What is a Satellite? – The History and Technology



A satellite is an artificial object that orbits (goes around) any planet. There are hundreds of natural satellites, or moons, in our solar system, but since 1957, thousands of artificial (man-made) satellites have also been launched into space. These have very diverse uses, such as capturing images of the Sun, Earth and other planets, or exploring space to study black holes, and remote stars and galaxies. There are also communications satellites, meteorological satellites, and the International Space Station.

The very first artificial satellite, Sputnik 1, was launched in 1957. which had an aluminum ball the size of a the beach ball equipped with four long antennas and connected by batteries. Inside were radio transmitters that sent out an unmistakable intermittent beep that could be detected around the world. The launch of this simple little satellite ushered in the space age.

Modern satellites are much more complex. Most of them are designed to be as strong and light as possible. They are built from the same basic model. One platform, called a bus, contains the main systems, such as batteries, computer, and thrusters. Antennas, solar panels and payload instruments (like cameras, telescopes and communication equipment) are attached to the bus.

Satellites must have their own power. For this, large solar panels (wings) covered with light-sensitive solar cells are usually used. Panels are several meters long and usually need to be folded at launch. Solar cells supply several kilowatts of power, although they lose efficiency over time. Most panels can be rotated to capture as much sunlight as possible. When the satellite passes into a shaded area, it receives power from rechargeable batteries.

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Artificial satellites generally consist of two parts: payload and satellite platform . The payload refers to various instruments and equipment for directly realizing the application purpose of the satellite or scientific research tasks. The satellite platform is the assembly of all guarantee systems used to support the normal operation of the payload [1] . Generally speaking, the design of the satellite platform is relatively stable for a period of time, and only minor improvements will be made before the upgrade. As long as the functions are appropriate, a certain satellite platform can carry a variety of payloads as needed. For example, the Chang’e 1 and 2 satellites both use the Dongfanghong 3 satellite platform, but their respective payloads are different. The satellite platform is divided into multiple subsystems:

Payload (different types of satellites are different, the common ones are:)

  • Ground camera
  • Stellar camera
  • Carrying payloads
  • Satellite platform (providing the environment and technical conditions for the operation of the payload, including:)
  • service system
  • Thermal control system
  • Attitude and Orbit Control Sub-system
  • Program control subsystem
  • Telemetry Subsystem
  • Remote control subsystem
  • Tracking and testing subsystem
  • Power supply and distribution system
  • Return subsystem (limited to returnable satellites )
  • Satellite structure platform

The side of the satellite facing the Sun reaches very high temperatures, while the shadow side gets very cold. This is a problem, as most satellite equipment is sensitive to extreme temperatures. Heat-conserving, foil-like layers are used to protect instruments, and radiators are added to reduce heat from electrical equipment.

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