There are a number of different types of robots and robotic machines at use in the space industry, but in general they can be broken into four main categories. Satellites are some of the best known and also the most used; these machines orbit the earth beaming signals and facilitate such things as real-time location services and globally available television programming. Rovers are car-like robots that are used primarily to explore and store data on foreign terrains, and are usually controlled remotely from space stations or hubs, either on earth or from ships in orbit. A number of probes and measurement tools can also fall within the “space robot” category, though these tend to be smaller and primarily focused on gathering a single sort of information, such as temperature, pressure, or wind speed. Finally there are a number of tools designed to help astronauts complete space missions. These can include things like cargo release tools, levers and machines for collection of specimens, and suit pressurization materials. In all cases, the main thing that distinguishes a space robot from an ordinary space machine is its ability to work independently. Most are controlled remotely, usually by computers, but many can also be programmed in advance, and they are often thought of as stand-ins for astronauts who, for various reasons, aren’t able to do the robots’ work themselves.
Satellites
Orbital satellites typically make up the majority of space robots. These vary in size and purpose, but in most cases are machines designed to capture information from one part of the earth, then beam it and make it accessible elsewhere. They are usually owned and operated by a specific national government or space agency, but the information they beam out is usually accessible to anyone or anything with reading capabilities.
Some of the first satellites had a strictly military purpose, but most of those in orbit in modern times are used for the world's communication networks. Digital television and most broadcasting is handled by satellite, for instance. Others are dedicated to mapping, and their main role is to take, store, and relay images of the earth. Mapping satellites have a wide range of purposes including measuring changes on the earth's surface, surveying the weather, and even spying on other nations.
Rovers
In contrast to satellites, which stay within and in fact usually depend on the earth’s orbital power to function, rovers typically travel beyond the earth’s orbit to land on and explore other planetary bodies such as the moon, Mars and Venus. These robots are rovers or stationary landers, and typically use airbags or retrorockets to land safely. After arrival, the robots use instrument packages to examine the soil and atmosphere.
For planets like Jupiter that have no solid surface, a different form of robot is necessary — and typically one that is able to send and receive transmissions quickly before being consumed and destroyed by the hostile environment. Jupiter-bound rovers typically use a parachute to slow their decent, then the robot transmits information back to Earth before being crushed by the planet's thickening atmosphere. Scientists back home usually find the cost worth the benefits, particularly if the rovers enable them to get important data to help them better understand the planet, what it’s made of, and hints as to how it might have been formed.
Probes and Measurement Tools
A similar class of robots explores the solar system without actually physically landing anywhere. These typically use cameras and a variety of instruments to measure conditions on other planets, moons, and the sun from some distance. Most of these use solar cells to power their instruments, but might also have to return periodically to a ship or space station hub for charging.
For probes that venture into deep space, radioisotope thermoelectric generators provide power. These generators typically use radioactive decay to produce decades’ worth of continuous electricity. Most scholars speculate that any robots launched to explore past the asteroid belt in the future will rely on this sort of technology.
Astronaut Assistance
Besides acting as explorers, space robots can also assist astronauts in manned spaceflight. One of the most notable examples is a device known as the Canadarm. Developed with funding from the Canadian Space Agency, the Canadarm became a permanent fixture on many American space shuttles and the international space station. With a human working a set of controls, the Canadarm — and other subsequent manipulators developed for use in outer space — moves within 6 degrees of freedom to transfer cargo, release satellites, and transport astronauts performing extravehicular activities to their work sites. It is all but certain that successors to the Canadarm will continue to be a part of future manned spaceflight, as will a range of other related and developing technologies.