The present invention has the object of simplifying apparatus configuration and avoiding a requirement for calibration. The present invention achieves the above object by forming a detection sheet element that retains in a predetermined array pitch a plurality of conductive detection lines that are lead lines formed by etching or the like on a non-conductive thin film that can be exposed in a space environment. A detection circuit connected to each detection line of the detection sheet element is provided. When an object flying in space collides with the detection sheet body, since a detection line on the detection sheet element is ruptured, constant monitoring of the conductivity of the detection line by the detection circuit enables detection of the object flying in space that has collided with the detection sheet element when a detection line is ruptured. Furthermore a means of solution is adopted in which an effective diameter of a colliding object flying in space can be detected from the number of severed detection lines.