Chinese Long March 4B conducts surprise Gaofen-8 launch

by Rui C. Barbosa

The Chinese have conducted another surprise launch on Friday with the launch of an Earth Observation System satellite called Gaofen-8. The launch took place at 06:22 UTC via the use of a Long March-4B rocket that set sail from the LC9 launch complex at the Taiyuan Satellite Launch Center.

Chinese Launch:

There is very little information about the GF-8 Ganfen-8 satellite orbited on Friday, other than the objectives of the mission – later released to the state media – that it was to provide country surveying, disaster response, agriculture mapping, city planning, land ownership marking and road network planning.

China announced plans for the launch of Gaofen-1 to Gaofen-7, but there was no news about an 8th Gaofen bird. The only information that can be found is it will be classed as an optical satellite planned under the civilian China High-resolution Earth Observation System (CHEOS).

The Gaofen satellites are a series of high-resolution optical Earth observation satellites of China National Space Administration. In English “gao fen” means “high resolution”.

The civilian High-Definition Earth Observation Satellite program was proposed in 2006, receiving government approval on the next years and initiated in 2010.

The plan was to launch six Gaofen satellites between 2013 and 2016. The first satellite, Gaofen-1, was launched on April 26, 2013, by the Long March-2D (Y18) from the Jiuquan Satellite Launch Center.

The main goal of the Gaofen series is to provide near real-time observations for disaster prevention and relief, climate change monitoring, geographical mapping, environment and resource surveying, as well as for precision agriculture support.

The major users of the observation data will be the Ministry of Land and Resources, Ministry of Environmental Protection, and the Ministry of Agriculture.

In 2010, the Chinese government approved to implement the China High-resolution Earth Observation System (CHEOS), which is an extension of the High-Definition Earth Observation Satellite program. The CHEOS series would consist of seven optical/microwave satellites.

The Earth Observation System and Data Center of the China National Space Administration is responsible for organizing the construction of the CHEOS program.

The CHEOS program comprises the elements of the spaceborne system, the near-space system, aerial system, the ground system and application system as a whole to realize Earth observation at high temporal, spatial and spectral resolution.

The implementation plan of CHEOS satellite series has a development period between 2010 and 2020. With the launch of GF-2 in 2014, by 2016 the next three satellites will be launched. The entire CHEOS series of satellites will be in orbit by 2020.

Launch vehicle and launch site:

The feasibility study of the Chang Zheng-4 began in 1982 based on the 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.

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.

2015-06-26-105039On 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 include 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 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 vacuum of 2,971 Ns/kg.

This launch was the 206th Chinese orbital launch and the 205th launch of the Long March launch vehicle family. It was also the 52nd successful orbital launch from the Taiyuan Satellite launch Center, the 1st launch from Taiyuan this year and the 2nd launch by China in 2015.

Z114Situated 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 centre, a mission command and control centre, and a space tracking center.

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).

Related Articles