Satellites are communications systems that use transponders, receivers and radio signals to communicate with astronauts and scientists on earth. Long before satellites enter orbit, they must be designed to withstand the pressures of atmospheric forces and have all the equipment they need to produce and relay vital information, including photographs, temperatures and weather conditions.
Satellites come in all sizes, ranging from small table-sized objects to massive pieces of equipment large enough to hold humans and act as mobile space stations. Some are manually operated, while others are controlled remotely. Regardless of size and function, all satellites have integrated responders, which are components that receive and transmit radio signals. Because they must travel into atmospheric zones with high levels of pressure and external forces, the satellites must be lightweight but sturdy. In space, they are subject to radiation and high temperatures; most are made of reinforced steel and aluminum, which provide protection from those forces without adding weight. Inside, satellites have communications systems, which consist of antennas, a power system and rockets as well as the transponders that transmit and receive signals. Most satellites also have thrusters, which act as turbo kits, making it possible for satellites to propel themselves through space.