1:1 Dongfanghong 2 satellite

The first launch was successful on April 8, 1984. Launched by the Long March 3 launch vehicle. Three dongfanghong-2 satellites have been developed and launched. It took nearly 16 years from 1970 to the launch of the third one.
Chinese name
Dongfanghong-2 satellite
brief introduction
It is developed by China Academy of space technology and has a design life of 3 years. It is a satellite used for long-distance television transmission in China at the end of the 20th century. The satellite is in geosynchronous orbit, with the first fixed point over the equator at 125 ° E.
significance
The successful launch of dongfanghong-2 satellite started the history of satellite communication with China's own communication satellite.
structure
The main body of dongfanghong-2 satellite is cylindrical, with a height of 3.6 meters, a diameter of 2.1 meters and a weight of 441 kg. The satellite is equipped with four C-band transponders, with an equivalent omnidirectional radiation power of 36 dB. The satellite adopts spin stabilization, and its orbit keeping accuracy is ± 1 ° from north to South and ± 0.5 ° from east to west.
Dongfanghong-2a satellite adopts paraboloid communication antenna, which is placed on the upper part of the star; adopts mechanical racer to keep the communication satellite antenna always oriented to the earth; nearly 20000 solar cells are pasted on the surface to provide power for satellite operation.
Synchronous satellite
If the period of the satellite around the earth and the earth's rotation are synchronized, it is called a geostationary satellite. Its advantage is that users can communicate with the satellite as long as they aim at it, without having to track the orbit of the satellite. The height of the synchronous satellite can be calculated by the third law of J. Kepler, H + e = r = AP2 / 3, in which period p = 0.99727, scale constant a = 42241, earth radius Er = 6378km, so the height of the synchronous satellite can be calculated as H = 35786km as shown in Figure 4. The disadvantage of synchronous satellite is that the space is highly limited and the transmission time of radio wave is delayed due to too long distance. For example, the transmission time of synchronous satellite is about 250ms (= 2 * 3.5 * 104 / 3 * 105) and the transmission power of radio wave is quite large due to too long distance.