noun, noun or participle which takes 'suru'
closest approach
Used in astronomy, navigation, and technical contexts for the point or event of nearest distance between two objects. Can also be used as a suru-verb.
彗星が地球に最接近するのは来月です。
The comet will make its closest approach to Earth next month.
最接近時の距離
The distance at closest approach is estimated to be about one million kilometers.