PURPOSE: To achieve an acquisition automatically by making deterioration and noises hard to affect even under a severe environment such as outer space to eliminate undesired collision.

CONSTITUTION: A transmitter 301 is mounted on an object 101 to be acquired and an attitude direction detector 201 on an end effecter 102 of a manipulator so that a movement/attitude command value in the normal application can be switched over to that obtained in an acquisition mode with a multiplexer 111. The switching command has a relationship with a mode switch 106 as follows: the-results obtained by adding up outputs of a receiving intensity detector 304 with an addition circuit 107 are compared with a prescribed value by a comparator circuit 108. When the results are above the prescribed value, a logic output 1 is outputted while the logical output 0 is outputted when they are below it. The results are transmitted to an operator or a controller as mode shiftable signal.