Space exploration satellites
Space exploration satellites are not really satellites at all; they are properly known as space probes. A satellite is defined as something that's orbiting something else, but space probes instead travel deep into the solar system. However, they are similar to orbiting satellites in design and function.
On their journeys, space probes send back detailed pictures and other data of faraway planets and other stellar phenomena. Space exploration satellites are responsible for many of astronomy's most important achievements. Jupiter's rings, for example, were discovered by a space exploration satellite.
Space exploration satellites must be built to last because it takes so long for the satellites to reach their destinations. Space exploration satellites are different from astronomy satellites because they do not operate from Earth orbit; they are actually sent out into deep space on their own.