Long March 4C launches Gaofen-3 Earth Observation Satellite
The long awaited launch of Gaofen-3 took place on Tuesday, lofted via the Chinese Long March-4C (Chang Zheng-4C) launch vehicle. The rocket, launched from the Taiyuan Satellite Launch Center’s LC9 Launch Complex at 22:55 UTC, successfully orbited the new addition to the Gaofen fleet of remote sensing satellites.
Designed by CAST (China Academy of Space Technology), Gaofen-3 employs the CS-L3000B bus configured with multi-polarized C-band SAR at meter-level resolution.
The new satellite has a designed lifespan of eight years and will mainly be used by the State Oceanic Administration (SOA) of China.
Development of the new satellite was initiated in December 2010, with the engineering development beginning in September 2013. The satellite was completed in March 2016.
Gaofen (meaning “High Resolution”) is a series of civilian Earth observation satellites developed and launched for the state-sponsored program known as the 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 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 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 a 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 uses a CAST2000 bus, configured with one 2 meter panchromatic, an 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 designed lifespan of over 5 years. It was launched on April 26, 2013.
Gaofen-2 employs the CS-L3000A bus, configured with one 1 meter panchromatic/4m multi-spectral camera, with designed lifespan of over 5 years. The satellite was launched on August 19, 2014.
Gaofen-4 was developed by CAST and is based on the new GEO remote-sensing satellite bus. It has orbital mass of 4,600 kg and was designed for a life span of 8 years. The satellite was placed into orbit by a Long March-3B launch vehicle from the Xichang Satellite Launch Centre on 29 December, 2015.
The future spacecraft, Gaofen-5, sports a SAST5000B bus and is configured with six types of payloads, including visible and short-wave infra hyper-spectral camera, spectral imager, greenhouse gas detector, atmospheric environment infrared detector at very high spectral resolution, differential absorption spectrometer for atmospheric trace gas, and multi-angle polarization detector.
It is designed for 8 years and is scheduled to launch in 2017.
On June 26, 2015, China launched the Gaofen-8 satellite. Developed by the China Aerospace Science and Technology Corporation (CASC), the satellite is part of a civilian program whose aim is to facilitate climate surveying, disaster response, precision agriculture mapping, urban planning and road network design.
Its imagery will be mostly used by the Ministry of Land and Resources, the Ministry of Environmental Protection, and the Ministry of Agriculture. The satellite was launched from the Taiyuan Satellite Launch Center using a Long March-4B rocket.
On September 14, 2015, another Gaofen satellite, Gaofen-9, was launched from the Jiuquan Satellite Launch Center, using a Long March-2D. Possibly a civilian version of the Yaogan Weixing-2 (Jianbing-6) satellite, Gaofen-9 will provide sub-meter class resolution optical images for city planning, road network design, land ownership determination etc. purposes.
Launch vehicle and launch center:
Gaofen-3 was launched by a Long March-4C launch vehicle. With its main commonality matched to the Long March 4B, 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 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.
It includes 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 vacuum of 2,971 Ns/kg.
Launch took place from the Taiyuan Satellite Launch Center (TSLC). Situated in the Kelan County in the northwest part of the Shanxi Province, 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 centre, a mission command and control centre, and a space tracking centre.
The stages of the rocket were transported to the launch centre 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 centre 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).