Analysis of Debris from the Collision of the Cosmos 2251 and the Iridium 33 Satellites

The collision between the active American Iridium 33 satellite and the retired Russian Cosmos 2251 satellite on 10 February 2009, is the first on-orbit collision between satellites. As of 1 December 2009, the U.S. space tracking system catalogued 1,632 fragments from the collision, many of which will stay in orbit for decades. This paper estimates the total number, size, area-to-mass ratio, and relative velocity of the catalogued fragments; calculates the lifetime and orbital evolution of the fragments; and evaluates the shortand long-term hazards they pose in the space environment. It is shown that previous estimates of the probability that an intact object in space will collide with another object appear to be lower than is indicated by observed collisions. How the collision probability depends on the shapes of the colliding objects is analyzed, and results indicate that including shape dependence will increase estimates of collision probability. Previous analyses have not considered the effects of satellites appendages, which lead to an underestimation of the long-term space debris population.