Unmanned Interplanetary Probe

a spacecraft designed for flight to other celestial bodies and for the study of interplanetary space, the moon, and the planets. An unmanned interplanetary probe has the necessary scientific apparatus on board. The measured results are transmitted from the probe to earth by means of radio systems, including television systems to send images of the surfaces of celestial bodies. An unmanned interplanetary probe is usually equipped with orientation systems and rocket engines for the correction of the trajectory in flight. The power for the apparatus on board an unmanned interplanetary probe is supplied by solar batteries. By Jan. 1, 1969, more than 45 such probes had been launched—the Soviet series Luna, Venera, Mars, and Zond; and the US series Mariner, Ranger, Pioneer, and others.