PURPOSE: To automatically avoid any collision with another object by inputting data from a microwave distance sensor to calculate a distance from an object, and judging whether the distance reaches a dangerous distance or not so as to control an injection actuator.

CONSTITUTION: An artificial satellite 1 comprises an automatic collision avoidance device including a microwave distance sensor 2, a dangerous distance judging circuit 4 and an injection actuator 3. The microwave distance sensor 2 measures the distance (d) between the artificial satellite 1 and another artificial satellite or a debris, the danger distance judging circuit 4 inputs the data, and calculates the distance between the artificial satellite and another artificial satellite or a debris 5. The injection actuator 3 is controlled according to a control signal from the dangerous distance judging circuit 4 and operated to enlarge the distance (d) from another artificial satellite or a debris 5 for collision avoidance.