The effect of self-focusing on laser space-debris cleaning

A ground-based laser system for space-debris cleaning will use powerful laser pulses that can self-focus while propagating through the atmosphere. We demonstrate that for the relevant laser parameters, this self-focusing can noticeably decrease the laser intensity on the target. We show that the detrimental effect can be, to a great extent, compensated for by applying the optimal initial beam defocusing. The effect of laser elevation on the system performance is discussed. A study of ground-based laser schemes for removing space debris concludes that beam self-focusing may be an issue. The concept of laser space cleaning entails using powerful lasers to knock debris out of its original orbit so that it moves to a lower orbit and ultimately burns up in the atmosphere. Alexander Rubenchik and co-workers have now studied the optical effects of transmitting such powerful beams through the atmosphere and conclude that nonlinear effects such as self-focusing, stimulated Raman scattering and turbulent broadening of the beam will need to be mitigated. Fortunately, locating the laser at an altitude of 4000 m above sea level and carefully controlling its beam size, pulse duration and initial defocusing can help to compensate for such nonlinear effects and thus make the approach feasible.