an optical remote sensing satellite in the official press releases announcing the launch. No other characteristics of the new satellite were revealed at this time, as can be the case with some Chinese launches.
The Gaofen civilian high-resolution remote sensing satellites (gao fen = high-resolution) are part of a program that is one of the 16 main programs announced by the State Council in a 15 year plan of Chinese national scientific and technology programs between 2006 and 2020.
This program will become the main civilian Earth observation project of China in the next years, combining the use of satellites as well as airplanes and even stratosphere balloons.
The program was started in 2010 and at least 14 satellites are planned, forming a near-real-time, all-weather, global surveillance network for agricultural planning, disaster relief, environment protection, and security purposes.
In May 2010, China officially initiated the development China High-Resolution Earth Observation System (CHEOS), 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.
The Earth Observation System and Data Center, China National Space Administration was established in Mar 2010. The Center is principally responsible for organizing and implementing as well as managing CHEOS. It is also responsible 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 develops space-based system, near space system, aerial system, ground system and application system as a whole to materialize earth observation at high temporal, spatial and spectral resolution, which is now in smooth progress. Overall, to meet the strategic demands of the national economic development and social progress.
The initial plan presented five satellites. Gaofen-1 employs a CAST2000 bus, configured with one 2 meter panchromatic / 8 meter multi-spectral camera and one 16m multispectral medium-resolution and wide-view camera. The satellite realizes an integration of imaging capacity at medium and high spatial resolution and with large swath, with a designed lifespan of over 5 years. It was launched on April 26, 2013.
Gaofen-2 employs CS-L3000A bus, configured with one 1 meter panchromatic/4m multi-spectral camera, with a designed lifespan of over 5 years. The satellite was launched on August 19, 2014.
Gaofen-3 employs CS-L3000B bus, configured with multi-polarized C band SAR at meter-level resolution, with a designed lifespan of 8 years. Gaofen-3 was launched on August 9, 2016.
Gaofen-4 is China’s first geosynchronous orbit remote sensing satellite featuring a visible light and infra-red staring optical imager with a common optical system.
Gaofen-4
The optical resolution is better than 50 meters, while the infrared resolution is better than 400 meters. GF-4 can provide an imaging area of 7,000 km × 7,000 km with individual scene covering an area of 400 km × 400 km, and with capacity for high temporal resolution remote sensing monitor at minute-level. The satellite was launched on December 28, 2015 – from the Xichang Satellite Launch Center using a Long March-3B/G2.
Gaofen-5 is configured with six payloads, including a VIS and SWIR (Shortwave Infrared) hyperspectral camera, spectral imager, greenhouse gas detector, atmospheric environment infrared detector at very high spectral resolution, differential absorption spectrometer for atmospheric trace gas, and a multi-angle polarization detector. Gaofen-5 was launched on May 8, 2018.
The Gaofen-6 is similar to the first Gaofen satellite launched on April 2013, carrying one 2 meter panchromatic camera, an 8 meter multi-spectral camera and one 16m multispectral medium-resolution and wide-view camera. Gaofen-6 was launched on June 2, 2018.
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 back-up launch vehicle for Chang Zheng-3 to launch China’s communications satellites.
Long March 4B via Chinese media
After the successful launch of China’s first DFH-2 communications satellites by Chang Zheng-3, the main 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 an electronic control.
Other modifications were an 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; 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 were 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).