DFH-3

In order to meet the requirements of the economic construction, to speed up the development of China's satellites and improve the reliability of satellites, Chinese Academy of Space Technology formulated the technological policy of following the satellite development road of common platform and serialization in the development and management of satellite engineering. Chinese Academy of Space Technology actively incoporates and uses the advanced experiences of other countries in the development of satellite engineering. Based on the mature technology, the academy has made technical innovation.

The DFH-3 provided a common platform for China's communications satellite, based on which we have developed a batch of new communications satellites successfully. Chinasat-22 launched by China in January 2000 was developed on the basis of the DFH-3 satellite platform. According to the operation of the DFH-3 communications satellite in orbit, Chinasat-22 was optimized and modified. So it is more advanced and achieved optimum results. Its operational performance is stable and reliable. The platform technology is more mature. Based on the satellite platform, two Beidou navigation satellites were developed and launched successfully. Now the two satellites are operating normally. Based on the satellite platform we will design and develop a small satellite constellation for disaster and environment monitoring and forecasting.

The DFH-3 generation spacecraft, long in development, is much larger (more than one metric ton on-station) than the DFH-2, utilizing 3-axis stabilization and bearing a resemblance to the GE Astro Space 5000 series spacecraft. More importantly, the communications payload consists of up to 24 6/4 GHz transponders for both telephone and television transmissions. The design life of the DFH-3 is double that of DHF-2, i.e., eight years compared to four years.

To meet China's market demand for large capacity communications and broadcasting satellites, the Ministry of Astronautics signed a contract on the cooperation on the DFH-3 satellite with DASA (now the Daimler-Benz Aerospace AG) in 1987, the first large program for Chinese cooperation with a foreign country in satellite technology.

Due to its size the DFH-3 requires a more capable launch vehicle than the DFH-2's CZ-3. To this end the CZ-3A was first tested on 8 February 1994, successfully placing a dummy DFH-3 spacecraft and a small scientific satellite into GTO. Nearly 10 months later on 29 November, DFH-3 1 followed, entering GTO precisely as planned. Unfortunately; however, the German-supplied apogee kick stage malfunctioned, causing Chinese officials to use the spacecraft's propulsion system to lift the vehicle into a sub-geosynchronous orbit where the spacecraft was declared lost. (DASA also contributed components for the communications antennas and solar array mechanism as well as provide overall design guidance) (References 228-238).

DFH-3B (also called ChinaSat-6), which was launched in 1997, has experienced malfunctions in attitude stabilisation which resulted in excessive fuel consumption that may reduce its operational life.

The main body of the satellite is a box-form structure with the size of 2.22m×1.72m×2.2m. The satellite has large deployable solar wings and communications antenna with 2m in diameter, which are folded when the satellite is launched and deploy when the satellite enters orbit. The wing span can reach 18.1m and their height is 5.7m. The satellite has 2260kg liftoff mass and 8-year-designed lifetime.

The DC power is 1700W at the end of the satellite's life. The satellite carries 24 C-band transponders with 16W TWTA and 8W SSPA power amplifiers, which serves customers in China. The pitch and roll accuracy of the antenna is ±0.15? and yaw accuracy is ±0.48? At the edge of service area, the EIRP value is 33.5dBW (8W SSPA channel) and 37dBW (16W TWTA channel), and G/T value is greater than -2dB/K.

The DFH-3 satellite is composed of the propulsion bay, service bay, communications bay, communications antenna and solar wings. It has 7 subsystems, including control, power supply, measurement and control, propulsion, structure and communications, etc.. The first 6 subsystems make up the satellite platform and the last one is the payload of the satellite.

Thanks to advanced technologies, all main performances of the DFH-3 had been improved and are much better than those of the DFH-2A.The communications capability of one DFH-3 satellite is equal to that of 12 DFH-2A satellites.

The DFH-3 is a medium capacity communications satellite. The payload of the DFH-3 satellite weighs 170kg with 900W power. Reducing platform weight and improving the performance of the power subsystem, the above two indexes can be increased by 30% and 13% respectively, which have been tested on the ground. Besides, it is under the definition of feasibility that the gallium arsenide solar cell will be used into the DFH-3 platform to greatly increase the payload power and life time, and serve meteorology.