On 10 February two satellites collided with each other, the American commercial satellite Iridium 33 and the Russian communications satellite Kosmos 2251 (the latter does not work). The collision occurred at almost 800 kilometers of altitude, and scientists are concerned that the residues generated from the crash jeopardize other satellites at that height or below. Among those located at the height of the shock are the satellites that move synchronized with the movement of the Sun, and among the much lower, the ISS station, for example. Therefore, they must now follow about 500 satellite fragments generated in the crash.