noun
orbiter
A spacecraft designed to orbit a celestial body, such as a planet or moon, without landing.
火星の軌道船が新しい画像を送ってきた。
The Mars orbiter has sent back new images.
探査機 is a broader term for any space probe, including orbiters, landers, and rovers.
Compound of 軌道 (orbit) and 船 (ship, vessel).