Orbital Debris, Re-entries, and the Stratosphere Environment

One approach to mitigating the risks posed by large orbital debris objects, i.e., derelict satellites and rocket bodies, is their deliberate deorbiting into Earth's atmosphere. During atmospheric reentry, a substantial fraction of an object's mass is ablated and burned, while the remaining material may survive and reach the surface. Controlled deorbiting of intact objects is therefore included among the mitigation strategies recommended in international orbital debris guidelines. However, this practice also has environmental implications for Earth's atmosphere. The ablation of spacecraft during reentry releases combustion by-products into the mesosphere, which can subsequently be transported into the stratosphere. These by-products consist primarily of metal vapors, particularly aluminum, and aluminum oxide particles. Such emissions may contribute to chemical processes that affect stratospheric ozone. This paper presents projections of future atmospheric reentries under different activity scenarios and evaluates the associated emissions of aluminum oxide released into the mesosphere and stratosphere, along with their potential impact on ozone depletion. Over a 100-year period, the modeled ozone depletion due to reentries is estimated at approximately -0.4 Dobson Units per year, corresponding to about 0.1\% of the total ozone column.