noun
unmanned exploration; unmanned probing
Refers to exploration or investigation conducted by unmanned vehicles, probes, or robots, especially in space or hazardous environments.
NASAは火星の無人探査を計画している。
NASA is planning unmanned exploration of Mars.
深海の無人探査にはロボットが使われる。
Robots are used for unmanned exploration of the deep sea.
有人探査 means manned exploration, contrasting with 無人探査 which is unmanned.
Compound of 無人 (むじん, 'unmanned') and 探査 (たんさ, 'exploration/probing').