Introduction to space communication

Radio communication between spacecraft, celestial bodies and earth stations. Also known as space communication. Earth stations include radio communication stations on the ground, in the air and at sea. Space communication has a long distance and weak signal. In order to ensure effective communication, the earth station must have high-sensitivity receiving equipment, high-power transmitting equipment and antenna with large effective aperture, and also apply advanced modulation and coding technology, such as increasing bandwidth in exchange for signal-to-noise ratio and lowering receiving threshold. Most space targets are moving, so when necessary, the receiving antenna should continuously track the target orientation. The output power of spacecraft launcher is limited, so the earth station must use large aperture antenna and low noise amplifier. In deep space communication, a parabolic antenna with high gain and controllable direction is used on the ground. The most commonly used antenna diameters are 18m and 27m. The communication equipment on spacecraft must be light in weight, small in size, radiation-resistant, long in life, able to withstand shocks and vibrations and high in reliability. Space communication uses a wide range of frequency bands, from ultra-long waves to millimeter waves and even lasers. The frequency band commonly used in satellite communication is 1 ~ 15 GHz, and the higher frequency band has been used. Space communication can be divided into voice communication, image communication, data communication, telemetry, instruction information transmission and so on.