Speaker
Description
During the last 15 years there has been an increasing number of launches, involving private actors, emerging countries and the transition to multi-object payloads. The number of operational satellites is expected to increase tenfold over the next decade, thereby also leading to a significant increase in the number of orbital launches. All types of re-entries of artificial space objects, either uncontrolled, semi-controlled or controlled, are responsible for the release of metals and particulate into the high atmosphere.
Just to give an example, during the last year, up to December 4, 2023, the mass of human-made orbital objects that re-entered the Earth’s atmosphere and fragmented at high altitude was on the order of 600 metric tons. Of these, nearly 36% was associated with large (Radar Cross-Section: RCS > 1 m2) intact objects (7% with spacecraft and 29% with rocket bodies) re-entered without control. About 5% of the returned mass was instead concentrated in medium (0.1 < RCS < 1 m2) intact objects, and nearly 3% in large orbital debris (mission related objects and fragments), still re-entered uncontrolled. Controlled re-entries of spacecraft accounted for a total returned mass of approximately 130 metric tons, 80 of which disintegrated into the upper atmosphere. The remaining 50 metric tons survived re-entry and reached the ground intact. Therefore, based on the estimated mass that might have disintegrated, controlled spacecraft re-entries were likely responsible for 13% of the mass subject to fragmentation. However, the greatest amount of re-entering mass was due to some 60 launches of Falcon 9, put in low Earth orbit and mostly deorbited within a few hours. With a mass around 4 metric tons each, these actually accounted for a contribution of nearly 43% to the artificial returned mass disintegrating at high altitude in 2023. Finally, considering that between 5% and 30% of the mass of objects not designed to survive re-entry may reach the ground in the form of macroscopic fragments, the human-made mass released into the atmosphere in 2023 could range between 420 and 570 metric tons.
This presentation will review the evolution of the artificial mass re-entered into the Earth’s atmosphere during the last 14 years, starting in 2010, highlighting the significant increase observed over the years, both for uncontrolled re-entries and for the increasing number of orbital launches, especially those of the US rocket Falcon 9.
