Collision rates and impact velocities for bodies in low earth orbit

Mutual collision probabilities and impact velocities for a set of 2700 earth-orbiting objects with perigee heights less than 1600 km, whose orbital elements are listed in the December 1988 Satellite Situation Report, have been computed using Wetherill's algorithm. This has been achieved by using a program developed by Farinella and Davis (1992) to study asteroid collisions on the nCUBE 2 multi-computer. The average and standard deviation of the intrinsic collision probability P(i) is 1.104 +/- 0.812 x 10 exp -9/sq m/yr; the corresponding value of the impact velocity V is 9.65 +/- 0.88 km/s. This means that a low-orbiting Space Station within a cross-sectional area of 50 sq m has an average collision rate of 0.09 percent per yr with the approximately 50,000 orbiting objects larger than 1 cm, which are probably capable of causing catastrophic damage to the station. The intrinsic collision probability is higher than average at altitudes at which the debris population has maximum density, implying that in these regions the danger of a runaway proliferation of debris due to mutual collisions is most acute. High collision rates also occur near the inclinations at which many existing orbits are clustered.